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Colliery Engineering

September, 1957

Work study techniques

Costain Mining Limited have introduced to Acorn Bank a work study unit and the technique has already shown that close attention to operating methods can yield considerable savings in time, effort and cost.

Work study has been applied to getting the facts necessary for keeping the major items of equipment operating at peak efficiency and doing their respective tasks in the most economic way. Some improvements in method have been achieved and more ambitious production plans thus made feasible.

It is hoped to gain from work study, comprehensive data, both for the control of the Acorn Bank contract, and for planning future contracts to a highly developed standard of efficiency.

Accommodation units

An accommodation unit, known as the Costain standard accommodation unit, has been designed which is claimed to be cheap, efficient, quick to build and pleasant in appearance. A constructional method has been discovered based on a 6 ft. module which satisfies all these aims and which lends itself for assembly into buildings to house all types of administrative offices, test laboratories and works canteen: in fact, the normal requirements of industrial administrative buildings. A view of the offices at Acorn Bank, which have been built on this system, can be seen in Fig. 9. The first standard accommodation unit was built at Acorn Bank in 1955 to house the National Coal Board area staff and Costain Mining Limited. In 1956 a large unit was erected at Westfield, Fifeshire, for the Opencast Executive, which is now occupied and functioning as an area office.

This year an extension to the Acorn Bank Office has been completed for the Opencast Executive, and two other area offices at Solway in Cumberland and Gatewen, near Wrexham, will be starting immediately. All these buildings are of the Costain standard accommodation unit design as produced by Reavell & Cahill, FF.R.I.B.A., of Alnwick, Northumberland, who are consulting architects to Costain Mining Limited.

Operating personnel

Costain Mining Limited has at Acorn Bank its resident managing director, K. H. Osborne, under whom are the agent E. Evans (in executive charge of all site work), the deputy agent and chief engineer D. Hutchinson (responsible for civil engineering works, surveys and planning), the plant manager (in charge of the plant depot and field maintenance crews) and the Company accountant (with responsibility for costing, wages, accounts and storekeeping), also a development engineer, field engineers, welfare officer and administrative staff.

In the field is a team of 400 operators of all grades, under a works superintendent, many of whom have been engaged continuously on the Company’s opencast coal contracts for several years. Some of the present staff, indeed, held positions in the first opencast contract undertaken by the Costain group 14 years ago at Waun-y-Gilfach in South Wales, where the largest machine then employed was a 1¾-yard shovel.

Since operations were started in the North East in March 1947, the best men have been retained and moved from contract to contract with the Company, being added to as the contracts grew in size and number; until now at Acorn Bank there is a team well suited to the scale of the operations. Daily and even hourly production figures are known throughout the site and evoke wide interest, particularly when there is a likelihood of bettering a previously-established record. It is the aim of the Company to ensure that every operator knows what is expected of him and how his task contributes to the development and efficiency of the method of working the site.

Restoration

Techniques in restoration have improved almost beyond knowledge since the early days of opencast mining. It is no longer simply a matter of removing first the topsoil, then the overburden, digging the coal and then returning the overburden and replacing the topsoil. Land which is taken over for coal recovery can now be returned to the farmer, tailor-made to suit his requirements. Drainage can be improved, unevenness removed, sloping land levelled down or the contours altered as desired.

So vast is the scale of operations at Acorn Bank that one of the contract conditions is that the land shall be progressively returned to agriculture as the contract proceeds.

The first 12 in., which is generally regarded as the topsoil depth, is removed by scraper and placed in a dump outside the working area. Once the topsoil has been removed the next 3 ft. depth of subsoil is removed in similar manner and also dumped outside the working area, and the earth moving can proceed without fear of damage to good soil.

After mining operations are completed the ground is regraded, hulking of the overburden generally making up for the loss of mineral removed. Subsoil is returned to a depth of 18 in., rooted and stonepicked, the remaining 18 in. spread and again rooted and stone picked, ready for the topsoil to be spread.

Some vital statistics are as follows.

Power available:
h.p.
	Electric	6,000
	Diesel	17,000
	Total	23,000
	Average horsepower per man	100 h.p.
Production per week:
tons
	Overburden removed	540,000
	Coal recovered	16,000
Production per manshift — 6.2 tons.

Coal transport

A new ”cut“ is formed every six weeks. The bulk of the coal is hauled by four 40-ton units to the screens two miles away, each hauler making 60 trips a week (250 miles). In addition, a fleet of 15-ton Euclids and 7-ton Bedfords is used and the coal fleet covers a total of 4,000 miles per week.

Euclids on overburden

This fleet moves 180,000 tons of overburden each week and the average round trip is one mile. Each Euclid carries 20 tons of rock, and the fleet, therefore, travels 9,000 miles per week.

Drilling

About 14,000 ft., or 2½ miles, of drilling is done each week. Since the start of the contract 170 miles have been drilled. Before the contract is finished, over 800 miles of 6 in. hole will have been drilled for blasting.

Area of the site — is 440 acres.

Total dig during contract — will be 120 million cu. yards.

Total dig to date — is 21 million cu. yards.

Coal produced during contract — will exceed five million tons.

Coal produced to date — is 720,000 tons.

Highest day’s output — is 4,017 tons on June 20, 1957.

The cut — is claimed to be the largest man-made hole in Europe. 9.9 million cubic yards of material were removed to form it. Before the contract is completed between 60 and 70 cuts will be made.

Drawings and Photographs accompanying the article