Dear All,
we are purchasing a two-phase (HC gas / condensate) relief valve for which all suppliers came up with the PSV's not compliant with API 526 standard. The client specified this compliance in their requisition form, however. The non-compliance is related to the maximum set pressure used...
Usually, the spring materials are changed due to corrosion issues, so it's best to check with your materials engineer. You can also check API 526 tables, which provide some guidance on normal set of spring materials for various valves.