Oil tanks
Tanks - general
Tanks should be located in the most unobtrusive position possible, however thought should always be given to the needs of safety, filling, maintenance and if necessary the provision of a head of oil above the burner.
Reference must be made to OFTEC – Technical Information note T1/133 covering the risk assessment of environmental damage being caused by spillage from oil storage tanks, this assessment must be completed by an approved OFTEC technician to establish the type of tank necessary.
There should be a minimum distance of 600mm from the tank and any foliage intended as a screen.
Oil storage installations fall into three classes – Class 1, Class 2 and Class 3.
Class 1 – are those installations where the boiler does not exceed 45kW or oil storage does not exceed 3,500 litres, these installations are covered in BS 5410 : Part 1 : 1997.
Class 2 – are those installations where the boiler exceeds 45kW or the oil storage exceeds 3,500 litres, these installations are covered in BS 5410 : Part 2 : 1998.
Class 3 – Large buildings and places of public entertainment or assembly.
In England, the control of pollution (oil storage) (England) regulations 2001 apply to storage over 200 litres for non domestic properties or for any installation over 3,500 litres.
These appliances would generally fall into Class 1. If the installation falls into class 2 or 3, OFTEC Book Three and technical information sheet T1/136 must be consulted.
Size of tank
It is recommended that the minimum size of tank for the Greenstar Camray boiler is 2,000 litres. However this can be adjusted accordingly to the customer’s requirements.
External tank installations
Building Regulations – England and Wales
In England and Wales installations in single family dwellings must comply with Building Regulations Part J. This in turn requires compliance with BS 5410 : Part 1 : 1997 and Part 2 : 1998. All tanks deemed to be at risk or with a capacity of more than 2,500 litres will require a bund.
Building Regulations – Scotland
In Scotland Building Regulation part F applies. This in turn requires compliance with BS 5410 : Part 1 : 1997 and 2 : 1998. All tanks deemed to be at risk or with a capacity of more than 2,500 litres will require a bund.
Northern Ireland
In Northern Ireland the building regulations do not cover the installation of Oil storage tanks, guidance should be sought from BS 5410 : Part 1 : 1997 and Part 2 : 1998.
Bunds – when are they necessary?
These are ‘enclosures’ designed to contain spillage from the oil tank. Reference must be made to OFTEC – Technical information note T1/133 covering the risk assessment of environmental damage being caused by spillage from oil storage tanks to determine if a bund is required.
There are two main ways to comply if a bund is required:
Bunded tanks – are now the most popular way in which to meet the standards and regulations if a bund is required, these tanks are in essence a ‘tank within a tank’ which prevent leakage from the inner ‘oil’ tank escaping into the environment by containing it in the outer tank. The use of these tanks avoids the work of constructing a masonry or concrete wall bund as in point 2. Integrally bunded plastic tanks must comply to OFTEC Standard OFS T100 and integrally bunded steel tanks must comply to OFTEC standard OFS T200. Both must have an OFCERT license to show compliance.
External bunds are masonry or concrete enclosures built around a single skinned plastic or steel tank and lined with an oil resistant material to contain the spillage. The bund must be constructed to CIRIA report 163.
Both of these bunds must be capable of holding 110% of the contents of the tank in the event of a leak or spillage during filling.
The following criteria must be considered before choosing the type of oil tank and its location:
British Standard 5410 : Part 1 : 1997 does not require tanks installed externally to be fitted with a bund unless its absence creates a hazardous situation. OFTEC has published a risk assessment form T1/133, which lists the requirements to be met if the tank is not to be fitted with a bund. The risk assessment must be completed in all cases. The assessment must be completed by an OFTEC approved technician. The below situations would require the provision of a bund in all cases:
Tank capacity in excess of 2,500 litres.
Tank sited less than 10 metres from controlled water.
Tank sited where spillage could run off into an open drain or to a loose fitting manhole cover.
Tank within 50 metres of a borehole or spring.
Tank on hard surfaced ground that could enable spillage run off to reach controlled water.
Tank sited in a position where the vent pipe outlet is not visible from the filling point.
Tank supplying heating oil to a building other than a single family dwelling.
Any other potential hazard individual to the site.
Internal tank installations
Always inform the local Fire Officer and Insurers of any internal installations.
Oil tanks installed internally must never be sited in a habitable area and must be within an enclosed chamber. This chamber comprises a fully enclosed ventilated space and must have 60 minute fire resistant wall, floor, door and roof with a self closing door that opens outwards. The door must be able to be opened from the inside without the aid of a key. The chamber must act as a bund so the door must open above the top level of any constructed bund. If the use of an internally bunded tank is made then the chamber only has to provide the correct fire protection, the door can be at floor level. The chamber must be vented directly to open atmosphere. Space for access to the tank in the chamber must be provided. In the case of steel tanks adequate space for painting and maintenance is required. Any electrical lighting should be of the bulk head type with switches mounted externally.
Oil storage tanks may be installed in a garage but the guidance in OFTEC Technical sheet T1/127 must be followed.
Underground tank installations
All underground oil storage tanks must be fitted with overfill protection.
In all cases the potential buoyancy of the tank should be considered if the water table in the area can rise above the level of the oil in the tank.
