By Davi Sampaio Correia
Fitness for service (FFS) encompasses various methodologies to evaluate cracks in equipment. These methodologies offer guidance in evaluating defects and deciding the safe course of action. This article will explore FFS methodologies and learn how they can be used in valves.
Badak LNG is one of the largest natural gas liquefaction plants in the world, located in Bontang, Indonesia. There are eight process trains capable of producing 22.5 million metric tons per annum of LNG using steam turbines for driving power generation and refrigeration compressors.
On January 27, 2011, a routine inspection detected several cracks on a 24” #600 gate valve located on a steam line. There was no replacement valve available and depressurizing the adjacent piping would require shutting down a sizable portion of the plant. Pressure vessels for the process industry, including valves, are designed according to well established ASME and API codes and standards. In truth, these standards provide rules not only for design, but also for fabrication, inspection, and testing of new equipment. The keyword here is new. Once flaws and damages start to appear, the original design documents offer little to no guid-ance on how to proceed.
