Gallagher recently released our High Performance Elastomer Seals for the Instrumentation Industry White Paper, available for download on our site. This was written by Russ Schnell, an Elastomer Consultant contracted by Gallagher Fluid Seals, and a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont. This white paper is now available for download on our Resources page.
The term instrumentation covers a wide variety of applications. In the broadest sense, instrumentation may be considered as any equipment used for measurements. This equipment may be in a process stream and include devices such as flowmeters, pressure gages, and inline probes. Data from these devices are used for process control. In automobiles, sensors are used for a variety of applications including measuring the exhaust stream to “tune” the engine to yield maximum performance. Analytical laboratory instruments such as chromatographs and flame ionization detectors are used to determine the composition of samples. Instruments are used in the medical industry for product analysis as well as analysis of blood and urine samples. Of course this is only a partial list of the many applications involving instruments.
All of the instruments for these analyses require seals to assure the sample is kept apart from the surrounding environment. Proper elastomer selection is also critical to assure that the elastomer seal does not contaminate the test sample. Standard elastomers are used in many applications, however many instrument seals are subjected to high temperatures, harsh chemicals, and/or aggressive cleaning solutions. These applications necessitate the use of high performance fluoroelastomer (FKM) or perfluoroelastomer
(FFKM) seals. When dealing with difficult sealing applications, selecting the correct elastomer seal and seal design are critical for accurate and reliable performance over the long term.
Fluoroelastomers are high performance products that have long been considered the workhorse of the chemical process industry. They are widely used in many industries because of their very good chemical resistance, service temperature up to 200°C, and cost effective price. These products provide excellent resistance to strong acids, aromatic and aliphatic chemicals. They are not suggested for use in strong bases, amines or steam. Fluoroelastomers also have excellent mechanical properties. The low temperature range for these products is generally -30°C. Specialty formulations are available for sealing requirements down to -40°C.
Perfluoroelastomers offer top of the line performance for both
chemical resistance and high temperature applications. For comparison purposes, fluoroelastomers are said to be resistant to over 500 chemicals, whereas perfluoroelastomers are said to be resistant to more than 1800 chemicals. These products are typically the most expensive elastomers, but provide tremendous value in use. FFKMs provide sealing in the most aggressive chemicals and some formulations can be used at temperatures up to 325°C. However, even with their excellent performance, there are subtle differences in formulations and understanding these differences is needed to select the best product for specific applications. In general the low temperature range for these materials is approximately -15°C. However, specific low temperature formulations can be used down to -40°C.