Abrasive media comes in many forms—from mining slurries to wood pulp and even substances as seemingly mild as liquid chocolate. This diversity rules out a one-size-fits-all solution for abrasive pumping applications. However, today’s broad range of materials, from carbon fiber packing to graphite-filled polytetrafluoroethylene (PTFE) bushings, includes products capable of meeting an equally broad range of abrasive wear requirements.
Carbon Fiber Packing
Few materials offer the abrasive resistance and heat dissipation of carbon fiber yarns. Braided compression packing made from this material excels under extreme conditions, including exposure to a variety of chemicals, temperatures approaching 850 F (454 C) in oxygen-rich atmospheres (up to 1,200 F/649 C in steam) and shaft speeds in excess of 4,000 feet per minute (fpm).
The strength of carbon fiber yarns combined with their ability to draw heat from pump shafts make them the material of choice for resisting abrasive wear. Unfortunately, they do not seal as well as graphite foil packing. Upon closer examination, however, the speed and temperature capabilities of these two materials are similar.
Consider this hypothetical scenario: An abrasive pumping application is under control using carbon fiber, except for excessive leakage across the packing set. Depending on the nature of the leaking media, it may not be desirable to have it pooling on the plant floor. Even if it is just water, excessive leaking media is lost profit. If the leakage is clean, the carbon fiber packing is effectively excluding abrasives.
Carbon Fiber Rings and Foil Packing
When dealing with clean media, graphite foil packing becomes an option. At a subsequent repacking, it may be advisable to use just two carbon fiber rings in the bottom of the stuffing box and use graphite foil packing for the remaining rings. Continue reading Pump Packing for Abrasive Materials