AUXILIARY FIRE APPLIANCES IN SERVICE
One of the auxiliary appliances of first importance is the standpipe. It is found installed in large apartment houses, office buildings, factory buildings, hotels, etc.
There are two types of standpipe systems, namely, wet systems and dry systems. The wet system is that system wherein there is always water. In case of fire it is only necessary to open an outlet valve on a riser and water is on hand. The ordinary supply of the wet standpipe system is a tank located on the roof of a building and connected to the riser, but many standpipe systems have direct connections to water mains at the lower level, or have fire pumps connected with the water mains which supply them. All standpipe systems should have outside Siamese connections at the sidewalk level for fire department usage.
In the wet standpipe system there is a horizontal check valve just inside the front wall of the building to hold the water in the system, and to prevent it from reaching the connection outside of the building where it might freeze. There is a small drain valve located in the standpipe between this check valve and the outside Siamese to drain off any leakage through the check. There are 2)4-inch outlet valves and connections on each floor, and also one in the cellar and one on the roof. Sufficient hose is provided and connected to the outlets on each floor to cover the entire floor. Where there is a fire pump connected to the system (and usually located in the basement) a check valve is provided just above the pump to prevent damage to the pump should fire engines be connected up to the outside Siamese connections. Where buildings are of excessive height, it is necessary that pressure regulating valves be placed at certain points on the standpipe system. For .instance, a building 200 feet in height, the static pressure on the standpipe at the ground floor would be approximately 83 pounds. With this pressure on the standpipe, if an employee or any other individual was to stretch a line of hose from and open the outlet, in case of fire, it is very likely that some one would be hurt or material damage might be done.
Beneath the supply tank, which is placed on the roof and at least twenty feet above the highest outlet, is usually found a gate controlling valve and on the main supply riser line within the building just below the tank is a swing check valve, placed in a horizontal position. This check closes when water is pumped up through the riser either from the outside Siamese connections or from the fire pump, and prevents the water from going into the tank and overflowing on the roof. This check valve is very necessary as it permits high pressure lines to be connected to the system and thus any necessary and possible pressure to be maintained on the system for fire department use.
Dry Standpipe Systems.
The dry standpipe system is a system wherein the pipes are empty and which are supplied through lines of hose connected to the outside Siamese connections from hydrants or fire engines upon the arrival of the fire department. In the dry standpipe systems, check valves are not required inside the building. The top of the risers are of course not connected to tanks, but are capped. What frequently happens at a fire, where there are dry standpipe systems, especially when the building is closed up at night time, is the failure to get or maintain pressure when the engines are connected to the system. On investigation, it is usually found that a number of the outlet valves on the standpipe have been opened and the water is flowing out on the wrong floors, incidentally weakening the pressure at the outlet where the lines are attached to extinguish the fire. The water damage in such cases is heavy, frequently greater than the fire damage. The orders of the New York Fire Department specify that a man shall go ahead and close all the outlets of a dry standpipe system on the way up, if possible. The dry standpipes are usually equipped with 2½ or 3 inch outlets and valves.
In both the wet and dry standpipe systems, the piping is, in nearly every case, of galvanized iron. Steel standpipes are seldom found. The standpipes are so uniformly well made that they are never broken by the pressure from the engines. They are required to stand a pressure up to 500 pounds to the square inch. Malleable iron fittings are employed. In any standpipe systems, the tanks are only intended to supply the house lines until the fire department arrives.
The desire of architectural interests to improve the outer appearance of buildings led them to advocate substitutes for the unsightly roof tanks. The result was the suggestion of pressure tanks which could be placed in basements and cellars. Such tanks, however, are not recommended or approved by the city for fire protection. It would be all right when pressure tanks were placed in cellars or at lower levels, if pressure therein were maintained at or above 70 pounds. But to maintain a pressure at this figure is next to impossible, for there is a certain amount of air leakage, and then again, the keeping of this pressure at the proper figure depends on the human equation.
The New York Fire Department permitted the use of pressure tanks on the condition that they be placed as required for the ordinary gravity tanks, twenty feet above the highest outlet. If a pressure tank is provided three supplies are afforded, namely: The pressure tank, the gravity tank, and the outside Siamese connection.
