Factors affecting heat affected zone root strains in pipeline girth welds and repairs

Technical Report · Mon Nov 01 00:00:00 EST 1993

OSTI ID:10169137

Graville, B A ^[1]

---

1. Graville Associates Inc., Georgetown, Ontario (Canada)

A recent study on hydrogen cracking in the heat affected zone (HAZ) of pipeline girth welds and repairs found that large strains in the HAZ transverse to the weld played a major role in causing cracking. The study quantified the effects of base metal composition and strength on the sensitivity to cracking, but the program did not address the factors that influence the degree of strain applied to the weld. It was the objective of the present project to study several of the possible factors that could influence root strains in girth welds including the effects of weld metal strength, pipe thickness and diameter, heat input, and weld length (repair length). The study was of a generic nature aimed at identifying areas of high risk of cracking. The approach included a literature review and simple analysis methods but no experimental work was undertaken. From the results it was concluded that high tensile stresses in the axial direction on the inside surface of the pipe result from the radial contraction of the weld and the consequent bending of the pipe. The largest effect on these stresses is from the welding procedure with the highest tensile stresses occurring with high heat input welds with few weld passes. Multipass welds result in a decrease of the tensile stress which becomes compressive above a certain thickness. The maximum net axial surface stress is independent of the length of the weld around the circumference. Base metal and weld metal strength have a significant effect on strain in the heat affected zone and some recommendations for bend testing are given. 33 refs.

• Research Organization: American Gas Association, Inc., Arlington, VA (United States); Graville Associates, Inc., Georgetown, ON (Canada)
• Sponsoring Organization: American Gas Association, Inc., Arlington, VA (United States)
• OSTI ID: 10169137
• Report Number(s): AGA-94015629; ON: UN94015629; CNN: Project PR-225-9325; TRN: AHC29416%%57
• Resource Relation: Other Information: PBD: Nov 1993
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
03 NATURAL GAS
42 ENGINEERING
PIPELINES
WELDED JOINTS
HEAT AFFECTED ZONE
HYDROGEN EMBRITTLEMENT
CRACK PROPAGATION
PARAMETRIC ANALYSIS
TENSILE PROPERTIES
STRESS ANALYSIS
MATHEMATICAL MODELS
DATA
360103
032000
420205
MECHANICAL PROPERTIES
TRANSPORT, HANDLING, AND STORAGE
TRANSPORT AND STORAGE FACILITIES