In many promotional materials, you see a bucket full of condensed liquid from a VRU, with the gas station owner smiling happily.
But have you ever stopped to ask:
Is this visible condensed oil truly the “saved oil” for your station?
Let’s look at actual data from our Green Guard VRU during operation at a fueling station.
This is from a station in China equipped with Green Guard.
Check the two operational records with red.
- When the unit runs at intervals within 2 hours, Green Guard maintains exhaust emission concentrations below 1 g/m³ (displayed as 0g due to system rounding, meaning <1 g/m³).
- On September 7, the unit ran every hour during the daytime. However, after 17:47, as nighttime temperatures dropped, tank pressure did not reach the 0.35 mbar startup threshold until 02:19 the next day—a gap of about 7 hours.
When it restarted, the vapor concentration inside the tank had risen significantly, and the emission reading showed 4 g/m³.
- After another 5‑hour interval, the next emission reading reached 12 g/m³.
Why did emissions rise?
Because vapor continues to evaporate inside the tank—even at lower nighttime temperatures—raising the VOC concentration.
This clearly illustrates two key points:
- Condensed liquid is not truly “saved.”
Even if you condense large amounts of vapor back into liquid and return it to the UST, evaporation continues inside the tank, turning liquid back into vapor. It’s simple physics. The sight of a bucket of “recovered” oil can be misleading. - Real savings come from preventing emissions.
The first and most critical step is to create a closed vapor system that locks vapor inside the UST. Only by controlling tank pressure and exhaust emissions through a VRU can you actually prevent loss.
How to truly measure savings:
Compare your station’s loss data before and after installing a VRU.
Use the equation:
Opening inventory + Delivered volume = Dispensed volume + Closing inventory + Loss
A real reduction in “Loss” is what truly represents saved oil.
This reveals a fundamental flaw in the traditional approach.
Most VRUs still use a single-pass condensation system. This technology originated from oil depots, where it’s used to liquefy vapor from tanker trucks—a one-time, batch process. For that application, simple condensation is the correct solution.
However, applying this same technology to a gas station with a permanently stocked Underground Storage Tank (UST) is a misdirected approach. It fails to address the core problem: gasoline is continuously evaporating inside the tank, and vapor is constantly being lost through the vent pipe. Condensing some of it into a visible liquid does not stop the ongoing evaporation and loss cycle; it merely creates a misleading symbol of “savings” while the real problem—the open system—persists.
So, how do you think – Is the condensed liquid really “saved” oil?
#VaporRecovery #VRU #Sustainability #CleanTech #OilAndGas #EnvironmentalCompliance #Innovation #greenguard #datian
