SELECTING MACHINERY AND EQUIPMENT 321 



Tanks holding 200 gallons are common, though larger ones 

 are gaining in popularity. The choice depends on the condi- 

 tions. A 100-gallon tank may be as large as can be handled 

 under certain conditions. 



4. The Agitator. Many spray materials are in suspension 

 rather than in solution. Emul- 

 sions have a tendency to sepa- 

 rate into their component parts ; 

 two or more solutions may not 

 mix freely ^Yhen put together. 

 For these reasons an effective 

 system of agitation of the spray 

 materials in the spray tank 

 is of great importance. Agita- 

 tion may be secured by means 

 of propellers attached to a 

 shaft running the length of the 

 tank near the bottom and con- 

 nected to the pump (Fig. 114). 

 The number of revolutions nec- 

 essary per minute will depend 

 on the size of the propellers^ but 

 should be from 50 to 60 for 

 large ones and a higher number 

 for small ones. 



Paddles which sweep the 

 entire length of the tank close 

 to the bottom to prevent sedi- 

 ment from accumulating are 

 also used. 



5. Transfer of Material from Tank to Pump. The transfer 

 may be by suction or by gravity. Suction feed gives less dan- 

 ger of clogging and does not carry over heavy or coarse sedi- 

 ment to the pump. A gravity feed is satisfactory for ma- 

 terials containing no sediment, but if sediment is present and 

 the machine goes out of action even for a short period the 



{Bardie Mfg. Oo.) 

 Fig. 114. The agitator operates 

 near the bottom of the tank. 

 Its speed may be changed by 

 altering the size of the sprocket 

 at the left. 



