Dry run failures in sealless pumps continue to be of major concern to users and, in some cases, have precluded the purchase of these types of pumps. Users are demanding robust pump designs that are more tolerant of dry running caused by system upsets and occasional operator error. Although silicon carbide is the best material choice for product lubricated bearings during normal wet operation, it will quickly overheat and seize in a matter of seconds, if allowed to run dry. There are other bearing material choices available, such as carbon-graphite and various polymer materials that will permit some degree of short term dry running, but sacrifices must be made in wear resistance, chemical inertness, and/or load carrying capability. The purpose of this study is to investigate the bone-dry run performance of amorphous diamondlike carbon (ADLC) coated silicon carbide bearings both with and without Teflon lubricating strips. The test pump was a 1.5×1×6 ANSI magnetic drive pump fitted with a nonconductive containment shell and rated for 7.5 hp at 3600 rpm. Ten bearing configurations were tested, including repeatability tests, cycle tests, and tests with covered suction and discharge flanges to eliminate the effect of air cooling. A baseline test was conducted for silicon carbide without the ADLC coating or Teflon strips in order to determine survivability under bone-dry run conditions. Not surprisingly, this configuration seized in under five sec operation and sustained the most massive damage of all configurations tested.
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