Satellites are subject to north-south drift in space, caused by the gravitational pull of the sun and moon. This gradually changes their orbit. To compensate for the deviation and maintain the desired orbit they have to achieve a speed change of about 45 to 50 meters per second per year. In the weightlessness of space no great forces are needed for such a correction. A small, precisely measured impulse from time to time is enough to adjust the position.

Light electric motor vs. heavy combustion engine

In contrast to the heavyweight burner of the rocket, ion thrusters – in particular so-called Hall Effect thrusters – are small and light: the thruster for a satellite weighing up to one ton weighs just 1.5 kilograms, and the gas tank holds only a few hundred kilograms of fuel, even for large communication satellites. The thruster is only ignited for a few minutes at a time for the correction maneuver and usually draws its energy from the solar collector that also supplies the space probe with electricity.

In an ion engine, a small amount of a gaseous propellant is ionized. An electric field is then used to accelerate the ions to speeds of up to 400,000 kilometers per hour and direct them into space through the outlet. The resulting recoil causes the desired change in position; after the targeted impulse, the engine is switched off again. In addition to satellites, space probes for space research also use this type of propulsion to penetrate into the depths of space. In both cases, the limited gas supply must last for many years of operation.

Ideal propellant

The noble gas xenon is particularly suitable as a propellant for ion propulsion; it is used in most of today's satellites and space probes. Krypton has been used much less frequently, but this could change in the future. Unlike some of the metals that were initially experimented with, the gases do not need to be vaporized first; they are also environmentally neutral and easy to handle. Ion propulsion is remarkably efficient: with xenon in the tank, the specific impulse by weight is more than six times higher than that of a thermal rocket engine.

The only source of both noble gases is the Earth's atmosphere. They are only present in the air we breathe as trace elements, but krypton, at around 1 ppm, is more than ten times more abundant than xenon, at 0.09 ppm. This makes it easier and cheaper to extract. Xenon, due to its higher atomic weight, enables more thrust with the same tank volume, but this difference is becoming less and less important due to the increasing efficiency of the latest engine types. For example, SpaceX's Starlink satellites are powered by krypton.

Gas quality ensures efficiency

The efficiency of an ion engine depends, among other things, on the filament, a glowing thread used to generate electrons. It reacts sensitively to various molecules; in particular, oxygen and oxygen compounds can trigger unwanted reactions on its surface. Therefore, the gas of the supporting mass must meet high quality requirements, which are specified very precisely by the manufacturers of the drives – but not at all the same. In addition to the degree of purity, the composition of the remaining impurities plays an important role. The extent to which the performance of an ion engine is affected depends crucially on the type and quantity of residual molecules.

Messer offers two gases with a reduced level of impurities, Xenon 5.0 and Krypton 5.0 for ion thrusters. They were developed specifically for this application and enable the thruster to maintain a high level of efficiency. The extraction and quality control processes are meticulously tailored to the special requirements of use in an ion drive. They go beyond the standard specification of a purity level of 5.0 – 99.999 percent by volume of the respective gas.

Quality control process for gas and cylinder

Given their minimal concentration in the atmosphere, the only way to make the production of the two noble gases economically viable is to use very large air separation units (ASUs). These can be found at steel mills, for example, where they provide a continuous supply of the large quantities of oxygen and nitrogen needed there. Messer operates a number of such plants in Asia, Europe and America. This ensures a continuous supply in all regions of the world.

The first steps of the quality process are carried out in the LZA after the separation of the noble gases with downstream cleaning processes. This further reduces the small amounts of other substances that remain, including oxygen, hydrogen, methane, CO and CO₂, as well as moisture. At the same time, the containers for the engine gases undergo a multi-stage process to ensure that the purity achieved is maintained until delivery.

The cylinders are made of particularly high-quality stainless steel with extremely smooth, electro-polished surfaces. This helps to prevent any possible buildup of water molecules from the humidity in the air. In addition, the cylinders are purged with high-purity nitrogen before filling. During the purge, the quantity and size of any solid particles present are determined by means of laser light absorption. The cylinders are only used if they comply with the strictly defined limit values. Quality control also includes a valve test to ensure that the fitting is free of grease and oil. The cylinder certificate contains the dimensions of the cylinder as well as pictures of its condition before delivery. All relevant components are recorded in the detailed documentation.

Comprehensive documentation and customized solutions

Filling after removal of the purge gas follows a documented standard operating procedure. After filling, the quality of the gas is checked again – in other words, in the state in which it reaches the user. For this purpose, Messer uses a gas chromatograph with thermal conductivity detectors that is specially calibrated for the analysis of noble gases. The values obtained are also documented in the quality certificate.

The manufacturers and users of ion thrusters have defined individual specifications for their various Hall Effect thrusters. In addition to standard products, Messer's range, therefore, also includes customized solutions with appropriate documentation in accordance with the relevant specifications. The sales organization relies on personal contact and individual advice in order to tailor the supplied gases precisely to the customer's requirements.

Austenite refers to an iron and carbon crystal structure which is found in many steels but is not always desirable. This structure only has a low degree of hardness and, as a rule, is difficult to cut, which considerably limits the processing possibilities. At Pilana, a Czech tool manufacturer, hardened steel is therefore frozen with nitrogen prior to machining, because at very low temperatures austenite is transformed into different, desirable structural forms. Messer has installed the technology for this and is supplying the nitrogen coolant. Among other things, Pilana produces wood milling machines and circular saw blades, as well as woodworking tools, plane blades and industrial cutters. The company employs 650 staff and is one of the largest tool manufacturers in Europe. The tools are manufactured in compliance with the DIN and ISO standards. A crucial factor here is, of course, the quality of the steel and this, in turn, is dependent on the crystal structure of the material. Depending on the tool and the application, the austenite in the steel needs to be transformed into a different crystal structure – martensite, which has an extremely high degree of hardness.

Lattice change
The classic method of transforming austenite into martensite involves repeated heating and cooling of the material. This takes a long time though and consumes a lot of energy. Cryogenic treatment offers a modern alternative, which saves both time and energy. In 2011, Pilana placed an order with Messer in the Czech Republic to install a facility for the cryogenic treatment of steel for cutting tools. This was designed to allow the steel to be cooled with cryogenic nitrogen to temperatures as low as minus 180 degrees Celsius and to be heated to a maximum temperature of plus 180 degrees Celsius. The centrepiece of the cryogenic process is the injection of liquid nitrogen into the refrigerated part of the chamber. Here, ventilators disperse the cryogenic gas so that its effect on the material is even. The entire cooling and reheating process is pre-programmed and centrally controlled to ensure accurate adherence to all the steel hardening parameters. This includes the cooling rate and time, the retention time for a predetermined temperature as well as the heating rate and time.

The advantage of controlled heating is that the entire process takes place in the box without air ingress. A further benefit is the rapid transition from the held temperature to ambient temperature, which saves a lot of time. Nitrogen and energy are also used very efficiently. Approximately two to three kilograms of liquid nitrogen is sufficient for one kilogram of material. A vacuuminsulated nitrogen supply pipe also helps to minimise the energy requirement.

Difference in quality
Besides being very efficient, the process also improves quality. When comparing the service life of cutting tool steels used in woodworking, there are measurable benefits from cryogenic treatment. The Austrian company Stora Enso Building and Living, based in Ybbs, has compared steel in tools (blades for removing tree bark) with and without subsequent cryogenic treatment at a minimum of minus 150 degrees Celsius. Cryogenic treatment reduces the tension in the material and facilitates the formation of particularly fine martensite needle grains – a prerequisite for a robust crystal structure. It therefore also facilitates improved cutting performance. Consequently, steels for tools that have been cryogenically treated have a significantly longer service life.

Hardening of steel is only possible by first allowing the carbon content to dissolve in the austenite at high temperatures followed by quenching of the work piece in liquid oil. This changes the steel’s crystal structure. The dissolved carbon content, hardening temperature and quenching medium determine the nature of the change as well as the properties of the hardened steel at room temperature. In practice, the quenching oils are usually maintained at a constant temperature of 50 to 70 degrees Celsius so that the heat treatment creates reproducible hardness and dimensional stability .. At these temperatures, however, the austenite is not completely transformed into martensite during quenching. In steels with a carbon content of more than 0.5 percent by weight, the formation of martensite during quenching to room temperature may not take place completely.

After hardening, the proportion of retained austenite in the steel can be up to 20 percent by volume. Retained austenite has an adverse effect on dimensional accuracy, wear resistance and hardness, as well as on processing qualities. It is also undesirable from a safety point of view. It is therefore essential to reduce its fraction in the steel. For these reasons, the cryogenic process is nowadays the method of choice, since it combines reproducibly better results with – compared to the conventional procedure – significantly reduced time and energy requirements.

Additional cooling of the hardened parts to temperatures as low as minus 150 degrees Celsius facilitates the transformation of retained austenite into martensite and, for certain alloys and proportions, makes this process possible at all. The hardened components are cooled in cold chambers under controlled conditions, the temperatures (typically between minus 80 and minus 120 degrees) depend on both the alloy involved and any particular requirements . After cooling they are then re-heated. This procedure should be carried out as soon as possible after hardening and repeated several times. The martensite finish temperature (Mf) is a decisive factor here. It indicates the temperature at which the expected rate of transformation will be achieved.

The key element of the cryogenic process is the injection of liquid nitrogen into the refrigeration area of the cold chamber where fans distribute the cryogenic gas, enabling it to act uniformly on the material.

The entire process of cooling and reheating is programmed and centrally controlled using up to date equipment like Messer’s Cryogen® cold chambers, thus ensuring that all parameters for hardening the steel are precisely maintained. These include the speed and duration of cooling, the time for reaching and holding the prescribed temperature,, as well as the speed and duration of heating.. Controlled heating has the advantage that the entire process takes place in a box without air contact, thus preventing the batch from becoming iced over. Another plus is the rapid transition from the holding to the ambient temperature, which saves a great deal of time. Nitrogen and energy are used very efficiently in modern cooling chambers: less than one kilogram of liquid nitrogen is sufficient to treat one kilogram of material. The use of a vacuum insulated pipe for conveying liquid nitrogen from the tank to the cooling facility allows for a further reduction in energy consumption. It is advantageous to use a piping system which is as short as possible; this should therefore be taken into account when planning the system as a whole.

Difference in quality

Not only is the process particularly cost effective, it also improves quality. Comparing the lifetime of cutter blades for wood machining gives a measure of the benefit of cooling. An Austrian company compared tool steels (for industrial blades for removing bark) with and without subsequent cryogenic treatment. The holding temperature used here was minus 150 degrees Celsius. The cryogenic treatment reduced the compressive stresses in the cutter blade and allowed particularly fine needles of martensite to form – a prerequisite for a resilient crystal structure as well as for increased cutting edge retention. The lifetime of tool steels that undergo cryogenic treatment also increases significantly.

The same is true for work pieces in which the accuracy of fine contours plays a crucial role. Moulds for yoghurt pots, for example, must comply with minimum tolerances, since even small variations can cause disruption to the process of preparing, filling and labelling the plastic pots. Cryogenic treatment increases the wear resistance and dimensional stability of the moulds and thus helps to reduce overall costs. Furthermore, cryogenically treated steels are easier to work with.

Typical products and applications

The benefits of cryogenic treatment are exploited for a wide variety of work pieces and applications. Alongside the tool steel and moulds already mentioned there are other typical examples. Cold treatment is used to improve the dimensional stability, among other things, of case hardened injectors, vacuum hardened plain bearing rings and the blades used in electric shavers. The safety aspect is also important in the case of specialised folding bellows,. Durability and safety are at the forefront in applications such as safety chains for the tyres of large vehicles.

Characteristic features of the martensitic transformation

The diffusionless and exothermic transformation begins with the nucleation of martensite at lattice defects in the austenite (dislocations, grain boundaries). The crystal volume increases by three to four percent after the transformation. Depending on the chemical composition of the alloy, a specific content of retained austenite remains. The final extent of transformation is primarily determined by the cooling profile applied.

Effects on the proportion of retained austenite during hardening and tempering

How much retained austenite remains in the material depends on numerous factors. The hardening temperature, the holding time as well as the level of carbon activity in the furnace atmosphere during the heat treatment play a role. During quenching, the type of quenching oil, the oil temperature, the rate of quenching and the oil circulation are factors alongside the work piece parameters (material, geometry, etc.). In the batch removal phase, the immersion time, the draining time, the quenching chamber temperature, and the storage and cooling times are significant. In the cleaning phase, important factors are the temperature of the cleaning solution and steam/spray treatment, as well as the drying and total cycle times. During cold treatment, significant factors are the rate of cooling, the temperature and its distribution, the holding time, heating up and tempering. In order to achieve reproducible quality, treatment specifications that include a work plan as well as monitoring of the process flow and the final quality are essential.

