I’m operating close to the set point on my valve. How can I keep it from simmering or lifting?
In general, the operating gap will vary depending on the system and valve type. Most pressure relief valves can be operated at up to 90% of the set point. Some metal-seated valves may get up to 94%, and some soft-seated valves over 101 psi can handle operating pressures up to 95% (for example, the Consolidated 1900 series with a soft seat can handle this higher pressure).
If you exceed those thresholds, the valve will simmer. This can damage the valve and will more than likely lead to leakage and system downtime. Here are three things you can do to reduce simmer on your valves.
- LOWER YOUR OPERATING PRESSURE
Many companies operate valves at higher pressures because they want to increase production. However, this often lead to the exact opposite result.
Here’s an example. Imagine a valve that opens at the tag pressure and has a 7% to 10% blowdown. That means the valve would blowdown to 90% of tag pressure. In other words, it would hold tight to 90%. If you were to operate that valve at 91% or 92%, you would push the valve into simmer and possibly actuate the valve with very little system fluctuation. This would more than likely cause valve leakage and valve damage, and increase your downtime.
Alternatively, if you were to operate the valve at 90%, rather than 91% or 92%, you would reduce the likelihood of pushing the valve into simmer or actuating the valve. This would, in turn, reduce the chances of valve leakage and damage, and decrease your downtime.
In other words, reducing your operating pressure can actually increase production, not reduce it.
- USE A PILOT-OPERATED RELIEF VALVE
In some situations, switching to a pilot-operated relief valve can allow you to operate at 95% to 98% of the set point.
- SWITCH TO A SOFT-SEATED VALVE
Particularly in areas with high vibration, a soft-seated valve will allow you to operate the valve at a higher pressure.