Interpretation Response #PI-15-0004
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
September 28, 2015
Mr. Rick Noecker
PHMSA Filing Coordinator
#19025, 237-4th Ave SW
Calgary, Alberta T2P OH6, Canada
Ref. No. PI-15-0004
Dear Mr. Noecker:
In a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA) dated April 30, 2015, you requested an interpretation on 49 CFR 192.112(b)(3) and 192.112(b)(2)(iii) with respect to crack arrestor spacing for gas transmission lines.
You stated that you performed fracture control calculations in accordance with § 192.112(b)(1) and found that the fracture arrest requirements of § 192.112(b )(2)(iii) cannot be intrinsically obtained with modern X-80 line pipe for an anticipated 2,075 psi design pressure, 42" diameter gas transmission line. You plan to utilize an alternative maximum allowable operating pressure design with crack arrestor spacing of 8 joints to meet the requirements of §192.112(b)(3). You are seeking guidance regarding fracture control crack arrestor requirements under 49 CFR Part 192.112(b). Specifically, you asked how the § 192.112(b)(2)(iii) requirement is applied with the use of mechanical crack arrestors since every crack arrestor is expected to arrest a running ductile fracture, and you stated that there is no guidance on this in industry consensus standards.
Section 192.112(b) requires the remediation of potential pipe crack initiation, propagation, and arrest of fractures to be based upon the full range of gas compositions, operating pressures, operating temperatures, pipe grades, and maximum operating stresses including maximum pressures and minimum temperatures for shut-in conditions that the pipeline will experience during its operating life. The fracture control described in § 192.112(b) limits the maximum fracture length to 8 pipe joints with a 99 percent probability of arrest through several possible methods an operator may select, which may include higher pipe toughness, heavier walled pipe, crack arrestors (either mechanical or composite) or a combination of these methods.
Therefore, it is your responsibility to make sure that the methods chosen are appropriate to the relevant operating factors and § 192.112 requirements are met. I hope that this information is helpful to you. If we can be of further assistance, please contact Tewabe Asebe of my staff at 202-366-5523.
John A. Gale
Director, Office of Standards
|§ 192.112||Additional design requirements for steel pipe using alternative maximum allowable operating pressure|