SMALL SAWMILLS, THEIR EQUIPMENT, ETC. 19 



with or open the safety valve. Let the steam outlets remain as they 

 are. In really dangerous cases draw the fires. 



In cases of foaming, close the throttle and keep it closed long 

 enough to show the true level of the water. If the level is suffi- 

 ciently high, feeding and blowing will suffice to correct the evil. 

 In cases of violent foaming caused by dirty water or a change from 

 salt to fresh water, or vice versa, check the drafts and bank the 

 fires in addition. If leaks start in the boiler, repair them at once. 



To blow off, clean the furnace and bridge of all ashes and debris. 

 Allow the fire box or brickwork, as the case may be, to cool down 

 for an hour or two before opening the blow-off. The pressure should 

 not exceed 20 pounds when a boiler is blown out. Blow out at least 

 once or twice in two weeks. In case the feed becomes muddy, blow 

 out some every day. When surface blow cocks are used they should 

 often be opened for a few minutes at a time. After blowing down, 

 allow the boilers to become cool before filling up again. Cold water 

 should never be pumped into a hot boiler; it will cause sudden con- 

 traction in the plate. In tubular boilers the handholes should often 

 be opened and all dirt and sediment removed. When boilers are fed 

 in front and blown off through the same pipe the mud and sediment 

 in the rear end should be cleaned out. Raise the safety valves cau- 

 tiously and frequently; otherwise they are likely to become fast in 

 their seats and useless. 



Should the gauge at any time indicate the limit of pressure allowed, 

 see that the safety valves are blowing off. Keep the gauge, cocks 

 clear and in constant use. Glass gauges are not reliable. In pre- 

 paring to get up steam after the boiler has been open or out of serv- 

 ice, great care should be taken in making the manhole and handhole 

 joints. The safety valve should then be blocked open, and the neces- 

 sary supply of water run or pumped into the boilers. In tubular 

 and locomotive boilers this should be until the water shows at second 

 gauge; in vertical tubulars a higher level is advisable as a protec- 

 tion to the top end of the tubes. After this is done fuel may be 

 placed on . the grate, dampers opened, and fires started. If the 

 chimney or stack is cold and does not draw properly, burn some oily 

 waste or light chips at the base. When steam issues from the safety 

 valve, lower the valve carefully to its seat, and note pressure and 

 behavior of steam gauge. Under all circumstances keep the gauges, 

 cocks, etc., clean and in good order and things generally in and about 

 the engine and boiler in a neat condition. "Wlien a blister appears on 

 the boiler there must be no delay in having it carefully examined 

 and trimmed or patched. Particular care should be taken to keep the 

 sheets and parts of the boiler exposed to the fire perfectly clean, and 

 all tubes, flues, and connections well swept. This is particularly 

 necessary where wood is used for fuel. 



