stevo,
I assume that the quoted class 800# should be a missprint, either class 600# or 900#, in accordance with API 6D. Please find below an "extract" from the API6D, ed. April 2008, Clause 7.2:
"Pressure-temperature ratings for class-rated valves shall be in accordance with the applicable rating table for the appropriate material group in ASME B16.34.
Pressure-temperature ratings for PN-rated valves shall be in accordance with the applicable rating table for the appropriate material group in EN 1092-1.
If intermediate design pressures and temperatures are specified by the purchaser, the pressure-temperature rating shall be determined by linear interpolation.
Pressure-temperature ratings for valves made from materials not covered by ASME B16.34 and EN 1092-1 shall be determined from the material properties in accordance with the applicable design standard."
Since the 1975 psi is exceeding the class 600# alltogether, then the temperature rating for 1975 psi in class 900# would be some 235-236 F, group material 1.1, as per ASME B16.34.
cheers,
gr2vessels
Class 800 exists in the ASME B16.34 notes:
(1) Class 800 is not a tabulated ASME B16.34 designation. It is an intermediate class that is widely used for socket welding and threaded end valves.
According to the current Vogt catalogue the rating is 1975 psig @ 100F for a Class 800 Forged A 105 Globe Valve.
Here is there statement on pressure temperature ratings and a link to the current catalogue.
2.5 Pressure/Temperature Rating
Proper selection of the pressure/temperature rating of the valve shall meet service requirements. If the valve application involves temperatures above 100°F (38°C), then the valve pressure rating at the service temperature must be verified to meet the requirements of the application. If system testing will subject the valve to a pressure in excess of its working pressure rating, then the intended testing pressure and a statement explaining whether the
test pressure is through the opened valve or a differential across the closed valve, should be included in the purchase
specification.
Source Reference for Vogt valves pressure/temperature ratings ASME B16.34 Valves, Flanged, Threaded, and Welded End VVACT0000, Vogt Catalog.
Vogt catalogue page 112 for pressure temperature ratings.
