Two refrigeration system ammonia storage vessels of this steel also showed scc in cold formed vessel heads near welds that were not postweld heat treated. This type of failure is referred to as stress corrosion cracking scc. Stress corrosion cracking international institute of. First, the part must be stressed, either from an applied force or due to residual stress usually from forming. The purpose of these guidelines is to provide ammonia refrigeration plant owners and operators. This is a widely accepted material for construction of pressure. Stress corrosion cracking in refrigeration systems request pdf. The refrigeration system contains ammonia and provides a chilling effect to. Many companies handling ammonia are cooperating by.
Cracking has been detected in ammonia storage tanks, spheres and. Small cracks grow up to become big cracks and big problems nh3. Stress corrosion cracking of linepipe steels in anhydrous. Principles and practices of mechanical integrity for industrial.
This recapitulation of experiences with stress corrosion cracking of steel in liquefied ammonia summarizes the subject over the last three decades. A company was retained by the refrigeration contractor to conduct. Stress corrosion cracking scc, mechanisms, and prevention measures. New informative appendix k emergency pressure control systems. This cracking can also occur when ammonia is intentionally added to process streams as a neutralizer by someone unaware of its potential effect on brass tubes. It is generally understood that stress corrosion cracking can occasionally affect the high pressure vessels in ammonia refrigeration systems, but the nature of the problem is often misrepresented in design codes, safety standards and textbooks and ways in which the initiation of stress corrosion can be prevented are ignored. The international institute of ammonia refrigeration makes no warranty or representation and assumes no. This type of failure is known as stress corrosion cracking, often abbreviated to scc. New informative appendix j stress corrosion cracking. Most backordered items can be rushed in from the publisher in as little as 24 hours. Avoiding caustic stress corrosion cracking of refinery equipment and piping.
Stress corrosion cracking is also a possible cause of failures at this weld location. Stress corrosion cracking of steel in liquefied ammonia. The stress corrosion cracking scc behavior of electricresistancewelded erw api grades x42, x46, x52, and x60 linepipe in liquid ammonia has been evaluated for the base metal, erw weldments, and girth weldments. Stresscorrosion cracking of steels in ammonia with. If there is evidence of cyclic fatigue, support stress, hydraulic shock, an. Carbon steel, alloy steel, and highstrength, quenched and tempered steel, when under applied or residual stress and especially when cold formed andor welded without subsequent thermal stress relief, are subject to failure by stress corrosion cracking scc in aircontaminated dry ammonia. American national standard for ansiiiar 22008, includes.
Stress corrosion cracking of steel in liquefied ammonia service a. The course will emphasize refrigerant piping and pressure vessels but. It is generally understood that stress corrosion cracking can occasionally affect the high pressure vessels in ammonia refrigeration systems, but the nature of the. Stress corrosion cracking in ammonia storage iffco. Anhydrous ammonia stress corrosion cracking scc incident. Guidelines for ammonia refrigeration plant equipment integrity. Contractor a company, organization or person who enters into a written agreement to. This report presents findings of causes for stress corrosion cracks scc and possible inspection. While it is rare, formed parts can develop fractures after they are placed in service. Ammonia stress corrosion cracking is a form of stress corrosion cracking that commonly occurs in brass tubes in cooling water service that has been contaminated with ammonia due to biological growths or other contamination. Stainless steels in ammonia production nickel institute. The contents of this report reflect the views of the contractor, who is responsible for the accuracy.