STRESS-CORROSION CRACKING IN AMMONIA HANDLING SYSTEMS AND ITS PREVENTION.

With an increasing number of fertilizer plants and with versatile uses of liquid ammonia as chemical and fertilizer, ammonia handling systems in plants and outdoor transportation units have multiplied. Pipelines, storage vessels or spheres, valves, cylindrical tanks, tank cars and agricultural ammonia applicators are some of such equipment or systems which handle liquid and vapor ammonia under pressure at low or ambient temperatures. In the recent past, a number of failures were encountered or cracks in such systems were detected which may have led to annoying or disastrous failures. This prompted scientists and engineers to investigate further to establish the reasons and suggest remedial measures. This paper aims at analyzing the mechanics of the failure (which had been established as stress corrosion cracking) and proposing a recommended practice for reliable and fail-safe design of ammonia handling systems and equipment.