Safe, rapid cooling in every situation

Messer cold chambers enable efficient and reproducible cold treatment in which the customer’s specific requirements can be exactly implemented. They are characterised by high cooling efficiency and operational safety. If the chamber is opened, for instance, the coolant supply automatically shuts off. All of our cold chambers are delivered ready for connection, which speeds up their initial operation at the desired location and thus ensures that all their advantages can be exploited immediately. In addition, the cold chambers can be rapidly and easily redeployed to a different location with minimal installation timel.

The injection of liquid nitrogen permits very efficient and cost-effective operation. It ensures that the cooling temperature is achieved quickly and uniformly. At the same time, a very rapid change in temperature and heating for a quick batch change is possible. Accurate control of the process steps is facilitated through processor controlled temperature regulation. . The high quality construction of the chambers guarantees a long service life. They are also suitable for high loading capacities. Last but not least, the size of the nitrogen tanks can also be specified to precise customer requirements. Experts from Messer consult with customers to determine their product quality needs and seek out appropriate solutions. Analysis of the processes and identification of the potential for improvement are used as a basis for the planning and design of the cold treatment. Once the process has been introduced, long term support and service are an integral component of our business relationship.

During the production of a tyre, up to 30 sorts of rubber are blended together to create different mixtures with proportions that depend on whether they are to be used to make summer or winter tyres, treads or side walls. The individual rubber layers are assembled layer by layer with the other components, such as textile fabrics or steel belts, and are then provisionally bonded with one another by powerful rollers. Only when vulcanised in the heating press do the layers finally merge to become an inseparable unit. It is here that the tyre also gets its tread, and the previously mouldable rubber mass transforms into the stable, but still elastic, material that we know in the form of car and bicycle tyres. Nitrogen (N₂) plays an important role in this critical step. In the heating press, nitrogen can be used in two separate processing steps. In the first of these, the so-called bladder is inflated with nitrogen. This is a kind of balloon that is located in the middle of the heating press and which presses the tyre blank into the mould with a pressure of about one bar. Steam was formerly used for this step. But it is safer with nitrogen since the press is still open at this phase. As a consumable item, the bladder is regularly replaced; however, any damage that it might suffer before replacement could lead to an uncontrolled release of steam and endanger the workers. Compressed air is out of the question due to the risk of ignition. Inert nitrogen offers the best possible protection here.

In the second step, the press is closed and the bladder is filled with hot steam at 15 to 20 bars. This supplies the heat and pressure that are needed for vulcanisation, but it is replaced with nitrogen after a short time because steam would heat up again too much under pressure. However, heat and pressure must be kept within an optimal range if the desired quality is to be achieved. The larger the tyre is, the longer the process takes. For conventional car tyres, it requires about 10 minutes; for the tyres used on heavy goods vehicles, which can be up to four metres across, it can take a whole day. The use of nitrogen guarantees a uniform distribution of heat over the entire period.

The improved pressure stability and uniform heat distribution during vulcanisation that results from the use of nitrogen reduce the cycle time while extending the service life of the bladder. This allows higher rates of production as well as lower production and maintenance costs.

Following on from the hot N₂, very cold CO₂ comes into play when removing excess rubber from the press mould. The use of carbon dioxide dry ice allows the moulds to be cleaned without disassembly and with minimal loss of time. Cryogenic dry ice pellets are “shot” at the moulds from a blasting machine, such as the ASCOJET from Asco Carbon Dioxide Ltd, at up to 300 metres per second. Thermal shock and impact energy completely strip away the contaminants. The pellets change into the gaseous state, leaving behind a clean and dry surface. The tyre mould of the heating press has small venting holes into which the rubber is forced during vulcanisation. This is what gives rise to the small nubs that are found on new tyres. When a new car is fitted with tyres for the first time, the tyres are not only deburred, but also “de-nubbed”. The method of choice for both: The protruding bits of rubber are made brittle with cryogenic nitrogen and are then simply brushed off.

With or without nubs, tyres roll optimally only when they are at the correct pressure. Here, too, nitrogen – or a mixture of nitrogen and argon – is clearly superior to simple compressed air. Tyres that are filled with nitrogen maintain their pressure better and hence retain their optimal rolling properties for longer. This helps to save fuel and, furthermore, prevents oxidation of the inner wall of the tyre, which gives the tyre a longer service life. In Formula 1, on vehicles transporting dangerous goods, on vehicles used in tunnels or mines and on commercial aircraft, the use of nitrogen to fill tyres is a safety requirement. When a jet lands, the tyres are accelerated to about 260 kilometres per hour in an instant as it touches down and thus become hot very rapidly. In order to prevent them from being able to ignite from inside, they are filled with nitrogen.

Gases are also used when recycling tyres. In order to reclaim the valuable raw materials from old tyres, they must first be reduced to small pieces. Cold grinding is used to achieve the best quality here. The ground material is cooled and embrittled with liquid nitrogen. A very fine grain can be achieved by grinding in this way. The raw materials in the tyres – rubber, metal and plastic fibres – can then be sorted into their different types, and some can be reused for tyre production.

Old tyres in which the load-bearing structure, the carcass, has remained undamaged can be reused by replacing the tread. This is a particularly common practice for old lorry tyres. The first step of retreading is to inspect the carcass. If it is in good condition, the old tread is stripped away, producing rubber “buffings” in the process. The new tread can then be laid down. There are two procedures for this: the cold and the hot retreading processes. In the cold retreading process, a pre-vulcanised tread is attached to the carcass and is then bonded with the carcass under pressure in an autoclave at about 110 degrees Celsius. An alternative to this is the hot retreading process. In this process, the new tread is laid down in the form of strands of extruded rubber mass and is subsequently vulcanised with nitrogen in a heating press. This fuses the rubber mass and the carcass into a single unit. Nitrogen offers the same advantages here as it does for the production of new tyres.

Every wine grower is glad of dry and sunny weather at harvest time. The grapes get one last ripening boost and the harvest stays healthy – only in this way can truly great vintages be created. However, a warm autumn also encourages premature fermentation. As soon as the grapes are pulled from the panicles and get slightly squashed in the process, the ubiquitous microorganisms start to attack the must. They multiply particularly quickly in warm temperatures. If the wine grower does not intervene, they will immediately start to convert the fructose into alcohol.

Golden October spells danger
While this conversion – the fermentation process – is what turns the juice of the grapes into wine, it would be premature at this stage, because the must needs some time to allow important constituents to be released from the grape skin. This includes some of the flavour compounds that help give the wine its fruity taste. The tannins, which are essential to the “body” of the wine, and the colour compounds, which give it its shimmering lustre, are also predominantly derived from the grape skin and extracted prior to fermentation.

Colouring bath of skins
To ensure that this subtle process is not interrupted by premature activity on the part of the alcohol-forming yeast cells, many vintners rely on so-called cold maceration. The process was originally developed in Burgundy to help give the not so intensely coloured Pinot Noir a darker density. In most cases, a temperature of approximately five degrees Celsius is aimed for. This is achieved by adding dry ice with a temperature of minus 78 degrees Celsius. The cryogenic carbon dioxide cools the must to the desired temperature and also keeps the ambient air away from it: It changes from the solid state to the gaseous state (sublimation) and rises above the must, remaining just above it as a blanketing CO₂ cloud since it is heavier than air. After a while, fermentation can finally begin. With good red wine, it takes place “on the skins” – the must and grape skins stay together. In the case of white wine, the two are first separated. The must is pressed, and this juice is then clarified, id est turbidities such as leftover particles of grape skin is removed.

Nowadays, with larger batch sizes, the flotation process is predominantly used for this step. Many wineries use nitrogen for this as it does not react with the sensitive contents. Nitrogen is fed into the grape juice inside a pressure tank. At a pressure of five to six bar, it remains absorbed in the liquid, but is then released again as soon as the pressure is reduced. Gas bubbles rise to the surface, taking with them the particles to which they are still adhering. This leaves clear must at the bottom, which can simply be drawn off. The process also works with compressed air, but the oxygen it contains can cause undesirable reactions, oxidation and a loss of flavour.

Tank flooded with gas
During fermentation, the microorganisms themselves produce plenty of carbon dioxide, thus preventing air from getting into the fermentation tanks during this phase. However, before these are filled, as well as a few weeks later when transferring the fermented young wine into the storage tank, the question of how to avoid contact with oxygen arises again. The best way to prevent changes in the flavour and colour of the wine is to use inert gases – nitrogen or argon for red wine and carbon dioxide for white wine. These gases displace the air during the storage, transfer or bottling of wine and thus prevent oxidation by atmospheric oxygen. They are stored in gas tanks or gas cylinders and dosed via pipes and hoses as required. There is another very simple method of tank inerting. This involves manually adding a measured quantity of dry ice to the empty tank. Inside the tank, it sublimates to gaseous carbon dioxide and pushes the air out through the opening at the top of the tank.

The same inert gas processes are used when different wines are blended to make a cuvée, as is the case with the majority of the fine Bordeaux wines for example. These expensive wines are made from the wines of different grape varieties, which are made separately before being mixed at a later stage. Here too, of course, it is desirable to avoid contact with oxygen, and this can be achieved by using inert gases. When the vintner bottles the wine later on by drawing it from stainless steel wine tanks, it is often done in several stages. This leaves a number of half-full tanks, quite often over a longer period of time. Inside these tanks, a layer of the relatively heavy noble gas argon offers the most efficient protection against flavour-destroying oxidation. It is generally used in a nitrogen-argon mixture and can also preserve a wine’s freshness and flavours in bottles that have been opened.

Many plastics can only be recycled in powder form before once again being put to their original use. Garden hoses are currently being ground at the Messer Group’s cold grinding centre in Willich near Krefeld (Germany). As a result, new garden hoses can be made from the pure plastic powder that is produced.

The cold grinding process involves cooling and embrittling substances with cryogenic liquid nitrogen or carbon dioxide. And the grinding process is cooled, in addition to the product. This prevents an increase in temperature from the conversion of electrical energy of the grinder motors. Particle sizes significantly below 500 micrometres can be achieved by means of cryogenic grinding, which would scarcely be feasible with conventional warm grinding.

From the feed hopper, the material to be ground is moved via the metering screw to the precooler, where it is cooled by a liquid nitrogen spray before finally being moved to the grinder together with the nitrogen. As a result, the grinding process in the grinder is cooled at the same time. The nitrogen also performs another function: the low temperatures cause the various components to separate – in the case of garden hoses this is the soft PVC and the reinforcing mesh of polyester fibres. The embrittling effect causes the soft PVC to be broken down into very small pieces, while the polyester fibres are not reduced in size due to their high tensile strength and dimensional stability.

To achieve preliminary reduction of the garden hoses, the hose components are granulated without cooling. This produces a soft PVC granulate with a grain size of approximately one to five millimetres. At this stage, the first polyester fibres are separated from the PVC. A cryogenic pin mill is used to produce very finely ground PVC powder. The size of the polyester fibres remains largely unaffected by this. The fibres are separated from the PVC powder by a final screening process. They join together on the screen deck to form balls of fibres while the PVC powder drops through the screen deck, which has a mesh size of 500 micrometres.

The resulting high-quality powder can be reused as a material – for example to make new garden hoses.

The principle of mixer cooling
In order to be able to maintain or set a particular product temperature during a mixing or shredding process, foodstuffs must be cooled continuously. This may be required for technical reasons related to processing or for reasons associated with food law. Depending on the specific case, the ability to set a particular product temperature for subsequent process units, to keep within defined temperature limits or to compensate for heat generated by mixing is indispensable. In meat processing, the heat generated by mixing is compensated so as to make the mixing process independent of any rise in temperature.

With conventional cooling techniques, the product is cooled either indirectly by a brine cooling in a double-walled mixing trough or by direct introduction of a coolant such as cold water or crushed ice. The addition of crushed ice can only be automated with a disproportional high amount of effort and is therefore generally performed manually.

Gas cooling
In contrast cooling with gases can be automated easily. Compared to direct mixer cooling with water or crushed ice, gas cooling functions residue-free. It is considerably faster and, at the same time, permits greater temporal flexibility in process control as well as arbitrary temperature ranges. During the production of reformed meat, for example, it is necessary to keep the product at about minus three degrees Celsius in order to prevent it from crumbling after reforming. Practically this is only possible with gas cooling.

The constructional details of a gas cooling system using a Messer Variomix process are substantially dependent on the geometry of the machine, the type of gas input and the type of gas itself. The aim is to ensure that the liquid gas is distributed uniformly inside the mixer. A distinction is drawn, on the one hand, between top or bottom cooling and, on the other hand, between cooling with nitrogen or carbon dioxide. Moreover, the cooling system must not hinder access to the machine and must come up to the product-specific requirements for hygiene.

