Listening for Pressure Relief Valve Release Events

by , | Aug 18, 2021 | Digital Transformation, Industrial IoT

Jim Cahill

Jim Cahill

Chief Blogger, Social Marketing Leader

The 4C Health, Safety & Environmental Conference is going on today through Friday in Austin. Emerson’s Marcio Donnangelo led a session on pressure relief valve (PRV) monitoring and how it’s undergoing digital transformation. Here is the session abstract:

Despite the efforts to stay compliance, operation isn’t totally free from unauthorized events to happen. If that happens, Affirmative Defense should be consider. However, not knowing the frequency of emissions events, the causes of the event, the quantity and its impact, the emission duration, the need for startup, shutdown, and maintenance activities, etc. could be unclear in the process evaluating the Affirmative Defense claim. Monitoring PRVs to immediately identify bad actors is critical to cover the gaps of these questions. Taking the action to replace PRV in minutes without disrupting the process it is also possible with PRV selectors. Join to this section to lean how.

pressure relief valve (PRV)Marcelo opened describing the role of PRVs to protect people and equipment against unexpected overpressure events. A PRV release is typically the consequence of a sudden, unavoidable breakdown of equipment or process. Having a better understanding of relief events will enable better regulatory compliance.

These PRVs are the last line of defense and critical to protect against unexpected overpressure events. They need to meet national and local safety rules & regulations. Their basic operation is as a basic mechanical device that is self-operated with no connection to systems to share their operation when triggered by overpressure events.

PRVs are pervasive across most plants and cause emissions and losses. They are critical for process availability and cannot be bypassed.

They are often installed in difficult to access locations. Periodic inspections are performed with portable testers. The frequency of these tests varies but are more frequently performed when flare rates are high. These inspections are costly in terms of time. New environmental and safety regulations require operations to record and report PRV releases and leakages. Testing and inspection cycles may be required by outside organizations including local or federal jurisdictions, insurers, etc.

Unfortunately undetected and unreported relief event often occur. One large North American refining complex performed a study with 10000 PRVs onsite and discovered the following:

Leakages can occur due to the nozzle sealing surface damaged by debris as the PRV opened to relieve the over pressure. As the pressure reduced the PRV closed on the debris resulting in a continuous leak.

Undetected overpressure events affect emission levels, production, reliability and safety. Releases and leakages can lead to fines and lawsuits, requiring meeting equipment leakage standards, identifying the source of releases to flare, and reporting emissions during startup and shutdown.

From a production standpoint, production and energy losses can annualize millions of dollars with leakages possibly remaining undetected for years, releases and leakages preventing process optimum performance, and unplanned service being costly and disruptive.

From a reliability perspective, PRV releases are often symptoms of process and operation problems. These include frequent overpressure wearing valves, overpressure stressing adjacent mechanical equipment, and PRV maintenance directly impacting process availability and uptime.

And from a safety viewpoint, undetected releases are unreported “Near Miss” safety events, no process safety root cause failure analysis, valves may stay stuck in a closed position, not opening when required, and checking PRVs on manual rounds is an occupational hazard.

The solution to providing continuous monitoring is using wireless acoustic monitoring transmitter to “listen” for releases. The non-intrusive sensor clamps directly onto the PRV vent pipe surface and installs in just minutes.

The Plantweb Insight software application collects the information from all the acoustic transmitters and provides alerts and reporting capabilities.

Visit the Rosemount 708 Wireless Acoustic Transmitter page on for more on ways to monitor your PRVs and drive improvements in safety, reliability, production and emissions.

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The opinions expressed here are the personal opinions of the authors. Content published here is not read or approved by Emerson before it is posted and does not necessarily represent the views and opinions of Emerson.

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