Newest in Metal Crushing Plants Operating In Ohau River

Chronicle (Levin), 26 February 1949, Page 4

Newest in Metal Crushing Plants Operating In Ohau River

Breaking Up. s|ontes in .way is a new plant recently installed on the nbrthern Qi ihe Ohau itiver,. just over the railway line. The only complete conveyor-operated plant in New Zealand,- it has the advanfage that at no tfme is the metal aetually touched hy hapd. The venture is a lo.eal one and the" company has not long been formed. The directors hope ta crush an average of 100 yards of metal daily with the plant, the cost qf whjch exceeded £12,000. % "

It was designed. by Mr. T. Bognu'da, of Lower Hutt, who has had 20 years practical experience in the operation and designing^ of crushing plants, and is managingdirector of one of the most. mqdern plants on fhe EEuft River. > The plant at Ohau .shqulU hh a much felt waht in the district in supplying was'hed concrete metal, and roading chips, which, in the| past, have had to be railed tq the district. Seekihg knowledge on the processing. of the rocks and metal which are to eventuaUy find their way on to the highway? and roads qf the district, a "Chronicie" reporter approached the manager, Mr. Eric Gbld, who ob iged by •describing the «functions of the variaus pai'ts of the machinery. An important point stressed was that no unsightly heaps" of dfscarded metal would remain ta form pennanent mqnuments ta the enterprise. E^ery stone brought from the river bed' was used — nothing was disearded, And would there not be deep and dangerous holes left in the river b,ed? Mr* Gold was asked. No, these, S.aid Mr. Gold, were filled in by the first big flrod and in fact wero a, blessing rather than a menace, as they did much ta obviate those dangerous panks Of metal ' forming lower down the river. The catehment board also he'd this view and the -scheme had its blessing. Three Cuts In River The company has made three different cuts across the river and has purehased hve acres of land on both sides fro.m which it will operate. A high eoncrete retaining wall provides a back to, a motai ramp and an eiectrically operated dragline bucket "proceeds backwards and forwarda over the river . bed. When a drag is made, the bucket is earried up the 5 ramp and its contents deposited: into the shoot leading. into. the first revolving screen. The first few cuts are the worst, but after the top surface is removed the going is much easier. In the first screen the se.veneighths inches metal is taken off and the bigger boulders are thrown through and faU intd. a shoot leading to a jaw-type crusher, which reduces the stones to a reasonable size. The sand from the first screen is washed by the continuou? current of water, through pipes and into'a settling bin, the water draining out and being cafried back into .the stream, leaving the sand behincf This is subsequently retailed .as washed sand. Meanwhile, the jaw crusher is still at its work of smashing up the bduldors and the parts are earried

up on a conveyer belt to a second crusher, known as -the hammer crusher, which reduces the sizes still further and deposits them in a large revolving screen with fiye difforent meshes. During the second crushing operation, the sand Whiph r%sults from a certain number of the stones pulverising _ is ** washed away through pipes and deposited' in another sand bin. This sgnd, which is absolutely free from djrt, is called manufacturfe-d sand fand is sold for concrete mix. : Incidentall'y the water used in the whoie process comes up from a deep well dug under the plant, and not from the a'ctual river. The reason for this is that river water would not always be clean, and clean water is essential. But what is going on in the main screen? Revolving at a set speed, it is sorting out the metal into the various sizes, which drpp down into bins immediately below each gauge. Conveyor belts, then carry the metal from each. bin to its respective heap, where it awaits the attention of the purchaser. Metal which is too large to pass through the various meshes is automatically ejected . out • of the end of the screen, and by a system of conveyor belts is earried away and put through the whole process again until it is, of the correct size. Plant Maintenance . Naturally a plant of this nat.ure kuffers considerable wear and tear to many of its parts. ParticuiaNy is this the case with the hammers, which have to be replaced every 30 to 40 hours. There are two hammers to the main crusher, mounted on an axle. They xevolve at high speed and hit the stones when they .are in the air, smashing them against fhe housing of the crusher. The hammers, when installed, weigh 40 Ibs. each/ but are worn and very light when taken out for replacement. The belts used for cohveying the metal have a li-fe of two years and the cost is £1 a foot. Twelve motors, ranging from three' to 40 h.p., operate the plant. At present there is a staff of three men and a youth. At no time, however, is the metal actually tauched by hand, and even when it is being loaded on to lorries, when sold, a mobile mechanical shovel is used. With each bite this shovel takes up three-quarters of a yard of metal and during the visit ,the reporter saw its usefulness when three yards of metal were loaded on to a truck in four- lifts, Not only -rocks are brought up from the river bed, 'but also. all types of queer objects and river deb.ris. A 14-foo,t steel rail, as used on the railways, found its way into the plant just the other day!