Advantages of gas cooling
As mentioned above, there are a number of reasons for choosing a method based on cryogenic gases for cooling mixers in the food industry. The most important of these are the preservation of quality, the reduction of resources and the increase in productivity due to process automation or to better utilisation of machine capacity. The low temperature of the gases and their direct introduction into the mixer ensure that cooling occurs as rapidly as possible, thus shortening the process. The amount and time of gas input can be accurately metered, which makes a very precise temperature control possible. Direct contact with the product also allows optimal energy utilisation of the coolant.

Frequently there is no alternative: Gas cooling is, for example, the only well-working process for the production of products such as reformed meat. In many cases, the process-reliable cooling system is mandatory by law and can only be accomplished reliably with gases. The coolant supply system is remarkably simple to install and can also be retrofitted to existing facilities without any problems.

With this combination of advantages, mixer cooling with cryogenic gases has proven to be the superior solution in most processes. The Clapet nozzles and Variomix processes developed by Messer are optimised for efficient cooling and the largest possible level of automation. They build on our comprehensive know-how in this area and give the user access to simple and (quality) assured utilisation of gas technology with the highest degree of cost effectiveness.

Nitrogen or carbon dioxide?
With regard to the heat balance for refrigeration, there are almost no differences between nitrogen and carbon dioxide. Common to both gases is that they are stored in liquid form in a pressure vessel. Because the coolant is in direct contact with the product, the different properties of the two gases must be considered in its selection.

Carbon dioxide (CO₂) has a bacteriostatic effect, and so impedes the growth and reproduction of germs. It dissolves in liquids and, as it does so, turns into carbonic acid, which lowers the pH value. When it is introduced into the mixing trough, expansion in the nozzle turns it into dry ice snow with a temperature of about minus 78 degrees Celsius. During the process the snow transforms into gas (sublimation) and the cooling energy is transferred to the product. Dry ice particles, however, can generate bubbles in reformed meat if particles are still present in the product when it is reformed. This can be prevented by allowing the product to rest after mixing until the sublimed gas has all evaporated out of it. As an alternative to CO₂, nitrogen can be used.

Nitrogen barely dissolves in water and, in addition, is pH-neutral. Its temperature on injection is about minus 196 degrees Celsius. Because of the enormous temperature gradient, liquid nitrogen evaporates very quickly and yields its coldness to the product in a very short time. Both gases have a cold content of about 320 kilojoules per kilogram.

Top or bottom cooling?
The gas cooling system is frequently integrated into the top cover of the construction. The introduction of coolant from above on to the product or directly between the mixer shafts is regarded as a good and simple engineering solution. Nevertheless, top cover installation does have disadvantages related to its design. Since the cover must be moveable, the gas flows through an also moveable metal hose. This hose is, however, severely stressed by the movement; it becomes worn and so must often be replaced. In addition, unwanted condensation can form on the injection equipment and fall from there into the mixer, which is undesirable, already on hygiene reasons. Furthermore, the gas consumption is relatively high: Firstly, this technique allows only the evaporative cooling of nitrogen or the sublimation cooling of carbon dioxide to be utilised. Secondly, the gas can only be extracted from above and hence in the vicinity of the injection nozzles. Some of the introduced gas, together with its cooling effect, is therefore lost before it can reach the contents of the mixer.

For this reason, it is usually more efficient to inject the gas into the product through nozzles in the trough bottom. This automatically gives a big distance to the extraction system. The gas moves in the “correct” direction, from bottom to top, and is able to transfer all of its coldness to the product before it is extracted.

Method of introduction
All various techniques must come up to hygiene standards and be in accordance with the high demands of an industrial food production. If nitrogen is used for cover or top cooling, the introduction system typically consists of a spray bar carrying individual nozzles, for example, in form of a rake. Snow horns are used for top cooling with carbon dioxide. They are better suited for this kind of coolant than nozzles. When it expands inside a nozzle, carbon dioxide would form tiny crystals of dry ice which, after a very short time, turn into gaseous form (sublime); this would then be deducted by the exhaust fan. The usable cooling energy would then be much smaller.

Conventional nozzles for introducing gas through the bottom of the trough are open and are installed with a down-grade so that any product residues can flow back into the mixer. In contrast, the Clapet nozzles made by Messer feature an integrated, spring-loaded non-return valve. They are water-tight and prevent the ingress of product residues, even when the product is a liquid. The Clapet nozzles are self-actuating and are opened by the drop in gas pressure across them; they need no additional input of energy or heating. This means that the setback piston opens and closes independently of the pressure of the coolant. Ideally, a single open/close valve in the common feed to the Clapet nozzles should therefore be sufficient.

Installation of Clapet nozzles
The installation of Clapet nozzles can be carried out quite easily. Any mixing trough can be retrofitted with them. However correct positioning of the Clapet nozzles plays an important role. The following factors should be taken into account when doing so: the principle of operation of the mixer, the workflow direction of the shafts as well as the path of the product through the mixing trough. Spraying coolant directly on to trough walls or product discharge flaps must be avoided, as well as an entry point directly below the extraction system. The positioning of the nozzles should, of course, also be suitable for production – what looks good on paper may be difficult to implement in practice.

The bottom plate should be reinforced in the areas where threaded holes are drilled for seating the nozzles. The nozzles must be mounted flush with the trough walls of the mixer in order to avoid collisions with the mixer paddles and to prevent any build-up of product. It is also important to allow for a sufficient number and suitable size of nozzles when planning the system – many small nozzles are better then a few big nozzles. A bushing with a suitable pipe thread welded on to the bottom plate may also be used in place of a reinforcement flange.

If liquid carbon dioxide is employed, each nozzle is actuated by a separate solenoid valve. The solenoid valve must be installed as close as possible to the point of injection in order to avoid blockages arising from dry ice particles. The easiest way to do this is to screw the injection nozzle directly onto the solenoid valve.

Cold surfaces within the reach of employees are to be avoided on reasons of occupational safety. Some mixer manufacturers clad their machines so that the components of the gas cooling system are hidden behind a cover plate. With others, the supply to the injection nozzles requires several distributor pipes.

Process management
The process management must be adjusted to the gas that is used, the introduction method and any specific requirements that are to come up to. When cooling with carbon dioxide and with consistent product parameters (quantity, composition, inlet temperature), introduction of the coolant can be controlled on a timed basis once the mixing process is underway. Temperature measurement is then not necessary. The mixing process must, however, not come to a standstill due to the danger that the surface of the product may become frozen and the product may not remain isothermal. If the product parameters are variable, or if nitrogen is used for cooling, temperature controlled input of coolant is required.

Enjoyable food for busy lives
There is much talk about slow food in the media. The deliberate “slowing down” of food is being propagated and no doubt practised by many – in the evenings, at weekends and on holiday. However, during the week, most of us prefer a slightly faster pace that meets the requirements of our busy everyday lives. At least that is what the constantly rising sales figures for fast-food restaurants tell us, as does the constantly growing retail space dedicated to the sale of convenience food in grocery stores. Such convenience products live up to their name and give consumers what they want: they are convenient and quick to consume.

However, the distinction between fast and fine has long since ceased to apply. Many convenience foods are produced to high standards of quality and freshness. Of course, the cold chain must also satisfy these standards in order to ensure that the high-quality products reach the customer at peak quality. This is basically not a problem – chilled and frozen food has been transported from producer to market in refrigerated trucks or cool boxes for decades.

Limits of conventional cooling
Conventional cool boxes are kept cool by precooled elements and can also be transported in non-refrigerated vehicles. But they have to be precooled and are not as flexible to use.

These disadvantages do not apply to the Siber system, which Messer developed in collaboration with Olivo, a leading manufacturer of refrigerated containers. The Siber containers on wheels are cooled by a dry ice charge with a temperature of minus 78 degrees Celsius. The low temperature is generated when liquid carbon dioxide under high pressure is filled into the refrigerated container’s reservoir. Under normal pressure, the liquid gas expands and turns into dry ice and gas. The dry ice has a very large refrigeration capacity.

Depending on the specifications, the Siber containers contain one dry ice compartment for fresh produce and one for frozen products. This allows refrigerated and frozen food logistics to be combined flexibly. The necessary refrigeration capacity is always guaranteed for a transport duration of at least 24 hours.

Precise logging
The CO₂ is dosed precisely for each container according to requirements. Thus, for example, the dry ice injection station can be fed with data from the ERP system. The quantity of CO₂ to be injected into the reservoirs is calculated on the basis of a number of factors: the refrigeration temperature (zero to plus two degrees Celsius for fresh products, minus 25 degrees Celsius for frozen food), the ambient temperature, the transport duration including loading time and the container model are taken into account in each case. This precise dosing makes the system highly energy-efficient. The gaseous carbon dioxide that is also produced during expansion is immediately extracted in its entirety and removed from the ambient air. This means that the injection unit can also be operated safely in the enclosed workspace of a cold store.

The Siber containers, which have a capacity ranging from 200 to 1,300 litres, can be transported in a normal truck alongside non-refrigerated goods. This reduces the number of delivery trips. No cold room is required for temporary storage at the delivery location. The roll containers can simply be wheeled directly to the shop’s refrigerated display units and unloaded straight onto the shelves. This not only maintains the cold chain, but also provides guaranteed proof of an even temperature throughout. The Siber containers can be fitted with commonly used data loggers that log all the relevant events from carbon dioxide injection through to door release. All the food-related legal regulations are thus satisfied for even the most sensitive products, as are the high demands of the consumers of convenience food.

Carbon dioxide (CO₂) has been used in the production of mineral water and beer since 1879, the year in which CO₂ started to be industrially produced. In the meantime, the list of beverages that have CO₂ added to them – in other words, which are carbonated – has grown significantly. Other gases, such as nitrogen (N₂) and argon (Ar), have also become indispensable in beverage production and filling. Besides carbonation, gases are primarily used for inertisation – which means in this case the displacement of oxygen – and for pressure stabilisation. In modern winemaking, they are used for stabilisation, as protection against oxidation and for cooling the mash.

What gases can do
Carbon dioxide can do more than just making beverages sparkle. The gas is colourless and odourless and readily dissolves in water. In high concentrations, it has a bacteriostatic effect and therefore extends the shelf life of beverages. Rising CO₂ bubbles displace the air above the surface of the beverage and thus reduce oxidation. When used as dry ice with a temperature of minus 78 degrees Celsius, CO₂ can provide over 570 kilojoules of cooling energy per kilogram.

Nitrogen and argon have a very low solubility in water, they are neutral and hardly react or don’t react at all with other substances. Furthermore, they are colourless, odourless, tasteless and non-toxic. They can displace the oxygen from a container and, as inert gases, prevent oxidation of the beverage. Nitrogen and argon are, like carbon dioxide, naturally present in air and are approved as food gases. Precisely dosed oxygen is used for controlled oxidation in winemaking.

Carbonation
Carbonation is the term used to describe the process of dissolving carbon dioxide in liquids such as beer (approximately five grams per litre), soft drinks (five to nine grams per litre) and sparkling wine (approximately 2.5 grams per litre). The degree of carbonation, i.e. the quantity of dissolved CO₂, depends on the pressure, the temperature, the air or oxygen content before the process, the surface area and the time period. The liquid should be degassed prior to carbonation. The temperature should be as low as possible during this process so that it can take place at a low pressure. Moreover, it is possible to save time if the area of contact between gas and liquid is as large as possible.

As all beverages consist largely of water, solubility in water is hereafter used as a reference point. It ranges from four grams per litre for beer or mineral water up to fourteen grams per litre for sparkling wine or champagne.

The sparkling effect, which is often highly appreciated, is created precisely because carbon dioxide readily dissolves in water. Alcohol or sweeteners can influence the saturation pressure of CO₂. Solubility also depends on pressure and temperature. The equilibrium pressure for seven grams of CO₂ in a litre of water is 2.5 bar at a temperature of five degrees Celsius, for example.

Technical solutions
In the simplest case, the product container is pressurised with CO₂. Depending on the pressure and temperature, the CO₂ dissolves in the product until it reaches the saturation point. This principle dates from the time when industrial production of carbonated beverages began and, for technical processing reasons, it is mainly used for beverages with a high CO₂ content. Systems with static mixers or nozzle systems, make it possible to dissolve the CO₂ in the product in-line. This happens largely irrespective of pressure and temperature. In many cases, it is possible to use the cooling energy provided by the CO₂ tank installation’s latent heat of vaporisation to save energy when cooling the product prior to carbonation.

Sparging
Sparging involves the introduction of gas into the liquid with the aid of a porous metal body, a frit made from sintered metal. This produces fine gas bubbles, increasing the surface area between gas and liquid. In carbonation systems, fine CO₂ bubbles can be introduced with the aid of a sparger in order to improve the dissolving process by increasing the surface area.

