Gaskets compatibility testing

Materials Compatibility Einally, any lubricant is required to be compatible with non-metallic components used in the engine, such as plastics, resins and elastomers. In particular, polymeric materials used in seals and plastics need to retain their integrity when in contact with the lubricant. ACEA and most OEMs have material compatibility tests to ensure that the lubricant will not cause undue degradation in key physical parameters of the polymer. These parameters include tensile strength, hardness, volume and crack formation. Any such loss of polymer integrity could be manifest as oil seal leaks or in more extreme cases as a blown gasket. Current engine test examples for American, European and selected OEM specifications are shown in Table 9.5. 

The simplest form of compatibility test is to immerse standard ASTM coupons in a liquid or vapor in the lab. Coupons can be installed in the field in a stream. However making a coupon assembly for installation in a pipe or a vessel may be difficult and persuading plant operators even more so. Lab testing is easy to carry out but will not replicate real life conditions such as flow, agitation, stress (compression for gaskets) and one-sided exposure. For this reason, lab dunk tests are usually done for screening reasons. Application temperature is easy to achieve by space heaters. 

Testing for seals and gaskets. Unlike lining for vessels, seals and gaskets cannot be tested in full simulation, so the total compatibility is determined piecemeal, i.e., chemical compatibility and evaluation of the material in the gasketed joint. It takes experience to put the information together to make a sound decision. 

Chemical compatibility of the material can be determined by a simple dunk test using either the gasket itself or a generically similar material. The exposure conditions should match the actual application condition. Visual observations and retained mechanical properties should yield useful information. 

The compatibility of CFC-alternatives with the internal plastic parts of many pieces of equipment is a concern. In many applications, parts such as the 0-rings, gaskets and seals will need to be changed to other polymer materials that are not affected by the new materials. This can only occur after large quantities of CFC-altematives are available for extensive customer testing. 

If gaskets are bought from suppliers or the elastomer composition is not known for other reasons, it is highly advisory to invest in a range of analytical tests to prove the fuel cell compatibility. Important from our point of view are solvent extractions to get information on type and quantity of elutable components as well as thermodesorption analyses to obtain information about volatile ingredients. 

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