Fighting Stress

the flaws, that’s a lot.” Instead, specialists talk about improving flaw detectors. “What impressed me in one of today’s presentations was the fact that in pipelines with many bends they installed an additional flaw detector. The sensors should be more sensitive,” the source added.

Solving the SCC Issue

Since 2000, Gazprom’s GTS uses only domestic in-line detectors produced by such companies as Spetsneftegaz, Orgenergogaz, Spektr. The development of more accurate in-line inspection tools is the first step en route to solving the problem of SCC, says Kharionovsky. “Secondly, we must improve the current repair technology at the stage of routine inspection, when the operators study the stress corrosion defects. We also must develop good technology that fights corrosion cracks,” Kharionovsky told OGE. “Thirdly”, says the scientist, “we already have a framework, and there are repair plants and sites in Kopeisk, Krasnodar and Yugorsk, which handle pipes with stress corrosion. We need to improve rejection methods and provide reliable protective coating. It’s desirable, despite the slight increase in cost, to coat the stress corrosion pipe with polypropylene to ensure a longer life-cycle.”

Talking about similar foreign experience, Kharionovsky highlights Canada’s “lateral” pipelines, where a large number of stress corrosion defects resemble the situation on the Russian pipelines from the technological viewpoint. The scientist believes that overseas repair technologies are largely the same as in Russia: “The repair methods may be the same. But, for example, they have wider range of repair methods using split couplings, that is, they use a larger number of different couplings. Polypropylene coating is used, too.”

“Most of the pipelines have been in operation for over 20 years, while more than a third have already exceeded their design lifetime of 33 years or are approaching it. Track records suggest that failures in aged pipelines are chiefly associated with corrosion damage of the pipe walls, which stems from damaged insulation coating,” says Vyalykh.

At the same time, the operators note that the service life of the polypropylene coating is usually about 10 years, meaning that over time its protective properties are completely lost in pipelines operated for 30 or more years.

Repair or Replacement?

Despite the fact that substantial work has been done in recent years to eliminate pipeline defects using in-line inspection, a number of questions remain. What SCC defects can be fixed? Is it possible to repair pipes with such defects in field conditions or must they be sent to a repairs plant? According to Kharionovsky, the adopted rejection methodology for field conditions must include a forecast on how many years a pipe will serve if the crack is remedied through repair. The conference members also proposed to create a catalogue of pipe defects, for easier decisions on maintainability.

“And yet, we can achieve success when our research centers work together with the industry,” concluded Kharionovsky. In his view, the key to successful development lies in returning to intensive work on the pipelines and running a sufficient number of full-scale tests whose numbers have dropped significantly