Inerting
Inerting involves transforming a reactive state into a non-reactive or inert state by adding inert substances. In beverage processing, the aim is to remove atmospheric oxygen from a container or a liquid using an inert gas in order to protect the beverage against oxidation. Otherwise the oxygen could adversely affect aroma, taste and colour as well as the composition of the ingredients. Nitrogen, carbon dioxide and argon are suitable for using them as inert gases.

One simple method is to purge empty tanks with an inert gas such as nitrogen or carbon dioxide until the desired degree of dilution of atmospheric oxygen is reached. The consumption of inert gas is usually 1.3 to three times the volume of the tank, depending on the degree of inerting required. Slim containers are easier to inert than those with a squat shape. When the diameter of the tank is large in relation to the height, some of the air flows back or circulates, making the inerting process more difficult.

In the case of partially filled containers, the space above the product – the headspace – is inerted. To achieve this, the inert gas has to be introduced through the upper tank opening in such a way that the displaced air can simultaneously escape from the headspace.

In this case, gas consumption is much higher than with tank inerting. At an atmospheric pressure of one bar, for example, the following applies as far as the consumption of nitrogen is concerned: to achieve two per cent residual oxygen, approximately three cubic metres of N₂ is required per cubic metre of headspace volume, while for one per cent residual oxygen, the requirement is five cubic metres of N₂ per cubic metre of headspace.

Blanketing
Here the objective is to maintain stationary covering of the product with inert gas. This involves striving for a residual oxygen content of zero per cent. When the product filling level changes, the gas needs to be topped up accordingly. In the case of non-pressurised storage, consumption is approximately 1.1 cubic metres of N₂ per cubic metre of product withdrawal. When the product is topped up, the displaced gas has to be able to escape in order to prevent overpressure.

In the case of pressurised storage with a tank pressure of 300 millibars, for example, the consumption of inert gas is 1.3 cubic metres per cubic metre of product removal. Here, too, the gas has to be able to escape in equal proportion via suitable venting valves in order to keep the pressure constant when product is added.

Stripping
Stripping involves fine bubbles of gas being introduced into a liquid, similar to sparging, but the aim here is to displace another gas. In practice, this method is used to remove undesirable oxygen from water, fruit juice or wine with the aid of nitrogen.

Filling
Many different systems are used for filling beverage containers. They are constantly being improved by the manufacturers in order to minimise the undesirable introduction of atmospheric oxygen. Two of the most widely used process principles are overpressure filling and pre-evacuation with gas reintroduced subsequently.

With overpressure filling, beverage bottles are pressurised to the product pressure with an inert gas. Filling along the inner wall of the bottle reduces the surface contraction and limits oxygen absorption to just 0.2 to 0.3 milligrams per bottle. In most plants, there is no provision for recovering the pressurisation gas, resulting in less efficient gas use. Gas consumption is two to three times the bottle volume and the priming process requires time.

A more efficient method is to first evacuate the bottles, then re-gas them with nitrogen or carbon dioxide and fill them after that. In this case, gas consumption is no greater than the bottle volume. The residual oxygen content is only about 0.1 to 0.2 milligrams per bottle.

When filling containers with non-carbonated beverages, a simple sparging device can be used to ensure that the headspace in the bottle is oxygen-free.

A frit is used to feed gaseous nitrogen into the product stream being filled. As nitrogen has a low solubility in water, fine N₂ gas bubbles rise to the top of the bottle, displacing the atmospheric oxygen before capping. The result is an oxygen-free filling of the beverage container. However, this method cannot be used for carbonated beverages as the nitrogen would also force the carbon dioxide out of the liquid.

Pressure stabilisation for beverage cans and PET bottles
Beverage cans and thin-walled PET bottles containing non-carbonated beverages are not stackable without pressure stabilisation. This can be changed by adding a few drops of liquid nitrogen onto the surface of the beverage prior to sealing. Evaporation of the nitrogen drops causes the pressure inside the sealed container to rise. This gives the containers greater stability, allowing them to be stacked. The nitrogen in the headspace protects the product against oxidation and extends its shelf life.

Wine
In winemaking, gases can be used in a variety of ways to improve the quality of the end product. Oxygen can also play a role here.

Cooling
Already when receiving the grapes, cooling with CO₂ dry ice protects the fruit against premature fermentation. The same applies to the mash when it is kept at a low temperature by adding dry ice pellets. This leads to the so-called cold maceration, which slows down fermentation and facilitates extraction of the flavouring substances from the grape skin. As a welcome side effect, rising CO₂ keeps atmospheric oxygen away and protects the mash against oxidation. Dry ice has a strong cooling effect and does not leave any meltwater. It ensures controlled beginning of fermentation and until then also provides the mash with microbiological protection.

Inerting of wine tanks
Inerting of wine tanks prevents the damaging effect of oxygen. For white wine, CO₂ is usually used as dry ice snow or in the form of pellets. For red wine, nitrogen or a nitrogen-argon mixture is better suited because potential excess carbonation is in this case undesirable. If the CO₂ content in the wine is too high, sparging with nitrogen can be used to reduce it to the required level. When putting the wine into, or taking it out of, storage, sparging can be integrated into the transfer process.

Micro-oxidation
Targeted oxidation of tannins with pure oxygen allows to achieve a nicely balanced wine even after shorter storage periods. This involves very small quantities of gas being added over a long period of time. Excessive oxidation, which would destroy the flavouring substances, must, of course, be avoided. Typical quantities used for micro-oxidation range between 0.5 and twelve milligrams per litre of wine and per month.

Without the technology of welding and cutting many constructions and consumer items would simply not exist. Cars wouldn’t drive, modern ocean liners wouldn’t sail the seas and airplanes couldn’t take to the skies. To a large extent, all these means of transportation consist of metal parts which have to be assembled using welding technology. The different energy sources applied determine the cost-efficiency and quality of the welding performance; beginning with the open fire some 5000 years ago, the oxyacetylene flame of a century ago and the electric arc through to the modern-day laser and electron beam. Other technologies related to the welding process include cutting, coating, modifying the inherent properties of matter, forming, and with special applications, primary forming. When this variety of processes is combined with different groups of materials, it is easy to explain Messer’s extensive product portfolio in this sector.

“The multifaceted selection of gases ranges from acetylene, oxygen and carbon dioxide, which originally were used exclusively up to nitrogen, argon and helium through to a variety of mixed gases,” explains Mr. Bernd Hildebrandt, Messer’s Head of Technology Management Welding & Cutting. At the same time, the consultancy package extends far beyond the field of gases. “Our customers expect all-round process knowhow, together with advice on quality and costefficiency, and on operational safety, which we also provide,” adds Hildebrandt. Messer also offers a selection of different forms of delivery. The most common “packaging” is the steel cylinder, which is available in the standard volumes of 10, 20, 30 and 50 litres, and consequently offers a high degree of flexibility. Filling pressures of up to 300 bars also provide further scope in capacity. For larger quantities, the cylinders can be combined to form clusters or arrays. Vacuum-insulated tanks are also available for storage in a liquid state.

As an all-round provider, Messer supports the entire range of processes related to welding and cutting technology in which technical gases are, or can be applied in the future. These processes can roughly be divided into joining (e.g. shielding gas welding), separating (e.g. plasma cutting), coating (e.g. thermal spraying) and other processes (heating and straightening).

Fuel gases from A to X
The technology of autogenous welding requires fuel gases and oxygen. Depending on the individual task, however, a number of parameter settings must be selected. For example, flame straightening demands a rapid, pinpoint flame with acetylene and oxygen, in contrast to soldering which uses a slow burning gas, such as propane in combination with air. Accordingly, the spectrum of Messer’s fuel gases range from A for acetylene to X for xenon.

In the field of arc welding technology, shielding gas welding, including its variants WIG (Wolfram Inert Gas), Plasma, MIG (Metal Inert Gas) and MAG (Metal Active Gas) assumes a leading role, with the electric arc providing the heat input. The shielding gas not only protects the highly reactive molten metal from the ambient air, but also systematically impacts upon the arc formation, the chemical reaction with the weld pool and the penetration profile. Depending on the type of material to be processed there are a large number of carefully tailored products available.

Well-conceived product names
“In contrast to many gas suppliers, whose product names furnish scant information about the composition and possible applications of their welding shielding gases, Messer has the right solution and an informative product name for every task,” emphasises Michael Wolters, Project Engineer for Technology Management Welding & Cutting. In detail, the spectrum of shielding gases comprises “Ferroline” for non- and low-alloy steels, “Inoxline” for high-alloy steels, “Aluline” for aluminium and non-ferrous metals, together with “forming gas”, which offers root protection for high-alloy and some low-alloy steels. Laser-cutting and welding are also finding increasing application, and set particularly high standards in terms of the quality and purity of gases. Developed to meet these exacting requirements, the Lasline product range contains gases and gas mixtures for cutting, and welding shielding gases for laser welding and soldering, in addition to operating gases for the CO₂ lasers.

As a highly reputable provider, we must continue to operate at the cutting edge of technology and identify new trends promptly in order to remain competitive on the market place over the long term. For this reason Messer nurtures contacts with market partners, including our sister company, Messer Cutting Systems. To keep abreast of the latest developments, we cooperate on a project-related basis with external research institutes. “Whenever new trends emerge which carry implications for the application of our gases, we endeavour to keep one step ahead of the competition,” states Wolters.

Technical training institutes and networks
In order to maintain close contact to customers and to the relevant specialist institutes, Messer runs a number of technical facilities at strategically favourable locations. “Points of support” are located in Budapest (Hungary), Krefeld (Germany), Dällikon (Switzerland) as well as Shanghai (China).

Beyond developing a technical infrastructure, Messer has also fallen into line with modern IT trends and built up an electronic network with colleagues from all our subsidiaries. In addition, Messer stages an annual network conference, which also offers training seminars staged by one of our market partners. And last but not least, Messer collaborates closely with other companies from our sector. “This not only enhances transparency in the market place, but also enables us to participate in discussions on new processes,” explains Hildebrandt. In this way, Messer is able to keep its range of products at the cutting edge of developments.

Dry ice blasting has already replaced other cleaning processes in many industrial sectors. For example, it is used for cleaning printing machines, motors, engines, facades and molds in plastic and rubber manufacturing. “Carbon dioxide in its solid form is suitable for removing lacquers, paints, oils, carbon black, plastic residues and many other stubborn residues,” says Thomas Böckler, Technology Manager Industry at Messer and contact person on matters relating to dry ice blasting.Blasting with dry ice can be compared to sand blasting, only it is much gentler. Grains of dry ice are small, solid and cold. When these pellets hit the contaminated surface with pressure, the dirt contracts under the cold conditions, breaks loose from the surface and is then simply blown away by the air pressure and the pellets that follow. Rod-shaped pellets with a diameter of approximately three millimeters and a length of one centimeter are used for this.

EFFECTIVELY DISSOLVED INTO THIN AIR
The principle of this blasting process is to embrittle the dirt by transferring the cold energy stored in the dry ice pellets, and then to break it up and remove it under pressure. In addition to the quantity of pellets, crucial factors for the cleaning process include the material properties of the object to be cleaned, such as the starting temperature, thermal conductivity as well as the type and thickness of the dirt. Optimal results can be achieved by adjusting the quantity of pellets and the acceleration pressure to suit the cleaning conditions. The advantage of dry ice as a blast medium is that the cold pellets, which have a temperature of minus 79 degrees, are converted to gaseous carbon dioxide during application and effectively dissolve into thin air. The result is no sand and no contaminated water – all you have to do after blasting is sweep up the dirt.

PERFECT IN MANY AREAS
The process cleans monitors, leaving them residuefree, and removes oils and fats from gauges without damaging the sensitive devices. Residues caused by welding robots are easy to get rid of as only a little kinetic energy is needed to remove them. For the cleaning of circuit boards, printing machines or casting molds, a grinder is used, which grinds the pellets into sugar-sized grains. The crystalline particles accelerate the subcooling of the base material and increase the removal rate without abrading the surface.Dry ice blasting is an alternative for cases where toxic substances have to be removed, since the contaminants are not mixed with other substances, making disposal much easier. “If the surface to be cleaned must not be damaged, sensitive parts cannot be removed or environmental regulations must be complied with, then dry ice blasting is the method of choice,” explains Thomas Böckler. “Applications that call for abrasive blasting, or where the base material and the layer to be removed have already started to form a chemical bond, achieve better results with a sand or glass blaster,” the dry ice expert adds.

FROM CO₂ TO DRY ICE
The different physical states of substances – solid, liquid and gaseous – are particularly well-known with regard to water: ice, liquid water and water vapor. Carbon dioxide, too, occurs in these states. Gaseous carbon dioxide is either extracted from ground sources or recovered as a waste product from a range of industrial processes. This means that the CO₂ that is used for dry ice blasting does not result in an additional increase in CO₂ emissions into the atmosphere. To turn the CO₂ into a solid, i.e. to change its physical state, it is first liquefied under pressure. Dry ice snow is then produced by sudden expansion. The snow is either pressed into blocks or pellets, the latter by using perforated plates.

