April 3, 1914. THE COLLIERY GUARDIAN. 735 Coaldust Experiments at Tirpentwys Colliery. BY AN ENGINEERING CORRESPONDENT. Among the various experiments which are being conducted in the South Wales and Monmouthshire coal- field to deal effectively with the deposit of fine coaldust in the main intake and haulage roadways, one of the most interesting, though simple, and, under certain condi- tions, most effective methods, is that devised by Mr. B. Nicholas, at Tirpentwys Colliery, near Pontypool. Mr. Nicholas has been experimenting for some time "Plaskfd %>"■ ^ramc Fig. 1.—Section of Frame in Roadway. THE USE OF WATER SCREENS. about 200 yards, the site chosen being a part of the roadway where a frame can be erected as close to the roof and sides as possible, and thus form a fairly tight air seal around the screen. In most cases cemented stone walls supporting steel girders, and lagged with sheet iron plates, have been constructed at these places, into which the frames, measuring about 10 ft. by 6 ft., are built, as shown in fig. 1. slope outwards at the bottom so that the water, from the spray pipe will fall on the front of it and form a water film across its whole surface. The screen (as shown in fig. 2) consists of three layers, the front A and back 0 layer being punched sheets with 50 per cent. 1 in. in diameter holes, and between these a wire-woven 18-gauge mesh screen B. The screen is made in five sections, four through which the air and wet dust is driven, and the fifth, D, a small door through which the workers can pass when necessary. A 2 in. diameter compressed-air main E is carried along one side of the roadway, with air at a pressure of 80 lb. per square inch. On the other side of the roadway a 2 in. water main F is laid, conveying water from the pipes in the shaft at a pressure of about 300 lb. per square inch. A branch standpipe Gr (fig. 3) is connected to this every 40 yards, and from this a f in. perforated pipe H is carried along the front of the screen. The water passing through the perforated pipe H covers the front of screen on the intake side, so that it will be driven through the apertures by the air current containing the fine coaldust in suspension. The coaldust on the roof and sides is dislodged by means of compressed air from the 2 in. main, through a 1 in. rubber hose connection fitted with a “ rose ” con- taining a number of very small apertures. The hose is about 40 yards long, enabling about 80 yards lengths of roadways to be cleaned from each connection to the compressed-air mains. To enable the operator to direct the force of the blast and keep well behind the dust cloud, a 6 ft. rod of wood is strapped to the hose at the outlet end w hich acts as a handle (fig. 4). The “ rose ” is directed against the roof and sides, dislodging the dust in dense clouds into the air-current. This dust is exceedingly fine, and most of it remains suspended in the air-current until it reaches the screens, at a distance of 200 yards, where it is caught by the water and deposited as a “ slurry ” at the foot of the screen. When the velocity of the air-current is very high, some of the moist dust passes through the screen for a few yards, but soon drops to the floor. On the occasion of a recent visit by the writer to Tirpentwys Colliery to inspect this system, he took the fRrea 1/5+7* 'Water Mom Z' Fig. 2.—Sectional Elevation of Screen. To 2//Vain (Tomfireesei JJir/fye. \ \ \Scrten. >- Fig. 4.—Arrangement for Removing Coaldust from Timbers, &c. past to find a suitable method of dealing with the coal- dust deposits on the roof and sides, where a general system of watering could not be applied on account of the softening action produced on the strata. Although the method in use at Tirpentwys has up to the present been more or less experimental, the results have been so satisfactory that Mr. Nicholas has decided to apply the . system generally throughout the whole of the colliery. One of the great difficulties to be faced in the South Wales and Monmouthshire coalfield with respect to the treatment of coaldust deposits is the crumbly nature of the roof in many of the mines, which not only prevents the application of water, but produces large falls (often reaching a height of from 20 ft. to 40 ft., and neces- sitating cogging on top of the timbers) forming cavities which act as traps for the finest particles of coaldust. The difficulty of stonedusting such cavities by hand led, in several cases, to the introduction of stonedusting by sprinklers through compressed-air injectors, but it was found that the force with which the stonedust was injected drove out large quantities of fine coaldust, which was carried toward the faces by the air current, rendering that part of the mine which is most difficult to stonedust exceedingly dangerous. It was thought by Mr. Nicholas that if the dust could all be driven forward against a screen covered with water all this coaldust might be collected and thus save the need for stonedusting. The general method adopted at Tirpentwys is to erect a screen at fixed intervals of Fig. 3.—Cross-section of Screen. Frame 77ai/ Leuet FSSS^-S ZMrMam. /tire M* J’ % It is now suggested that recesses should be formed in these walls, and the screens fixed permanently by being made to fold into the recess so that they could be readily drawn across the roadway when required. The frame (as shown in fig. 3) fits tightly against roof, sides and floor, and the screen is simply laid against it and kept in position by a few wood wedges. It is made to opportunity of traversing the road from the screen to the point where the coaldust was being dislodged—a distance of about 60 yards—to form an idea of the amount of dust which had collected in the interval between that date and the previous cleaning, which in this case was only eight days. It was surprising to find the dustcloud so dense that breathing became very