A Study of Allowable Piping Loads on Double-suction Centrifugal Pumps : 1st Report, Casing Stress Distribution Produced by Piping Loads with Added Internal Pressure

Abstract

Pump casing stress caused by external piping forces and moments in addition to internal pressure was investigated. The test pump type was a axially split, single-stage double-suction volute with foot support. A stress analysis by FEN(MSC/NASTRAN) was first performed, after a FEM model had been accurately constructed applying a CAD system. Then, actual external piping loads were applied to four test pumps and casing stress was measured with strain gauges. Good agreement between analyzed and measured results of casing stress was obtained. When plural loading were applied, it was found that the magnitude of the loads but also by their direction. When nozzle loads based on API 610-6th standard were applied in addition to internal pressure, the highest stress was observed on the nozzle surface in the vicinity of the foot connection, and the magnitude of this stress was rather great. One of the conclusions from this study was that sufficient consideration must be made for casing stress caused by API loads, especially in the case of low pressure pumps.