MAOP Addressed At Mears Seminar

By Alan Eastman, Mears Group | January 2012, Vol. 67 No. 1

PHMSA says records must be reliable, verifiable and traceable. Historically, operators have relied on pressure testing to validate the required operating margin of safety. This includes mill and field testing, where standards have varied over the years. Field testing has ranged from MAOP to >90 percent SMYS. Some pipelines built prior to the 1960s, may have only received a “leak test” at MAOP.

There are numerous other factors affecting MAOP some of which are time dependent. These include external, internal corrosion and stress corrosion cracking. Non-time dependent factors are manufacturing defects, fabrication and construction defects, equipment related defects, 3rd party or mechanical damage, incorrect operations and weather or outside force related events. Considering all factors, operators have options ranging from replacing the line, to re-pressure testing or institute an ILI or DA program.

The key is to develop a strategy going forward to know and maintain your margin of safety, which is based on recorded and verifiable data. Based on numerous factors this could involve anything from replacing the line, to re-pressure test, institute an ILI or DA program.

Tethered pipeline inspection

Mears announced a working alliance with Microline to offer tethered ILI. The Microline Group consists of six companies including: Microline: NDT Research & Development; Inline Devices: ILI Technology & Services; IonEarth: SBD Satellite Communications.

Their technology came from the oilfield, developing tools to inspect drill pipe and casing. Technology exists for lines two to 32-inches. Tethered systems were developed for lines that are considered unpiggable - shorter line segments or lines without pig launchers and receivers. This can include oil and gas production lines, gas storage and distribution lines, airport fuel lines and other product lines, power generation and water process lines, refinery piping, river crossings, cased crossing in HCA areas. Lengths can go from hundreds of feet to 20,000 feet under the right conditions. The limiting factor is dynamic friction affecting the tool and tether.