SMALL SAWMILLS, TLIEIE EQUIPMENT, ETC. 21 



and some form of tannic acid as tlieir base. Tannic acid has a slight 

 action on the iron of the boiler and is reasonably efficient in prevent- 

 ing scale from sticking. 



To prevent scale, or at least to diminish the injury it does to 

 boilers, the feed water should be heated by live steam under boiler 

 pressure in a separate vessel before going to the boiler. By allowing 

 the water to settle for some time, sediment, mud, and dirt will be got 

 rid of. Oil from the engine cylinder is particularly injurious to 

 boilers, and, when noticed in the condensed steam, should be carefully 

 removed. 



STEAM PUMPS. 



If water can not be obtained under sufficient pressure to cause it to 

 flow into the intake by gravity, some sort of pUmp is necessary. 

 Usually the pump runs by steam. If the pump runs badly, make sure 

 the water valves and water pipes are all right before examining the 

 steam end. When the pump is not in use in cold weather open all 

 the cocks and drain plugs to prevent freezing. Always see that the 

 pump has a full and steady supply of water to work on. Do not take 

 the pump apart to see what is inside as long as it does its work well. 

 Set a pump on a level solid foundation so as to avoid undue strain on 

 the pipes and resulting leaky joints. Long pipes should be larger 

 than short ones, to allow for increased friction. All pipes should 

 be as short and straight as possible. A foot valve and strainer 

 should be attached to the suction pipe. 



Use few elbows, tees, and valves, substituting full round bends for 

 elbows, and wyes for tees; sharp bends greatly increase the friction. 

 Care must be taken to guard against leaks in the suction pipe, as a 

 very small leak will supply the pump with air to its full capacity, and 

 little or no water will be obtained. A suction air chamber made of 

 a short nipple, a T, a piece of pipe smaller in diameter than the 

 suction pipe and from 2 to 3 feet long, and a cap, screwed upright 

 into the suction pipe close to the pump, are always useful, and when 

 the suction pipe is long, in high lifts, or when the pump is running 

 at high speed, it is a positive necessity. Its use insures a steady 

 and uniform flow of water through this suction pipe and prevents 

 " pounding " or " water hammering." 



Use good cylinder oil, and oil the steam end just before stopping 

 the pump. Keep the stuffing boxes full of good packing, well oiled, 

 and just tight enough to prevent leakage without excessive friction. 



WATER POWER. 



As a general thing, water power is not practicable for a portable 

 mill. It may be found in one location, but not in the next. It is 

 cheaper than steam, but the source of power is neither uniform nor 



