Common Causes of Historical Failures in High Pressure Tubes

LUIS JOSE OTEGUI; P. FAZZINI; P. BARCIA; M. J. SCHMIDT

Houston Texas, USA

Congreso; Technology Transfer Workshop VI; 2005

Society of Plastics Industry

The causes and mechanisms of damage that caused the propagation of cracks in ten curved tubes of the polymerization reactor R5600 were analyzed. Chemical, tensile, impact and hardness tests, fractographic, metallographic and residual stress analysis were carried out on samples from five of the failed tubes.All previous failures initiated in the OD, but cracks in the original curve 57 initiated in pre existing cracks in the inner surface of the tube, while cracks in its replacement began in the mid thickness of the tube wall. All failures are characterized by intergranular and branched cracks, for the most part circumferential. Those initiated in the OD have been identified with a stress corrosion cracking (SCC) mechanism, due to chemistry of the cooling water.