Sand-Grading Equipment

Press, Volume CII, Issue 30146, 1 June 1963, Page 15

Sand-Grading Equipment

Three large pieces of equipment for grading and purifying sand were demonstrated to 40 sand and gravel producers from many parts of New Zealand at the Farrier-Wai-mak plant at Coutt’s Island, on Thursday. Two of the guests were from Melbourne. Each piece of equipment is the only one of its kind at work in New Zealand, although the company, which will manufacture them all under licence, has just sent one sand classifier to Auckland

The sand classifier produces sand to specifications for the first time. It first separates the sand from the shingle, then pumps the sand and water to a classifying tank mounted on an 80ft-high structure The sand is divided u. o four or five sizes in the tank, de-watered, split again, and blended to the classifications required The different grades come down chutes to separate stockpiles The company says that until it imported its sand classifier two years ago it was not possible to grade sand With ungraded sand, users had to compensate for the poor quality by using more cement The classifier has already produced the 25.060 yards of sane used for the concrete lining the Christchurch-Lyt-telton road tunnel. The machine for removing impurities from sand is called simply a jig It takes out such things as water-logged wood, shale clay and peatall the impurities that are not wanted in building materials Yesterday the visitors were shown how it removes pumice

from sand—an Auckland district problem. The jig separates the materials mechanically, according to their specific gravities Gravel impurities are not a problem in Canterbury, but they are elsewhere

The jig's capacity is 40 tons an hour, but this can be multiplied by using a bank of jigs. It is an American patent.

The third piece of equipment is called an upward

current cone It separates impurities from sand, and its main application is in cleaning siloa sand for the glass industry. Impurities are floated off the sand—mainly clay and iron impurities Clay in the sand tends to produce yellow glass and iron gives the glass a greenish colour. The purification process will enable glass-makers to produce glass of better quality, according to the manufacturers of the equipment