A vapor recovery unit only delivers value while it's actually capturing vapor at design efficiency — and that's a narrower window than most facility teams assume. EPA's default compliance assumption is that a VRU captures 95% of tank vapors, with the remaining 5% accounted for as normal annual maintenance downtime. The problem is that real-world VRU performance degrades well before a unit fails outright: a drifting pressure setpoint, a worn blower, or a condenser losing efficiency can quietly drop recovery well below 95% for weeks before anyone notices a flare stack lit that shouldn't be. iFactory's continuous VRU monitoring platform gives operations and compliance teams the pressure, flow, and component health visibility needed to catch that degradation while it's still a tuning fix, not an emissions event.
Why the EPA's 95% Assumption Doesn't Mean Your VRU Is Performing at 95%
Regulatory agencies use a default capture efficiency of 95% for VRUs operating under 40 CFR Part 60 NSPS OOOO/OOOOa requirements, with the remaining 5% representing assumed annual maintenance downtime. That figure is a compliance baseline, not a continuous performance measurement. A VRU drifting at 85% recovery for three months because of a worn blower or a misconfigured pressure switch won't necessarily trip an alarm — it will simply route more vapor to the flare or relief valve, and the operator typically finds out from an inventory discrepancy or an inspection rather than from the unit itself. Facilities that have moved away from assumption-based compliance and toward measured recovery often Book a Demo to see how iFactory closes that visibility gap with continuous pressure and flow tracking at the tank and the VRU skid simultaneously.
- Recovery efficiency assumed at 95% based on regulatory default, not measured
- Pressure setpoint drift discovered during a manual field check, if at all
- Blower wear identified only after a high-temperature trip or compressor shutdown
- Condenser performance loss invisible until vapor breakthrough increases
- PM scheduled on a fixed calendar regardless of actual component condition
- Recovery efficiency calculated continuously from real-time pressure and flow data
- Setpoint drift flagged the moment suction pressure trends outside its control band
- Blower vibration and motor load trended to catch wear weeks before failure
- Condenser delta-T monitored to detect fouling before breakthrough occurs
- PM triggered by actual component condition data, not a fixed interval
The Three Failure Points That Quietly Drop VRU Recovery Below Target
A VRU is a relatively simple system on paper: a suction scrubber, a wet gas compressor, and a pressure-sensing control pilot that starts and stops the unit based on tank vapor space pressure. In practice, recovery efficiency depends on three components staying within their design tolerances simultaneously, and degradation in any one of them reduces captured volume long before the unit actually shuts down.
| Failure Point | What Goes Wrong | Effect on Recovery Efficiency |
|---|---|---|
| Pressure Setpoint Drift | Control pilot setpoint shifts outside the 0.25–2 psig design suction range | Compressor cycles incorrectly, venting vapor instead of capturing it |
| Blower/Compressor Wear | Wet gas compressor loses suction capacity as seals, bearings, or vanes degrade | Reduced vapor throughput, higher proportion vented or flared |
| Scrubber/Condenser Fouling | Liquid separator or condenser loses efficiency from NGL or water carryover buildup | Wet gas reaches the compressor stage, accelerating further wear and breakthrough |
What Continuous Recovery Monitoring Actually Tracks
Calculating true VRU recovery efficiency requires comparing the volume of vapor entering the system against what's actually compressed and routed to sales, fuel gas, or compressor suction — not just confirming the unit is running. iFactory's monitoring approach tracks the parameters that determine whether that comparison holds up over time, not just whether the compressor is powered on.
Why Sustained Recovery Matters Beyond the Compliance Number
A VRU operating below its design recovery rate isn't just a compliance exposure — it's lost product. Recovered tank vapors are BTU-rich hydrocarbon that would otherwise be sold as fuel gas, routed to compressor suction, or sent to a sales line, and every percentage point of recovery lost below target represents volume that's either flared or vented instead of monetized. Book a Demo to see how iFactory ties recovery efficiency trends directly to estimated hydrocarbon value, giving operations teams a clear economic case alongside the compliance one for keeping VRU performance close to design.
Expert Perspective: Treating VRU Efficiency as a Measured Metric, Not an Assumption
We had been reporting 95% capture efficiency on our tank batteries for years because that's the regulatory default — nobody was actually measuring it against real pressure and flow data. Once we started tracking suction setpoint drift continuously, we found two units running closer to 80% recovery because of a blower issue nobody had flagged. The fix was straightforward once we could see it. The bigger shift was operational: recovery efficiency stopped being a number we assumed and became a number we managed.
Conclusion: Recovery Efficiency Is Only as Good as Your Visibility Into It
A vapor recovery unit's value depends entirely on whether it's still performing at design recovery efficiency months after commissioning, not just whether it passed its initial compliance test. Pressure setpoint drift, blower wear, and condenser fouling are common, gradual, and individually unremarkable — but together they're the most common reasons a VRU fleet quietly underperforms its assumed 95% capture rate. Continuous monitoring closes that gap by turning recovery efficiency into a measured, trended metric rather than a regulatory assumption, giving operations teams the lead time to fix degradation before it becomes a flaring event or an emissions inventory problem.
Vapor Recovery Unit Efficiency — Frequently Asked Questions
EPA and most state regulators use a default capture efficiency of 95%, with the remaining 5% attributed to routine annual maintenance downtime under NSPS OOOO/OOOOa.
Pressure setpoint drift on the control pilot is among the most common causes, since it directly affects when the compressor cycles relative to actual tank vapor pressure.
Yes. A VRU can remain powered and cycling while recovery efficiency has dropped well below design target due to blower wear or scrubber carryover, with no obvious alarm.
iFactory compares continuous tank vapor pressure and flow data against compressor throughput and run-time, identifying the gap between expected and actual captured volume.
Yes. Recovered vapor is sellable hydrocarbon, so sustained recovery efficiency directly improves captured product value in addition to supporting emissions compliance.
