[Posted 2 April 2014 by:John E. Schroeder]
At Kalsi Engineering, we offer a variety of elastomer material choices for the manufacture of the correct rotary shaft seal for your application. Each elastomer has different strengths and weaknesses when used as a seal. Understanding the basic resistive qualities can provide a guideline for selecting the type of seal that will perform best in your operation.
HNBR, Hydrogenated Nitrile, offers the best combination of characteristics for use in oilfield drilling operations. This elastomer provides a strong abrasion and compression resistance. HNBR has a high resistance to acids, animal fats, water and steam. It should not be used with esters or ketones. The material also offers a higher temperature operating range and strong chemical resistance. In cold temperatures, diesel based fluids can reduce the life expectancy of HNBR.
NBR, Nitrile Butadiene Rubber, offers a strong resistance to petroleums, crude oil, brines, glycols and mineral oils. NBR is a synthetic copolymer of acrylonitrile and butadiene. XNBR is Carboxylated Nitrile. XNBR is not compatible with acids or ketones.
EPDM, Ethylene-propylene, works best with synthetic lubricants. This material provides a strong resistance to fire resistive hydraulic fluids, but has a low resistance to petroleums. EPDM offers good abrasion and compression resistance and provides the lowest operating temperature transition point for brittleness, -90°F (-68° C).
FKM, Flourocarbon rubber, is often known under the trade name Viton, associated with Dupont. FKM is a composite that offers a high resistance to petroleum-based fluids, corrosives, esters, acids, halocarbons and solvents. This material also provides solid high temperature and compression resistance for use in shaft seals.
All of the characteristics of each elastomer must be considered in your selection. Other considerations include tear strength as well as abrasion, extrusion and compression resistance. We are happy to provide elastomer testing and rotary shaft seal testing. One testing method employed is an immersion test, ASTM Test Method D 471-98, for media compatibility at your specified time and temperature. If you need, we can recommend a third-party testing lab.
We have been providing consulting, analysis and testing services since 1978. Our products are developed using finite element analysis (FEA). Let our experts help you choose the best materials to ensure long-lasting seal life.