NB 3113 Service Conditions

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cheers

Basically what NCA-2142 is trying to say is that you, as a designer, have to set up your pipe specifications to define four levels that your piping needs to withstand. NCA-2142 gives you some broad based definitions.

I asked a co-worker (who used to do US nuclear plant piping design) and the following is his "in a nutshell" explanation. He recommended looking at the NRC's NUREG-0661 for more information (which I have not done.)

Service Level A is your normal condition. It generally includes analysis for internal pressure and deadweight. A typical stress limit is S[sub]H[/sub].

Service Level B is an off-normal condition that the piping must withstand these loadings without damage requiring repair. It generally includes analysis for internal pressure, deadweight, and a operating basis earthquake. A typical stress limit is 1.2S[sub]H[/sub].

Service Level C is an upset condition where the piping may have large deformations and require repair. It generally includes analysis for internal pressure, deadweight, and a safe shutdown earthquake. In some cases, it will also include transient loads. A typical stress limit is 1.8S[sub]H[/sub].

Service Level D is a faulted condition where the piping will have gross deformation and will require repair or replacement. It generally includes analysis for internal pressure, deadweight, safe shutdown earthquake and transients. In some cases, it will also include design accident loads. A typical stress limit is 2.4S[sub]H[/sub].

As the above information was provided to me off-the-cuff and I really have not verified it, you should be very careful about taking the information as an absolute.


Patricia Lougheed

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