NEW GAS CONTAINER

Otago Witness, Issue 4038, 4 August 1931, Page 48

NEW GAS CONTAINER

STRUCTURAL WORK COMPLETED HAST PLATE RIVETED YESTERDAY. On Thursday afternoon, in the presence of the Mayor (Mr R. S. Black), several city councillors, and others, the last rivets were driven in and hammered home on the domed roof of the new gas container at the City Gasworks. The first pile for the foundation was driven in in September of last year, and the first plate was laid on March 5. The cost of the foundation, which is of what is known as the raft type, consisting of something in the nature of a hollow concrete pontoon, was £13,378, while it is estimated that the container itself will cost somewhere in the vicinity of £14,000. The capacity is 500,000 cubic feet, this being just half that of the gasometer at Kensington. Contrary to the usual belief, the whole of the superstructure is not available for the storage of gas, the lower section to a height of some feet being filled with water —in the case of the new container amounting to 5111 tons —through which the gas is led in mains, and which acts at the same time as a gas-proof seal and a safety valve. While the gasometer is being filled and until the full capacity is reached the pressure of the water effectively prevents the escape of gas through the bottom of the container. As soon as 000.000 cubic feet of gas have been forced into the holder, however, the pressure of gas becomes greater than that of the water beneath, with the result that

the gas commences to force its way through the water and escape, in much the same manner as does steam through a safety valve. The gasometer itself is built in three separate sections, each upper section being smaller in circumference than the one beneath and folding within it. When the container is empty these three sections are lowered, each within the one beneath it. Upon the gas mains leading into the container being opened the top and innermost section rises first. As the bottom of the section reaches the level of the top of the one outside it an interlocking device comes into play, and the second section is drawn up also, in turning lift the third and last section. By the time this has been fully raised the container has reached it maximum capacity, and should more gas be forced in the safety valve action of the water beneath commences to function, allowing the surplus gas to escape. The actual structural work having now been finished, about one month will be occupied in testing and painting the container, which will then be ready for use. The contract has been in the hands of the English firm of Messrs Firth, Blakeley, Sons, and Co., Ltd., which has carried out the work with every satisfaction, and will shortly hand over to the City Council the latest addition to the gas services of the city.