Testing of Low-Friction Seals

February 1, 2016

Ryan Gehm

A new test service introduced by Bal Seal Engineering, Inc. offers verified performance results for the company’s low-friction spring-energized seals used in rotary/face applications. Rotary/face seals are frequently used in dynamic housings and mounts to protect electronics and other internal components from environmental contaminants that can compromise performance. To minimize stick-slip and meet motor torque requirements, the seals must exhibit very low friction—but they also must minimize leakage over long periods of exposure. Bal Seal’s seal test equipment measures friction and leak rate using customer-defined hardware tolerances and operating conditions, including pressure and speed. Fixtures can accommodate seals up to 22-in OD, and can be modified for larger seal dimensions. The fixtures can produce a range of pressures and exert specific frictional forces to accurately simulate a seal’s performance under real-world conditions. Rotating plates on the fixtures are connected to digital force testers, which measure the friction of rotation. A vacuum tester simulates airflow over the housing. The tester pulls a vacuum across the plates, creating suction inside the seal to measure the leak rate across its surface. Both friction and leak rate are measured simultaneously. Bal Seal’s low-friction spring-energized seals, which are machined from polymer-filled polytetrafluoroethylene (PTFE) materials, exhibit a low dynamic coefficient of friction. The seals minimize “stiction” to facilitate smooth rotation and bi-directional motion, and they can be used against a range of material hardnesses/finishes. They are energized with a Bal Spring canted coil spring, which ensures even wear and longer service life.