GRAPHALLOY^®
Bushings That Increase MTBR in Raffinate Service

A pump company engineer informed us that a major refinery in the U.S. Gulf Coast had problems with some of their vertical pumps.  These are 4-stage vertical can pumps with 18-inch diameter bowl assemblies.  These pumps are in Raffinate service with an operating temperature of 100°F.

Raffinate is used as a gasoline additive to help meet stricter emissions standards for summer product and is often blended with the more expensive alkylate and reformate blendstocks for various gasolines.

This refinery was using Graphalloy nickel-grade bushings in some of these pumps and PEEK material in others.  One of the pumps fitted with PEEK experienced a failure where the material came apart in the center of the bearings and flowed out at the ends, coating the shaft. 

The pump engineer that spoke with Graphite Metalizing’s engineer about this failure speculated that there may have been some intermittent flashing/dry running that increased the temperature causing the PEEK material to flow.  This is probable as the 100°F operating temperature is well within the PEEK material’s operating temperature range. 

The Refinery’s Rotating Equipment Engineer indicated that the PEEK material is lasting 2-3 years while the GRAPHALLOY fitted pumps are lasting 7-10 years in this service.

The pump engineer told us that the refinery’s new directive is that all these types of pumps, with raffinate, should now be fitted with Graphalloy due to the extended MTBR and because Graphalloy  is “much nicer to the pump” than PEEK.