SUCCESS DEPENDS ON PRESSURE TOO
The effectiveness of dry ice blasting depends on the amount of cold energy and the kinetic energy. In order to remove heavy contamination, an optimum nozzle as well as an air pressure of more than ten bar is usually necessary. The nozzle and jet pipe of the gun are adapted to the compressed air conditions. “The Messer experts check all the parameters on-site and fine-tune them in order to achieve an optimum and efficient cleaning result,” says Thomas Böckler, describing the support Messer provides to customers.

The use and combination of gases depends on the character of the wine and the expectations of the consumers. Carbon dioxide is particularly suitable for the treatment of rosé and white wines. For red wines, on the other hand, nitrogen is used to a greater extent. The gases that are used in the treatment of wine can be divided into two groups. The first group includes inert gases such as nitrogen and argon. They do not react with the individual components of the wine. The second includes gases such as oxygen and carbon dioxide, which influence the character of the wine.

Nitrogen and carbon dioxide are used in winery management. Both gases are used separately as well as in combination with each other. Carbon dioxide, however, dissolves much more readily in liquids than nitrogen.

Wine growers can use gases in the various stages of wine production – from the grape harvest through to improving the shelf life. Here is an overview:

GRAPE HARVEST
If temperatures during the grape harvest are over 25 degrees Celsius, there is the danger that the grapes will start to ferment prematurely. Here, the use of carbon dioxide snow offers the ideal solution for cooling the grapes. The advantage of this method compared with normal ice cooling is that there is no water formation when carbon dioxide snow melts.

WINE PROCESSING
The removal of the atmospheric oxygen from the must provides microbiological protection against oxidation and prevents premature fermentation. This is done by either putting dry ice pellets directly into the press or adding them to the prepared must.

COLD MACERATION
The technology of cold maceration facilitates an enhanced extraction of fruit aromas. With this process, the wine growers prolong fermentation through low must temperatures. In order to prevent oxidation, they treat the ripe, healthy grapes with carbon dioxide prior to processing.

MUST PURIFICATION
Flotation technology is one of the most modern methods of must purification. During this process, the must is continuously filtered before being mixed with nitrogen or carbon dioxide in a pressureresistant container. Finally, the must is exposed to atmospheric pressure. This pressure causes the clear liquid to be separated from the suspended solids.

STORAGE
The inerting of tanks – the removal of atmospheric oxygen from the liquid – provides protection against oxidation. Carbon dioxide in the form of gas or snow is used for white wine. Nitrogen or a mixture of nitrogen and argon is used in red wine tanks.

FRESHENING
Wine growers use carbon dioxide to freshen the wine. This creates a fresher taste and fruitier aroma.

HOMOGENIZATION
Carbon dioxide is used for the effective mixing of different vintages or types of wine. This prevents oxidation of the different wines.

BOTTLING AND GASTRONOMY
A special gas mixture also offers oxidation protection after the bottle is opened.

VINOCOR, THE INVISIBLE CORK – PROTECTIVE GASES IN MODERN WINERY TECHNOLOGY IN AUSTRIA
In Austria, too, quality-oriented wineries are increasingly using protective gases in wine production.In particular, high-purity nitrogen and Vinocor, a mixture of high-purity nitrogen and carbon dioxide, are used.The Federal Office of Viticulture in Austria has tested Vinocor and confirmed that the wine retains its very good quality for two to three weeks if Vinocor is added within a few hours of opening.

This procedure avoids the changes in taste and color caused by oxidation and preserves the existing quality of the wine.

The Vinocor-Gastro appliance is specially designed to meet the needs of the professional user. It is extremely robust and can either be mounted on a wall or a stand. A hose line connects it to the gas cylinder containing the gas mixture. In almost every case the gas cylinder is situated directly under the bar. Dispensing of the gas is electronically controlled.

Anyone who has ever had surgery is familiar with the instruction to “count slowly to ten” when the breathing mask is put on. But hardly anyone manages to count to ten; most people stop at five at the latest. The gas takes effect as desired, inducing anesthesia.

In modern medicine, the use of gases in this way is part of everyday life. These volatile substances help to prevent pain and often save and sustain lives. However, they are not only used as breathing or anesthetic gases: “Gases are also used, for example, as aids in minimally invasive surgery or for direct oxygen enrichment of the blood in heart surgery,” explains Matthias Thiele, Senior Vice President at Messer. “Cryosurgery and diagnostics also require the special properties of certain gases.” In addition, laboratories also use gases and gas mixtures. Overall, there is an extensive range of special gases and gas mixtures as well as breathing air for use in medicine and healthcare. Two aspects play a major role here: (Two aspects are of particular importance here) firstly, offering an individual solution for every need that achieves optimal results and secondly, ensuring the impeccable quality of the gases so that they meet the high standards required in healthcare.

Medical oxygen is indispensable
Breathing is one of the fundamental functions of life. After just two minutes without oxygen, irreparable damage to organs can occur. That is why artificial ventilation in ambulances, operating rooms, and hospital wards is one of the life-saving and life-sustaining therapies. Depending on requirements, air, pure oxygen, or oxygen-containing gas mixtures are used as breathing gases.

In addition, the anesthesia team uses oxygen as an indispensable component of anesthetic gas mixtures. For example, it serves as a vital carrier gas to which nitrous oxide (nitrogen oxide, N₂O) or other inhalation anesthetics can be added. For therapeutic purposes, doctors use the gas for all disorders of natural oxygen uptake in the lungs.

“In its liquid state, which oxygen attains at minus 183 degrees Celsius, it requires only 1/854th of its gaseous volume under atmospheric pressure,” explains Matthias Thiele. Unsurprisingly larger quantities are preferably stored in this state. Messer offers a central on-site oxygen supply to large-volume customers such as hospitals and university clinics. The liquid oxygen stored in vacuum-insulated standing tanks is vaporized as needed and fed through a pipe system to the extraction points. There, it is made available for extraction by using high-precision connection devices.

Practical solutions for clinics, practices, and home care
Messer not only acts as a supplier of medical gases, but also offers comprehensive solutions for their use in clinics, practices, and for the care of patients at home. These include, for example, tailor-made concepts for hospitals that include medical gases, the associated consumables and the equipment – such as hospital-wide central gas supply systems. Messer also offers training courses for specialist staff.

 Physicians benefit from practical solutions for their specific requirements: compact cylinder systems, reliable supply chains, and comprehensive advice. Messer is active worldwide in the home care sector and, through its own companies, ensures a safe and continuous supply of medical oxygen and other gases to patients. These are delivered directly to the patient's home, guaranteeing compliance with the highest quality and safety standards. In Latin America, Messer owns and operates several specialized clinics where its own hospital staff provide high-quality care using selected therapies and state-of-the-art medical technology.

Therapy concepts for NO applications
Nitric oxide plays a particularly important role in many different types of therapy. Messer is one of the few suppliers worldwide that can provide not only the gas (NO) but also the entire application solution from a single source—from the production and punctual delivery of the gas to the equipment required for its use and the training of users. Nitric oxide is registered as a drug in more than 20 countries. Messer develops and manufactures NO devices at one of its subsidiaries, which are always state-of-the-art thanks to continuous innovation and cutting-edge technologies.

Service and maintenance are carried out by competent employees or experienced cooperation partners. Regular training courses are available for hospital staff, both online and on-site. There are also specific training courses for doctors covering new applications and areas of use. In addition, Messer is actively involved in research into nitric oxide in order to further expand its therapeutic potential, for example, in new clinical pictures or in specialized medical fields.

Innovation in nitrous oxide-oxygen mixtures

With a newly developed mixture of nitrous oxide and oxygen, Messer offers a safe and efficient solution for sedation and pain relief. This product is also registered as a medicinal product in over 20 countries; the consumables and equipment required for its use are also available for simple and safe application. Since nitrous oxide has a strong impact on the climate, Messer offers specially developed devices for nitrous oxide-oxygen therapy. These completely avoid environmentally harmful emissions, as they do not simply release the exhaled nitrous oxide, but first break it down into its harmless components, nitrogen and oxygen.

The climate-neutral use of nitrous oxide is also an example of close cooperation with the medical technology industry. Messer is not only a provider of complete solutions for existing therapies, but also acts as a reliable partner in the innovation process. This includes constant monitoring of the market and current research in order to be able to offer additional therapy options with new and further optimized products. Together with equipment manufacturers, Messer develops tailor-made gases and gas mixtures for this purpose.

Just as our roads are filled with a huge variety of models, the car factories themselves abound with a vast range of application technologies for which Messer supplies the gases. Welding and cutting technology, which finds its application in the construction of chassis and car bodies, involves the extensive use of gases (see on air No. 6). But it’s not just at the production stage that gases play their part: once the driver gets behind the wheel, he and his passengers will still be very much dependent on their use – and by that, we don’t just mean ‘stepping on the gas’.

Noble gases to light up dark roads
For example, the noble gases argon and krypton when added to halogen compounds find a use in modern headlights (halogen lamps). Optimum illumination of the road is increasingly being achieved with the use of xenon. ”Xenon lamps are remarkable for their high luminance, low power consumption and extremely long service life“, explains Dr. Hermann Grabhorn, Vice President Specialty Gases.

Airbags too play their part in protecting drivers and passengers from injury. In contrast to previous practice, modern systems no longer exclusively rely on pyroelectric gas generators but are increasingly making use of hybrid or cold gas generators. The gases used to fill these maximum pressure generators are chiefly argon, nitrogen and helium.Helium is also ideal for use as a tracer gas for identifying leaks. Grabhorn describes its benefits as follows: ”The early identification of faults in production makes a significant contribution to keeping costs down.“

Using a tracer gas, it is possible to perform straightforward and low-cost tests for leaks in pipelines and heat exchangers, for example in air-conditioning systems.

Caring for the environment
Air conditioning is the key word for yet another gas that finds extensive use around the motor car: carbon dioxide. ”From a modern research point of view, this gas represents the most promising substitute for CFCs in vehicle air-conditioning,“ explains Grabhorn. When air-conditioning units are first filled on the assembly line, special CO₂ supply systems are required. Messer is able to offer individual solutions in this regard.

In recent years, stricter regulations on CO₂ emissions from private cars have led to design changes in engines and more powerful systems for dealing with exhaust fumes. When a vehicle goes in for its regular check-up exhaust air, the engineers there will use highly accurate calibrating gases and ultra-pure operating gases for determining its emissions class for tax purposes and for general quality control.

A question of hardness
The strength and hardness of a metal is crucial for its use in the manufacture of car bodies. Heat treatment plays an important role here. The inert gases required for this process can be directly produced from nitrogen and methanol in an oven.

At a temperature in excess of 750 degrees Celsius, methanol is thermally separated into two-thirds hydrogen and one-third carbon monoxide. Carbon donors such as propane or natural gas for carburisation are injected directly into the heating chamber. The endogas thus produced can be carefully regulated in its carburising effect so that, depending on the carbon content required by the material, these components can be only hardened or carburised.

Different hardening processes require different gases. For example, after heat-treatable and case-hardened steel has been quenched, there can still be unacceptable levels of residual austenite in the structure that considerably reduce the dimensional stability of the components. ”In practice, we therefore carry out cold treatments with temperatures as low as minus 120 degrees Celsius using nitrogen as the main refrigerant,“ explains Hans-Peter Schmidt, Technology Manager Metallurgy at Messer. The process known as nitration makes use of ammonia, nitrogen and carbon dioxide, which at temperatures of up to 580 degrees Celsius form a coating layer of iron nitrides and a nitrogen diffusion zone. Components treated in this way have an ultra-hard and corrosionresistant surface whilst maintaining high dimensional stability.

Flame hardening, which involves the use of gas burners operating with a mixture of oxygen and natural gas or propane, is applied to bring large gear wheels or long crankshafts up to hardening temperature; these components are subsequently quenched in water. Induction hardening is a similar process with the heat energy being channelled into the outer edge or surface of the component via electrical induction fields.

Individual solutions
Other components are manufactured from grey or spheroidal cast iron by moulding and are only later modified in their resilience and hardness by means of a series of careful processes. These thermal treatments take place in furnaces with a choice of nitrogen or argon as the inert gas, depending on the alloy in question. There are numerous other applications for gases in the automotive industry.

Take, for example, carbon dioxide which is used as a foaming agent with liquefied plastics to produce the foam components of car seats. Or dry ice, used for blast cleaning (see on air No. 2). Messer provides individual solutions for all of these applications.

Whether the gas comes in cylinders or tankers, whether it is produced on site or pumped in via a pipeline, there is always a suitable mode of supply.

