Development of Simplified Weld Cooling Rate Models for In-Service Gas Pipelines

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Abstract:

Deliverables: 164 Page Research Study & DOS-based version of Thermal Analysis Models with Users Manual

Need: For some time, the gas transmission industry has been faced with the problem of standardizing guidelines for welding on "in-service" pipelines. Such guidelines would permit the welding engineer to safely and accurately assess field operations either prior to or during welding.

Result: Edison Welding Institute (EWI) and Battelle Memorial Institute (Battelle) separately developed models for predicting hot-tap/repair welding conditions for "in-service" pipelines. EWI researchers developed a field-adaptable technique for "in-service" welding of pipelines that requires actual field measurement of the pipeline's heat-sink capacity. The measured value, in conjunction with extensive experimental field data allows the assessment of acceptable welding procedures to avoid underbead cracking. Battelle researchers devised a different approach to the problem of "in-service" welding. Thermal-analysis computer models were devised that determine acceptable welding parameters to avoid cracking and burnthrough based on heat-transfer equations. Both of the original EWI and Battelle methods were validated through extensive field trials. The result of this work by EWI, Battelle and Kiefner & Associates integrated these two (2) methods into a single "standard" approach suitable for predicting safe welding procedures for welds made on "in-service" pipelines. This report describes the field-adaptable technique, the thermal-analysis models and the validating experimental data. This report further delineates how the EWI and Battelle hot-tap methods were integrated into a new approach to welding on "in-service" pipelines. A PC-based version of the thermal-analysis models and a User's Manual are provided for use in selecting welding variables. Also contained in this report are "heat-input selection curves", for use with the field-adaptable, heat0-sink-measurement technique.

Benefit: This research study, report and software provides an acceptable industry standard that allows the welding engineer to first predict anticipated weld cooling times/rates using the thermal-analysis models, and then, to verify such predictions with the heat-sink-capacity technique before pursuing actual field operations. Use of this welding standard improves the safety of "in-service" welding operations, enhances the efficiency and productivity of operations while minimizing follow-on maintenance and repairs.

Price: $1,195.00

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