PHMSA Updates FAQ’s for Alternative MAOP Regulations

PHMSA has posted several updates to the list of frequently asked questions concerning the Alternative MAOP regulations found under 49 CFR 192.620. The latest revisions are posted below. To download a complete list of these FAQ’s, go to the following website: http://primis.phmsa.dot.gov/maop/docsf/faqs.pdf.

1. What is the alternative MAOP Rule?
The alternate MAOP Rule was promulgated by PHMSA to allow certain gas transmission pipelines to operate at higher pressures and pipeline stress levels than regulations previously allowed when designed and operated with more rigorous safety standards. By allowing pipelines to operate at higher pressures and stress levels, greater efficiencies and gas product throughput can be achieved (73 FR 62148).
Revised: 9/11/09

11. How will PHMSA handle Special Permit requests to allow pipeline operation at higher stress levels that were submitted prior to the issuance of the alternative MAOP Rule?
Formerly pipeline operators were allowed to submit Special Permit requests to PHMSA to request approval to operate at pressures greater than allowed by the former regulations. Operators of those pipelines must comply with the final rule in order to operate their pipelines at a higher alternative MAOP. PHMSA will examine special permits that have already been granted, as appropriate, to determine if any modifications are needed.
Revised: 9/11/09

16. Can existing pipelines that have experienced a failure indicative of materials concerns qualify for the use of a higher alternative MAOP?
49 CFR 192.620 (b) provides for the performance of a root cause analysis to determine if a failure is indicative of a systemic problem and precludes use of a higher alternative MAOP only if a failure is determined to be systematic in nature. Results of the analysis must be reported to regulators (PHMSA Regional Office or applicable state regulatory authorities).
Revised: 9/11/09

20. How is overpressure protection addressed when operation is at a higher alternative MAOP?
The alternative MAOP is higher than the upper limit of the required overpressure protection under previous regulations. 49 CFR 192.620(e) increases the overpressure protection limit to 104 percent of the MAOP, which is 83.2 percent of SMYS for a pipeline segment operating at the alternative MAOP in a Class 1 location.
Revised: 9/11/09

23. Why include conditions on plate or coil quality when operating at a higher alternative MAOP?
All steel pipe is made from either plates or coils. If these steel plates or coils are of superior quality, then the pipe will also be of superior quality. Assuring quality requires that the mill that made the plate or coil had an inspection and quality control program to limit variation and to improve the quality of its final product – the plate and/or coil. The condition simply requires that operators verify that such a program was in place at the mill.
Revised: 9/11/09

24. Why are mill test reports required for the Alternate MAOP rule?
The alternate MAOP rule allows operators to establish MAOPs higher than previously allowed by 49 CFR Part 192. One of the requirements is to have mill test reports (mechanical and chemical properties) on the steel that went into the pipe that will operate under the higher stress levels allowed by the alternate MAOP rule. This requirement was included because PHMSA needs assurance that the pipe operating at higher stress levels does not to pose a risk to the integrity of the pipeline. To provide this assurance, an operator must have documented proof of the actual yield strength, tensile strength, and chemistry properties of the steel used in the pipe.
Revised: 9/11/09

26. Does the recent advisory bulletin ADB-09-01 (Docket No. PHMSA-2009-0148 – “Potential Low and Variable Yield and Tensile Strength and Chemical Composition Properties in High Strength Line Pipe”) affect pipelines that are planned to operate in accordance with the MAOP Rule?
The advisory bulletin informs pipeline system owners and operators of the potential for high strength line pipe installed in recent pipelines may exhibit inconsistent chemical and mechanical properties. Yield strength and tensile strength properties that do not meet the line pipe specification minimums have been observed. This advisory bulletin pertains to microalloyed high strength line pipe grades, generally Grade X-70 and above. PHMSA has reviewed metallurgical testing results from several recent projects indicating pipe joints produced from plate or coil from the same heat may exhibit variable chemical and mechanical properties by as much as 15% lower than the reported strength values by the pipe manufacturer. The advisory bulletin can be obtained online here.

PHMSA expects operators of pipelines under the alternate MAOP to perform in-Line Inspections (ILI) that will identify (remove) all threats to the pipeline. The operator should plan to use a high resolution deformation tool in lieu of a geometry tool to address the threat described in the Advisory Bulletin. The deformation tool must include multi-finger sensors and have an accuracy of +/- 1% to identify expanded pipe and dents.

The results of the initial ILI must be integrated with the initial CIS and DCVG/ACVG surveys required in accordance with §192.620(d). The operator should evaluate and repair all anomalies, expanded pipe and dents in accordance with the MAOP Rule prior to increasing the pressure above the 72% SMYS MAOP to the alternative MAOP of 80% SMYS for Class 1 locations.

The results of all deformation and geometry tool run results for expanded pipe and dents should be analyzed and submitted to the PHMSA Regional Director. All pipe exhibiting an indicated diameter greater than 1.00 % (based upon pipe diameter) above the nominal pipe diameter should be noted on the report of potential deformations.

The operator should review with PHMSA Regional Director, the deformation and/or geometry tool reports. This analysis will consider pipe properties and property distributions, hydrostatic test pressures and reported test behavior, and pipe end to center variations. Based on local pressure and expected behavior, any expansion exceeding anticipated expansion by more than 1.50% may be investigated by excavation to determine actual expansion and, if necessary, to verify pipeline special permit segments yield and ultimate tensile strengths, elongation and chemistry. This guideline may be modified by PHMSA if initial verification reviews by PHMSA Regional Director show negligible integrity risk.
Revised: 9/11/09