Development of HAZ Hardness Limits for In-Service Welding

Fast Facts
Financial and Status Data
Research Entity:	DNV Columbus 5777 Frantz Road Dublin, OH 43017-1386
COTR:	James Merritt, james.merritt @ dot.gov, (303)638-4758
Contract #:	DTPH56-07-T-000004
Project #:	216
Contact Info:	William A. Bruce - 614-734-6128 - bill.bruce @ dnv.com
Partners:	David Nolan - University of Wollongong - 011-61-2-4221-5549 - dnolan @ uow.edu.au
Peer Review	Very Effective (PHP-3-2008, May 1-14, 2008)
Peer Review	Effective (PHP-4-2009, Apr 1-15, 2009)
Project Status:	Closed
Start Fiscal Year:	2007 (07/01/2007)
End Fiscal Year:	2009 (06/30/2009)
PHMSA $$ Budgeted:	$125,000.00
$$ Co-Funded:	$278,700.00
Total Project Cost:	$403,700.00

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Main Objective

The objective of the proposed project is to develop heat-affected zone hardness acceptance criteria that can be used to evaluate welds during the qualification of procedures for welding onto in-service pipelines.

Public Abstract

Welds made onto in-service pipelines are particularly susceptible to hydrogen cracking. During qualification of welding procedures, limits are often imposed on heat-affected zone hardness (e.g., 350 HV max.) as a way to avoid cracking. The hardness level below which hydrogen cracking does not occur is not a fixed value, but varies as a function of several parameters. The results of previous work resulted in the development of hardness evaluation criteria that can be used to quantify the trade-offs that can be made between HAZ hardness, hydrogen level, and the chemical composition of the materials being welded for welds made onto in-service pipelines. Further development and validation is required prior to the widespread use of these criteria, particularly for microalloyed materials used for modern high-strength pipelines. The use of these criteria will reduce the cost and increase the reliability of pipeline modifications and repairs. The project will be conducted by a team consisting of CC Technologies and University of Wollongong (UoW).

Final Report

Final Report – finalized version that includes revisions and additions to draft final report that was submitted in May 2009.