Design and validation of new cavity profiles for diaphragm stress reduction in a diaphragm compressor

Abstract

The application of diaphragm compressors is severely limited by the low reliability and short life of diaphragms. The cavity profile has considerable influence on a diaphragm's stress level and therefore on its fatigue life. This experimental and theoretical analysis of the traditional cavity profile (as defined by a single-parameter generatrix) indicated that the short life of diaphragms may be caused by the superposition of peak radial stress and additional stress due to the discharge holes in the central region that occur when the diaphragm clings to the cavity surface. Therefore, two new kinds of cavity profiles are proposed to decrease the diaphragm's radial and total stress. The new cavity profiles based on different generatrices were designed in an attempt to reduce the peak radial stress in the central region. These cavities were manufactured to experimentally validate the designs. Experiments were carried out under various design conditions to investigate the radial stress distribution in the diaphragms. The reductions of radial stress on the diaphragms in the new cavities were compared with stress levels found in the traditional design. Although their cavity volumes and radii were all the same, the radial stress levels on diaphragms in the cavities designed by the new generatrices were less than those found in the traditionally designed cavity. The greatest decline in radial stress on the diaphragms in the cavities based on new generatrices was 13.8%. With the additional stress taken into account, the decline in radial stress in the diaphragm's central region reached as high as 19.6%.