Underground installation can be located closer then 1,800mm to an adjacent building and 760mm to a boundary without additional protection.
All underground tanks must be specially constructed to withstand the pressures placed upon then by the surrounding ground. GRP tanks in either single or double skinned versions are suitable, Polyethylene models are also suitable. If steel tanks are used they must be of the double skinned type.
Steel tanks
Steel tanks are available but are being out dated by maintenance free plastic tanks due to their need for siting on piers and painting.
They must be positioned with a slight back fall away from the oil outlet (40mm per metre) to the drain/sludge cock at the opposite end to enable any water or sludge to be drain out of the tank.
Steel tanks should be constructed to comply with OFTEC Standard OFS T200 and must be covered by an OFCERT license.
Galvanised steel tanks and pipework should never be used in oil storage or supply.
Plastic tanks
Plastic tanks do not require painting and can be sited directly onto the ground (no need for piers) as they do not suffer from corrosion, although the head of oil above the boiler’s burner should always be considered and access for cleaning the oil filter and water trap be available.
Plastic tanks should be constructed to OFTEC Standard OFS T100 and must be covered by an OFCERT license.
Position in relation to buildings and boundaries
The position of the oil storage tank relative to buildings and boundaries needs consideration in terms of fire protection, the storage tank itself does not constitute a fire hazard but needs protection from a fire which may originate nearby. For Class 1 installations, as mentioned earlier, no special fire protection is needed if the tank is situated more than 1,800mm away from the building and not less than 760mm from the site boundary.
Figs. 4 to 9 illustrate the requirements of a Class 1 tank installation in relation to buildings (combustible wall and non combustible wall) and boundaries (combustible and non combustible).
De-aeration devices
A de-aeration device is a container of oil about the size of a pint glass with an automatic air vent on top and three connections on the bottom. It saves running a return oil pipe back to the tank from the burner as in Fig.11. Its function is to provide a reservoir of oil from which the oil pump draws oil whilst venting any air in the oil to the atmosphere preventing nuisance ‘lockout’ of the burner. Not all the oil drawn is consumed and any excess is returned to the deaeration device, so whilst the burner is firing there is a continuous flow and return of oil. The third connection is for the main fuel line from the oil tank. There is usually a nonreturn valve located in this connection to prevent oil draining back towards the oil tank under gravity and creating a vacuum. When the burner is firing the whole fuel supply system is under negative pressure i.e. suction, therefore it is imperative that all joints on the fuel supply system are sound. Whilst there may be no obvious signs of an oil leak externally, when the burner is firing it may be possible for air to be drawn in through a bad joint, reducing the pump’s capabilities, resulting in a lack of fuel to the oil pump and nuisance ‘lockout’. This may manifest itself as a very low level of oil or ‘foaming’ of the oil inside the de-aeration device whilst the burner is trying to fire.
Most de-aeration devices are made of plastic and vent to the atmosphere. For this reason they must always be located externally, if sited internally they would constitute a fire hazard (see Fig. 12).
Metal types do exist which do not emit vapour. These can be located internally or externally. Plastic pipe specifically for oil lines does exist and is acceptable but must only be used underground.
Top outlet oil tanks should have the non return valve removed from the end of the oil feed pipe within the tank if installed in conjunction with a de-aeration device.
Supply pipe The oil supply pipe itself would normally be annealed copper tube with a protective plastic coating which is easily manipulated around bends and usually enables the fuel line to be run in a continuous length without joints. If joints must be used, they must be accessible, even if underground (via an access duct) and should be of the manipulative type.
Plastic pipe specifically for oil lines does exist and is acceptable but must only be used underground.
Galvanised pipe, fittings and soldered joints must not be used in oil lines.
More advice on fuel lines can be sought from OFTEC Book Three and Technical sheet TI/134.
Supply pipe sizing
The diameter of the oil supply pipe itself is subject to the distance from the oil tank to the appliance and the head of oil whether it be positive or negative.
Tables 1 and 2 give the required diameter of supply pipe when cross referenced with the head. Table 3 gives the diameter of the supply pipe when the use of a de-aeration device is made.
Table 1 Single pipe gravity feed system
Table 2 Double pipe sub-gravity feed system
Table 3 Single pipe suction lift with de-aerator
Oil filters
Oil filters must always be incorporated in the oil supply line, one on the outlet from the oil tank to filter deposits from within the tank or fuel and one near the appliance to filter deposits from within the fuel line itself. They are supplied and fitted by the installing engineer and are not part of the boiler’s components. They should be able to be serviced without the need for draining down the fuel supply line. There must be sufficient clearance below the filter to enable servicing operations to be carried out easily. Filters must comply to OFTEC standard OFS E104.
Fire valves
A fire valve is an essential part of the oil supply system. It is supplied and fitted by the installing engineer and is not part of the boiler’s components. Its purpose is to cut off the flow of oil outside the building in the event of fire within the boiler area. The valve should be located at the point of entry into the building of the fuel line. For external versions the fire valve must be at least one metre from the casing. It must be activated by a remote sensor located over the burner. A clip is provided within the appliance for the sensor. Fire valves must comply with OFTEC standard OFS E101.
Two pipe systems
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