Bolted Flanged Joint Creep/Relaxation Results at High Temperatures

An ASME Class 300 NPS12 flange connection between a control valve and a pipe has been evaluated at a temperature of 1100° F with testing and Finite Element Analysis (FEA). The goal of the testing was to validate the FEA simulation. The valve side of the test sample was a cast structure, the pipe side was a forged flange butt welded to a pipe section, and the gasket was a Thermiculite filled spiral wound gasket. The valve, flange, and piping material are SA-217, SA-182, and SA-335 (2 ¼ Cr – 1 Mo) steel respectively. The bolt length and flange geometry was measured before and after loading the bolts, and before and after heating the sample in order to measure changes in the bolt load and flange rotation which would indicate creep/relaxation in the joint. Tests were run with two types of bolts, B16 (SA-193) and 718 (SB-637), and also with two gasket arrangements, no gasket and then a spiral wound gasket. The results of the completed test and the correlation to an FEA analysis will be presented.