Steam-turbine casing flanges: A three-dimensional photoelastic study

Abstract

Photoelastic tests have been made on simplified three-dimensional models of a steam-turbine casing subjected to bolt preload and internal pressure. An examination was made of the flange interface-pressure distribution between adjacent bolt holes for two different values of bolt pitch. The results revealed that for both bolt pitches investigated in these tests, the minimum interface pressure at the inner edge occurred at a position corresponding to the bolt centre-line. The maximum interface pressure occurred on the inner edge at the mid-pitch position for the small pitch and on the inner edge at a distance of approximately one-quarter of the pitch from the bolt centre-line for the large pitch. The overall flange interface-pressure distribution had a minimum at a position approximately mid-way between two adjacent bolts and one-third of the flange width from the inner edge. It has been verified from these tests that the determination of flange parameters using the two-dimensional design curves described in an earlier paper is valid for practical designs of flange.