PUMPING MACHINERY 267 



split or ornamental. It is a great advantage in fitting the 

 standard to a driven well to have the base adjustable, 

 doing away with the necessity of cutting the pipe an 

 exact length in order to have the base rest upon the 

 pump platform or having to build the platform to the 

 pump base. 



379. Force pumps. Force pumps are those designed 

 to force water against pressure or into an elevated tank. 

 In order to do this the pump rod must be packed to 

 make it air tight. Force pumps are also provided with 

 an air chamber to prevent shocks on the pump. It is 

 common practice to use the upper part of the pump 

 standard for the air chamber. It has a vent cock or a 

 vent screw to permit the introduction of air when the 

 pump becomes waterlogged. With tubular wells it is 

 an advantage to have a pump standard with a large open- 

 ing its entire length and a removable cap to permit the 

 withdrawal of the plunger or cylinder. The two most 

 common methods of providing for this are to have the 

 pump caps screwed on and to have the cap and the pump 

 top in one piece. In the latter case the entire top is made 

 air tight by drawing it down on a leather gasket or 

 washer on the top of the standard. 



380. Double-pipe pumps or underground force pumps. 

 This class of pump is used where the water is to be forced 

 underground, away from the pump to some tank or reser- 

 voir. These pumps are built with either a hand or a 

 windmill top. A two-way cock is provided, manipulated 

 from the platform to send the water either out of the 

 spout above the platform or through the underground 

 pipe. As the piston rod of these pumps has to be packed 

 below the platform where it is not of free access, we 

 find in use a method of packing known as the stuffing- 

 box tube to take the place of the ordinary brass bush. 



