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November, 1933

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The property operated by the Harton Coal Co. Ltd. comprises four collieries — Harton, St. Hilda, Boldon and Whitburn — in the neighbourhood of South Shields, Co. Durham, and a group of limestone quarries and lime works at Mars den, the whole being interconnected by private railway lines with the single exception of Boldon colliery, which, however, is conveniently situated on the Pontop—South-Shields branch of the London & North Eastern Railway. As will be seen by reference to Fig. 1, the private lines, together with a branch of the L.N.E.R. from Boldon, connect with two shipping staiths on the River Tyne. These are also the private property of the coal company, which has thus excellent facilities for the disposal of its products. At the Low Staiths two towers and loading belts are installed, each capable of handling 600 tons of coal per hour; this equipment was supplied by Goodall, Clayton & Co. Ltd., of Leeds, and is driven by electric motors totalling 278 h.p. A single loading belt, by Sir W. G. Armstrong Whitworth & Co., having a capacity of 400 to 500 tons per hour, is provided at the High Staiths, and is furnished with motors totalling 76 h.p.

With the exception of the 3½ miles of line between Whitburn colliery and the Westoe Lane Station (Fig. 1), which is worked by steam locomotives, the Harton Company's railway traffic is handled by electric locomotives on the overhead trolley system. Ten of these are in use, some being equipped with duplicate 50-h.p. motors and others with four 70-h.p. motors. They are operated, of course, from a D.C. supply, which is derived from three 430-kW. rotary converters situated in the company's own railway substation. A bulk power supply, of which more will be said later, is available from the mains of the North Eastern Electric Supply Co. Ltd.

The steam locomotives consist of two 15-in, by 22-in. shunting type, and six 17-in, by 24-in, six-wheel coupled tender locomotives. As the sketch plan in Fig. 1 has been slightly distorted to get the essentials in a limited space, it may be mentioned that there are over two miles of route between Westoe Lane and Harton colliery, one and a-half miles between Westoe Lane and St. Hilda, and rather over a mile between St. Hilda and the High Staiths. These lines lie for the most part in a highly urbanised district, and their electrification has preserved the amenities to some extent, besides forming the most economic solution to the haulage problem.

Particulars of the various colliery shafts, together with the seams worked, are given in Table I. The original St, Hilda shaft is over 100 years old, and the Harton shaft. which was sunk in 1844, was worked as a separate pit until 1865, when it was arranged for Harton to be a second outlet for St. Hilda. In 1910 both these collieries were provided with additional shafts, that for St. Hilda being situated at Westoe on account of the congested nature of the original site. Both the newer shafts are used for men drawing and ventilating purposes only, the output being drawn from the older pits.

Table I — Particulars of Shafts
Colliery and Shafts	Date Sunk	Depth of Shaft Ft.	Diameter of Shaft Ft.	Seam to which Sunk
Harton
Coal drawing	1844	1,284	14	Bensham
Men drawing	1910	1,267	16	Bensham
St. Hilda
Coal drawing	1827	968	11-12	Hutton
Westoe
Men drawing	1910	1,092	18	Hutton
Boldon
Coal drawing	1866	1,580	13	Hutton
Men drawing	1866	1,526	12	Bensham
Whitburn
No. 1 shaft	1874	1,088	12	Brockwell
No. 2 shaft	1874	670	13	Bensham

Steam winders serve the St. Hilda and Whitburn pits, the remaining shafts being equipped with electrical plant, the two winders at Boldon colliery having been put into commission only this year. Particulars of the various winders are given in Table II. The steam engines at St. Hilda have 36-in, by 6-ft. cylinders and use steam at 70 lb. pressure, while both the sets at Whitburn are fitted with 48-in, by 6-ft. cylinders and take steam at 60 lb. pressure.

With regard to the electrically driven winders, Table II gives perhaps all the data that are required, apart from the two new installations at Boldon, of which full particulars will be given later, when the electrification of this colliery is discussed.

The steam supply at St. Hilda consists of four hand-fired Lancashire boilers, each 30 ft. by 8 ft. diameter, and fitted with economisers and superheaters, the steam pres sure being 75 lb. at a temperature of 450°. At Boldon, six similar boilers were in service, together with two high pressure water-tube units, but this plant has been disused since the colliery was electrified. The steam-generating plant at Whitburn is at present being modernised, and when the scheme is complete will consist of four B. & W. boilers of 40-45,000 lb. per hour capacity at 165 lb. per sq. in. pressure and at a total temperature of 520° F. Four Lancashire boilers from the original plant have been retained to serve as receivers to take the heavy peak load of the winders off the water-tube units. A modern boiler-house, fitted with mechanical coal- and ash-handling plant, is being erected for the water-tube units.

Underground haulage is effected on the main-and-tail system, the larger units being driven by motors ranging in power from 50/ 80 and 250/500 h.p. and taking current at 2,600 volts. For the smaller auxiliary haulages. which are driven by motors of anything from 7½ h.p. upwards, the current is stepped down to 600 volts. A number of small compressed-air haulages are also in use in the immediate neighbourhood of the coal face. Most of the face machinery at this group of collieries is operated by compressed air, and the compressing plant is fairly extensive in consequence.

