The Graphite Metallizing Corporation, manufacturer of self-lubricating Graphalloy bushing materials, has announced the success of its iron grade bushings in molten sulphur pumps at a major refinery.
Molten sulphur pumps require a high temperature bushing material and the refinery was using nickel chromium bearings. It opened up the bearing clearances to .020–.025-in to avoid bearing contact with the shaft but this caused high vibration issues approaching 1.0-in/second peak.
The refinery’s rotating equipment engineer contacted Graphalloy engineers to determine if it could reduce its running clearances by replacing the bushings with Graphalloy, a graphite metal alloy, which is self-lubricating, non-galling and can handle temperatures up 750°F.
Due to its non-galling qualities, the refinery was able to rebuild the pumps using iron grade Graphalloy bushings with a running clearance of .006–.007-in. The overall high vibration level decreased to a maximum of .21-in/second peak. The refinery has since rebuilt three additional pumps to the same standards using Graphalloy bushings.