68 BULLETIN 801;, U. S. DEPAETMENT OF AGKICULTUEE. 



feet of floor area. However, a greater number of heads is very 

 desirable, one head for every 80 square feet being preferred.^ 



The dry-pipe system demands the use o:^ an air compressor for 

 maintaining air pressure in the pipes. A hand compressor is not at 

 all burdensome for warehouses not exceeding 10,000 bales capacity. 

 If the pipe joints are tight the leakage of air should be so slight that 

 the system will need to be pumped up only once a week. The pressure 

 valve, however, should be read every day, 



AH valves supplying the sprinkler system should be kept open and 

 sealed or tagged conspicuously and inspected frequently in order to 

 insure prompt action of the sprinklers. It is well for the manage- 

 ment to keep a record of systematic inspections. Several members 

 of the force and all foremen should be familiar with these valves. 



^The position of the head with reference to the ceiling ancl goods is of the 

 utmost importance. Usually the distance of the head below the ceiling should 

 be from 3 to 10 inches, 6 or 7 inches being preferred. In the case of fire- 

 restrictive construction, protection of the ceiling is of less importance, and the 

 drop of the head may be increased. These requirements are appreciated 

 when the roof contains monitors or saw-tooth skylights. ■ In any case the 

 sprinkler head preferably should be as much as 3 feet above the surface of 

 cotton bales, while this distance should not be less than 18 inches, even if 

 sprinkler heads are only 8 feet apart. Care should be taken to see that heads 

 are not placed so close to the side of beams that the spray is obstructed. 



The arrangement of piping and the size is of vital importance to effective 

 sprinkler operation. If pipes are too small in proportion to their length and 

 to the number of heads supplied, the efficiency of the equipment is vitally 

 impaired in case of a number of heads opening, as this results in a marked 

 reduction in pressure and volume of water delivered. 



This suggests the importance of a suitable location for the sprinkler " riser " 

 which supplies water to the system. A comparison of the plans previously 

 illustrated will show that for compartments 50 by 100 feet the riser is placed 

 in a corner; for compartments which are 100 feet square the riser should be 

 at the center of one side, while for compartments less than 100 feet in one 

 dimension and greater than 100 feet in the other, the riser should be located 

 at the center of the long wall ; and if the compartment is greater than 100 

 feet in both dimensions, the riser should be at the center of the area, as shown 

 by the photograph in Plate XXII, figure 2. It is desirable that the riser 

 always be placed at the center of the area, but there are frequently practical 

 difficulties involved. For example, in a story of 8i feet the clear height below 

 beams is usually only 7 feet or less ; obviously the lateral supply pipe extending 

 from the riser and at right angles to the beams (between which the branch 

 lines carrying sprinkler heads are located) would have to be so low as to 

 seriously obstruct truckers — hence the advantage of having this supply line 

 next to a wall. On the other hand, there are instances where alternate beams 

 are carried by a line of girders, in which case it may be best to place the supply 

 line under the girders in order that the branch lines may be kept well up 

 between the beams. In the ease of reinforced concrete girders of very great 

 depth it is sometimes desirable to provide pipe thimbles (holes) in the girders 



