B31.3-2004, 302.2.6 (a) gives the limit of calculated stresses due to occasional loads. It does not define the corresponding duration permited for the occasional load.

Paragraph 302.2.4 gives the allowances for occasional variations for pressure and/or temperature for pressure design.

Is Paragraph 302.2.4 (f) (2) interpreted to apply to occasional loads or have I missed elsewhere where the occasional load duration is defined?

The application is for the evaluation of safety relief valve loads.

I think occasional loads are defined in hours per functioning hours of the system, and is stated in the code. Somehow tries to differentiate the occasional from the repetitive loads. The duration itself for the phenomena varies in nature. A relief valve, water hammer or a seismic load durations are different by nature, and that can not be limited by the codes.

Regards,

The comittee has not defined the occasional in this usage (302.2.6).

The infamous 302.2.4 is the most mangled an misinterpted part of the code it pertains to pressure design only.


Send us an inquiry I'm not sure what we would say.

Imho in a properly designed and operated system a relief device would be occasional according to 302.3.6

Thank you both for reponding.

I'm wondering if it can be stated at what duration of operation of a relief discharge does lack of responsiveness from operations personnel result in a load that is no longer "occasional".

Sending an inquiry appears appropriate.

our next meeting is coming up March 27th thru 29th....

Agreement on an occasional time limit will be difficult... my own opinion this instant is to leave it as is undefined and up to the designer to impose a more stringent limit if they feel it is required....

the comittee may give you something, maybe nothing, or maybe you will get something you won't like good luck, prepare the inquiry per the recomendations in the back of the code and email it to Noel Lobo.... get her email adress off the ASME web site....