ASME B31.3 302.2.4 - Pressure / Temperature Variations in Piping
ASME B31.3 302.2.4 - Pressure / Temperature Variations in Piping
(OP)
I have a question involving ASME B31.3 302.2.4 Allowances for Pressure and Temperature Variations. Does this portion of the code allow for pressure variations in components such as valves? I have a piping system in which in the worst case the pressure may temporarily spike above design and allowable pressure-temperature rating of the valve set forth by ASME B16.34. There is no relieve valve or rupture disc in the system so I can not take into account the allowable 10% given by B16.34. Can I account for this variance in a valve or am I limited to B16.34?
In my case I have a Class 900 Valve at 300F which is rated for 1680psig. Pressure could spike to 1748 psig. Is this allowed by B16.34 without any type of Relieve device in place (2.5.1 Safety Valves, Relief Valves, or Rupture Disc)?
In my case I have a Class 900 Valve at 300F which is rated for 1680psig. Pressure could spike to 1748 psig. Is this allowed by B16.34 without any type of Relieve device in place (2.5.1 Safety Valves, Relief Valves, or Rupture Disc)?





RE: ASME B31.3 302.2.4 - Pressure / Temperature Variations in Piping
For this level of variance, what I think you need to do is compile a report giving all the relevant details, codes, wording etc and show that in piping terms you remain inside the requirements (note 302.2.4.d) - max 1000 variances over 25 - 30 years?? ) explaining how and why the pressure spike cannot exceed your stated value and noting all the normal 10% / 20% clauses.
Then it is up to you to conclude whether this is satisfactory and submit it to the owner or someone further up the line for review / approval.
My concern would primarily be how you can calculate such a precise overpressure (and not one say 100 psig higher) and why you can't put in some sort of relief valve. This would need to be explained very well in your report / technical note.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: ASME B31.3 302.2.4 - Pressure / Temperature Variations in Piping
Thanks again for your help.
RE: ASME B31.3 302.2.4 - Pressure / Temperature Variations in Piping
It sounds like you have all the data available, just gather it together and write it down.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: ASME B31.3 302.2.4 - Pressure / Temperature Variations in Piping
MJCronin
Sr. Process Engineer