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Where: Q = Capacity, gpm D = Net fluid transferred or displaced by one cycle, ft3 N = Rotation or cyclic speed, revolutions/minute, cycles/minute S = Slippage, ft3/min (The quantity of fluid that escapes the full discharge cycle through clearances or other leak paths) The impellers, rotors, shafts, and casings are the pump components which should generally have the longer lives when compared to bearings and seals. With good designs and proper material selection, the reliability of impellers, rotors, shafts and casings should remain very high. In order to properly determine total pump reliability, failure rate models have been developed for each pump component. Pump assemblies are comprised of many component parts including seals, shaft, bearings, casing, and fluid driver. The fluid driver can be further broken down into the various types common to pumps including the two general categories for centrifugal and displacement pumps. For displacement pumps, it will be broken down into two further categories: reciprocating and rotary. For reciprocating pumps the fluid drivers can be classified as piston/plunger type or diaphragm type. For rotary pumps the fluid driver is a vane type for single rotors and for multiple rotors it is common to find a gear, lobe, or screw type of fluid driver. The total pump failure rate is a combination of the failure rates of the individual component parts. The failure rate for centrifugal pumps and displacement pumps can be estimated using Equation (10-2). ^P ~ ASE + 4sW + KE + ^CA + (1 0-2 ) Where: AP = Total failure rate of the pump ASE - Total failure rate for all pump seals, failures/million operating hours (See Section 10.4 and Chapter 3) ASH = Failure rate for the pump shaft, failures/million operating hours (See Section 10.5 and Chapter 20) ABE = Total failure rate for all pump bearings, failures/million operating hours (See Section 10.6 and Chapter 7) ACa = Failure rate for the pump casing, failures/million operating hours (See Section 10.7) AFD = Failure rate for the pump fluid driver, failures/million operating hours (See Section 10.8) Pumps 10-10 Revision C

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