Abstract
In the oil and gas industry non-conformances and lack of quality control such as mix up of metallurgy and the use of non-NACE compliant material are sometimes encountered at the component fabrication or repair stage which may go unnoticed for years till a problem occurs. From a corrosion point of view, some of these non-conformances may not be detrimental. However, the presence of fabrication defects, which may open up after years of service can contribute to major failures resulting in unscheduled shutdowns, production loss, environmental contamination, as well as health and safety hazards.
This paper highlights two such cases: (1) the SOHIC failure of a non-NACE compliant T-fitting in a sour crude pipeline, and (2) the cracking of a weld joint in a crude pipeline where a section of low alloy piping was welded to the carbon steel piping. Both failures lead to unscheduled shutdowns. In both cases, during the component fabrication stage, materials were used without verification of the metallurgical status of the alloy, or the composition of the components through Positive Metal Identification (PMI). Additionally, there was a lack of proper understanding of the impact of non-conformance or quality control on the integrity of the pipelines during service.
