Safety relief valves: The unsung hero in your plant
If a tank’s safety relief valve fails, an accident is sure to happen. Learn the important role it plans and why you can’t ignore it.
ASME Safety Relief Valves.
A possibly dry topic to be sure, but it's one piece of equipment in your facility that should not be installed and forgotten.
Well, a picture really is worth a thousand words.
Tank failure during a pressure test
Relief valves are the last line of defense against accidents like this one.
They’re an important part of your facility’s safety equipment and they can prevent lost revenue, downtime AND – most importantly – injury to people.
There are three main things you should do to keep the ASME safety relief valve ready to do its job should it become necessary.
1. Periodically test the valve
The National Board of Boiler and Pressure Vessel Inspectors is one of the governing bodies for the testing and/or repair of ASME Safety Relief Valves.
Within their Code, they recommend a written procedure be created for testing these type valves.
We recommend that the test is performed by an authorized testing facility. A list of these facilities can be found on the National Board’s website.
You can also find other companies that perform this service by typing "relief valve repair" into your favorite internet search engine.
Pressure relief valve testing standards
Based on the National Board Code, which bases their inspection intervals on what type of service the valve is used for, the following intervals are suggested:
- Steam Service: Annually
- Air and Clean Dry Gas Service: Every 3 years
- Propane or Refrigerant: Every 5 years
- All others: Per inspection history
- For valves installed for liquid service, our experience suggests that these should be checked annually.
2. Properly size the valve's outlet piping
It should be at least as large in diameter as the valve's outlet.
If not, the piping could form back-pressure on the valve's outlet, causing the valve not to open properly.
Also, keep in mind that this piping should be oriented so that no liquid relieved through this piping can flow back and rest on the ASME safety relief valve's outlet port.
Doing so could allow corrosion to occur within the valve's internal components and prevent the valve from opening.
3. Set the maximum operating pressure
Set your tanks’ maximum operating pressure to at least 10% below the valve's set pressure.
This will prevent the valve from “creeping” open.
The ASME relief valves are set to fully open at its “set” pressure but will begin to partially open before then – normally at 10% below its set pressure.
If your valve is allowed to do this, trash and/or corrosion can set in over time which could prevent the valve from either closing completely or from fully opening, either of which is not a favorable solution.
Stay on top of your ASME safety relief valve
Pressure relief valves are an often neglected and overlooked safety feature in your facility.
Take some time to inspect them.
You never know when they may be called on to save your life.