Centrifugal spinning for making storage tanks

Press, 18 June 1982, Page 7

Centrifugal spinning for making storage tanks

The centrifugal spinning process used by Hume Industries (New Zealand), Ltd. to make concrete pipes, has been adapted for use as a method to construct water storage tanks.

L'se of the high-speed technique is seen as a big breakthrough in the tank construction business by staff at the Christchurch factory of Humes where the process was adapted. The spun concrete tanks were first released onto the market in February after being subjected to rigorous testing.

Spun tanks will be able to be constructed in any of Hume’s pipe-making plants. Although the tanks are only made at Christchurch at present. the firm's parent company in Australia is expected to investigate the possibility of manufacturing spun tanks there also.

Discovery of the spun-tank technique was made by staff at the Christchurch factory who were looking for other uses of the pipe making machinery, according to the firm's South Island sales manager (Mr Des Fitz patrick). The company was developing sheds for the storage of dangerous goods when it was found that pipe structures

could be adapted for use as water tanks, said Mr Fitz patrick. After 18 months development work, the company can produce tanks which are structurally sound and water tight. Spun tanks have many advantages over the conventional labour intensive method of constructing tanks with ferro cement. Using the same semi-automated machines required for making spun pipes, the labour content is minimal and the tanks can be made to accurate dimensions and with walls of a uniform density. Humes have used the spun concrete process to make pipes for more than 60 years. By using selected aggregates, careful mixing, centrifugal spinning and machine vibration at high speed, the concrete is of a strong, high density. The same process is used to make the water tanks which, because of the low labour input, results in cost savings which are passed on to the purchaser. The tanks are the lowest priced perlitre tank on the market. Two Humes 11,250-litre spun tanks cost less than one 22,500-litre plaster tank and also have the advantage of being easier to install in a

confined area. Spun concrete gives a smooth finish and is the most dense concrete ever made. Because manufacturing time is kept to a minimum, the tanks can be delivered-with-out delay. Specially-rigged transporters make it possible to deliver and unload under difficult site conditions. The tanks are available in eight sizes ranging from 1125 litres, which has a diameter of 1.32 m and a height of 1.52 m. to a tank of 11,250 litres, with a diameter of 2.7 m and a height of 2.76 m. Where large capacities of water are to be stored, two or more smaller tanks can be coupled together. When extensions to its Christchurch factory have been completed, the company plans to produce five tanks per day.

Construction of the tanks involves the same principle as the pipes. A mixture of sand, crushed stone and cement is fed into a revolving mould which is vibrated and then spun at high speed. After being steam cured overnight, the thin shell is carefully removed from the case and affixed, with an epoxy glue to a concrete base and top. The completed tank is structurally sound and very robust.