CEMENT PRODUCTION.

Otago Witness, Issue 3829, 2 August 1927, Page 7

CEMENT PRODUCTION.

NEW WORKS FOR DUNEDIN. PELICHET BAY TO BURNSIDE. In close keeping with the constantlygrowing extent of Dunedin’s manufactures has been the realisation and recognition, on the part of manufacturers, of the duties of capital. “Noblesse oblige.” It is the duty no less than the right of capital to launch out and expand for the ultimate advantage of the community to which it owes its existence. There have been many instances of late of business firms and manufacturing concerns in Dunedin branching out on a hitherto unthought of scale, and the achievement of the objective in each case has added yet another stone to the edifice of commercial soundness and progress which this city has built up in the past half-century. The latest case in point is that of the Milburn Lime and Cement. Company, Ltd., which is removing its plant from Pelichet Bay. and installing new machinery in spacious premises now in the course of erection and renovation at Burnside. This company’s operations are well known, and a great many people in Dunedin will welcome the news that its directorate has decided to launch out afresh and to erect the most up-to-date works in New Zealand and Australia, replete with facilities that will assure a continuous supply of the finest quality Portland cement. PAST OPERATIONS. It is a far cry back to the old cement works at Fairfield, owned by Mr James M'Donald, from whom the original members of the present company purchased their humble beginnings. Having acquired Mr M’Donald’s diminutive plant and stock, the Milburn Lime and Cement Company set about the establishment of a (then) up-to-date plant at Pelichet Bay. Operations were commenced there in 1890, and for the past 36 yeais the cement making industry has been carried on with more or less success. For a long time Pelichet Bay itself provided the bulk of the' raw material for the works, but at best it was an erratic supply that was secured by means of a small dredge purchased from the harbour board. At times the clay from that source would produce the finest quality cement, but there were also occasions when shell-grit and other impurities made the manufacture of a high-quality article very difficult. The position was not improved in any way by the discarce of the city sewage in the locality, and finally the company decided to abandon these deposits, and look further afield for a more reliable supply. It was then that the company commenced to draw upon the marl deposits at Burnside and further south of Dunedin, and it has been upon thtfee supplies that it has been working for some time past. The Pelichet Bay works accomplished what they were intended t:. io. and sufficed for a good many year- producing an average output of 2800 tor-; a month. OLD SITE TO BE USED The adoption of new and more efficient methods in- other countries, however, and the increasing demand in New Zealand for cement, resulting in the need for greater production, compiled the directors to a consideration of revising their methods and installing a new and up-to-date plant. Thus it was that the company decided to utilise the premises of the old Burnside Cement Company for the establishment of new works. It will be remembered that some years ago the Milbum Company absorbed its smaller rival concern, and closed up the works at Bumside, where little progress was being made in the treatment of the marl deposits in the vicinity. The buildings have been deserted foi a long time. Now, “the stone that the builders rejected has be come the chief corner stone.”

Our representative went out to Burnside last week, and saw the extensive excavations that are in hand, and the sinking of giant foundations, and erection of bridges and the general work of construction, a vast amount of which is necessary before the old buildings that

wore the Burnside works are fit to house the new plant.

MODERN BRITISH MACHINERY. New methods predisposed improved machinery and facilities, and with this end in vew the general manager of the company (Mr J. H. Stewart) and Mr Davidson were sent on a tour of investigation through America. England, and the Continent, where a close study was made of the methods and plants in use. The machinery eventually decided upon was that of a British firm, Messrs Edgar, Allen, and Co., of Sheffield. This plant is now on order, and the first DO tons of it will arrive in Dunediii by the Cambridge from London next week. The erection of this machinery should provide New Zealand with cement works as up to date and efficient as any in the world, capable of producing the finest quality article.

The dry process in use at Pelichet Bay will be discarded and replaced by what is known as the “wet” process, by which the raw material is first reduced, bv the addition of water, to a thick slurry. This will eliminate the dust nuisance in a large degree and facilitate better control of the raw material and the manufacture of a more uniform product. The electrical installations f.o be used include 32 electric motors, the aggregate power of which amounts to 1685 horsepower. Two of the heaviest of these are 450 horse-power Auto-Synch motors for use in the grinding mills’ which will make exceedingly fine grinding—essential to good cement —comparatively easy. These mills will be of the combination tube tvpe. Three immense silo storage tanks will be elected for the accommodation of the slurry prior to its treatment in the giant rotary kiln for which the foundations are now being constructed. This kiln, the largest in New Zealand, is 9ft in diameter 210 ft long, and is one of the new articles of plant rendered necessary by the adoption of the wet process. The works are to be as nearly selfcontained and independent as it is uossible to make them. The plans include a carpenter’s shop, a smithy, and an electrical service station for the motors. To cope with the supplies of raw material on delivery a large railway tippler is provided for in the specifications. Tins will allow of the discharge of a 12-ton delivery in less than two minutes. THE “WET” PROCESS. The plans of the new works were shown .to our representative by Mr Stewart. The various processes through which the marl passes before it is bagged as the best Portland cement are full of interest. The raw material passes first through a great wash mill at the quarrv. Here it is reduced to a sloppy, uselesslooking mass, churned and agitated until it has been converted into a slurry, liquid enough to flow through feeder pipes into the combination mill, where further treatment takes place. Here the. limestone is added, and when the mixing is complete the slurry passes into the three great silo storage tanks, where its chemical ingredients are checked, and the proportions of its various constituent parts are brought up to specifications. While stored in the silos the solution is kept constantly on the move by means of a compressed air apparatus.

Leading from the tanks arg the pines which feed the enormous rotary kiln. The slurry, after the correct period of baking, changes its form, and later emerges from the kiln in clinker form. This is where the functions of the 40 horse-power motors commence. They drive the grinding mills which reduce the small, hard clinkers to the white powdery substance which forms the basis of so much modern building. This is, perhaps, the most important stage of the work. The grinding largely determines the quality of the finished article, and the best’of machinery is none' too good. The work of erection and preparation at Burnside is being pushed ahead as quickly as possible, but it will be some time vet before the old Pelichet Bay works are abandoned altogether and the new machinery commences on it s output of nearly 5000 tens per month. A feature of the plant is the ease with which the material in its various stages can be transferred from process to process. The various parts of the whole are scientifically placed on the plans, so that there shall be no waste effort or energy, and the whole process will be much more in the nature of automatic production than the old method was.