A carefully planned and carried out maintenance program extends centrifugal pump life, maintains high pump dependability and rated performance, and reduces overall operating costs. The three primary areas of pump care are general effects of erosion and specific problems of packing and bearings.
The main parts, a centrifugal pump consist of are casing, impeller, shaft, bearing, and sealing.
Turbulent flow is detrimental to a centrifugal pump during handling of abrasive fluids. The drilling industry has standardized centrifugal pumps with concentric casings and wide impellers, a design that has proven to offer less turbulence and greatest pump life. The walls of a concentric style of casing (Figure 1) are an equal distance from the impeller throughout the impeller circumference, resulting in a smooth flow pattern. A volute style of casing (Figure 2) has a cutwater point that disturbs the fluid flow pattern, creating an eddy.
The function of the centrifugal pump casing is to:
- Direct fluid into the eye of the impeller through the suction inlet.
- Minimize fluid recirculation from impeller discharge to impeller suction.
- Capture fluid discharge from the impeller in the case volute to most efficiently utilize work performed by the impeller and direct fluid away from the impeller. (See Picture 1. and 2.)