Pressure relief valves (PRVs) are a critical part of many industries, providing overpressure protection by releasing excess process media when needed. The challenge, however, is that PRVs often include bellows, which can be prone to damage. This can lead to significant performance problems and environmental leakage. My article in the December 2023 edition of Hydrocarbon Engineering, titled “,” talks about a new PRV design that minimizes bellows damage’s negative effects and technology for detecting leaks right away.
Bellows protect against backpressure
A PRV uses a calibrated spring to keep a disc against the valve inlet nozzle until the process media pressure becomes great enough to lift the disc, venting excess media. However, backpressure can cause issues by affecting the PRV’s setpoint. To solve this problem, many PRVs include bellows installed above the disc to shield it from backpressure. But these metal bellows are prone to damage, which can lead to media leakage through the bonnet vent. We found that up to 6% of bellows PRVs are damaged, causing overpressure and fugitive emissions.
Balanced pistons improve bellows PRVs
To fix these problems, a new PRV design adds a pressure-balancing piston above the bellows. This piston is matched with the size of the disc holder, so even if the bellows fails, it balances the pressure properly. This significantly reduces leakage through the bonnet vent if the bellows gets damaged.
Leak detection provides immediate awareness
In addition to the new design, a bellows leak detection technology has been developed. This system adds a wired or wireless pressure instrument to the valve to measure the pressure below the piston. If the bellows gets damaged, the pressure increases, and this is detected immediately by the transmitter. This quick detection provides data for continuous calculation of the fugitive emission leak rate.
