Issues regarding the pressure-temperature ratings of low-temperature materials for valves and flanges
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In GB/T 9124.1-2019 \"Steel pipe flanges – Part 1: PN series\", tables 93 to 104, which list the pressure-temperature ratings for flanges, why are the materials belonging to the three groups 7E0, 7E2, and 7E3 missing? Chemical Engineering Discussions
This post was last edited by ds136 on 2025-7-24 at 16:46. These two sets are used in low-temperature conditions; according to 5.2.5 (9124.1-2019), the maximum allowable operating pressure of flanges in low temperatures should not be greater than that in normal temperature conditions. In Tables 93 to 104, the normal temperature for the pressure-temperature ratings of flanges refers to the nominal pressure. These three sets are also not needed at high temperatures (above room temperature). So there’s no need to list it.
Thank you for your reply, but in refrigeration systems there are heat defrost pipes, and with alternating high and low temperatures, materials suitable for low temperatures must be used; at high temperatures, the temperature-pressure ratings need to be taken into consideration.