STANDARDS
Figure 4: While ASME Special Class valves have the same pressure rating as Standard Class valves at ambient temperatures, they have elevated pressure ratings at higher temperatures.
Figure 5: Some valves are inherently overdesigned and can be certified to a higher Intermediate Class. The maximum pressure rating at elevated temperature may not significantly exceed a Special Class valve, but the pressure rating at ambient temperatures will be much improved.
temperatures versus 3750 PSI for the Standard and Special Class CL1500 valves. An Intermediate Class valve does not require any additional NDE testing, but it is only offered in a limited range of weld end valve body styles. It does require the Standard Class pressure rating to be removed and replaced with a new pressure rating, so there is some additional cost, though less than the NDE testing and certification of a Special Class valve. Similar to the Special Class valve, an Intermediate Class alternative may present significant savings if it avoids having to move to the next pressure class rating.
ASME Intermediate Special Class pressure ratings
A third ASME approved pressure rating is the Intermediate Special Class. Essentially, this rating is a combination of the Special Class and Intermediate Class. Certain weld end bodies can be re-rated to an Intermediate Class, NDE
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