Taking a Vapor Recovery System from Bolted to Verifying: An On-Site Commissioning Roadmap
A brand-new three-stage membrane vapor recovery unit arrives on site as a collection of skids, valves, piping and wiring. What turns it into a working system is commissioning: the structured process of checking, tuning and verifying every part before the station depends on it. Skip this step, or rush it, and the unit will spend its first months chasing faults that should have been caught on day one.
This article sets out a practical, on-site commissioning roadmap for a membrane-based vapor recovery unit, from the first mechanical check to a final performance verification, and explains what each stage is really testing.
Why Commissioning Is Not the Same as Installation
Installation bolts equipment together; commissioning proves it works together. The distinction matters because a unit can be installed perfectly yet still fail to operate correctly. Piping can be routed to spec while a single valve is left in the wrong position. Wiring can be wired to the diagram while two signals are swapped at the controller.
Commissioning is done in a logical order, and each step depends on the one before it. Trying to verify electrical interlocks before the pneumatic valves have been actuated by hand, or tuning the controller before the sensors have been checked, only creates confusion about which fault is real.
Stage One: The Mechanical and Tightness Check
Before any power is applied, the system must be inspected mechanically. This begins with a visual walk-around: check that all flanges are bolted and torqued, that supports and hangers are in place, and that no foreign material, tools or debris are left inside the piping.
The essential mechanical test is a pressure-tightness check. The vapor side of a recovery system must not leak, because leaks defeat the entire purpose of the installation. A common approach is to pressurize the system with an inert gas to a modest test pressure and hold it for a set time, watching for pressure drop. Any drop points to a leak that must be located and fixed before commissioning moves on. It is far cheaper to find a leak with test gas and soapy water than to find it later with real gasoline vapor.
During this stage, every manual valve should be stroked open and closed, and every pneumatic valve actuated by hand, to confirm the valve seats properly and the position switches report correctly.
Stage Two: Electrical Continuity and Signal Checks
With power available but the system still isolated, each instrument and actuator is verified individually. The pressure transmitters should read a sensible value at atmospheric pressure. The temperature probes should match a handheld reference. The flow meters should show zero flow with no vapor passing.
Every input to the control unit should be checked at its actual signal level, not just by looking at the display. This catches swapped wires and reversed signals, which are among the most common commissioning faults. The control unit’s outputs, the solenoids, relays and alarms, should be forced one at a time to confirm the right device responds.
Stage Three: Controller Logic and Interlock Testing
Modern recovery units use a programmable controller with start, stop, alarm and interlock logic. The functional logic should be tested end to end, without relying on real vapor. This is done by simulating the sensor conditions that trigger each mode.
Test the automatic start: simulate a rising inlet pressure and confirm the vacuum pump starts, valves move to the run position, and the system enters recovery mode. Test the automatic stop when pressure falls. Then test the safety interlocks: an over-temperature signal should isolate the unit, a low-vacuum or high-level signal should stop the pump and raise an alarm. Each interlock must be proven to act, not assumed to work because the wiring looks right.
This stage is also the time to confirm alarm settings match the values in the design documentation, and that alarms appear on any remote monitoring panel the station uses.
Stage Four: First Operation Without Product
Before real gasoline vapor is admitted, the unit should be run through several cycles with air or inert gas. This verifies the whole sequence in motion: start, pressure control, condenser heat-up, and shutdown. It also lets the commissioning engineer watch for mechanical problems under operating conditions, such as unusual vibration, excessive pump temperature or leaks that only appear under vacuum.
On an air-cooled membrane unit, this dry run is also the moment to confirm the cooling fans cycle correctly and that condenser temperatures reach their operating set point and hold there.
Stage Five: Performance Verification with Real Product
Only when every earlier stage has passed should the unit be connected to real vapor flow. The first real run should be supervised closely, with readings logged at short intervals. The recovery process should be observed from cold start through several complete cycles to confirm it stabilizes and repeats.
Performance verification means measuring the actual recovery rate and outlet emissions under normal operating conditions, and comparing them to the values the unit was designed to deliver. A single run that looks good is not enough; the unit should be observed over a number of cycles, or over a representative operating period, to confirm the performance is repeatable and not just a lucky reading.
Documenting the Commissioning Result
A commissioning that is not documented is, in effect, a commissioning that did not happen. The final step is a complete record: the tightness test result, the signal check list, the interlock test results, the alarm settings that were verified, and the performance verification readings. This record becomes the baseline that all future maintenance is compared against.
It is worth keeping this baseline evidence safe. When a unit’s performance drifts months later, the commissioning record is what tells the maintenance engineer whether the drift is real or whether the unit never quite met its specification in the first place.
The Value of a Thorough Commissioning
A disciplined commissioning process typically takes longer than most people expect, but the time pays for itself many times over. Units that are commissioned properly tend to have fewer early faults, a more accurate baseline, and shorter troubleshooting later. When you are preparing a new vapor recovery unit for service, treat commissioning as an investment in reliability rather than a delay to be trimmed, and the whole lifecycle of the system will be smoother for it.