Bunded Fuel Storage Tanks – 5 Questions Answered

What is a bunded oil storage tank?

Bunded fuel storage tanks, or “double skinned tanks”, are used to store hazardous substances, such as domestic heating oil and diesel fuel. They differ from other oil storage tanks, such as ‘single skin tanks’ because they have a secondary containment tank or ‘outside skin’ (also known as a bund). This means that if any oil leaks from the main storage tank, the fuel will still be safely contained within the secondary containment area, or bund, to prevent it spilling out into the environment.

As this strong, protective layer makes the tank more robust (for safer oil storage), it is also more expensive than a ‘single skin’ tank that stores the same amount of fuel.

When is a bunded oil tank required?

A bunded fuel tank must be used by most agricultural, commercial and industrial premises (i.e. the ones that require an oil tank with a storage capacity of more than 200 litres). They are also a legal requirement at most domestic installations, where siting of the tank requires it, according to OFTEC’s requirements. Tanks over 3,500 litres capacity will also need to be bunded. Up to this storage limit, it really depends on the pollution risk. For example, a bunded tank is essential if the container needs to be sited in an area that carries the risk of an oil spillage reaching a public water source, lake, river or stream.

If you are unsure of the type of tank you need, the best step to take is to contact your local OFTEC-registered installer, who will carry out a risk assessment for you and let you know whether a bunded tank is essential in your circumstances.

What additional safety features can you expect on a bunded tank?

Aside from having a ‘second skin’ to prevent oil leaks, bunded tanks have several additional safety features as standard, and these vary according to the make, model and size of the bunded oil tank.

Typical standard safety features include:

• A tank gauge, to assess how much fuel is left in the tank and whether a refuel is needed.
• A lockable fill point to help prevent fuel thefts.
• A secure fuel inspection hatch designed to access the fuel and clean the tank.
• An alert system to warn of any sudden drop in fuel (either due to leakage or oil theft).
• An overfill protection device to prevent putting too much oil in the tank.

How much fuel can the bunding hold?

In the event of an oil leak, the outer section has been built to hold more than the capacity of the inner tank, and it will also store the pipes and vents. The amount of fuel this additional layer can contain depends on the make and model of the tank, but the minimum is 110% of the fuel capacity of the inner tank.

What further benefits do they have?

Bunded fuel storage tanks are considered the environmentally-friendly option, as their strong protective layer helps prevent any damage to the surrounding area caused by fuel leaks. The double layering also helps prevent fuel theft, as the extra wall makes it harder to steal fuel from the inner section of the tank. Another advantage is that the outer bund wall affords the inner tank wall some protection from impact damage. However, we always recommend that tanks are positioned to avoid damage from vehicles or machinery or, where this is unavoidable, barriers are erected to help prevent accidental crash damage.

For more information and to see the full RPM Fuels and Tanks range of Titan, Carbery and Harlequin ITE plastic bunded oil tanks ranging from 650 to 10,000 litres, click on the link above. We also supply a high-quality, varied range of steel bunded oil tanks.