Study to determine Stress Concentration Factors (SCF) for alternative design on branch connections

Completed

Fossil Fuels: Oil Gas and Coal(Oil and Gas, Refining, transport and storage of oil and gas)

Applied Research and Development

ENGINEERING AND TECHNOLOGY (Mechanical, Aeronautical and Manufacturing Engineering)

Not Cross-cutting

Project Contact
National Grid Gas Transmission

Network Innovation Allowance

Ofgem

01 February 2013

01 July 2014

17 months

£61,000

Energy

London

Network Innovation Allowance

Project Contact, National Grid Gas Transmission

This study will seek to establish whether the stress concentration factors (SCF) of a number of alternative designs of branch connections are bounded by those used in the pipe work stress analysis code IGEM/TD/12. If so it will provide National Grid with a broader range of potential designs and suppliers of branch connection pipe work than are currently available increasing construction efficiency and reducing costs. If the 3D FEA SCFs are comparable with those determined by the methodologies given in the IGEM/TD/12 standard, it will provide evidence that the standard (non FEA) methodologies of SCF determination are appropriate for the newer designs of WICI such as insert weldolets. This will assist in their adoption and use.

One of the principal methods for making branch connections to transmission pipe work is to use a fitting generally known as Welded-in Contour Insert (WICI). These come in two distinct forms: The traditional version, usually referred to by its trade name Sweepolet, which has a smooth swept transition from the edge weld into the carrier pipe through to the branch. A newer design, sometimes referred to as an Insert Branch Outlet or an Insert Weldolet, is of a more compact and stockier shape but still exhibits a smooth transition but less swept. A number of the major weldolet manufacturers are now producing variations of the insert weldolet design and their adoption could potentially offer a wide range of benefits to National Grid. The original method was to use 3D finite element analyses (FEA) to determine the stress concentration factors (SCFs) of two sizes of insert weldolet that have the most extreme ratios in header to branch diameter. These two finite element analyses have been successfully completed and stress concentration factors determined. The results have been reviewed and the conclusion is that additional analyses are necessary to be able to define a range of geometries over which the SCFs can be used for the insert weldolet. It has been established that the eight additional models will be required to be assessed in order to successfully determine if the SCFs of the insert weldolets are bounded by criteria used in the pipe work stress analysis code IGEM/TD/12. These models will be performed via FEA as per the original method.Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above

14/12/18