WRC 473:2002

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External Bending Moments on Bolted Gasketed Joints: Part 1 and Part 2

Published By	Publication Date	Number of Pages
WRC	2002	67

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Category: WRC

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Description

Part 1: External Bending Moments on Bolted Gasketed Joints: The Effects Of Bending Moments On Bolted Gasketed Joints

This bulletin reports the research on two separate PVRC projects (97-04 and 97-09) on external bending moments on gasketed bolted flanged joints. This work is part of an experimental and analytical program to investigate the effect of the external bending moment on the integrity and leakage of a bolted joint and to develop a new or alternative procedure for use in the ASME design rules for bolted flanged joints. This bulletin is the third in a series covering the tests in the program. The first in the series is published in WRC Bulletin 450, which reports the test results on NPS 4" Class 150 weld-neck and lap joint flanges. The second in the series is published in WRC Bulletin 461, which covers tests using a full size 16" Class 300 flanged joint.

Part 1 of this bulletin covers an experimental study on the effect of bending moments on two different type of flanges: Class DN 200 ISO PN 50 (NPS 8" Class 300) and Class DN 40 ISO PN 50 (NPS 1 ½" Class 300). The objective of the tests is to determine the effect of increasing and decreasing bending moments on gasket tightness and bolt loads. Different gasket materials are tested; non asbestos fiber sheet material, graphite sheet material, PTFE and Spiral Wound gaskets. The general conclusion that can be drawn from the test results is that the effect of bending moments on the leakage behavior of these tested joints is not significant.

Part 2: External Bending Moments on Bolted Gasketed Joints: Effect of Gasket Type on the Behavior of NPS 4 Class 150 Bolted Joints Subjected to External Bending Loads

Part 2 of this bulletin covers a study on the effect of gasket type on the behavior of NPS 4" Class 150 bolted joints subjected to external bending loads. This study is closely related to tests presented in WRC Bulletin 450. In Bulletin 450, a single type of gasket, NBR/asbestos sheet gasket was used. In this bulletin, four types of gaskets were tested: a virgin PTFE sheet, an expanded PTFE sheet, a spiral wound graphite filled gasket, and graphite coated corrugated metal gasket. The conclusion drawn from this study is that the gasket stress computed with the current ASME Code equivalent pressure method is on the conservative side. However, since the ASME Code calculations of the equivalent pressure are based solely on the equilibrium of the forces and moments, the combined effect of the rigidities of the flange and the gasket cannot be taken into account in the design. In order to optimize the design, a method needs to be developed that will predict the bolt load variations and the gasket stress distributions accurately. The test data presented in this bulletin can be used as basis to develop such a method.

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