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PRCI PR-185-01128
- Refinement of Cooling Rate Prediction Methods for In-Service Welds
- Report / Survey by Pipeline Research Council International, 07/14/2003
- Publisher: PRCI
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L51942e
Edison Welding Institute
Need: Welds made onto in-service pipeline are particularly susceptible to hydrogen cracking because of the fast weld cooling rates that tend to result from the ability of the flowing contents to remove heat from the pipe wall. The most commonly used procedures for controlling the risk of hydrogen cracking rely on the use of a sufficiently high heat input level. Two methods currently exist for predicting required heat input levels for welds made onto in-service pipelines: thermal analysis computer modeling and the heat-sink capacity measurement method.
Result: The objective of this project was to refine these two complementary methods, and to investigate alternative approaches. The project was divided into three distinct tasks: further refinement of the PRCI Thermal Analysis Model for Hot Tap Welding, standardization of heat-sink capacity measurement, and investigation of alternative approaches to cooling rate prediction. The primary link between the PRCI model and the heat-sink capacity measurement method is the ability of the model to predict the heat-sink capacity of an operating pipeline. Detailed descriptions of user interface modifications required to incorporate the ability to enter the individual heating parameters of interest and have the model calculate the heating rate were developed.
Benefit: The results of this project will assist in assessing the feasibility of, and in developing and qualifying procedures for, welding onto pipelines operating at full line pressure and full flow. The use of these results will allow both economic and environmental benefits to be realized by avoiding pipeline shutdown and interruption of service.
Edison Welding Institute
Need: Welds made onto in-service pipeline are particularly susceptible to hydrogen cracking because of the fast weld cooling rates that tend to result from the ability of the flowing contents to remove heat from the pipe wall. The most commonly used procedures for controlling the risk of hydrogen cracking rely on the use of a sufficiently high heat input level. Two methods currently exist for predicting required heat input levels for welds made onto in-service pipelines: thermal analysis computer modeling and the heat-sink capacity measurement method.
Result: The objective of this project was to refine these two complementary methods, and to investigate alternative approaches. The project was divided into three distinct tasks: further refinement of the PRCI Thermal Analysis Model for Hot Tap Welding, standardization of heat-sink capacity measurement, and investigation of alternative approaches to cooling rate prediction. The primary link between the PRCI model and the heat-sink capacity measurement method is the ability of the model to predict the heat-sink capacity of an operating pipeline. Detailed descriptions of user interface modifications required to incorporate the ability to enter the individual heating parameters of interest and have the model calculate the heating rate were developed.
Benefit: The results of this project will assist in assessing the feasibility of, and in developing and qualifying procedures for, welding onto pipelines operating at full line pressure and full flow. The use of these results will allow both economic and environmental benefits to be realized by avoiding pipeline shutdown and interruption of service.
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