A vapor recovery unit that has been out of service for weeks or months rarely restarts exactly the way it stopped. Seals take a set, small quantities of liquid find their way into places they should not, instruments drift, and control valves that have not moved become stiff. A short, ordered set of checks before return to service costs a fraction of the time lost to a failure in the first day of operation.
Why a long shutdown is different from a short one
After a brief stop, most conditions inside the unit are still close to normal. After a long stop, the unit has had time to settle: liquid has drained into low points, seals have relaxed, and anything that was marginal before the shutdown may have moved past the point where it works reliably. Treating the restart as a first start, rather than a routine start, is the safest approach.
Visual and mechanical checks first
Start with the unit itself before anything electrical. Look for signs of leakage or weeping, check that insulation and cladding are intact, confirm that supports and fixings are sound, and inspect the internals of anything that was opened for maintenance and closed again.
Checks that catch the common surprises
| Area | What to check | Why it matters after a shutdown |
|---|---|---|
| Seals and joints | Condition and freedom from weeping | Seals relax and can start to pass after a long stop |
| Low points and drains | Liquid accumulation, drain freedom | Liquid collects where the unit is not running |
| Moving parts | Valve stroke and freedom to move | Valves that sat still can become stiff |
| Instruments | Reading against local indication | Drift shows up after a period without power or reference |
| Electrical | Terminations, protection devices, insulation | Damp and inactivity both affect electrical integrity |
| Filter elements | Condition and correct fitting | Storage conditions affect elements that were left in place |
Return-to-service sequence
- Confirm the area is safe to work in and that the isolation points are in the right position;
- Check and clear all drains and low points before running anything;
- Verify instrument readings against local indication and confirm alarm settings;
- Exercise control valves through their full range while the unit is not carrying load;
- Run the unit on a light load first and watch pressures, temperatures and cycle behaviour closely;
- Return to normal operation only when readings stabilise within the recorded baseline.
Comparing against the baseline
The most useful reference at restart is the commissioning record. Comparing the readings taken now with the values recorded when the unit was first put into service turns a vague sense that something feels different into a specific question about a specific reading.
Frequently asked questions
How long a stop makes these checks necessary?
It depends on the site and on how the unit was left. Where the unit was isolated, drained and protected, a shorter check may be enough. Where it was simply switched off, treating it as a first start is the safer approach.
Should the unit be run at full load immediately?
Better to bring it up gradually. A light load first lets the unit stabilise while readings are easy to interpret, and it makes any developing problem obvious before it is masked by full load.
What if a reading does not return to the recorded baseline?
Investigate before returning to normal service. A reading that settles away from the baseline usually has a specific cause, and finding it while the unit is still under observation is much easier than finding it during a peak period.
Luoyang Wohong Petrochemical Equipment Co., Ltd. designs and builds vapor recovery units, membrane separation skids and condenser based recovery packages for fuel terminals, depots and service stations. Contact us to discuss a system selection or upgrade study.