The responsibility as to the condition, availability for immediate use and the maintenance of a standpipe system in a building is directly up to the owner, and if a fire should extend owing to faulty standpipe equipment such owner and not the fire department would be subject to censure and possible suit for damage, if such action were instituted.
In apartment houses, and other classes of buildings where the gravity tank is utilized both for fire line purposes and for ordinary house service, the supply pipes for the domestic supply must be connected to the tank at such point to insure a proper and positive reserve supply for fire service. The domestic line is connected above the 3,500 gallon mark and the fire service line is connected from the bottom of the tank. Fig. 115 shows such arrangement.
Where pressure regulating valves are required it is necessary that horizontal swing check valves be placed in a bypass on each side of the regulating valve, to permit the water which may be pumped up through the riser from the outside Siamese connection to pass up through the riser without injuring the regulating valve and to prevent the water from the tank from flowing down the riser without going through the regulating valve.
There are many ways through which standpipe systems may become defective and wdiere defects in construction may render the system faulty. The principal causes of such defects may be enumerated as follows: 1st: check valves being placed backwards: 2nd: horizontal line from Siamese to riser clogged with sediment; 3rd: valve below tank closed; 4th: horizontal line from tank or riser beneath roof clogged with dirt washing down from tank; 5th: mud caking around horizontal check valves and preventing proper seating of same; 6th: wood, brick, mortar or other material left in pipes by workmen upon completion of job; 7th: caps on outside Siamese rusted or corroded and stuck so same cannot be removed; 8th: Siamese or outlet valves having non-uniform or non-standard threads.
In theatres the standpipe system is usually provided with a 250-gallon pump, automatically and electrically operated. This pump is connected directly to the standpipe system and receives its supply from a suction tank. A direct connection is provided from the street mains to the pump direct. The regulations of the Fire Department require that a constant pressure be placed and maintained on the standpipe system in the theatre, and just as soon as any outlet on the system is opened, the flow of water therefrom causes an immediate drop in the pressure on the system which causes a starting device to operate throwing in the electric switch controlling the motor on the pump and causing the pump to operate; a relief valve is provided to prevent an excessive pressure being built up on the system and qs soon as the pressure reaches the point at which the relief valve is set, the excess water is by-passed through a line back to the suction tank.
In all standpipe systems where there arc more than one riser, cross-connections must be provided in the basement or lowest story, to prevent the necessity of water flowing up to the top of the building, across the top floor and then down the other side of the building to reach an outlet where it is required to be used.
In cases where it is found that it is not possible to make a connection to the outside Siamese owing to defective threads or where the caps cannot be removed, it is necessary for the Fire Department to stretch a line inside the building and make a connection to the first floor outlet by using a double female connection, placing the double female on the outlet and connecting the male butt of the hose to the other end of same. When such connection is necessary, the loss of friction is very great, owing to the small inlet and the direction the water supply is forced to take. Fig. 116 shows how the double female is used in making this connection.
One point which is mentioned in relation to the use of standpipe systems in high buildings, where the location of fire on the upper floors requires an excessive pressure on the standpipe to reach the floor where lines may be stretched. This point also applies particularly where employees or even trained men may stretch a line on a lower floor in a building where, owing to its height, an excessive pressure may be present on the standpipe at the lower floor. Always open the nozzle slowly. It may be that the pressure reducing or regulating valve is inoperative and the undiminished pressure of the full column of water of the height of the building will be applied to the nozzle. In closing the nozzle, always close it slowly, or the sudden banking up of the pressure may cause injury to those handling it.
Do not give up when the hose docs not fit the Siamese connection of a standpipe system. Sometimes you will have a reducer or other coupling which has been worn and which, although not having the same number of threads per inch as the standpipe connection, will fit sufficiently tight to meet the emergency.
The sidewalk Siamese connections of standpipes are made with both single and double clapper valves. The latter is probably best suited for the purposes, as there is less danger of the clapper sticking. In the single clapper, the clapper is hinged vertically, while in the double clapper valve the valves are hinged horizontally.
(To Be Continued.)