Concrete is undisputedly the principal building material worldwide. According to the German Association of Cement Works (VDZ), 27 million tons of cement were processed into roughly 90 million cubic metres of concrete last year in Germany alone. This quantity is enough to build 225 cathedrals each as large as the Dom in Cologne. Concrete is capable of bearing high loads, permits flexible processing, remains stable for an eternity, and is available in many different variants.

By modifying its formulation, concrete can be tailored to meet diverse requirements posed by the construction of underground structures, roads, and buildings. Whether the requirement is to cast a storey ceiling or tunnel wall, prefabricate load-bearing elements for a market hall or produce watertight pipe sections for public sewage systems: concrete can be brought into every conceivable shape and processed, in conjunction with adequate reinforcement such as steel, to produce strong foundations, dams or bridge piers. As a prerequisite, however, no faults must occur at any stage of processing. Fresh concrete should ideally be processed at between 5 °C and 25 °C, as temperatures outside this range spoil the quality of the concrete. Based directly on the chemistry of cement, this aspect is explained by considering the relevant details. Concrete has three essential ingredients: (1) aggregate such as sand, gravel, crushed stone or chippings, (2) water and (3) cement. Cement is a mixture of limestone, clay, sand and iron ore burnt at 1450 °C and subsequently ground. In its dry state, grey cement powder is completely non-reactive. When mixed with water, however, cement forms a kind of glue which gradually hardens or “sets”, as a construction engineer would say.

THE RIGHT TEMPERATURE RANGE
Cement sets in a chemical reaction with water (hydration) accompanied by a release of heat energy (hydration energy). In this process, the cement’s ingredients form mainly stable, needle-shaped crystals which gradually grow and mesh together. The sand, gravel and reinforcement steel, i.e. all basic materials intended to increase concrete’s durability and strength, are bonded together firmly as a result.

For hydration to yield satisfactory results, it is necessary to set certain basic conditions such as a temperature of at least 5 °C during processing of fresh concrete; below this temperature, the cement loses some or all of its bonding capability. Measures to ensure that the building material hardens properly, especially in winter, include pre-heating the additives or using thermally-insulated formwork. Whereas the tempering effect of hydration is beneficial in winter, it can pose problems during the warm summer season. At high temperatures, say above 30 °C, the concrete’s additives start to lose their liquefaction capability, thus spoiling fresh concrete’s fluidity and processability. Moreover, the heat generated by hydration proves significant especially in the case of bulky components. Thermal expansion of concrete can cause strain, resulting in cracks extending deep into the concrete core. Air and moisture can pervade these cracks and attack the concrete as well as its enclosed reinforcements.

THE REQUIREMENTS DEFINE THE COOLING TECHNIQUE
To maintain fresh concrete’s temperature in summer within the optimal processing range of 5 °C to 25 °C, Messer offers efficient solutions incorporating cryogenic gases: liquid nitrogen (LN₂) or liquid carbon dioxide (LCO₂).

In numerous experiment series, the company’s specialists investigated a variety of now proven techniques for cooling concrete and its additives.

To cool small and medium quantities of concrete by a few degrees, for instance, LN₂ is introduced via lances on the truck mixer into the building material. Termed lance cooling, this rapid process can be executed directly at the construction site.

A much more efficient method, however, especially at high ambient temperatures, is to instead cool the cement (we have named this method cryoment). Two variants are available here: firstly, the cement’s temperature can be adjusted to the required level directly during storage in the local silo (we have named this method cryoment-flow). Secondly, it is possible to cool the cement just in time, i.e. immediately before processing. Advantage: no need for storing cold cement, so that cooling losses are lowered at all events.

Which of these methods is more suitable for a particular application depends significantly on the quantity of concrete requiring cooling as well as the anticipated cooling period and rate. The necessary fine adjustments are determined in meetings between Messer’s experts and the customer.

Messer has literally got to the root of a problem in Vienna. The citizens of the Austrian capital are extremely protective of their trees. But what do you do when trees – naturally – do not abide by the general rules of coexistence and, as in our case, the roots of three protected elm trees threaten to destroy a fountain? Peter Bauer and his colleagues from Messer in Austria came up with the solution: 15 lances were inserted to a depth of 17 metres around the fountain and connected to a loop. Liquid nitrogen was pumped, via this loop, into the groundwater zone until the water temperature inside the fountain had reached 1 degree Celsius. This caused the fine water roots of the elm trees, which had become firmly embedded right round the fountain, to be frozen off without harming the trees. As a result, the fountain will be safe for approximately two years.

Flight into the future
The “Nephelios” airship, which was unveiled to the public by SOL’R at the end of last year, will in future lift off with helium from Messer. The only solarpowered manned airship in the world, which was de - signed and built by a team of 50 experts from SOL’R and several French engineering colleges, is vastly superior to planes and helicopters in terms of load capacity and energy consumption. The “Nephelios” prototype holds 350 cubic metres of helium and gets all its energy from flexible photovoltaic modules mounted on the airship. This technological advance is of major significance for the future of airships and aviation as a whole.

Floating film
On a slightly smaller scale, but no less innovative, are the radio-controlled “Videodrone” blimps, which also defy gravity with helium. Logos or entire films can be projected onto the blimp’s illuminated exterior via the on-board video equipment. The spectators on the ground feel like they are looking at a screen that is floating freely in the sky. “Videodrone” has already captivated audiences at numerous events. Messer is planning to use this dynamic communication tool at a number of events in France.

Full moon for vampires
Vampires were on the loose in the Hungarian town of Miskolc at the end of last year – creeping eerily through the bright moonlight. We are talking about a film set, of course – but here too, helium from Messer was used. Most of the scenes take place at night. In order to create a mysterious atmosphere, diffused light was needed to imitate the light of a full moon. This was achieved with helium-filled balloons – containing special lights – floating above the film set and bathing it in artificial moonlight.

Pellets in top shape
Speaking of films: a visit to the cinema often goes hand in hand with popcorn and cola as well as the occasional ice cream. What about one of those fruit sorbets in the form of pellets? A Messer process – the Cryogen-Rapid pelletising process – plays a major role in their production. The fruit juice drips into a liquid nitrogen bath, forming pellets in a matter of seconds. Direct contact between the drop of liquid and the cryogenic liquid nitrogen causes the surface of the product to harden.

Frozen mounds of cream
Staying with the pleasurable things in life: have you ever wondered why the cherries on top of a frozen Black Forest gateau didn’t disappear into the mounds of soft cream during the production process? The secret lies in the freezing rates that can be achieved with cryogenic nitrogen and carbon dioxide. Sprayed directly into a freezer, nitrogen boils and carbon dioxide snow sublimates.

Thermal energy is removed from the product, causing it to cool extremely rapidly. Surface hardening during production therefore also allows beautiful decorations to be applied to soft cream.

Noble gas keeps out antartic cold
The completely opposite effect, namely that of protecting against the cold, is achieved with noble gases such as argon, krypton and mixtures thereof. Beneficiaries include the researchers at the Belgian Princess Elisabeth Station in the Antarctic. The company Van Geystelen Eurotherm used krypton from Messer for the station’s double-glazed windows. The principle works as follows: double-glazed windows in which the cavity between the panes is filled with noble gases provide considerably improved thermal insulation and therefore yield significantly reduced heating costscompared with normal air-filled double glazing. Moreover, the use of heavy noble gases such as krypton or xenon also have the advantage of improved sound insulation.

Gentle Decontamination of art treasures
Moving on to another subject within the realm of culture: wooden art treasures such as sculptures and altars are prominent features in churches, chapels and museums. Temperature fluctuations and high humidity lead to considerable changes in the wood moisture level, which almost inevitably results in damage by wood pests such as insects and fungi. In the past, many of these cultural assets were therefore treated with pesticides, which today are viewed as posing a danger to people and the environment. A specially developed cleaning process, in whose technical implementation Messer was involved, uses carbon dioxide as a solvent to deep clean the wooden objects. The process is based on high-pressure extraction and, in contrast to other established cleaning processes, leads to effective decontamination of contaminated wooden objects. This extraction process makes use of the good solvent properties of carbon dioxide in its supercritical state – this is the state of a substance above its critical point. CO₂ has a comparatively low critical temperature (31°C) and critical pressure (74 bar). This is particularly useful when dealing with tem - perature-sensitive materials such as wood. Another important advantage is the inert character of CO₂, which virtually rules out any chemical reactions with the materials during decontamination.

Testing the quality of seawater and beaches
Our last port of call is the Dutch coast, where the Oceanographic Institute (N.I.O.Z.) is using pure gases such as liquid nitrogen and special gases to investigate the impact of human and industrial activity on the quality of the seven seas and their beaches, and also to analyse sediment composition in the areas covered by the study. The N.I.O.Z. aims to gain scientific insights into our seas and oceans and make this knowledge available in order to document changes to our planet.

Growing pressures for productivity, economy and quality demand new solutions and technologies in the area of welding and cutting. One result of these constantly growing demands is laser technology. With its cutting gases Nitrocut^® and Oxycut^® and the product series MeGaLas^® ,Messer Gases for Laser material processing, Messer, the largest privately managed industrial gases specialist, provides all the gases and gas mixes required for laser material processing.

Areas of application of process and working gases
Gases used in laser material processing are classified as auxiliary materials and are required in a variety of different process steps depending on the process and the laser source used. In spite of their invisibility, the choice of gases is one of the crucial factors for the optimum success of laser technology. A distinction is made between process gases and working gases. Process gases are required for the function of the CO₂ laser resonator, whereas working gases assist the laser beam as a shielding gas for welding or as a cutting gas.

The purity of the gases
The purity of the working gases for CO₂ lasers is subject to very strict requirements. But purity is also decisive for economy and quality in working gases and gas mixes for welding and cutting. The degree of purity of gases is indicated as a percentage – a number with many places after the decimal point. In order to simplify the designation, an internationally recognised coding system exists. The codes consist of a digit, a point and a second digit. The first digit indicates the number of nines and the digit after the point represents the last digit of the whole value. The code 3.5 thus means that the gas has a minimum purity of 99.95 per cent. Further examples are shown in the table.

Process gases
Process gases are gas mixes. These are used as a ready-mixed gas or are mixed from their individual components in the laser system before use. The purity, quality and constant composition of these gas mixes play a major role – for good reasons. Even small traces of moisture or hydrocarbons can cause equipment failures. Hydrocarbons may cause damage to the sensitive and costly optical components, while moisture interferes with the excitation discharge, reducing the overall efficiency of the laser. Other faults may occur as a result of dust particles, which can scatter the laser light and disrupt the process. So it is essential for faultless laser operation that the gases used are of high purity and free of troublesome contaminants. The purity requirements mentioned apply equally for the gas supply system.

Laser cutting, the pioneer in laser material processing
Laser cutting, in comparison with other thermal cutting techniques, is known for its high precision, high cutting speeds, low heat input and low component deformation. Possible applications exist in many sectors, such as automobile and aircraft construction, metal and sheet metal working, shipbuilding, the textile industry and medical technology.

Laser cutting techniques are fundamentally classified into three process variants, flame cutting, fusion cutting and sublimation cutting. Which of these processes is employed depends on the material, the quality and economy requirements and the cutting gas used.

Flame cutting with pure oxygen is similar to oxyfuel flame cutting. The material is heated to ignition temperature and then burnt in the jet of pure oxygen. This is conditional on the suitability of the material for flame cutting. In other words, its ignition temperature must be lower than its melting point. This is the case for unalloyed and low alloy steels. But it does not apply for high alloy steels and non-ferrous metals. Here, while flame cutting with oxygen is possible, it is not recommended for reasons of quality and economy.

Materials which are unsuitable for flame cutting are cut using the fusion cutting technique. For this process, the material has to be heated to melting point and then driven out of the kerf by the cutting gas at a pressure of up to 25 bar. The cutting gas used is mostly nitrogen, but argon is also used in special cases. This applies, for example, for titanium, tantalum, zirconium and magnesium, as these materials react chemically with nitrogen. For quality purposes, unalloyed and low-alloy steels may also be cut by the fusion cutting technique using nitrogen. This produces cut surfaces free of oxidation. The cutting speed, however, is significantly slower.

Materials without a melting point, such as wood, plastics, composite materials, perspex, ceramics or paper, are cut by sublimation. Here, the material is directly converted from a solid to a gaseous state. The cutting gas keeps the particles and vapours away from the optical system.

Cutting gases
The choice of cutting gases depends on the material to be cut and the quality demands for the cut surfaces produced.

Materials suitable for flame cutting are cut with pure oxygen. Here, the purity of the oxygen has a major influence on the cutting speed (see figure). With high purity, the cutting speed can be increased, according to sheet thickness, by up to 20 per cent. This further reduces the depth of the heat-affected zone, which is anyway low in the case of laser cutting. As a result, the purity 3.5 has become established for flame cutting.

