188S 



ENCYCLOl'EDIA OF PUACTICAL 1101tTiCUl,TUKE 



Nos. 1 and 2 are about tlie liesived size to 

 give the inaxiniiim of iluiability and elTici- 

 ency. The niininium size, shown in Fis- -. 

 No. 2, should not be less than three-quar- 

 ters inch in diameter, and the upward 

 range may extend to one and three- 

 eighths inches in diameter, as in Fig. 2. 

 for the maximum size, in large power 

 pump. Small hand pumps may have l)all 

 valves as small as one-half inch in diam- 

 eter. Poppet valves should be much 

 larger in proportion to the amount of 

 liquid passing through them than should 

 the bronze ball valves. It is well to re- 

 member that, w'hen the pumji is running, 

 the valve becomes as much lighter in 

 weight as is the weight of the amount of 

 liquid it dispatches, hence a much heavier 

 valve can be used than a novice might 

 suppose. 



FiK. 



Hall Valves. 



Swing check and steam check valves 

 are types designed for use in water and 

 steam pipes. Both types work well in 

 spray pumps when they are new, but 

 their lasting qualities in a spraying ma- 

 chine are yet to be demonstrated. A flat 

 face in any valve wears unevenly and 

 makes a leaky valve when in combination 

 with a flat valve-seat. Threads or waste 

 sucked through the strainer often lodge 

 across the square edge of the valve-seat 

 and hold grit, hence the desirability of 

 having bevel edges in valve-seats so that 

 such material will not catch. 



Valvc-.Scats 



Valve-seats are built to receive the type 

 of the valve used, and are made corre- 

 spondingly cheap or costly. Iron valve- 

 seats are common, and are usually found 

 in ordinary well pumps. Some few mak- 

 ers use a rubber or leather ring as a 

 secondary seat, which prevents back flow, 

 througii its elasticity, when the weight of 



the liquid or the pressure above holds the 

 valve down. One company has equipped 

 a pump with hard rubber valve-seats, but 

 the majority of the manufacturers use 

 a removable brass valve-seat. Strange 

 to say, no company, so far as I know, 

 seems to have tried to build valve-seats 

 of the harder, non-corrodible alloys — that 

 is, those not affected by spray solutions. 

 In valves, a large part of the wear is on 

 the valve-seat, especially in the case of 

 the bronze-ball types. The ball may wear 

 some, but constant turning keeps it a 

 perfect sphere, while the valve-seat is 

 hammered and worn away at every stroke 

 of the pump, making plain the desirabil- 

 ity of using a harder metal for a valve- 

 scat than is used for the ball. I think 

 that any man who has had experience 

 with pressure pumps will also concede 

 that a large ball valve is the most efficient 

 and durable type made, especially for 

 gritty solutions such as many of the spray 

 mixtures are known to be. Fig. 2 shows 

 valve-seats, and the accompanying balls 

 are on the left and right of the valve- 

 seats. 



Plungers 

 Plungers are fitted with various types 

 of packing. Very few pumps are equip- 

 I)ed by their makers with poor packing, 

 but leather hardens so rapidly that it is 

 almost worthless as a packing for a spray 

 pump, and hence should not be used for 

 plunger-cups when other material can be 

 obtained. The following materials are 

 used for plunger packings: hemp, candle- 

 wicking. steam packing, paraffine canvas, 

 cotton cloth reinforced with rubber, and 

 various other packings which go under 

 trade names. Most of the packings are 

 treated with oils, graphite or paraffin, but 

 this does not include those in which rub- 

 ber has been incorporated. Plungers are 

 usually designed to carry a special kind 

 of packing, and they work better with 

 that kind of packing than with almost 

 any substitute. A packing that is cheap, 

 easily renewed or replaced, and that will 

 last for a considerable period of time 

 without wearing away so rapidly that it 

 requires constant attention to keej) it in 

 shape, is the most desirable. 



