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September, 1935

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The installation of the Hardy air picks at Firtree Colliery, is an innovation which has amply justified the expenditure, the increase in output and the general reduction in working costs having been most notable features since the picks were installed. Their smooth running and the ease by which they are utilised by the coal getters, is a particularly favourable property of these machines.

The machines used is the "Type 37" and is the latest design of Hardypick Limited. It is easy to handle, simple to operate, and has a strong hitting force, and its lightness makes it a particularly suitable tool for coal getting. Other main features are low air consumption (36 cu. ft. per min. at 70 lb. per sq. in.) and low cost of maintenance and repair, once they have been thoroughly inspected before being put in use.

The photographs, Figs. 1 and 2, show the picks in actual operation. Fig. 1 shows the miner using the pick for cutting across the cleat, and in Fig. 2 the pick is being used for cutting in. The way in which the pick is held by the miner shows that its lightness (21¾ lb. with tool), is a great aid, as it enables him to use it in any desired position with no undue fatigue.

Its short overall length (32 in. with tool) allows him freedom of movement, particularly in low places where space is a big consideration. The average thickness of the coal, shown in Figs. 1 and 2, is 2 ft. 6 in.

A comparison of output between the outputs obtained by the picks and by hand-hewing is shown on the graph Fig. 3. This is the output of an average coal getter for a working week, filling tubs of 7 cwt. capacity. The variation of output shown each day is due to local conditions, such as hitches and rolls. These obstacles have to be overcome before the coal can be worked, and timbering has also to be carried out. It will be noticed the picks increased the lead at the start and have held it ever since. Before the picks were installed the coal getters had also to use blasting powder. This was an additional cost, and also involved loss of time due to drilling and firing the shots. There was also the employment of extra men for the removal and stowing of the stone. This necessitated a previous shift of stonemen to prepare the coal face, and to timber and make height in the working places.

The seam worked is the Victoria, and ranges from two to three feet in thickness, with a roof of blue shale. The method of working the coal, is by the bord and pillar. A sketch plan of the workings is shown in Fig. 4. This also shows the air main and distribution of the picks to the working places. With the use of the picks, the coal getters have no need to use blasting powder, and they do the stone ripping and heading. This is included in their shift, while at the same time they have been able to increase the output of coal.

The compressor is a steam-driven unit, capable of developing a 144 cu. ft. per min. at a pressure of 80 lb. per sq. in. The air is piped to the workings by means of a 3 in. main, see Fig. 4, having Victaulic flexible joints, supplied by The Scottish Tube Co. Ltd. The flexibility of these joints renders them very suitable for this kind of work, any variation of alignment being easily taken up. At the headings, a 2 in. reducing tee piece is fitted, and branches led off to the bord ends. There another tee piece is fitted, with the addition of a ¾-in. reducing pipe. Before the hose is fitted, a Hardy stop valve is screwed on to the pipe end, see Fig. 5. The advantage in using this valve is that it obviates the use of stop cocks and other accessories, being automatic in action. When the hose connection is coupled to the valve by means of the coupling, the spindle valve is forced back by the nozzle end, see Fig. 5. This allows the air to pass through the ports in the spindle, and so to the picks. The spindle valve is held in position by the tension spring, which automatically closes the valve, when the hose connection is taken off or screwed back. The valves are fitted to all the pipe ends, preventing loss of air and avoiding waste in making additional joints.

Drawings and Photographs accompanying the article