Stage I and Stage II Vapour Recovery Explained
Vapour recovery is, very simply, the process of collecting and storing the gasses that rise from the surface of fuel when it’s stored in a tank. It doesn’t matter if you’ve got an underground tank that holds 20,000 litres of petrol, or a car that holds 50 litres. When petrol comes in contact with air, small amounts will vaporise and rise into that air.
Stage I vapour recovery is the process of collecting that vapourised petrol from a large storage tank, and returning it to a tanker, as the storage tank is filled. Logic dictates that as petrol is pumped into a storage tank, it displaces the vapourised petrol, forcing it out one way or another. Instead of venting this petrol vapour into the atmosphere, it can be collected, ready to be condensed and sold.
Stage II vapour is concerned with collecting the fuel vapour as it is displaced during the refuelling of a motor vehicle. Because the volumes of fuel and vapour are considerably smaller when dealing with trucks and cars, the goal is not necessarily to collect the vapour and resell it.
The reason service stations, commercial depots and other filling stations employ vapour recovery units is to prevent that vapour from being vented into the atmosphere. If this volatile gas escapes the vehicle filling point, it surrounds the vehicle and presents a fire risk.
In summary, stage II petrol vapour recovery stops vapourised petrol from entering the atmosphere when it gets pushed from the tank of a vehicle during refuelling.
Why do you need Vapour Recovery systems?
The two key reasons to recover the volatile organic compounds (vocs) that are present in a vehicle’s fuel tank are money and safety. When dealing with tanks found in lorries, trucks and vans, the maximum fuel tank size is around 450 litres. If the entire tank is being filled, a considerable amount of vapour can be collected and returned to the storage tank. When this collection multiplied by hundreds of thousands of litres sold in a year, considerable savings can be made by filling station operators.
Adding a vapour recovery system improves safety, as the volatile gasses that would have otherwise escaped the filler neck, are safely recovered through the nozzle. This change allows the Hazardous Zone 0 to drop from 300mm from the nozzle to just 150mm, halving the highest risk area. The Zone 1 risk drops proportionately, reducing to just 200mm when vapour recovery is installed.
Who should install vapour recovery?
Operators of fuelling stations, depots and other refuelling facilities who dispense more than a few thousand litres of petrol per year should consider a vapour recovery system. Not only could it be a way to reduce your fuel budget, but it also helps you control your VOC emissions and improve the safety of your site.