Pipeline Hydro Test Pressure Determination
This increase in d/t ratio reduces the ligament between the adjoining defects. This effectively reduces the stress required to propagate the discontinuity. The other factor affecting the pressure reversal is the damage to the Crack Tip Opening (CTO). The CTO is subject to some compressive force leading the crack tip to force-close during the initial test. On subsequent pressurization to significantly lower pressure this “force-close” tip starts to open-up and facilitates the growth of the crack. Hence, if such a pressure cycle is part of the design, then the point of pressure reversal should be considered.
- It may also be noted that there is a modest reduction in puncture resistance with both increasing SMYS and increasing design factor. Note that the maximum design factor is, in some instances, constrained by practical limits on D/t.
- In any event, it should be noted that only a small proportion of large excavators are capable of generating a puncture force exceeding 300 kN and that the reductions in puncture resistance noted would have to be assessed for the integrated approaches to the management of mechanical damage threats.
Ramesh Singh is Senior Principal Engineer (Materials, Welding and Corrosion) for Gulf Interstate Engineering, 16010 Barkers Point Lane, Houston, Texas 77079-9000, 713-850-3687, Fax: 713-850-3554, E-mail: firstname.lastname@example.org.
49 CFR Part 192 Part-V, “Pipeline Safety: Standards for increasing the Maximum Allowable Operating Pressure for Gas Transmission Pipelines,” Final Rule issued Dec. 17, 2008.
Anonymous, 1996. National Energy Board Report on the Public Inquiry Concerning Stress Corrosion Cracking on Canadian Oil and Gas Pipelines.
Anonymous, 2005. 6th Report of the European Gas Pipeline Incident Data Group,” EGIG 05R.0002. See EGIG website: http://www.EGIG.nl.
ASME B 31.8 Gas transmission and Distribution Piping system.
Chen, Q., Fuglem, M., Stephens, M., and Zhou, J., 2001. “Reliability-Based Design for Mechanical Damage,” 13th Biennial PRCI/EPRG Joint Technical Meeting, Paper 1.
Driver, R.G. and Zimmerman, T.J.E., 1998. “A Limit States Approach to the Design of Pipelines for Mechanical Damage,” Proc. 17th OMAE Conference, Paper OMAE98-1017.
Duffy, A.R., McClure, G.M., Maxey, W.A. and Atterbury, T.J., 1968. “Feasibility of Basing Natural Gas Pipeline Operating Pressure on Hydrostatic Test Pressure,” PRC/AGA NG-18 Report L30050.
Eiber, R.J., Hopkins, P., McLamb, M., and Abes, J., 2004. “Operation of New Design and/or Conversion of Existing Gas Pipelines to 80% SMYS Operating Stress,” GRI Report GRI-04-0152.
EN 10160 - 1999, Ultrasonic testing of steel flat product of thickness equal or greater than 6 mm (reflection method).
ISO 12094 - 1994 Welded steel tubes for pressure purposes-Ultrasonic testing for the detection of laminar imperfections in strip/plate used in the manufacture of welded tubes.
Rothwell, Brian, Staff Engineer, TransCanada PipeLines, “History and Operating experience of design factors above 0.72 in Canadian gas transmission pipelines.”
Texas Eastern, Technological Review of Hydrostatic Testing. Dec. 04, 1985.
- Coatings, pipe joint
- Compressor components
- Contractor, pipeline
- Contractor, river crossing/ directional drilling
- Directional drilling rigs, large
- Fittings, valves: plastic
- Meters, flow
- Pigs, cleaning
- Pigs, intelligent
- Pigs, scraper/ sphere launchers/ traps
- Scada systems
- Ultrasonic inspection
- Vacuum excavators/ potholing
- Valves, ball
- Welding systems, automatic