Oil-storage tanks

The size of an oil-storage tank depends on the boiler loading and, therefore, the amount of fuel consumed, plus the space available. The tank should be large enough to hold at least an eight-week fuel supply. Calculated at a maximum rate of consumption.

Fuel is also cheaper when bought in larger quantities. Tanks are best sited in the open and above ground. There may be local requirements to be met if it is installed within a building, such as a garage.

A storage tank needs substantial supports, either brick piers or steel framing. The latter is best and usually comes with the tank.

With brick piers, great care is needed when fitting the tank on the top, so that you do not topple the brickwork. A waterproof membrane must be placed between the tank base and the top of the pier.

A concrete raft should be built to accommodate the tank support and should consist of 150mm of concrete on well-tamped hardcore, overlapping the edge of the construction slightly all round.

The tank is connected to the boiler by a flexible oil line, which can be either above or below ground and should be run in the most direct manner.

This line can be either of black metal or copper, and encased in a proprietary tape to prevent corrosion, or in a bituminous solution. A line should have a minimum diameter of 6mm and a maximum length of 9.15m. Over this distance, 10mm pipe should be used to a maximum of twice the length.

Joints should be of the manipulative type, belled with a small tool, if copper, and should use threaded joints, with a petroleum jointing compound, on black metal.

The feed line should contain a filter. A fire safety valve must be located in the pipe at an accessible point. If you fit a tee-piece in the line, this enables a flow-rate gauge to be fitted. A sensing element to operate the fire valve should be fitted above the boiler burner.

The pipe outlet from the tank should be not less than 300mm high and the top of the tank not more than 305m above the level of the burner of the boiler.

A draw-off valve should be fitted directly or close to the tank in the oil-feed line. If put on the tank, it must be some 50mm above the bottom, to prevent the intake of sediment.

Other fittings are a fill or offset fill pipe, a 50mm vent, isolating valve, drain valve and contents gauge. The fill valve must be extended to the edge of the tank and be in such a position that the delivery hose is easily connected. This pipe should terminate in a 50mm male-thread hose-coupling connection, with a non-ferrous screw-on cap.

Where the tank has to be located at some distance from a roadway, an offset fill line may have to be provided. This is usually of 38mm diameter and in black steel, terminating in a 50mm male connection.

If this line is over 24.40m long, the diameter should be increased to 50mm. A valve to prevent oil spillage while the hose connection is being made should be fitted. The valve gland packing or diaphragm must be of a pattern suitable for use with fuel oil.

An isolating valve, for connecting the oil supply to the burner, should be fitted in an accessible position. Again, the gland packing, or diaphragm, should be compatible for use with fuel oil.

Tanks must be fitted with a vent pipe, taken from the highest point and be as short as possible. The vent must terminate in the open air and should be fitted with an open-mesh wire balloon.

A drain valve should be fitted in the lowest part of the tank, to remove sludge. The contents gauge should be of an unbreakable type and fitted on to the side of the tank. These are of two basic types. The simplest consists of a sight-level tube, which allows the contents level to be read in the same way as a thermometer.

A gate valve should be fitted to the underside of the tank, to remove any small quantities of water which may have condensed in the internal walls of the tank and collected at the bottom.

10. November 2011 by admin
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