SMALL SAWMILLS, THEIR EQUIPMENT, ETC. 19 
with or open the safety valve. Let the steam outlets remain as they 
are. In really dangerous eases 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. When 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. 
