Exceptions to Basic Requirements

The basic practices therein may require modification to suit service conditions in some cases. In such cases, the designer may specify more stringent requirements in the engineering design, including heat treatment and hardness limitations for lesser thickness, or may specify less stringent heat treatment and hardness requirements, including none. 

When provisions less stringent than those in Table 11.13 are specified, the designer must demonstrate to the owner s satisfaction the adequacy of those provisions by comparable service experience, considering service temperature and its effects, frequency and intensity of thermal cycling, flexibility stress levels, probability of brittle failure, and other pertinent factors. In addition, appropriate tests should be conducted, including Welding Procedure Specification (WPS) qualification tests. 

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