28 ROUGH-AND-TUMBLE ENGINEERING 



tell you further on why a stop ock is preferable to a 

 globe valve. While the cross head pumps may diiV 

 to location and arrangement, you will find that they 

 require the parts described and that the checks are so 

 placed that they bear the same relation to each other. 

 No fewer parts can be used in a pump required to lift 

 water and force it against steam pressure. More check 

 valves may be used, but it would not do to use less. Each 

 has its work to do, and the failure of one defeats all the 

 others. The pump barrel is a hollow cylinder, the 

 chamber being large enough to admit the plunger, which 

 varies in size from J^ of an inch to i inch in diameter, 

 depending upon the size of the boiler to be supplied. 

 The barrel is usually a few inches longer than the stroke 

 of the engine, and is provided at the cross head end with 

 a stuffing box and nut. At the discharge end it is tapped 

 out to admit of piping to conduct water from the pump. 

 At the same end and at the extreme end of the travel of 

 the plunger it is tapped for a second pipe, through which 

 water from the supply reaches the pump barrel. The 

 plunger is usually made of steel and turned down to fit 

 snug in the chamber, and is long enough to play the full 

 stroke of the engine between the stuffing box and point 

 of supply and to connect with the driver on the - 

 head. Now, we will take it for granted, that, to begin 

 with, the pump is in good order, and we will start it up 



