A vapor recovery unit that stops mid-delivery is usually doing exactly what it was designed to do: protecting itself and the station from a condition it cannot safely continue through. The stop feels like a failure on a busy forecourt, but the machine has almost always left a written clue in the alarm list. The difference between a five-minute restart and a week of repeated trips is the order in which those clues are read. Rushing to reset and finish the delivery skips the information the unit just handed over.
What a Mid-Delivery Stop Actually Means
Protective stops cluster around a few physical causes: liquid arriving where only vapor should, temperatures climbing beyond the machine’s comfort, vacuum or pressure moving outside the range the process expects, or a sensor and power condition that makes the controller distrust its own view. Each family of causes has its own alarm, and each alarm has a first response that makes sense for it. That is the whole logic of working through alarms in order: the machine sorts its complaints by importance, and the list preserves that order even when the forecourt is impatient.
The Usual Suspects, Grouped
| Alarm family | What typically triggers it | First check on site |
|---|---|---|
| Liquid in inlet | Condensate pushed forward during unloading | Drain the pot as trained; note what came out |
| High temperature | Long run at high load, fouled cooling, hot weather | Let it stop; do not restart until it cools and the cause is known |
| Vacuum or pressure out of range | Blocked or restricted path, line changed, valve closed | Look for recent changes along the vapor path |
| Sensor or power fault | Loose connector, tripped protection, supply dip | Note the code; leave electrics to trained hands |
Working Through the Alarm List
- Read the active alarms first, then the history: which came first often names the true cause.
- Handle only what your training covers, such as draining the pot, and record what you found.
- Check for recent changes: closed valves, new line work, weather, a different fuel grade.
- Attempt one restart only if the alarm list is clear and the display invites it.
- If the same alarm returns, stop trying and call the service line with the codes and times.
When Restarting Is Safe and When It Is Not
A liquid alarm that clears after draining, with history showing a single event, usually justifies one supervised restart. A temperature alarm deserves the opposite treatment: heat means the machine was struggling, and restarting into the same load before the cause is known deepens the damage. Sensor and power faults belong to the technician unless the display itself guides a safe reset. The rule of thumb worth training into every shift is simple: mechanical housekeeping may be retried once; anything involving heat or electrics waits for advice.
What to Tell the Service Line
The call goes better with specifics: the alarm codes in order, the times they appeared, what was already checked and drained, what the delivery looked like, and whether anything on site changed that day. A technician who receives that package arrives with the right parts and the right suspicion, which is why the log matters more on the day of a stop than on any quiet day before it.
Making the Next Stop Shorter
Stations that work the list calmly once usually handle the next stop faster, because the routine is already in muscle memory. The pattern also feeds prevention: repeated liquid stops point at slope or seals upstream, repeated temperature stops point at cooling or duty, and repeated electrical faults point at a connection nobody has tightened yet. Every mid-delivery stop is the machine filing a report; stations that read the report get fewer of them.
Can we just reset the alarm and keep unloading?
Only for the alarms your training names, after the first response it prescribes, and once. A returning alarm means the cause is still there. Resetting repeatedly to finish a delivery converts a small fault into a large one.
The same alarm trips every hot afternoon. What does that suggest?
A load and cooling pattern rather than a random fault. Long high-load periods in heat push the weakest link first, often temperature or vacuum margins. Collect the times and codes and let the service technician size the machine or the cooling against that pattern.
Who may restart the unit after a stop?
The person trained on that unit, following the alarm sheet, and only when the active alarm list is clear. Anything involving temperature or electrical faults waits for the service technician, whatever the queue at the forecourt looks like.
Luoyang Wohong Petrochemical Equipment Co., Ltd. manufactures vapor recovery units and equips station teams with plain-language alarm procedures for exactly these moments.