When BP discovered that the PTFE-bronze bushings on two of the reactor pumps at its hydrocarbon processing plant in Grangemouth, England were wearing out in six months, they turned to plastics specialist 3P to solve the problem. Working with the pump manufacturers, 3P recommended switching to bushings made with Victrex PEEK™ polymer, a non-brittle carbon fiber reinforced composite which 3P markets under the trade name Xytrex. The result has been a major reduction in downtime at the plant.
According to BP mechanical engineer David Dickson, "Once we were sure that there was no risk of the composite contaminating our sensitive polyethylene production process, we installed the PEEK polymer bushing on one of the pumps. It has been running now for over 12 months."
After six months, BP engineers opened up the pump to check the bushing.
"There was not even a scratch," says Dickson. "Once we were satisfied that this bushing could solve our problem, we decided to install a similar bushing on the second pump. It has been running now for over seven months."
Bushings made with PEEK polymer are non-galling and non-seizing in contact with metal and can operate at a continuous temperature of up to 350°F (177°C).
"PEEK polymer is a naturally good low friction and wear resistance material," explains Kevin Jennings, general manager for Victrex USA (a division of Victrex plc), manufacturer of PEEK polymer. "Its self-lubricating properties combined with high temperature capability make it an ideal choice for replacing metal wear components in pumps. And, because it expands less than stainless steel at high temperatures, sealing rings can be machined to closer clearances, increasing pump efficiency through reduced recirculation."
Because PEEK polymer is a hard material -- harder than the PTFE-bronze used on the original BP bushings -- it can extend the wear life of components.
"For example," says Jennings, "a shaft running on a bushing causes high pressure which can actually wear away the bushing. If you use a hard material such as PEEK polymer that can resist that pressure, the bushing won't wear out as fast. This is especially important in the hydrocarbon processing industry where reducing the downtime is critical."