The importance of selecting the correct elastomeric seal for critical applications cannot be underestimated. In factories and chemical plants around the globe, a leak, or perhaps a major seal failure, can result in downtime, damaged equipment or an environmental incident.
In this and forthcoming issues of Sealing Express, we answer some of the most frequently asked questions about elastomer seals:
Answer: There are numerous reference sources available to assist in material selection, both in hardcopy and on the web. Unfortunately, you may not find a material recommendation that exactly fits your set of application conditions. Use your references to narrow the material choices, and then contact your elastomer part supplier for product advice. Finally, obtain samples of the best candidates and evaluate them in your specific application environment. DuPont Performance Elastomers has online tools, such as the Chemical Resistance Guide and the Kalrez® Application Guide, which can guide you in the proper selection of an elastomer. (See "KAG and CRG - your guides to better elastomer selection" in this issue).
 |
| In a trisolvent test for volume swell, an FKM seal (left) swelled considerably more than the Kalrez³ part (right). |
Answer: Many of us have labs available for test work, but not equipped for extensive elastomer testing. However, it is still possible to determine expected elastomer performance. On the simplest level, expose the elastomer samples to the process chemicals and temperature for at least two weeks. Look for any changes in the sample surface. Also consider weight gain, and if possible, volume swell and hardness change. Typically, the material with the least property change is the one to select. If there is a weight gain over 15%, then consider a different product for the application. High-performance elastomer products, i.e. FFKM (e.g. Kalrez® perfluoroelastomer parts) and FKM (e.g. Viton®), usually exhibit the least property change.
|
