THE STORAGE OF PETROL.
Page 17
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Details of the Bywater Hydraulic Displacement System.
IN AN ARTICLE on the storage of petrol which appeared in our issue for August 19th, we dealt with some of the dangers and difficulties of storing petrol in bulk unless proper precautions arc taken, and we concluded by saying that in future articles we would describe in detail . several of the storage systems which have proved to be safe and reliable in every way. One of the best known of these systems is that patented by Bywater and Co., of 121, Kings
way, London, W. C.2. ,
In our previous article an instance was given of a river flooding and forcing the petrol to rise through the porous-ground. owing to the petrol's lighter specific gravity. Advantage has been taken of this property in the storage system which we are about to describe.'
The principle of the system is based on the use of water power, and the method adopted is to displace the liquid in store by water, and, of course, any liquid lighter than water and unaffected by it may be stored in a similar manner. . By this method the use of pumps is entirely eliminated, whilst labour and maintenance costs are reduced to a minimum. A special advantage lies in the fact that the petrol delivered is entirely free from. water and foreign matter, as it is forced to the top of the storage tank, and any foreign dirt is left in the water at the bottom. There is also practically no limit to the volume of petrol which can be stored at one -place if 'the ground area is sufficient. . .
Storage by 'displacement is particularly useful when petrol has to be kePt in places where the ground is marshy. At certain. places where systems have been installed water is reached,at 6 ft. below the ground level, and in cases like this it is almost impossible to keep an empty tank underground, as it becomes so buoyant that it bursts through the thin cevering ef earth. With the displacement system the tank is never empty ; it is always full either of water or petrol or a proportion of each : also, at no
time 1s there any space in the tank for air or petrol vapour, and, of course, petrol is entirely unaffected by being in contact with water. •
As usually installed, the system consists of a steel storage tank of the necessary capacity, placed underground so that its top is covered•by about 2 ft. of earth, "Water is fed intd this tank from the bottom, whilst the petrol is fed in from the top. As the petrol enters the tank it displaces -the water, which is forced out of the bottom of the tank through a two-way cock and a ineasuririg meter and into a drain, so that an accurate check is kept on the amount of petrol entering the tank. The height of water in the pipe leading to the drain is such that it is quite impossible for the petrol to leave by the same passage. In order. to provide tho necessary water pressure, a pipe from the main leads into a cistern provided with a ball cock and situated at such a height that no water can be forced out
of the petrol' delivery valve: •
When' it is desired to draw off the petrol,the two-way eOck, which p+evionsly ' shut Off the Water • froin the cistern and put the bottom of the tank into .communication with the waste pipe; 'is turned SO• that the waste SpiPe is 'Ant off and the tank is placed in connitunication with the Cistern. Any petiol thendraiiin off must be and is automatically replaced by an equivalent volume of water which enters the tank from the 'cistern.
Petrol meters are provided at each point where there is a draw-off valve ; the latter is known as a pistol valve aud is provided with a trigger,, which, when pulled, opens a, small poppet valve, releasing just the quantity of petrol required. If this drawoff be . dropped, the valve_ automatically !closes and there is no danger of leakage.
The petrol meter measures •on the main dial-from • one to any given quantity of gallons required, and it has a set-back hand ; at the same time the total petrol delivered is continuously' registered... It is constructed with outlets in all sizes from in. to 2 ins., giving .a flow Of from 5 to 100 gallons per minute.
There is practically no Mint to the distance at which the draw-off valires may be situated. In some of the. plants which have been put down at Government aerodromes the draw-off points are threequarters of a mile from the storage tanks.
The Admiralty has Bywater storage plants to a total capacity of over 200,000 gallons, and the R.A.F. of over 300,000 gallons.
As showing the immunity of this system from danger by fire, it is interesting to note that fires have actually occurred directly over' Bywater, storage plants containing thousands of gallons. At one fire -Which occurred at the garage in Camden Town of the British Automobile Traction Co., Ltd.; even the flexible hose of the system was burnt., but no damage was done to the tanks, and they did not take fire.
The fact that no vaporization took place was due to the comparatively small area of the tank near the surface, the insulation by 'the earth covering, and the: cooling effect of the water.in the tank, the specific heat of water being much higher than. that of petrol.