Choosing the right three-stage vapor recovery unit starts with one number: processing capacity. Get that number right, and the unit runs quietly in the background for years, keeping the station in compliance and returning recovered fuel to the tank. Get it wrong, and the station faces either pressure buildup with unprocessed venting, or an oversized unit that wastes capital and energy. This article explains how to think about capacity for three-stage vapor recovery, what the processing range really means, and how selection connects to installation and daily operation.
Why Processing Capacity Matters
Three-stage vapor recovery systems treat the vapor that storage tanks release during unloading and when pressure rises as fuel warms. The system is installed at the tank breather valve: when tank pressure exceeds a set threshold, or when a tanker unloads, the unit starts automatically, treats the vapor, and returns recovered liquid fuel to the tank. Capacity is the rate at which the unit can process that vapor, expressed in cubic meters per hour.
If capacity is too small for the station, vapor generation outruns treatment. Tank pressure climbs, the system runs continuously without catching up, and vapor can be pushed out through the vent untreated. If capacity is far larger than needed, the station pays for a bigger compressor, more membrane area, and higher energy consumption than the job requires. Matching capacity to the station is therefore the first and most important selection step.
The Processing Range and What It Covers
The WHSH series covers a processing range of 4 to 20 cubic meters per hour. That span is designed to match the real spread of service station sizes. A small neighborhood station with one or two tanks and low turnover needs less capacity than a highway station that receives multiple deliveries per day.
As a practical starting point, consider three common situations. A small station with modest daily throughput fits comfortably at the lower end of the range. A mid-size station with several tanks and regular deliveries sits in the middle. A high-throughput station with frequent unloading needs the upper end of the range. Because the series is built around the same membrane separation and compression-condensation architecture across the range, moving up in capacity does not change the operating principle; it changes the throughput the unit can sustain.
How to Estimate Your Station’s Demand
The most reliable way to size a unit is to use real operating data: tank volume, unloading frequency, and measured vapor generation. Stations that have completed vapor emission testing already have concentration and flow data that map directly onto capacity selection. Where measured data is not available, base the estimate on tank volume and delivery pattern, and leave a sensible margin so the unit is not constantly running at its limit.
It is also worth considering the future. A station that plans to grow its fuel sales, add tanks, or increase delivery frequency should leave headroom in the selected capacity rather than buying the smallest unit that fits today’s numbers. Upgrading a unit later is more expensive than selecting correctly the first time.
Emission Performance: The Other Number That Matters
Capacity is only half the selection equation. The emission level the unit achieves is what regulators look at. The WHSH series keeps non-methane hydrocarbon concentration in the exhaust below 10 grams per cubic meter, a level that meets current environmental requirements for service station vapor emissions.
When comparing units, ask for the emission figure at full rated load, not just at light load. A unit that performs well at low throughput but drifts at rated capacity is a risk at the exact moments when it matters most: during unloading, when vapor generation is at its peak.
Selection Connects to Installation
Selection decisions affect installation, so they should be made together. WHSH series units are skid-mounted: the compressor, condenser, membrane module, and control system arrive assembled and factory-tested. On-site work is limited to connecting power, connecting vapor lines, and commissioning. That design is deliberately friendly to existing stations, where space near the tank area is often tight.
The unit runs on three-phase AC 380V power and is designed for outdoor installation near the tank area. It occupies a small footprint, and because it is skid-mounted, it can be relocated with a crane if the station layout changes. Installation planning should confirm the power supply, the routing of vapor lines to and from the tank breather valve, and a level base that keeps the unit stable.
Safety Design That Selection Should Never Compromise
Vapor recovery equipment operates in an atmosphere that can contain flammable gas, and safety design is not a place to economize. The WHSH series uses an explosion-proof junction box inside the enclosure with sealed surfaces that must never be opened while the unit is running. Maintenance and commissioning personnel are required to use combustible gas detection instruments and verify that gas concentration is below the safety limit before opening any part of the system.
These requirements should be part of the selection conversation, not discovered after installation. Confirm that the unit’s safety features match the station’s operating environment and that the station crew can follow the required procedures.
Operation and Maintenance After Commissioning
Once the unit is sized, installed, and commissioned, daily operation is largely automatic. The system monitors tank pressure, starts and stops on its own, and displays operating data on the touchscreen. What the station must provide is a maintenance rhythm: regular checks of the compressor, the membrane module, and the air-cooled heat exchanger, whose cooling efficiency directly affects performance.
Routine inspections should also track operating data over time. Gradual changes in pressure behavior or emission readings are early signals that a component needs attention. With a proper maintenance routine, a correctly sized unit operates reliably for years, keeps the station in compliance, and quietly converts vapor that used to escape back into usable fuel.
Putting It Together
Selecting a three-stage vapor recovery unit is a matter of matching three things: processing capacity to the station’s real vapor generation, emission performance to regulatory requirements, and safety and installation requirements to the site. When those three align, the unit becomes a dependable part of station operations. Start with the station’s actual numbers, choose within the 4 to 20 cubic meters per hour range with headroom for the future, and keep safety design at the center of the decision.