Full encirclement repair sleeves with fillet-welded ends are often used as permanent repairs on pipelines to reinforce and develop pressure retaining repairs on areas with defects, such as cracks, dents, or corrosion. In-service failures have occurred at sleeves as a result of defects associated with the sleeve welds, such as hydrogen-induced cracks, undercut at the fillet welds and inadequate weld size.
After completion of a sleeve fillet weld, it is currently common practice to carry out a visual inspection and magnetic particle inspection (MPI) to determine whether weld toe defects exist. With continuing advances in nondestructive examination (NDE) technologies, the ability to not only inspect for toe and root flaws but also to size these cracks and inspect and size root flaws is becoming a reality.
Previously, there were no reliable methods to carry out a quantitative fitness for service assessment for a sleeve fillet weld with a weld fault because:
- The stresses at the sleeve end fillet weld roots and toes are not easily determined
- Stress intensity factor solutions are not available for the sleeve fillet weld geometry
- Current inspection procedures cannot effectively define the size of weld defects
BMT Canada Limited (BMT) completed a PRCI project that developed stress intensity factor solutions for a range of sleeve end fillet weld cracking scenarios which can be used in engineering critical assessment procedures for sleeve repairs on all grades of pipelines.
Module/Application
- Overview of SEFW SIF Equations
- Software Workflow
- Using the Results
- Software Validation
- Sensitivity Studies
References
- In the Matter of an Accident on 19 February 1985 near Camrose, Alberta on the Pipeline System of Interprovincial Pipe Line ”, National Energy Board, Canada, 1986.
- F. Cross and C.A. Robertson, “Northeast U.S. products line upgraded after major line break”, Oil and Gas Journal, February 15 1988, Vol. 86, No. 7, pp 35 40.
- “Development of Sleeve End Fillet Weld Fitness for Service Assessment Tools”, PRCI Contract Num- ber PR-214-114504, April 22, 2016.
- API 579-2/ASME FFS-1 “Fitness-for-Service, American Petroleum Institute and the American Soci- ety of Mechanical Engineers, June 2007.
FAQ
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PRCI Hot Tap results not showing on reports
This can be attributed to one of the following reasons: Check Out
- Calculation not executed
- Engine Crash
- Update made to input data
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PRCI Hot Tap Hardness value for Multipass Welds
For multiple pass welds the original hardness gets tempered so the hardness is reduced. The current model predicts a single pass weld so it is a worse case scenario since no tempering has occurred. Check Out
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PRCI Hot Tap Hardness Model
The PRCI hardness model is the predicted Vickers hardness of the weld HAZ using a 10-kg load. The hardness curve is based on the Yurioka equations which are based on Vickers hardness with a 10-kg load. Check Out
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How can we account for Sleeve/Fitting material?
The current model (V 4.2.2) doesnt allow predicting hardness of two different materials. The inability to predict hardness of two different materials is an issue with the current model. Check Out
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Does the model consider the composition entered in the “Max Hardness” area for both the pipe and the sleeve?
The model does not currently allow for modeling two materials however a current project looking to update the model will allow this option (Hot Tap V5 will have this feature). Check Out
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Validation checks enforce in PRCI Hot Tap Model
Below is a list of all input data entry validation checks that are integrated in the PRCI Hot Tap model. The model runs all the below input data range checks as part of the input data validation loop before the case model is executed. Check Out
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Clarification on Heat input and Arc energy in Hot Tap Model
The reported value used for “Enter Heat Input” entry is the arc energy even though it is referred to as heat input. This has always been an issue since all the historical work on in-service welding always referred to arc energy as heat input and that has continued with this model. How the model addresses different welding process is by the arc efficiency option selection. Check Out