THE STORAGE OF PETROL.
Page 13
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Details of the Bowser Underground System.
IN CONTINUATION of our previous articles on the storage of Petrol we will Proceed to describe
• a system of storage which has gained a considerable number of adherents, and of which there are installations comprising many thousands of gallons in use in this country as well as in America. We are alluding to the Bowser system of petrol storage. In this system also the petrol tank is buried-underground, and "is, of course, surrounded by the usual concrete easing enforced by the regulations on the subject.
In the Bowser system the petrol is poured straight into the tank through a filler which protrudes from the ground, and the petrol is pumped up from the bottom of the tank by a, pump of special design arranged to give any required number of gallons.
In order to allow petrol to enter the tank, it is necessary to, provide an exit for ainy air which may previously be there, but it is important to prevent the escape of large quantities of petrol vapour. A vent pipe is therefore Carried from the top of the tank as high as possible up the wall of some conveniently-situated building. The importance of having a high vent pipe is that the petrol vapour will not rise beyond a certain height in
this pipe, except under the influence of sudden pressure. This is owing to the fact that the vapour re,condenses when subjected to a pressure beyond that of the normal column of vapour in the vent pipe ; that .is to say, if the tank is filled at a comparatively slow rate, any vapour which tends to leave by the vent pipe will recondense, though, of course, if the tank be filled quickly the vapour will be driven into the atmosphere. • Many tests have been conducted to show the safety of this system. A sparking plug was installed in the vent pipe of one tank and sparks were passed between the points whilst the tank was being filled. All fumes escaping from this pipe had to pass over thesparks, and no explosion was ca-used, owing tothe . absence of air as an essential to combustion. In other tests. burning petrol was poured into the filling pipe, but the fire would not enter the tank itself.
During one drastic trial a Bowser tank, containing 50 gallons of petrol, was surrounded by wood,saturated with paraffin. This wood was ignited, and the petrol was seen brought to the boil
ing point, petrol vapour escaped through the vent and inlet pipes, but, though this took fire, there was no fire within the tank, and no explosion occurred.
During the disastrous earthquakes and fire in San Francisco some years ago over One hundred Bowser storage plants were situated in the districts affected, and all of these came through without damage beyond that of the upper gear, such as plumps. At another fire a building was burned to the ground on the top of a 700-gallon Bowser tank containing 300 gallons of petrol. Most of the pump parts were melted away, but the petrol was. actually drawn from the tank a. week after the fire, and the tank itself was quite undamaged.
The measuring pump of the Bowser system is of very neat construction. The handle of a gauge is turned to whatever quantity of spirit is required, and this limits the lift ef the pump, giving the requisite quantity of petrol, or if this be too great for the capacity of the pump, several strokes, which willgive exact multiples of the amount marked on the dial, may be used. An armoured flexible tube, provided with a cock, is fitted to the pump.
One of our illustrations shows aset of storage tanks with a,total capacity
,000 gallons of 31,000 gallons, piped and ready to be covered in. This set is being in
. stalled in America.
It might he thought that there is danger of drawing air into the tanks while withdrawing petrol ; if this did occur it would be serious, for the air and petrol vapour when mixed might form an explosive mixture. What actually happens is that, as there is always a slight pressure in the, tank equal to the weight of the column of vapour in the vent pipe, withdrawing petrol from the tank momentarily decreases the vapour pressure. The liquid petrol immediately gives oft sufficient vapour to nia.ke up the pressure, and hence no air is able to enter the tank