256 COALFIKLDS AXD COLLIERIES OF AUSTRALIA. 



filtering area, and is easily cleaned. Experiment has proved 

 that the surface through which feed water is filtered should 

 be at least 250 times the area of the feed water pipe. The 

 filtering medium employed is cocoa-nut fibre, which has a 

 great affinity for oil, and being of a porous nature four plies 

 can be used round each mantle without fear of choking the 

 filter. There are six mantles, each of which passes over a 

 hollow support attached to a round table, which can be re- 

 volved by the spindle (E), Fig. 163. To pass the feed water 

 through the filter, the valves (A and B) are opened, and the 

 valve (C) closed. To pass the water direct to the boilers (C) 

 is opened and (A and B) are closed. The drain cock is opened 

 once or twice a day for a few seconds to blow out the heavy 

 deposits that may lodge at the lower part of the filter. The 



Fig. 164. Portable Electric Drill. 



scum cock on the top of the dome (D) is also opened occa- 

 sionally to blow off the light impurities that gather on the 

 surface. When the pressure gauge shows 20 per cent, above 

 boiler pressure, it is time the mantles were cleaned or changed. 

 In using this apparatus, before removing any of the filtering 

 mantles, open the valve (C) and close the valves (A and B), 

 run the filter dry by the sludge cock on the underside ; remove 

 the dome (D), and each mantle can be removed and a new one 

 put in its place, as each tube carrier is moved round. To 

 clean the inside of the filter, first open the valve (C) and close 

 the valves (A and B), run the filter dry as before, fill it up 

 with clean cold water, which can be done with a 

 head of water through the sludge cock. Admit a little 



