New MAOP Leeway Pretty Narrow

The U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration (PHMSA) finalized new rules allowing transmission companies to operate pipeline segments in Class 1 locations at 80 percent of specified minimum yield strength (SMYS) of the steel.

But what PHMSA calls “rigorous” requirements will kill the attractiveness of the new leeway for almost all of the 320,000 miles of interstate pipeline in the U.S. Terry Boss, senior vice president at INGAA, says the association will file a “petition for reconsideration” protesting two specific areas in the final rule.

PHMSA’s own estimate forecasts that only 3,500 miles of existing pipeline will be uprated to 80 percent from the current cap of 72 percent of SMYS. The operating pressures in more populated Class 2 and Class 3 locations are limited to 60 and 50 percent of SMYS, respectively. They, too, can be increased to 67 and 56 percent of SMYS, respectively. Since 1990, the American Society of Mechanical Engineers has had in its B31.8 Code that pipelines could operate safely at stress levels up to 80 percent of SMYS.

In the final rule published on Oct. 17, PHMSA said, “Many pipeline operators are expected to find the cost of using the alternative maximum allowable operating pressure (MAOP) to be too high. For instance, fitting and pressure vessel replacement costs may prevent some pipeline operators from converting to a higher MAOP. Additionally, the costs associated with converting nonpiggable lines are expected to be prohibitive.” PHMSA estimates total costs will be between $239 billion and $165 billion over 20 years, depending on the rate of inflation. Benefits from lower fuel and capital costs would be between $1.5 trillion and $1.1 trillion.

PHMSA has already given a number of major pipelines approval to operate at 80 percent of SMYS under special permits. Now any pipeline can self certify that it meets the PHMSA safety requirements and uprate its segments on its own, subject to post uprating certification either by PHMSA or the state agency.

But there is probably not going to be much of a rush to take advantage of the new MAOP ceiling. According to Boss, the two biggest shortcomings in the final rule have to do with construction specifications for new steel pipelines and the time lines for fixing anomalies which are discovered after in line inspection of existing pipeline. With regard to the latter, PHMSA in the final rule sets two categories of anomalies: the first having to be repaired immediately, the second within one year. Anomalies are sorted into the two categories based on a “conservative” view of their risk based on a pig inspection. “We think the time frames are unduly conservative, and don’t have a good technical basis,” says Boss.

PHMSA has already used those conservative criteria in Corrective Action Orders (CAO), the most recent one issued to Transco. In that case, a leak near Appomattox, VA, on Sept. 14, 2008, resulted in an explosion which destroyed two homes and caused multiple injuries. The CAO PHMSA issued to Williams’ Transco unit listed five pages of exacting requirements that Transco would have to meet for a section of its Gulf of Mexico to New York pipeline running through Virginia. Those have to be met immediately, and were imposed without prior notice or a hearing.

PHMSA seems intent, according to Boss, on applying those same type of exacting anomaly repair criteria not just to CAOs and pipelines uprating under the new MAOP rule, but to all pipelines operating in high consequence areas. That was the direction PHMSA indicated it was heading at a workshop it held on Oct. 22.

The centerpiece of the PHMSA workshop was a report by Advantica, a consulting company, which looked at the standard assessment methods used by the pipeline industry. Advantica concluded that failure predictions on pipe with real corrosion defects were shown to be conservative using the ASME B31G, Modified ASME B31G and RSTRENG methods. Failure predictions were, in the argot of the report, “non conservative” where defects were greater than 40 percent of the pipe wall and in line pipe of grade X52 and above.