Materials unsuitable for flame cutting are mostly cut with nitrogen. Its inertising effect leads to cut surfaces free of oxide. Here, slight impurities of oxygen or moisture may cause discoloration on cut surfaces due to oxidation. For high quality requirements, the purity 5.0 has proven itself as the standard.

Materials such as titanium, tantalum and magnesium are among the oxide and nitride formers, as they react strongly with oxygen and nitrogen. For cutting these materials without reworking such as milling, grinding or pickling, argon is recommended. Here too, the greater the purity of the argon used, the cleaner the cut surfaces. In the course of further welding, any nitrides and oxides present may be transferred into the weld seam.

The different types of welding
Thanks to its special characteristics, laser welding solves welding problems like no other technique. Its main feature is the highly concentrated heat input. Laser welding offers high welding speed, a narrow heat-effect zone and low deformation of the component. Another advantage is the low heat input. There is even something special about the joints in comparison with other techniques. The laser is capable of piercing right through a component. This makes welding possible in otherwise inaccessible areas. This is particularly useful in the automobile industry, where weld points on the bodywork, for example, are often concealed. At the same time, the laser fulfils the desire for high welding speeds and low distortion. Laser welding is also suitable for medical technology and micro-electronics.

In remote welding, complex components are welded from distances of up to two metres. The main advantage of this method is the quick positioning of the laser beam. This is carried out from a central unit by means of multiaxially adjustable mirrors. Other advantages are the saving of time and the fact that no complex mechanical components are required for guidance of the beam. The shielding gas is added in this case via the mounting jig. Alternatively, a chamber may also be used.

Heat conduction welding only requires low outputs. The energy of the laser is converted into heat on the surface of the component, forming a molten pool that passes on the heat energy by convection. As in the case of arc welding, this convection can be influenced by the shielding gases and the penetration profile can be adjusted to meet the welding requirements.

Deep welding requires higher outputs, as the metal is not only melted, but is also vaporised. In this case, the laser penetrates deep into the workpiece, cutting a so-called keyhole. In this keyhole a plasma column forms, which absorbs the energy of the laser and passes it on to the material. The result is a continuous welding process. The plasma cloud escaping from the vapour channel (keyhole) must be blown away by the shielding gas, as it would otherwise absorb the laser energy without passing it on to the welding process.

The hybrid technique is a combination of more than one process. An obvious candidate for combination with laser welding is MAG welding. Here, the economy of laser welding is applied to thick plates with the high melting power of the MAG process. The shielding gas chosen must be compatible with both parts of the process. In practice, mixes of argon, helium and an active gas component such as carbon dioxide have proven effective. In addition to the combination with MAG welding, combinations with TIG and plasma welding are also possible.

Laser soldering is similar to heat conduction welding. Here, however, the energy requirement of the solder also has to be taken into account. This technique has established itself, in particular, in automobile construction. In addition to the familiar advantages such as low heat input and low distortion, the corrosion resistance of the solder and its easier mechanibility also play an important role. The security of the joints and their long service life make laser soldering a good alternative.

SHIELDING GASES - AUXILIARY MATERIALS FOR AN OPTIMAL RESULT
As before in cutting technology, the laser is now also becoming firmly established in welding and soldering. A distinction is made here between four variants, heat conduction welding, deep welding, hybrid welding and laser soldering. Welding can be carried out with or without a welding auxiliary material. The welding of different or dissimilar metals and alloys such as aluminium and steel or black and white is also possible.

A shielding gas has a number of functions. One of its main tasks is protection of the hot material from the atmosphere, for this could lead to the absorption of nitrogen or moisture or cause oxidation of the surface. The shielding gas also ensures the continuous removal of the plasma cloud above the workpiece.

Like other shielding gas processes, the laser welding process can also be specifically influenced by the use of optimised shielding gases. The basis of these gas mixes is argon. By the addition of CO₂, oxygen, helium, nitrogen or hydrogen, it is possible to influence the welding process both thermally and metallurgically. Typical gas mixes here are argon/helium, argon/oxygen and argon/hydrogen. The constituents used depend on the material to be joined.

Welding without shielding gas 
Welding without shielding gas is often encountered, especially when solid state lasers are used. It leads to the correct appearance of the weld seam, but that alone is not the crucial factor. Without shielding gas, as in other welding processes, the weld can absorb nitrogen, oxygen and moisture, leading to weld imperfections such as pores and hydrogen cracks. Particularly in the case of unalloyed and low-alloy steels, nitrogen leads to premature ageing and brittleness. In most cases, the consequences are visible after several years, when the component has been subjected to corresponding stresses.

Successful shielding gas blanketing thanks to laminar flow
When gassing weld or solder points, a laminar flow is a precondition for successful shielding gas blanketing. If the speed of the shielding gas is too high, eddies are created which entrain the atmosphere in the gas jet. This is one of the most frequent reasons for welding faults. Different shielding gas mixes can also influence the laser beam.

For shielding gas blanketing during laser welding, coaxial, lateral, peripheral and annular nozzles are available.

In the case of coaxial shielding gas feed, the whole area of the beam between the nozzle and the lens is filled with the shielding gas. Damage to the lenses can occur here as a result of the formation of a plasma column.

When shielding gases are fed from the side, an injector often forms, resulting in air also being sucked into the weld area. The welding process then takes place in a shielding gas/air mix. The consequences are pores, annealing colours and other welding faults.

If an annular nozzle is used, it is advisable to use small quantities of an additional purge gas, such as nitrogen or helium. This prevents shielding gas reaching the area of the laser optical system. An annular nozzle guarantees uniform shielding gas blanketing of the melt pool.

Messer gases  - a wide-ranging product portfolio 
Messer offers a comprehensive gases programme, which is not always the case. This starts with the right gases for each application with comprehensible, application-oriented naming of the products and extends to the development of new gas mixes to meet customer requirements and wishes.

Smaller quantity requirements, such as the supply of laser gases, are covered by gas cylinders. Single cylinders with a capacity of ten or fifty litres are mostly used for this purpose. For cutting, oxygen or nitrogen is supplied in tanks.

The gas supply - from the cylinder to the working place
A crucial factor for an optimum gas supply is the transport of the gases to their destination. No contamination must occur during this process. This depends on the correct installation of the hardware, a considered choice of gas valves and a demand-oriented supply of gases of the required purity. Additional insurance is provided by the use of a particle filter. The gas supply to the resonator also demands maximum purity. That applies both for the resonator gases and the feed through pipes and hoses. For the supply line through fixed parts of the system, pipes of copper or CrNi steel are ideal. The pipes must be free of oil and grease and their ends should be sealed with plastic caps during transport. When welding or soldering these pipes, attention should be paid to adequate back shielding.

With hoses, the inward diffusion of nitrogen, oxygen and, in particular, moisture is always a risk. Special materials can reduce this risk.

Nothing new: The natural resources of fossil fuels, such as oil and natural gas are limited. It could already come to shortages in this century if the demand keeps on rising at the present rate. However, several years ago, drilling experts discovered that the introduction of CO₂ into a sealed oilfield helps to bring more oil to the surface. In 2004 the industrial gas specialist Messer successfully tested oil recovery in Croatia with carbon dioxide for the first time in Eastern Europe.

Obtaining carbon dioxide through chemical processes and reusing
The goal was to check the effect of introducing CO2 in an existing oilfield. For the first two test cycles, two 16,000-ton shipments of liquid carbon dioxide were delivered to the drilling location of the client in Ivanic Grad. There it was stored in appropriate tanks and pumped into the earth at a pressure of about 100 bar. The results of the first two test cycles were completely convincing: INA Naftaplin decided against three further test phases and started the main project on a larger scale.

The extra amount of oil that can be extracted in this way is enormous, often ten to fifteen percent of the oil reserve (OOIP – "original oil in place") is possible. This can prolong economic oil production by several years – as seen in the case of Croatia. A study elaborated for Messer indicates a potential of 1300 million barrels of additional yield throughCO₂-technology on the European continent alone. This is enough to completely supply Germany for over a year. Another benefit is that the injected CO₂ stays in the oilfield and does not return to the environment. On average for each barrel of oil which is additionally produced, one third of a ton of carbon dioxide remains stored. A double benefit for the environment!

In addition to the economic success and the important contribution against global warming, the project had another positive effect: it underscored just how forward-looking and strong the Croatian economy is – which sends out a clear signal on Croatia's way to becoming an EU Member Country.

Environmental protection through a variety of uses of carbon dioxide
For Messer, the use of carbon dioxide for oil production is one of many environment-friendly applications for the gas known in Germany as the "climate killer". Part of the core competency of the world's largest family-managed industrial gas company is to develop new solutions or improve existing ones, and thereby relieve the strain on the environment. This involves reusing, i.e. recycling, the carbon dioxide which forms as a waste product in industrial processes. High-purity carbonic acid for the food and beverage industry, in contrast, originates from ground wells. In the food industry, the ultracold gas is generally used for cooling/freezing or as carbonic acid. In many cases, blasting with dry ice pellets has already displaced other blasting procedures in the manufacturing industry. Pellets made of dry ice are small, solid and cold. If pellet are shot under pressure onto a soiled surface, the dirt contracts and thereby detaches itself from the surface. Then it is simply blown away by the air pressure and the subsequent pellets. The result is pure dirt – it is not necessary to dispose of sand or wastewater. In purification plants and water treatment facilities, the addition of CO₂ ensures a controlled pH, which means that chemical agents or aggressive mineral acids are no longer required in such large quantities. There are many sides to carbon dioxide!

Beverage processing and bottling involves the use of various gases, which are mostly supplied in liquefied form in vacuum-insulated tanks. Liquid carbon dioxide (CO₂) is particularly important here. It has to be returned to its gaseous state for the purpose of beverage carbonation. This is done by means of air vaporisers or electrically heated vaporisers. However, this process step does not make use of the cooling energy contained in the gas.

The process principle: cold extraction in the heat exchanger
Integrated into the cooling system’s cooling circuit, the heat exchanger forms the centrepiece of the EcoVap process. Both the cryogenic liquefied gas and the cooling system’s heat transfer medium (e.g. cooling water or brine) flow through the unit. The heat transfer process involves the "exchange" of heat for cold.

The construction consists of a special tube bundle heat exchanger. The facility’s special design ensures that, despite the extremely low temperatures of the liquid gas, the temperature of the heat transfer medium does not drop below freezing point as it flows through the unit. As the liquid gas vaporises during its passage through the EcoVap system, it extracts a considerable amount of energy from the coolant, significantly lowering its temperature. The coolant is conducted from the cooling circuit’s return line into the EcoVap unit, where, for the most part, it passes the heat exchanger jacket and is thus cooled. It then flows to the refrigerating machine – as before without EcoVap –, where its temperature can be further regulated as required. After this process, the refrigerating machine requires significantly less electrical energy to achieve the desired cooling effect thanks to the reduced input temperature.

Electric vaporisers unnecessary in winter
At the EcoVap system’s outlet, the gas, which was liquid before, has completely vaporised. The gas temperature mainly depends on the temperature of the heat transfer medium. In contrast to air vaporisers, EcoVap is not dependent on weather conditions. As a rule, no condensation forms on the pipes either.

Another advantage of EcoVap is the reduced requirement for electric heating to vaporise the liquid gas. Especially in the winter months, air vaporisers are often not enough on their own to supply the liquid gas with the heat required for vaporisation since the temperature difference between the ambient air and the gas is too small. In this case, it is necessary to use electrically heated vaporisers. When using EcoVap, these are only required as a potential back-up, plus they do not use any electricity in normal operation.

Cutting costs: a real-life example
By installing the EcoVap process, a beverage producer was able to save around 560,000 kWh a year for vaporisation and heating of 2,500 kg of CO₂/h and simultaneous cooling of process water. The investment paid for itself after just two years.

The EcoVap principle can be used not only for carbonation in beverage production but in any industrial application that involves the vaporisation of liquid gas with a simultaneous requirement for process cooling. Further possible applications include the wastewater neutralisation with CO₂ the CO₂ greenhouse fertilising.

Carbonation in the beverage industry
Soft drinks generally contain 5 to 9 g of CO₂/l. If required, wine is carbonated with about 2.5 g of CO₂/l. The gas produces the characteristic feel of freshness (sparkle) and improves the biological shelf life of beverages. The carbonation process requires carbon dioxide in its gaseous state. Generally speaking, the process of dissolving gases in liquids depends on the composition of the liquid, the temperature, the pressure, the exchange surface and the dwell time. A cooling circuit ensures optimal temperatures. Thanks to EcoVap, you can make a double saving: firstly, there is no need for an electric vaporiser for the gas, and secondly, there is a reduced load on the refrigerating machine.

