Start with the Vapor Generation Rate
The single most important number when sizing a vapor recovery unit is the peak vapor generation rate at the site. Vapor is produced whenever fuel is delivered, whenever the tank breathes during daily temperature changes, and whenever product evaporates from the liquid surface.
For a typical service station, vapor flow peaks during tanker unloading and during high-throughput dispensing periods. For terminals and loading racks, vapor flow is driven almost entirely by loading operations. A conservative sizing approach uses the worst-case combination of unloading flow plus breathing losses.
Key Specifications to Compare
- Processing capacity (m3/h or cfm): the unit must handle the peak vapor flow without bypassing or venting untreated vapor.
- Recovery efficiency (%): the portion of incoming vapor converted back to liquid. Look for 95-99% across the operating range, not just at one test point.
- Emission performance (NMHC): check the non-methane total hydrocarbon concentration of the discharge stream. Vohon units typically run around 10 g/m³ – comfortably inside the 25 g/m³ national emission limit.
- Operating temperature range: the unit must perform reliably in your local climate, from hot summers to freezing winters. Cold-weather packages may include heating and insulation.
- Power consumption: total connected load of compressor, refrigeration, and controls, plus expected average energy use per liter recovered.
- Explosion protection: motors, sensors, and electrical enclosures must be rated for use in hazardous areas. Verify the equipment class and temperature rating against your site classification.
- Materials of construction: stainless-steel wetted parts resist corrosion from sulfur compounds and moisture in the vapor stream.
- Footprint and noise: skid dimensions, weight, and sound levels matter for retrofit sites with limited space or nearby neighbors.
Match the Technology to the Application
Three common technology families are used in modern units:
- Condensation-based systems are simple, robust, and ideal where vapor loads are steady and electrical power is available. Deep-cooling versions reach very high recovery levels.
- Membrane systems are efficient at low vapor concentrations and are often combined with condensation in 3-stage designs. Vohon’s membranes are self-developed and purpose-built for gasoline vapor streams, giving full control over separation performance and replacement cost.
- Adsorption systems provide excellent final polishing and are frequently used as the third stage to capture trace residual vapor.
A 3-stage combination (condensation + membrane or adsorption) delivers the best balance of recovery efficiency, energy use, and operating flexibility for most sites.
Don’t Forget the Site Conditions
- Available electrical supply (voltage, phase, capacity) and backup power needs
- Vent stack location, height, and local siting rules
- Distance from tanks to the unit, which affects vapor line sizing and pressure loss
- Access for maintenance, and local availability of spare parts
- Permitting and reporting obligations for the discharge stream
Get a Sizing Proposal
Selecting a vapor recovery unit is an engineering decision, not just a price comparison. Vohon’s engineers can size a 3-stage unit from your tank configuration, throughput data, and site drawings, and provide a performance guarantee in the proposal. Send us your site data for a no-obligation evaluation.