The ASME Codes address the needs of industry and the public for the construction of safe equipment for pressure containment. The two basic philosophies underlying the requirements of the ASME VIII sections are “rules based” design versus “design by analysis”.
Code contributors have written extensively on the need for Code users to apply common sense when using the Code. This message is often lost in the confusion when atypical mechanical design details have been intentionally or inadvertently used. Those atypical design details that can be identified during the review process can be easily resolved; details that are discovered after construction completion and, worse yet, just prior to operation can be devastating to a project. The Code places emphasis on education, experience and the use of engineering judgment but, these can never be used to overrule mandatory requirements or specific prohibitions of the Code.
A specific incident is reviewed wherein the regulatory authority of the jurisdiction intervened and de-registered a vessel design due to Code non-compliance. Although the deficient detail was thought to be better, based on consideration of engineering principles, than the detail strictly meeting Code requirements, the as-constructed detail was rejected by the regulatory authority. Extensive field rework ensued to modify the detail to conform to Code, and of course the costs were very high. This paper reviews the engineering issues, illustrates the motivation for the Code requirements, and serves as a reminder to Code users to be vigilant in the details of Code construction.
