What is the drifference when recertification between PRV/PSV on HC and Steam valves

[Magnar]

In my company we have different maintenance concept with requirements to PRV/PSV on HC compare to steam. All in all I think a spring operated valve have more or less the same requirements independent of what media. To reduce the scope of discussions, my question is applicable for valves specified in API 526.
All PRV/PSV. I'm familiar with the acceptance criteria and difference in ASME SEC I and VIII, but are there other criteria? Can I specify +- 3% as acceptance criteria for all types of valves?
Maintenance in one way or another what we do will be more or less as API RP576.
Leakage test according to API 527 which accept a small bubble leakage. Is the requirement for leakage 0 in steam valves? 0 on steam or gas (N" or air)?

 

[The Obturator]

Your question would be best posted in the safety/relief valve forum.

First of all, ASME I safety valves do not come under API-526.

ASME I safety valves are primarily steam boiler valves. The required characteristics of opening/closing etc., are more stringent.

Although API-527 has a section for testing on steam, this is for process (non boiler) valves. ASME I safety valves are required to have a closer gap between operating and set pressure (typically 3 to 5%) than process (API-526/ASME VIII, XIII) valves which typically have a 10% gap or differential and hence are leak tested at 90% set pressure.

ASME I valves should be tested on steam and display no leakage, at a predetermined test pressure in ASME I. However, this mainly not always possible and in-situ testing is often conducted.

ASME I (2023) Paragraph PG-73.5.3 explains the minimum leak testing expected of the manufacturer. This should be followed following any maintenance. Other criteria such as blowdown (valve closing), ring settings must also be observed.

In summary, ASME I steam service safety valves must follow definitive tests which are different to API-526/ASME VIII, XIII Pressure-relief Valves.