(BTW There is a separate forum for Safety Relief Valves).
Your question will for sure generate many comments. Lets start.
You state that your PRVs have been certified and this lasts for one year.
Is this in addition to the testing done at manufacturer?
Is this what the organisation certifying have said?
Are the valves actually installed?
Typically, if the PRV's are not installed, they should be kept indoors and away from moisture laden environment. A 12 to 18 month storage time is a typical time. Ideally, any testing should be done as close to installation as possible.
What is the manufacturer recommending? Your guarantee may be timed from date of shipment or installing, whichever comes first, and provided that no 3rd party has broken the PRV seals. In any case, it is you the end user that is bearing ultimate responsibility.
Going forward, it is wise to have a documented procedure and maintenance/service schedule for PRV's. Users establish these over time dependant on the service applications, the number of times the PRV's have opened, dirty or clean service etc. etc. You may find that your plant insurance requires this. At some point, someone will come to sign off the integrity and safety of the installation.
You will also find that most PRV's are based on USA API and ASME codes and standards. These give a good idea of what is required;-
API-576 - Inspection of Pressure Relieving Devices
NBIC (National Board Inspection Code) - Part 4 Pressure Relieving Devices
(In the USA any overhaul/repair etc., requires the organisation doing the work to be certified)
In UK there is the Pressure System Safety Regulations PSSR-2000 - Guidelines issued by the HSE but these do not focus on PRV's just overall cautions.
Hope that helps you somewhat.
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
