106 



A plunger pump must be given proper care in order to work efficiently 

 and keep it in working condition. It should be carefully cleaned and oiled 

 and at the close of the pumping period it must be emptied in order that it 

 will not be damaged by freezing and the cylinders and water passages 

 cleaned and oiled to prevent rusting. 

 Choice between Centrifugal pump and power plunger pump. 



The choice between a power pump and a centrifugal pump will depend 

 on the lift and capacity. 



In irrigation work power pumps are best adapted to high heads above 

 75 feet and to small or moderate volumes of water, usually under 200 

 gallons per minute. For these conditions the efficiency of a power pump is 

 usually greater than that of a centrifugal pump. For greater volumes the 

 plunger pumps are comparatively expensive and centrifugal pumps are 

 usually preferable unless the lift is excessive. The centrifugal pump has 

 the advantage that it is simple in construction with no parts to get out of 

 order, and that it is cheaper than a power pump. The selection should be 

 made only after careful consideration of the first cost of the pump and the 

 annual cost of fuel, operation and maintenance. Where the lift is high the 

 fuel cost will be considerable and it is good economy not to select the 

 cheapest pump obtainable but one that is guaranteed for a high efficiency. 

 On the other hand if the pump is only to be operated a very small portion 

 of the season it would be poor economy to invest a large capital in a high 

 grade pump to save in fuel cost. 



3. Classes of Engines or Driving Power. 

 Methods of eonnet'tion of pump and engine. 



Centrifugal pumps and power pumps are generally driven either by gaso- 

 line engines, steam engines or by electric motors. The pumps are usually 

 either direct connected or connected by means of belts, gears or chains. 

 Direct connection is preferable when possible, it is more economical in fuel 

 consumption and does away with the adjustment of belt or chain necessary 

 with belt or chain driven pumps. 



The connection of the pumps and driving power must be such that the 

 pumps will be given the speed or number of revolutions per minute for 

 which they are designed and for which highest efficiency is obtained. For 

 this reason direct connection can only be used where the driving power 

 and the pump have the same speed. 



The speed of centrifugal pumps is usually high and so is that of electric 

 motors and for that reason they can, if properly designed, be direct con- 

 nected; this is done usually by means of a flexible coupling. Gasoline and 

 steam engines are generally operated at a much lower speed than centri- 

 fugal pumps and for that reason are not direct connected unless the engine 

 and pump are specially designed. This is done by some manufacturers. 



Power plunger pumps are operated at a slow speed and for that reason 

 are not direct connected to the driving power. 



When connected by gears, belts or chains the driving gear and driven 

 gear, and the driving pulley and driven pulley must be proportioned so 

 that the pump will be given its correct speed. When a plunger pump is 

 built as a single machine with a steam engine, with the piston or plunger 

 of the water cylinder on the same driving rod as the piston of the steam 

 cylinder it is called a direct acting steam pump. The fuel consumption of 

 a steam pump is greater than that of a steam driven power pump and for 

 that reason steam pumps will not be considered. 



