Overfill Prevention

Diesel Tanks: Overfill Prevention

Overfills are one of the most common causes of oil-related pollution incidents in the UK and Republic of Ireland today. However, they are also one of the easiest to prevent. Whilst there is no obligation whatsoever to fit overfill prevention devices at many Diesel storage installations, they are fitted as standard to a growing number of fuel tanks today. European Standard EN 13616 (British Standard BS EN 13616 in the UK and Irish Standard IS EN 13616 in the Republic of Ireland) described 2 separate overfill prevention systems – Type A and Type B. Both systems are designed to reduce the risk of an overfill occurring at a Heating Oil storage installation.

Type A Mechanical Overfill Prevention Devices

Type A devices are mechanically activated, overfill prevention valves (OPV) incorporated within a Diesel Tank’s Fill Point or Fuel Supply Line. When the level of fuel inside the tank reaches the maximum permitted, the valve closes and discontinuing the supply of fuel to the tank. Simple and straightforward in operation, Type A systems have a number of benefits:

  • They’re affordable;

  • They can be fitted to almost any Diesel Tank;

  • They require little maintenance;

  • To prove effective and unlike Type B systems, they’re not dependent upon fuel being being delivered from a compatible tanker.

They have a number of drawbacks too:

  • On Diesel Tanks which do not incorporate an offset or a remote fill point, Type A devices can often be bypassed e.g. delivering fuel via a tank’s inspection point;

  • Type A devices can prove difficult to fit to existing tanks;

  • They can reduce the useful storage capacity of the tank.

However, their biggest drawback is they are a non-failsafe system. So, in the event of product failure, an overfill can result. Reassuringly however, instances of reported product failure are rare.

Type B Electronic Overfill Prevention Systems

Type B Systems are probe mounted electronic thermistor units, fitted to the tank. When delivering fuel, delivery personnel attach an electronic handheld unit to the probe. When the level of fuel inside the tank rises and makes contact with the probe, the handheld unit sends a signal to the tank, to switch off the delivery pump and discontinue refuelling. Type B devices offer a number of advantages:

  • They are failsafe in operation;

  • The probe usually costs less than a Type A device;

  • They are sealed units, which require little maintenance;

  • They can be quickly and easily fitted to almost any new or existing tank.

Their biggest drawback is that to provide overfill protection during refuelling, fuel must be dispensed from a compatible tanker. Otherwise, whilst the tank can still be filled as normal, a risk of overfill remains.

Type B systems are widely used in the aircraft refuelling sector. They are also used in several European countries, where overfills have all but been eliminated following their introduction. However, the unwillingness by many fuel distributors in the UK and Republic of Ireland to prioritise investment in failsafe overfill prevention technology, makes suitably equipped tankers are a rarity on British and Irish roads.

Overfill Warning Devices

A number of other systems beyond the scope of EN 13616 are available. These include audible and visual alarms, together with handheld devices which operate in conjunction with oil tank contents gauges. Unlike overfill prevention systems, these systems are not designed to prevent an overfill from occurring, but instead to sound an alert, allowing delivery personnel to cease refuelling before an overfill occurs. When installed alongside either a Type A or Type B Overfill Prevention Device, they can provide a ‘belt and braces’ approach to the issue of overfill prevention.

Should I fit an Overfill Prevention / Warning System?

Whilst some Diesel Tanks are supplied with either a Type A or Type B Overfill Prevention Device as standard, under current regulations, it’s only strictly necessary to fit an Overfill Prevention Device at installations where:

  • The vent point of the tank is not visible from the fill point;

  • The tank incorporates an offset or remote fill point, and / or;

  • Another site-specific hazard exists.

Queries? Questions?

If you have any queries or questions on overfill prevention systems, you’re very welcome to contact our Customer Support Team. As a leading supplier of Diesel Tanks to customers across the UK, Republic of Ireland, Channel Islands and Isle of Man, we can help you find the ideal tank and the ideal overfill prevention system to go with it. You can call our Customer Support Team on 01789 632 151 in the UK, Channel Islands and Isle of Man, call us in the Republic of Ireland on 01 5268 642 or e-mail hello@fueltank.store. We’re open from 9am to 5pm weekdays and