Compatible Sealing Materials

Seals required on the membrane elements vary with the membrane type and the module geometry. Many flat-fihn designs employ thermal and ultrasonic welding techniques and thereby avoid the introduction or minimize the use of dissimilar seating materials. 

Membrane manufacturers frequently have as much technology and art invested in the selection and processing of the tubesheet and sealants as in the membrane itself. Understandably, much of the details about tubesheet and gasket material selection and processing is considered proprietary and trade, or closely guarded, secret information by membrane manufacturers. 

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Compatible sealing materials - Are sealing and tubesheet materials available that are compatible with the gases and process streams involved in the intended appHcation and with the module manufacturing process ... 

Are liquids used to cool or purge seals compatible with materials processed in the equipment If so, are temperature, pressures, and materials appropriate for the seal components and reflected in procedures ... 

In a fully synthetic FR fluid, the fire resistance is due to the chemical nature of the fluid in the others, it is afforded by the presence of water. The other main distinction between the two groups is that the fully synthetic fluids are generally better lubricants and are available for use at operating temperatures up to 150°C (272°F), but are less likely to be compatible with the conventional sealing materials and paints than are water-based products. 

Both physical and process-material considerations influence the choice and use of shaft seals in the industry. It is essential that the seal material is compatible with any process material and the operating variables. 

Nitrile rubbers, including fiber-reinforced varieties, are used both as radial shaft-seal materials and as molded packing for reciprocating shafts. They have excellent resistance to a considerable range of chemicals, with the exception of strong acids and alkalis, and are at the same time compatible with petroleum-based lubricants. Their working temperature range is from —1°C to 107°C (30°F to 225°F) continuously and up to 150°C (302°F) intermittently. When used on hard shafts with a surface finish of, at most, 0.00038 mm root mean square (RMS), they have an excellent resistance to abrasion. 

Face-seal materials can be chosen from filled, molded or reinforced resins with which water, hydraulic fluids, mineral oils or synthetic oils are all compatible. Their maximum temperature in service depends on the brittle point of the resin but, generally, the range is from —50°C to 100°C (122°F to 212°F). Abrasion resistance is generally good but, as far as possible, resins are not used in the presence of foreign solids. 

Overall, the component reliability is a challenge to fnel cell mannfactnrers as well as their component snppliers. The stack is only one of several snbsystems in a PEM fuel cell system with hundreds of parts and components. Component compatibility, which includes both chemical and mechanical properties, plays an important role in system reliability and overall performance. To select the best materials/design for a system component, one mnst first stndy its properties (physical, chemical, mechanical, and electrochanical) nnder relevant conditions snch as temperature, pressure, and composition. Eor example, the reactant side of a PEM fuel cell bipolar plate (all sealing materials and plate components) mnst be able to tolerate high humidity, temperature... 

What is material in contact with product (heat seal material) Query compatibility against material specification including any constituents in plastic. 

Lao 75Cao,25) 1.01 Fe03 is formed at the seal. Since the third multicomponent metalUc oxide is identical to the composition of the ceramics to be joined, the thermal expansion coefficient of the joint material closely matches the thermal expansion coefficient of the (Lao.75Cao,25)i,oiFe03 parts that were joined. The joint thus has about the same thermal cycUng stability as the parts themselves. The joint also has the same chemical properties as the membrane material and therefore, the seal will be as resistant to the process atmospheres as the membrane material itself There are also no concerns with reactivity or chemical incompatibility of the seal material and the membrane material since the membrane and the joint material are chemically identical after the joint has been made. The invention of Butt et al. [33, 34] thus produces a ceramic-to-ceramic seal that has the very attractive properties of being expansion matched to the membrane material chemically identical to the membrane material just as chemically compatible with the process gas atmospheres as the membrane material just as thermodynamically... 

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