Recycling
Refrigerator recycling is a two-stage process: first the cooling compressors are removed and any oil or coolant contained in them sucked out. If done carefully, these substances can be collected without major losses. In technical terms, it is a relatively straightforward task as the harmful substances are obtained in liquid form.

In the second stage, the empty refrigerators are crushed in a shredder. The reusable materials subsequently undergo various separation processes, resulting in almost completely pure material types at the end. However, the crushing process also produces gaseous pollutants. Especially in the case of old refrigerators where the manufacturing process involved the use of CFCs as a foaming agent for the insulating layer, these gases escape when the foam pores are opened during shredding.

Since these substances represent a serious environmental hazard, the harmful gases and vapours must be collected and conducted to a waste gas cleaning system. The effectiveness of emission avoidance depends to a large extent on the design of the shredder, its seals and material airlocks, as well as the waste gas cleaning system’s recovery rate.

Waste gas cleaning
Messer has developed the DuoCondex process for waste gas cleaning. This involves the flow of waste gas being conducted through special condensers that are cooled with liquid nitrogen. The extremely cold temperatures of the liquid nitrogen (minus 196 degrees Celsius) cause the harmful substances to be frozen out in the condensers, allowing them to be separated from the waste gas flow. When the condensers are frozen over, they are heated, causing the harmful substances to melt and flow into a container in liquid form. They are then disposed of.

The liquid nitrogen that is used to cool a DuoCondex unit’s condensers vaporises in the apparatus and exits the unit in a gaseous state. The gas can then be easily conducted into the shredder, where it acts as a protective gas, virtually eliminating the risk of fire or explosion. This is necessary because an increasing number of refrigerators using pentane-foamed insulation are also being processed. Pentane-foamed insulating materials are environmentally friendly and are now being used in place of CFC materials. These refrigerators therefore account for a constantly increasing percentage of appliances being recycled. However, pentane is flammable and requires effective protection against fire and explosion.

The replacement of CFC refrigerators with appliances using pentane-foamed insulation is a crucial step in terms of environmental protection. Nevertheless, the proportion of CFC appliances in recycling often still exceeds 80 per cent and is only expected to drop to below 10 per cent in 2020. CFCs damage the atmosphere’s ozone layer and contribute to global warming (greenhouse effect). The following comparison is provided to illustrate the impact on global warming resulting from a single CFC refrigerator that has not been recycled properly (rounded figures):

Legend
One CFC refrigerator that has not been disposed of properly causes the same contribution to the greenhouse effect as a small household’s annual electricity requirement or a private car’s annual mileage. A photovoltaic installation on the roof of a detached house would have to generate electricity for a year in order to compensate for the environmental damage caused by the emissions from a single CFC refrigerator that has not been disposed of properly.

Overall process
The process chain from leaving a refrigerator by the roadside to its complete dismantling at a recycling facility has several weak points where CFCs can escape as a result of improper handling. The total technically feasible CFC recovery rate of 90 per cent is therefore not achieved by a long way – in fact often it is even less than 50 per cent. The biggest "sinners" are the scrap metal thieves who cut out the compressors from refrigerators that have been made ready for collection, resulting in the direct release of the CFCs contained in the coolant. During transportation and storage, CFC losses occur as a result of mechanical damage to the foam insulation as well as through rainwater penetration leading to softening of the foam. The next potential weak point is the coolant extraction system for compressors. CFCs can escape if the equipment is not connected properly. Controlling the gas flow in the shredder is difficult as the refrigerators have to be put into the machine and the materials discharged via airlocks. Sealing the shredder and its input and output systems is technically very demanding, particularly because of the high mechanical stress levels as well as influencing factors such as temperature, moisture and dust.

Also, there are often CFC residues in the discharged PU foam if it has not been completely broken down. Moreover, the material contains matrix-bound CFCs that have to be removed from the polyurethane by increasing the pressure and temperature in a special post-treatment stage and then conducted – in parallel to the waste gas – from the shredder to the waste gas cleaning system.

The waste gas cleaning process itself is also a potential source of CFC losses. However, in modern systems, this process has been developed to such an extent that further reductions in CFC losses are hardly possible. If, for example, a DuoCondex unit is used here, residual CFC loads of less than 20 milligrams per cubic metre can be achieved at the clean gas outlet in accordance with the official regulations (TA-Luft – German Technical Directive on Air Quality Control). This extremely strict limit stipulates that CFC losses in the waste gas cleaning process must be less than 0.1 per cent.

In refrigerator recycling, there are therefore many technical and organisational means to significantly reduce CFC losses. A clear climate protection effect can be achieved with comparatively modest additional expenditure.

That is why food packaging under protective gases (Modified Atmosphere Packaging, or MAP for short) has established itself as one of the most effective methods of extending the shelf life of foodstuffs. The process involves specifically altering the ambient atmosphere during packaging by means of protective gases.

Messer offers a range of food grade gases for modified atmosphere packaging of food products. The company’s Gourmet brand includes carbon dioxide, nitrogen, oxygen and argon – all of which occur naturally in the atmosphere. Nitrogen (Gourmet N) – an inert, reaction-inhibiting gas – displaces oxygen and thereby prevents oxidation. However, due to its low solubility in food, nitrogen is also used as a supporting gas to prevent the packaging from collapsing. At 78.08 per cent by volume, it is the main component of air. Argon (Gourmet A) is another inert gas that is used as a displacement and supporting gas. In addition, it inhibits enzymatic activities and increases the bacteriostatic effect of carbon dioxide. CO₂ – carbon dioxide (Gourmet C) – is colourless, tasteless and odourless. It is also highly soluble in liquid and fatty phases of foodstuffs. The associated decrease in the pH value has a bacteriostatic effect and reduces the growth of bacteria and mould. Oxygen (Gourmet O) – making up 20.95 per cent of ambient air by volume – is only used in specific cases in modified atmosphere packaging, for instance to preserve the red colour of meat or inhibit anaerobic bacteria. However, oxygen is also important for respiration when packaging plant-based food products such as fruit and vegetables. The gas mixtures are always tailored to the specific product and comply with all the laws and standards governing food products, for instance concerning purity or traceability. In most cases, the mixtures consist of at least two of Messer’s Gourmet gases. They are either supplied as ready-made standard mixtures in cylinders or mixed individually on site at the customer location.

The different types of packaging
In the food industry, packaging has a number of important functions to fulfil. It is supposed to protect the preserved product from the environment and prevent mechanical damage while at the same time satisfying all the marketing strategy and visual requirements and being commercially viable. Particularly with fresh products, the packaging must not only prevent contamination by germs but also ensure that the desired environmental conditions inside the packaging are preserved over an extended period. For this reason, the packaging material itself also plays a key role in food preservation. Ideally, it should be impervious to microorganisms, gases, water, steam, aromas and light – an exception being fruit and vegetable packaging, where a certain degree of exchange with the ambient air is desirable in order to support controlled plant respiration (EMAP – Equilibrium Modified Atmosphere).

Apart from the product type (solid, pasty, liquid), factors such as the shelf life requirements, costs, marketing strategy and ecofriendliness also determine which packaging materials are used in each particular case. The most common types of packaging include tins, plastic film packaging, composite cans, jars, preformed plastic containers, thermoformed packs, tubular bag packaging and side-sealed bag packaging. Tins are completely sealed, impervious to light and dimensionally stable – the drawback, however, is that the product itself is not visible, unlike with jars or plastic film packaging. The latter is available in wide-ranging levels of quality.

Shelf life extension
The highest levels of hygiene are always an absolute must, no matter what kind of packaging and which method of shelf life extension is used. The most effective methods include cooling, freezing, heat sterilisation, lowering of the pH value through chemical additives or the addition of carbon dioxide, as well as natural acidification by means of lactic acid fermentation. These shelf-life-extending measures have one thing in common: they already represent an initial phase of preparation. The situation is different when it comes to modifying the atmosphere or pressure inside the packaging through the use of Messer Gourmet gases – this process involves little or no change in the freshness characteristics of the food products. Further methods of shelf life extension include drying and vacuum packaging.

Shelf life of beverages
Beverages, too, must be produced with the longest possible shelf and storage life. CO₂ is also used for carbonation and impregnation in the beverage sector due to its high degree of solubility in liquids as well as its capacity to restrict – or inhibit altogether – the growth of harmful microorganisms. This not only produces the sparkling carbon dioxide bubbles that lend the beverage its refreshing quality; it also displaces atmospheric oxygen from the container, allowing oxidation reactions to be significantly reduced. Beverages mixed with CO₂ thus have a longer shelf life and retain their flavour throughout the entire production process as well as during storage and transportation. Messer supplies the necessary quantity of carbon dioxide for carbonation in liquid as well as gaseous form: in storage vessels, steel cylinders or bundles.

In the case of non-carbonated beverages such as still mineral water or fruit juices to be bottled or canned in thin-walled PET bottles or cans, the cryogenic injector is used. This involves liquid nitrogen being injected onto the surface of the liquid immediately before the beverage container is sealed, after which it evaporates in the sealed container. In this way, it displaces the oxygen from the headspace of the bottles or cans, thereby extending the product’s shelf life. Thanks to the increased internal pressure that is produced as a result of the cryogenic injection process, the containers themselves remain stackable even after extended periods of storage and transportation.

Nitrogen has the added advantage that it allows the use of very thin-walled containers, which in turn leads to substantial savings on the cost of materials. Over and above that, it changes neither the flavour nor the character of the beverage.

Gas supply systems
The right gas supply system also plays an extremely important role in modified atmosphere packaging – not just in terms of a seamless and reliable supply, but also with regard to cost efficiency. Besides selecting the optimal gas, it is also necessary, of course, to choose the appropriate hardware such as valves, pressure regulators, withdrawal points, expansion stations and accessories. And, of course, there are also regulations that have to be complied with. In this regard, Messer offers everything from a single source – from technical know-how and comprehensive expert consultancy to all the necessary components and complete automation of the gas supply. Messer’s portfolio of protective gases includes its own Gourmet gases as well as all the usual commercially available gases of the highest standards of quality, along with custom gas mixtures.

Extremely cold
In its liquid state, helium has the lowest boiling point of any gas at 4.2 Kelvin or minus 269 degrees Celsius. Liquid helium is therefore the coldest liquid on earth. It is used as a cooling medium wherever extremely low temperatures of less than minus 200 degrees Celsius must be reached. This is the case, for example, in applications involving the generation of very strong magnetic fields using superconducting magnets. The most important technical applications are magnetic resonance imaging (MRI) in medicine, nuclear magnetic resonance spectroscopy (NMR), and other basic research applications. Helium is extracted from helium-rich natural gas sources, which are found in only a few locations worldwide. Messer uses several reliable sources worldwide to supply the European market. Messer operates a fleet of special, super-vacuum-insulated tank containers with a capacity of 40,000 liters each. These are used to transport the helium to our European filling plants in Mitry-Mory (France), Lenzburg (Switzerland), Gumpoldskirchen (Austria) and Pancevo (Serbia). In the filling plants Messer transfers the helium into smaller, also super-vacuum-insulated transport containers (Dewars) intended for customer supply. Gaseous helium is also filled here.

Ultra-pure gases and gas mixtures
Many technologies require pure gases or gas mixtures of defined composition and quality for safe and efficient operation. In insulating glass panes, the noble gas filling ensures improved heat and sound insulation. The highest demands are placed on gases when they are used to operate sensitive analytical instruments in environmental analysis, safety engineering, or quality assurance. In addition to carrier and operating gases for instruments and detectors, gas mixtures with a defined, precise composition are used in gas analysis to calibrate the devices. “There are only a few standard products here; Messer usually produces calibration gases individually according to customer specifications,” says Jerry Girardi, Sales Manager Specialty Gases at Messer in Switzerland. Due to the wide range of applications, there are very different requirements for the quality and delivery form of the gases. Messer offers a comprehensive range of standard products. The purities range from “technical” to “6.0 quality” with a purity of 99.9999 percent. Messer delivers the gases according to demand. The range extends from one-liter cans to cylinders and bundles to trailer or liquid supply.

Knowing how to do it...
The production of specialty gases consists of various steps, from cylinder pretreatment and filling technology to quality assurance analysis. In-depth expertise in all individual areas and reliable mastery of the entire process chain are essential. “Thanks to our many years of experience in local specialty gas plants, Messer is able to supply almost any technically feasible gas mixture in the desired composition and with the required accuracy,” says Dr. Frank Wallasch, Head of Specialty Gas Plants at Messer in Switzerland. Many calibration gases can optionally be supplied with a certificate from one of our accredited laboratories. However, special gases also require special expertise in their application. To ensure that the desired quality reaches the point of use from the storage tank, special precautions must be taken during installation. Not every fitting that has proven itself in technical applications can be used for specialty gases. Together with Spectron Gas Control System, a leading manufacturer of gas withdrawal equipment and gas supply systems, Messer offers suitable solutions for every application – from planning to complete installation.