The updated EPA HON (Hazardous Organic National Emission Standards for Hazardous Air Pollutants) introduces stricter expectations for the monitoring of pressure relief devices (PRDs) across oil, gas and petrochemical facilities.
At one chemical manufacturing site in the US, this created a requirement to implement monitoring across approximately 170 pressure relief devices (PRDs) to detect and report release events.
PRDs (including pressure relief valves, pressure safety valves, burst discs etc) are critical safety components designed to protect process systems from overpressure. Under HON, facilities must now demonstrate continuous and reliable monitoring of these devices including reporting every release event, significantly increasing the need for robust, plant-wide sensing solutions.
The challenge
The site needed a cost effective monitoring approach that meets regulatory requirements without introducing operational risk or excessive complexity.
Key challenges included:
Challenge of implementation
- ~170 PRDs across multiple units required monitoring
- Accessibility difficult in some places due to height and density of the pipework (impacting wireless transmission range)
- Different types of PRDs (valves, rupture discs), brands and sizes to install onto
Regulatory compliance requirements
- Real-time continuous monitoring of PRD activity
- Reliable detection of release events
- Data suitable for compliance reporting
Technology validation requirements
- Zero tolerance for false positives (no signal interference from plant noise)
- Stable and secure data connectivity
- Always-on to capture all events
Operational constraints
- No disruption to live process systems
- Minimal installation complexity (particularly around quantity of gateways installed)
- No modification to existing valves
- Long range wireless required to reduce costs of high gateway to node ratio
Project objectives
The site partnered with Tribosonics to evaluate whether their acoustoSENSE™ technology could provide a compliant and scalable solution.
A first project was mapped out. The project aimed to:
- Validate monitoring across a representative PRD population
- Demonstrate reliable detection of PRV release events
- Prove zero false positives in a live operating environment
- Confirm no interference from background plant noise
- Ensure robust connectivity and continuous data capture
- Provide clear, auditable data aligned with HON expectations
This first project evaluation was structured as a 1-month pilot deployment, prior to roll-out across the plant.
The solution: acoustoSENSE™
Tribosonics deployed its acoustoSENSE technology at the site to monitor the PRDs acoustic signature during operation.
Key implementation features included:
Non-invasive installation
- Sensors quickly and simply mounted directly onto valves
- No modification to PRDs or pipework required
Rapid deployment
- 5 systems installed for duration of pilot
- No process shutdowns required
Continuous monitoring
- All instrumented valves monitored 24/7 over a 1-month period
- Real-time detection of acoustic events associated with valve activity
Event detection capability
- Detect when a PRD release occurs
- Record the time and duration of that event
- Alert operators immediately of a release
Validation and performance evaluation
To ensure engineering confidence, the project combined live plant monitoring with controlled testing. Continuous monitoring was carried out across installed PRDs during live operations, allowing for the assessment of false positives, signal interference and overall data reliability.
Alongside this, a dedicated test skid was instrumented with acoustoSENSE, where PRD release events were simulated under controlled conditions. This setup enabled direct correlation between release events and the corresponding acoustic data, providing a clear demonstration of system response and supported the validation of detection thresholds.
Together, this dual approach ensured both real-world robustness and a controlled proof of capability.
Results and performance outcome
The system successfully met all evaluation criteria:
Zero false positives
- No incorrect event detections recorded during the trial
No interference issues
- Reliable operation in a high-noise industrial environment even during a violent storm that hit the facility
Stable connectivity
- Continuous data capture with no loss of signal
Clear event detection
- PRV release events accurately identified and time-stamped
- Controlled test skid confirmed data accuracy and repeatability
The results provided the level of confidence required for compliance with HON monitoring expectations.
Deployment
Based on the positive outcome, the site has taken the decision to proceed with acoustoSENSE with the initial rollout expected to cover over 170 PRDs on this one site. Future expansion is anticipated across other plants.
Conclusion
By validating a non-intrusive, continuous monitoring solution under real plant conditions, the site has established a clear pathway to compliance with updated HON regulations.
Using acoustoSENSE technology, the site can now:
- Continuously monitor PRD activity
- Detect and record release events with confidence
- Eliminate false positives and unreliable signals
- Deploy at scale without operational disruption
This project demonstrates how acoustoSENSE can provide a practical, scalable solution for meeting evolving environmental regulations in the petrochemical sector.
Download our whitepaper
To help other plants scale their PRD monitoring to become compliant with the updated EPA HON regulations, we’ve created this practical guide for engineers, which is free to download.
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