Table III shows the capacity of the plant installed at the various pits, that at Boldon colliery being illustrated in Fig. 2. These three sets have only recently been put to work and have replaced a turbo-compressor, which was formerly run on a mixed-pressure steam supply. They are driven by dual-frequency asynchronous synchronous motors of English Electric manufacture, and are at present running on a 5,500-volt, 3-phase, 40-cycle supply, the changeover to 50-cycle current not yet having been effected in this area. On this supply the motors develop 865 h.p. and run at 218 r.p.m., but ultimately the speed will be increased to 231 r.p.m. and 920 h.p. developed.

Each colliery is provided with two main ventilating fans, one of which is kept as standby. At Harton two 11-ft. Sirocco fans are installed, each driven by 175-h.p. motors and having a capacity of 160,000 cu. ft. per min. at 3.5w.g. St. Hilda is served by an 8-ft. double-inlet Sirocco fan capable of circulating 230,000 cu. ft. at 3.5 in. w.g., and a 26-ft. Walker fan with a duty of 250,000 cu. ft. at 48 in. w.g., the motors being of 305 h.p. and 410 h.p. respectively. At Boldon there are duplicate 26-ft. Walker fans of 310,000 Cu. ft., 5 in. w.g. capacity, driven by 370-h.p. motors, and at Whitburn duplicate 24-ft. Walker fans of 180,000 cu. ft., 4.2 in. w.g. capacity, are driven by a 350-h.p. motor in the one case and in the other by a 450-h.p. steam engine.

The screening arrangements follow general practice in that they combine shaker screens and hand-picking belts for making the usual varieties of household coals. The centre of interest in connection with this part of the Harton Company's activities is the new central cleaning plant which has been erected at Westoe to deal with the small coal (2 in. to zero) from any of their pits. It will be seen from the sketch plan (Fig. 1) that the site is conveniently situated for all the collieries in the group and, moreover, is quite near the staiths on the Tyne.

As mined, the coal is, practically without exception, bone dry. This, together with the facts that the cleaning plant is in a very exposed position near the sea shore and is close to a residential district, renders it not only necessary to ensure that the whole of the air used in the process is efficiently filtered, but also to eliminate any nuisance due to any dust that is raised when the raw coal is dumped into the elevator boot and when the cleaned products are loaded into wagons. The special arrangements made for avoiding any dust nuisance in handling the raw coal are illustrated in Figs. 4 and 10. Immediately above the bunker is a reinforced-concrete chamber. into which the wagons are run, provided with pneumatically-operated rams and doors. Two suction pipes with adjustable openings are provided beneath the edges of the coal boot so as to give the air-borne dust a downward tendency, the dust-laden air then being drawn off to the filter system. This part of the installation, which is completely effective, was designed jointly by the Harton Coal Co. Ltd. and the Birtley Co. Ltd , the work having been carried out by the former.

From the boot, the raw coal is taken by a totally enclosed bucket-type elevator to the top of the building and screened, at in., in the latest type of Hum-mer units. These screens (type 400) are fitted with a vibrator at each corner, thus keeping the whole mesh surface clear of obstruction. The 2-in, to ¾-in. material is fed to a mild-steel surge bunker above its respective separator, and the undersize is rescreened at 1/8 in. ; the ¾-in. to 1/8-in. coal being bunkered above its separator, and the 1/8-in. to zero being collected by a scraper conveyor and distributed over the two bunkers. The actual sizes of the screening can, of course, be varied to suit the requirements of the trade. The coal from each bunker is aspirated, and the aspirated coal treated on two separators. Refuse from all the separators is collected on a belt conveyor and discharged to wagons by means of a second cross conveyor. All the middlings can be collected on a belt conveyor and returned by means of a chute to the raw-coal elevator for re-treatment, or, alternatively, can be mixed with the dust and taken out as boiler fuel.

The clean coal is in each case delivered to a common belt conveyor running the full length of the plant and discharged into wagons. This conveyor, it may be mentioned has sufficient capacity to handle the whole of the clean coal should the plant be duplicated. Provision has also been made for this conveyor to be extended so that the entire cleaned products can be taken to a future screening plant should it eventually be desired to make screened sizes. The separated dust can either be loaded on to the clean coal conveyor or, alternatively, taken out for use as boiler fuel. Dust from the filters and aspirators is collected in specially designed totally enclosed conveyors, which are so regulated that only a certain maximum amount of dust can be handled. Any overloading and consequent spillage is thus avoided.

As regards the general construction of the plant, the main building is of the steel-frame brick-panelled type. provided with patent glazing, while the dust filters are of reinforced concrete. All the belt conveyors are of the five-shaft ball-bearing type and are fitted with mild-steel hoods for their entire lengths. As is now the standard practice in Birtley plants, the main units are driven by separate motors, which are started up in their predetermined sequence by an automatic contactor gear. Also, should any motor fail, the other motors in direct sequence are automatically shut down, so that any flooding and consequent breakage is avoided.

A point of special interest in connection with this plant is that it is handling a gas coal of high quality — the Harton Coal Company's output consisting almost exclusively of unscreened gas coal, which has the best of reputations in London amid the export trade.

(To be continued.)

Drawings and Photographs accompanying the article