Old timer keeps pace

Press, 19 May 1981, Page 33

Old timer keeps pace

The Japanese attack on Pearl Harbour during the Second World War caused massive destruction to the United States military installation located there.

To get the base back in operation required a quick reconstruction programme, and a large concrete batchingplant was hastily sent out from the United States to assist. This was the Johnson Batcher, and after re-build-

ing Pearl Harbour, the plant was purchased as war surplus by the New Zealand Government.

This is the same plant which on May 19, will have made one million cubic yards of concrete . for the Upper Waitaki Power De-, velopment.

There are five basic inputs to the plant — cement, water, additives, sand and aggregates. Cement is railed bulk to the Kurow railhead just on 100 kilometres from Twizel, and then trucked by bulk tanker to the cement storage silo at the Batcher. When required, the cement, along with water from the .Twizel town, supply and additives from the mixing shed.are fed to the Batcher. •

Course aggregates and sand come from gravel pits five kilometres from the Batcher and are trucked to huge stockpiles which are kept in trim •by bulldozer. Each stockpile has ia conveyor belt system running in a tunnel underneath, and the aggregate is taken to a washing plant and then ,to the top of the Batcher. At the crown of the Batcher is a screening plant which sorts the aggregate into the. four particle sizes, and along with the sand • is' fed into the respective holding bins. ■ - • ’ - : ■ There is sufficient material in the- bins to keep, the Batcher going at full capacity — eight yards every four minutes — for four hours production. However, under normal conditions the Batcher output is more like 60 yards an hour and it can keep this up 24 hours a day. . To produce a “batch” of concrete, the. Batcher operator weighs up the cement, water and additives, aggregates and sands, and feeds them into four two, cubic yard mixers. There are different “recipes” for different types of cement, and the Batcher can be ordered to select any one of 31 different types. . ’ It.only takes four minutes to mix the. materials to produce what is known as a “wet batch.’” Samples may be taken at this stage to be tested for air content, and made into cylinders; which are tested to destruction to determine; strength.. :