128 SPRAY MACHINERY AND SPRAY MATERIALS 



of which it is made. Some of the most important parts are 

 the cylinders, valves, valve seats, plungers, agitators, supply 

 tanks, and nozzles. 



Cylinders. — The cylinders should always be made of brass. 

 Sometimes brass tubing of heavy weight is threaded to fit 

 the cylinder heads. Some firms use brass tubing clamped 

 between the cylinder heads, while still others use a solid 

 cast-iron chamber with a brass liner. A cast-iron cylinder, 

 enamelled with porcelain has been used some, but the greatest 

 difficulty with this cylinder is the unevenness of the enamel, 

 and because of this defect it is not generally satisfactory. 



Valves. — There are four kinds of valves found in the spray 

 machine, namely, the ball, poppit, swing check, and steam 

 check. These valves are used in various places in the machine 

 and are used to control the flow of the liquid and to regulate 

 the pressure of the air. Valves are made of rubber, steel or 

 bronze and the bronze valve is the most durable for all kinds 

 of work. 



There are many variations in the four kinds of valves, due 

 to minor changes in the construction of some part, but these 

 are too numerous to discuss in detail. 



Valve Seat. — The valve seat is the place into which the 

 valve fits. The seats are built to receive the particular type 

 of valve which is used. Many of the valve seats are made of 

 iron, with a secondary seat of leather or rubber to prevent 

 back flow. Occasionally hard -rubber seats are used, but the 

 majority of pumps are equipped with removable brass valve 

 seats, which are the most durable and the most desirable. 



Plunger. — The plunger or piston is that part which fits 

 into the cylinder and gives compression. Plungers are fitted 

 with various types of packing. Some of the most common 

 materials used for this purpose are cloth reinforced with 

 rubber, hemp, steam packing, and paraffin canvas. The most 

 desirable packing is one that will last for a considerable period 

 and does not require constant attention to keep it in shape. 



Agitators. — An agitator is a device for stirring the material 

 in the tank during spraying. In a small tank or a barrel the 

 swinging paddles are fairly satisfactory, but in the power 

 sprayers the sliding agitator or propeller are preferable. The 



