Stage-3 Vapor Recovery: Answers to the Questions Stations Ask Most
When a service station begins looking at a stage-3 vapor recovery unit, the same questions come up again and again. This article answers the most common ones, based on the WHSH-M membrane-based unit.
1. What does the unit actually do?
It treats the vapors that accumulate inside underground fuel tanks. Vapors are drawn from the tank, passed through a membrane that separates hydrocarbons from air, and the recovered hydrocarbons are returned to the tank as liquid. Clean air is discharged.
2. How much vapor can it handle?
The WHSH-M has a processing capacity of 4–20 m³/h, which covers the tank vapor load of typical service stations.
3. What recovery efficiency can we expect?
Under normal operation, NMHC treatment efficiency is above 99%, and the discharge concentration is far below the national emission limit. Field measurements at operating stations are typically around 5 g/m³.
4. Does it run all the time?
No. The unit starts automatically when tank pressure rises above the preset start value and stops when pressure falls below the stop value. It runs only when the tank actually needs pressure relief.
5. How much electricity does it use?
The membrane-only model draws 1.3 kW and the air-cooled plus membrane model draws 2.7 kW. Specific energy consumption is under 0.2 kWh per cubic meter of vapor treated.
6. How noisy is it?
The membrane-only model operates at ≤63 dB(A) and the air-cooled plus membrane model at ≤75 dB(A).
7. How long does the membrane last?
The membrane module has a design life of 10+ years under normal operation. There are no consumables to replace during that period.
8. How long does installation take?
Typically one day. The unit is set on a level pad, the inlet (DN50) and return (DN20) lines are connected, and the unit is commissioned. The mid-height connections allow recovered liquid to flow back by gravity, so no raised platform is needed.
9. Is it safe for a petrol station environment?
The unit is explosion-proof rated (Ex db eb ia mb IIB T4 Gb, IP55) and operates in ambient temperatures from -40 °C to +70 °C. It includes a flame-arresting vent, emergency stop, and automatic pressure control to keep the tank near atmospheric pressure.
10. Can we monitor it remotely?
Yes. The unit supports RS485 communication and WiFi/4G connectivity, uploading data to a cloud platform. Environmental data is recorded every 30 seconds, and running and alarm history are stored for review.
11. What maintenance is required?
Monthly checks cover the power supply, electrical cabinet, grounding, piping connections and the area around the unit. The vacuum pump oil level is checked through the sight glass and the oil is replaced periodically. All maintenance is carried out with the main power switched off.
For more information: +86 135 2699 0215 / lixiang@vohonoilpipe.com