Bearings That Solve NGL Pump Problems
There has been a dramatically increased use of natural gas liquids (NGL) pumps in North America.
These pumps are generally smaller diameter horizontal multistage pumps that are basically vertical turbines turned on end. The pumps are part of an HPS (horizontal pumping system) and usually have between 70 & 100 stages, developing high head and low flow.
As described above, these pumps have a high head pressure thus developing a high thrust load in the axial direction opposite that of the flow. Each pump is fitted with a specially designed thrust chamber that sits between the pump and the electric motor. This thrust chamber can only handle thrust in one direction axially. In this application, the customer was experiencing thrust in both directions. This situation was due to a design problem within the terminal. These kinds of problems are occurring all too often in these plants as they are designing and building them as fast as they can. The pumps were failing in as little as 1 week of service.
This OEM has been using GRAPHALLOY® bushings exclusively in these types of
pumps for years because it can handle the low viscosity liquids being pumped. The engineer contacted us for help in designing a solution that would allow the GRAPHALLOY material to also handle the inherent axial thrust loads. Working with Yonkers engineering, we designed a flanged bearing that would handle the loads and allow the unit to operate under normal conditions. Babbitt-grade Graphalloy was chosen as the bearing material and the customer has been using that Graphalloy grade for several years.
The Graphalloy flanged bushings were installed in some test pumps and were successful. The pumps in the field were upgraded to Graphalloy and have been in service for several years now. The customer is happy that they have a solution for those situations that require additional protection against the possibility of load in the “wrong” direction.
Graphalloy is the standard for many HPS pumps pumping low lubricity fluids and gases and is included as the OEM bushing in the brochure of a major pump manufacturer.
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