CONSTRUCTION AND FIRE PROTECTION OF COTTON WAREHOUSES. 69 



The effectiveness of the sprinkler system depends kirgely upon the 

 immediate avaihibility of water under adequate pressure. A sprinlder 

 supplied with water at 10 pounds pressure will discharge about 20 

 gallons of water per minute, while with the pressure at 60 pounds 

 the head will discharge nearly r>0 gallons per minute and distribute 

 the water better. The pressure adopted should be governed by the 

 resulting pressure under flow considered with the cost under the 

 given conditions. For example, gravity tanks, generally used as a 

 primary supply, should have such elevation that the bottom of the 

 tank will be at least 30 feet above the highest sprinkler head. This 

 subject is discussed further under the head of " water supply." 



The automatic alarm service which the sprinkler system affords 

 is a most valuable feature. These alarm gongs may be controlled 



in order that the supply line may be run through them, but this arrangement 

 should be avoided if possible. 



All pipe lines should be supported securely and in such manner as to secure 

 a permanent grade for drainage of the system. Sprinkler heads always should 

 be turned up. 



In the arrangement of piping and heads for reinforced concrete buildings of 

 several stories there will be found frequently a great advantage in the use of a 

 " flat-slab " system of construction in that fewer sprinkler heads may be re- 

 quired or a reduction in story height may be permissible. In any type of con- 

 struction a slight increase in cost of the building, due to spacing or arrange- 

 ment of beams, etc., may be more than justified by a saving In cost of sprinkler 

 equipment. Therefore, it is well to plan always for the possible use of sprinkler 

 equipment even though it can not be installed immediately. 



It is of primary imix>rtance that there be a proper arrangement of supply 

 lines and control valves. It is essential that the control valve be so located 

 as to be accessible during fire for conditions may arise making it desirable to 

 cut off the supply of a section, as, for example, if the roof of one compartment 

 collapsed; otherwise the water supply and pressure may be dissipated to such 

 an extent as to impair the operation of the whole system. Therefore, it is de- 

 sirable that each compartment system be controlled by a post indicator gate 

 valve (a valve which registers whether open or closed) located if possible 40 

 feet or more from the' building. There should be no valve inside the com- 

 partment as they may be closed inadvertently. In the case of a dry pipe sys- 

 tem one dry valve may be used for the equivalent to five single-story com- 

 partments each 50 feet by 100 feet. In such case it is desirable that the dry 

 valve be located 50 feet from the building, with the supply from the dry valve 

 controlled by a post indicator valve. On the discharge side of the dry valve, 

 and beyond the dry-valve by-pass, mains should be takeui off to each com- 

 partment, each main controlled by a separate gate valve, preferably of the out- 

 side screw and yoke type. These valves, with the exception of the post indicator 

 supply valve, should be located, pi*eferably, in the pit with the dry valve. 

 Some plants provide the dry valve near or inside of a compartment, thus af- 

 fecting a considerable saving in piping. Such an arrangement is satisfactory, 

 but is not so good as that previously described. 



When the dry valve is used, it should be placed in a frost-proof pit under- 

 ground or in an insulated frost-proof room. It is an easy matter to prevent 

 freezing of the valve at locations in the cotton belt, but farther north a small 

 amount of heat must be provided. 



