PHMSA held a public meeting on Reconsideration of Maximum Allowable Operating Pressure for Class Locations on March 21, 2006. The current gas pipeline regulations contain design factors that are used to determine the Maximum Allowable Operating Pressure (MAOP) of each pipeline segment. These design factors vary with the Class Location of the pipeline, which is determined by the population around the pipeline. The highest design factor currently allowed by the PHMSA regulations is 0.72 (except for a few grandfathered pipelines). Other nations allow pipeline operators to use design factors up to 0.80, with good operating experience.
The Office of Pipeline Safety is willing to consider granting waivers to allow pipeline operators in the U.S. to use higher safety factors, as long as certain design and testing criteria are met. This will allow pipeline operators to move more gas through existing pipelines, and to design future pipelines more cost-effectively. The presentations at the meeting covered the following topics:
- The economics of increasing design factors are favorable.
- Some pipelines already operate at higher design factors without any additional problems.
- Pipeline risk is influenced by many variables, not just the design factor.
- Modern design, construction, and inspection techniques can effectively offset the risk of a higher design factor.
OPS intends to evaluate each request to operate with a higher design factor on its own merits, and does not intend to issue blanket criteria that will apply to all pipelines. Each operator will be required to conduct detailed engineering evaluations of each affected pipeline segment to justify the use of a higher design factor.