This paper on "Thermal Transient Analysis of a Sulzer Boiler Feed Water Pump" was presented at the NAFEMS World Congress on Effective Engineering Analysis - 25-28 April 1999, Newport, Rhode Island, USA.

Summary

The present investigation was performed in order to establish, whether the horizontally split-ease multistage pump design is capable of withstanding the service conditions as specified for combined cycle boiler feed water pumps. A very large nonlinear FE-model was created, for the 3D analysis of the steel casing, containing some 400000 elements and 1.8 Mio degrees of freedom for the static calculation. Various thermal transient loads cases were simulated on a derivated thermal FE-model and the temperature distributions were read in as loads for the static calculations. Stresses and displacements were calculated together with the pretension of the bolts and the internal pressure distribution.
Special attention was paid to the resulting bolt stresses and loads, the gasket compression and opening, the casing deformation and stresses and the local bore deformation to assess a possible rub condition with the rotor. During warm up the casing expands while the bolts stay much longer cold. This results in an additional bolt loading, which could lead to overloading. The analyses showed, that the bolts are not overstressed at any operating condition. During cool down, the opposite effect can be observed which results in a loss of pretension and the danger of leakage from the pump. The computations showed, in every operation load case, that the pretension of the bolts is always sufficient to prevent leakage of the gasket. The highest casing stresses are around the bolt holes, caused by the bolt loading. Because these are local pressure stresses, they will not lead to failure of the casing. The highest membrane and bending stresses in the casing occur due to the hydraulic pressure load case. Two different kinds of bore deformation must be judged in order to assess a possible rub condition between the rotor and the casing. The first is a rigid body motion of the casing bore. A bending is thus forced into the rotor. The second component is the local deformation of the bore itself. It can be shown, that no rub should occur between the rotor and the casing.