THE IN'JECTOR 385 



5. Using water which naturally contains a large percentage 

 of certain minerals conducive to foaming. 

 The Injector. — The injector on the boiler frequently causes 

 the operator some annoyance by refusing to work. The common 

 causes of this are: 



1. Too low boiler steam pressure. 



2. Steam obtained from a pipe already supplying steam for 



other purposes. 



3. Leaks in suction pipe due to shortage of supply pipe 



or holes in pipe. 



4. Too hot supply water. 



5. Scale in injector, preventing proper working of valves. 



6. Steam containing too much water. 



Oil-separators. — Considerable saving can be accomplished in 

 a creamery if the exhaust steam is utilized. This steam may be 

 used for pasteurizing the skim-milk, for heating the milk previous 

 to separation, for heating the creamery, and for heating the water 

 for the boiler. 



The exhaust steam contains considerable oil and should be 

 purified before it is used for any other purposes. Several forms 

 of steam purifiers are on the market. They are simple, inexpen- 

 sive, and can be attached to the exhaust-pipe of any engine. 



All steam and water pipes should be carefully drained in the 

 winter to prevent freezing. 



Belt, Pulley and Speed Calculation. — The length of a belt 

 may best be determined by measuring over the two pulleys 

 with a tape or a string. 



To calculate the size of a drive pulley when the speed of it is 

 known the diameter of the driver pulley is multiplied by its speed 

 and the product divided by the speed of the driven puUey, the 

 quotient will be the diameter or size of the needed pulley. 



To calculate the speed of a driven pulley, multiply the 

 diameter by the speed of the driver pulley and divide the product 

 by the diameter of the driven pulley; the quotient is the speed or 

 number of revolutions per minute. 



