

PUMPING WATERS. 89 



but in the smaller sizes are liable to easy breakage 

 and uneven thickness of casting. They should be 

 vertically cast in dry sand. 



Each pipe before fixing should be examined and 

 struck gently with a hammer, to detect faults, and the 

 bore should be even throughout. They should be 

 laid with as few bends as possible and with as uni- 

 form a slope as the ground will permit of; a check 

 valve near the pump is an advantage as it relieves 

 pressure at starting. The size of a delivery pipe is 

 usually stated by the makers of the pump ; it should 

 be about J to a -J- the area of the working barrel, and if 

 very long should be increased in diameter to reduce 

 friction according to the conditions laid down in the 

 previous chapter. 



The joints of these pipes may be simple flange 

 joints, with four bolts having square nicks fitting in 

 square holes in the flanges, the packing consisting of 

 a lead ring. In high-class work the flanges are 

 drilled to template and faced in the lathe, red lead 

 being used to finish the joint. In most cases, how- 

 ever, the spigot and socket joint made with run-lead 

 and caulked, or the turned and bored joint, will be 

 found as good as any. They will be described in 

 the next chapter. 



Pipe lines from pump should be so designed that 

 the speed in them will be less than 250 ft. per minute, 

 because it must be borne in mind that fluid friction 

 always varies as the square of the velocity. 



It will be seen from the illustrations that a bottle- 

 shaped casting appears on the delivery side of pumps. 

 It is known as the air vessel, and is for equalizing the 

 flow of water and cushioning it. It relieves the valves 



