THE STORAGE OF GAS 627
Four-lift Holder. Three-lift Holder.
Rat.in Depth Of top lift • • • • . 0-18 0-21
Diameter
Total height 0-64 0-50
Diameter
Weight of steel tank . . 336 tons 405 tons
„ crown rest framing ■ 52 „ 63 „
„ guide-framing . 230 „ . 223 „
Total, tank and framing 618 tons 691 tons
Top lift ... . 128 tons 146 tons
Second lift 68 „1 80 „
Third lift . . 68 „ 74 „
Fourth lift 60 „ —
Weight of bell . 324 tons 300 tons
Total weight • 942 „ 991 „
It will be seen that the four-lift holder shows some considerable saving, cliiefly in the construction of the tank, in weight of metal, and therefore in expenditure.
The depth and diameter of the various lifts of gasholders are readily arrived at by any one of experience, the following being the usual proportions ad bered to :—
Ratio of Height to Diameter of Holder
For single-lift holders the height varies from 0-3 to 0-4 of the diameter. With telescopic holders the normal proportion varies between 0-6 to 1*0 of the mean diameter. In both cases the figurc given refers to the height of the bell only, and does not include the depth of the tank.
Depth of Lifts
Each lift will be approximately of similar depth ; i.e. the depth of each. is equal to the total height of the beil divided by the proposed mimber of lifts, due allowance being made for the depth of cups and grips.
Diameter of Lifts and Size of Cups
For the smaller holders the width of the cups should be 8 inches. Medium-sized and larger holders are preferably provided with a 10-inch. cup, although. in the case of the largest sizes 12 inches is occasionally found. It will be understood that the diameter of the second lift is greater tlian the diameter of the top lift by an amoimt equal to three times the width of the cup ; the diameter of each succeeding lift increasing by the same amount. The depth of the cups must be such as to carry a water seal sufficient to withstand the maximum pressure thrown by the holder. In general, it may be said that no telescopic holder would be provided with cups less than 16 inches deep, whilst for the largest holders the figure would not exceed 24 inches.
Rise of Crown
The rise given to the domed crown of a holder varies in accordance with the stresses induced; the greater the rise, the stronger the crown. The dorne should