THE STORAGE OF GAS
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is the case, but a series of experiments carried out with scale models has shown that the magnitude of this restraint is actually very small.
In designing tanks for gasholders it is usual to calculate the required thickness of the side plate by considering the head of water as equal to the depth above the centre of gravity of the plate, and not the depth to the base of the plate. The autlior is of the opinion that such a practice is inadvisable and that the depth to the base of each row should be taken when the stability of that row is being calculated.
When arriving at the thickness of the bottom row of side plates, some allow-ance, as before men-tioned, is often made by designers for the restraint due to the floor plating. The most ready means of doing this is to make a deduction from the total depth of the tank. This deduction usually amounts to aboirt 3 per cent, of the depth. It should be borne in mind, however, that owing to the restraining in-fhience of the bottom curb, however slight this may be, the bottom row plates will be prevented to a certain extentfrom joining in the expansion of the remainderof the ring.
Accordingly, bending stresses will be set up in the lowest ring plates, for which due allowance should be made.
So far as the autlior is aware, the largest Steel tank erected is that at the Kingsbridge works of the New York Consolidated Gas Company. The holder has a capacity of 10 million cubic feet, willst the diameter of the tank is 251 feet 3 inches. with a depth of 46 feet 4 inches. The tank shell is composed of nine rows of plates, the lowest row of which is inches thick, the plates being 4 feet in height. Tlie topmost ring consists of | incli plates, 6 feet in height. All the vertical seams—and
This hole is bottom curb- dril led on Job.
_________________1'.6"______> length o f cover. Internal elevation oP joint cover, to be preferred to one below.
Fig. 422.—Showing Constbuction ot Bottom Curb of Steel Gasholder Tank.
Internal elevation of Joint cover.
4 curb
Tank bottom curb Joint cover formed o f T p/ate bent to fit into root or angle curb.
iStipple "denotes planing.
Black denotes caulking