INTERNAL DIAGNOSIS OF STRESS CORROSION DAMAGE IN MAJOR GAS PIPELINES

摘要

Russia operates a highly developed network of major gas pipelines of total length over 150 thousand km, whose technical characteristics have no analogs elsewhere in the world. Pipelines with large diameters (1020-1420 mm) constitute over 60% of the total. The enormous energy present in these pipelines requires special attention to safety such as preventing emergencies and failures. In the mid-1990s, in spite of the maintenance of the volumes of capital repairs, there was a tendency for failures to increase because of the progressive ageing in the pipeline system. Increasingly, the gas pipes show stress corrosion cracking (SCC) in the form of superficial groups of cracks and individual ones oriented mainly along the pipe axis. Failures due to stress corrosion cracking constitute a considerable fraction of the total (Fig. 1). Stress corrosion cracking is the most researched form of damage amongst the causes and mechanisms of major pipeline failure. The hazard from stress corrosion cracking is that these cracks are difficult to detect by the use of diagnostic facilities. Here we describe the manufacture and field testing of a within-pipe flaw detector representing the first in Russian and world practice for the diagnosis of stress corrosion cracking in pipelines. An important step concerned the identification of the main distinctive features of stress corrosion cracking.