Effects of Analysis Method, Cover Plate Thickness, and Bolt

Preload on the Behavior of Bolted Flanges of Different

Sizes

Chris WowkMANE 6970

Master’s Project

Bolted, flat faced flanges are typical for fluid power applications when disassembly of the joint is required for maintenance or access to the internals of the system. The design of these flanges is typically governed by requirements outlined in the ASME Boiler and Pressure Vessel Code. For flange designs that come into contact with one another outside of the bolt circle, additional analysis is required to account for the interactions that occur due to the flexibility of each flange.

Introduction

Separation of this joint leads to leakage and

higher than predicted bolt prying loads

Fluid Pressure

Prying Load Outside Bolt

Circle

Problem Statement Design and analysis of these bolted joints are

covered by Appendix Y or ASME Boiler and Pressure Vessel Code (BPVC)◦ Plate bending approximated as flexure of discrete beams

An alternate method of analysis using Plate Theory was proposed by Galai for identical flange pairs

Finite Element Analysis using ABAQUS provides deeper analysis into the behavior of the joint

The primary goal of this project is to determine the agreement between the three methods selected to analyze bolted flange joints with contact outside the bolt circle. Shortcomings and strengths of each analysis method will be discussed.

Design equations exist in Appendix Y of ASME BPVC to determine joint separation and flange stresses

Plate method proposed by Galai for identical flange pairs will be adapted for a flange-cover joint

Symmetry will be exploited for FEA analysis

Methodology

Fluid Pressure

1/8 (45° Segment) ABAQUS Model

(8 bolts)

Cylindrical Symmetry Boundary Conditions

Contact Defined to Govern Joint Behavior

Approach Configuration Variables:

◦ Pipe Size (4 & 16 NPS)◦ Thickness of cover plate

(t=minimum thickness required by ASME B16.5)

◦ Bolt Preload (0, Equal to Pressure Load, & 80%YS)

Results to be Investigated◦ Separation of flange-cover

joint due to pressure◦ Additional loading of

fasteners due to prying effects

◦ Location of cover/flange contact

Nominal Pipe Size

Cover Thickness Preload

4 0.5t 04 0.5t Equal4 0.5t 80%YS4 1t 04 1t Equal4 1t 80%YS4 2t 04 2t Equal4 2t 80%YS

16 0.5t 016 0.5t Equal16 0.5t 80%YS16 1t 016 1t Equal16 1t 80%YS16 2t 016 2t Equal16 2t 80%YS

ASME Boiler and Pressure Vessel Code Galai, Hichem, and Bouzid, A.H, Analytical Modeling of Flat

Face Flanges with Metal to Metal Contact Beyond the Bolt Circle, Journal of Pressure Vessel Technology, ASME, Vol 132. December 2010

Schneider, R. W, and Waters, E. O, The Background of ASME Code Case 1828: A Simplifying Model of Analyzing Part B Flanges, Journal of Pressure Vessel Technology, ASME, Vol. 100, No. 2, May 1978

References