NEW YORK FIRE COLLEGE COURSE
(Continued from page 147)
HIGH PRESSURE SYSTEMS.
The concentration of tall and highvalued buildings in the business sections of large cities, and especially where streets are comparatively narrow, and the attendant hazard of conflagration, with its tremendous loss and paralyzation of industry, are well sufficient to warrant the very best of protection from fire obtainable. The success of the high pressure system in New York and other cities seems to indicate that such a system is a formidable adjunct to the firefighting force, making possible the use of sufficient number of streams of effective size and pressure to handle almost any fire that may occur. In the following paragraphs the New York high pressure system is briefly outlined, and such data given as may make its operation clear. The object of presenting such information here is to familiarize the members of the fire department with the capabilities of this system, and not to describe it from a technical standpoint.
There are three distinct and separate high pressure water systems for fire service in Greater New York, as follows: Borough of Manhattan system, with two pumping stations; Borough of Brooklyn system, with two pumping stations, and Coney Island system, with one pumping station. All of the stations except that at Conev Island use electric power. The Coney Island station is equipped with gas engines which furnish the power for pumping. All pumping stations have two sources of wafer supply, fresh and salt water, except the one known as the Upper Station in Brooklyn, which has only a fresh water supply.
The importance of knowing the boundaries of the high pressure system is apparent. Suppose there is a fire in the neighborhood of the high pressure zone, and the pressure in the domestic supply mains is low and the simply insufficient. Tn this case it is practical to run lines of 3-inch hose to connect with high pressure hydrants and a practically unlimited supply of water under good pressure can be obtained. It makes little difference if the friction loss amounts to forty or fifty pounds, for the nozzle pressure can still be maintained at a very effective figure. Quantity and pressure are what are needed, and the high pressure system assures both of them.
*Copyrigtit, 1918, by Fred. Shepperd.
Duplex, or two parallel lines of mains, are laid on Houston street from the Bowery to the East River, and all other streets south of Houston street and running north and south are equipped with dual mains. The balance of the system is composed of single mains. In order to determine on which lines hydrants are connected, the hydrants’ tops have been painted either white or green, the white indicating one line and the green, the other. Should a break occur in one of the mains, the pressure will fall in both lines and the pressure in all hydrants will, be noted to fall. As soon as the engineer at the pumping station discovers the drop in pressure, he immediately closes the valve in either of two duplex mains to determine in which one the break has occurred. When he finds the pressure begins to creep up when one of the mains has been cut out, by means of the electrically controlled valves, he is safe in.assuming that the main into which he is pumping is the one still in working condition.
Hence when operating at a hydrant and the pressure drops, the men should wait until the pressure either fails entirely or until it again picks up. If the former is the case, the men should immediately connect .their .lines up. to the other hydrants, i. e., if operating on the green hydrants and the pressure finally fails entirely, connect the lines up to the white hydrants. It is always best to have one man go to the hydrant when the pressure, fails to be ready to disconnect if such is necessary.
The principal features of the system in Manhattan are a gridironed svstem of underground pipes. 12 to 24 inches in diameter, to. which is connected two pumping stations taking water from the Central Park Reservoir, and each supplied by a 36-inch line. At each station the 3.6-inch line passes through the wall and is tapped by the suction pines of the various pumps. There is also at each intake of the pumps a connection to connect up with the salt water lines from the East River and North River, respectively. Each station is supplied with two 36-inch salt water intake lines. When pumping fresh water the pumps are ordinarily fed under the reservoir pressure of 36 pounds, but when salt water is to be used it must be lifted from the river. To take care of this lift, auxiliary pumps, known as vacuum pumps, are used. The function of the vacuum pump is to expel the air from the centrifugal pump, which, bv itself, is unable to create a suction without first “priming” or filling with water. The vacuum pump removes the air within the pump chamber and intake pipe, producing a vacuum, and the atmospheric pressure without forces the water up into the intake pipe and into the chamber of the pump. Of course the same rule applies here regarding maximum suction lift that applies in the case of any fire engine, that it, the water, cannot be lifted more than 34 feet under any condition, and usually not more than 25 feet.
Each station is equipped with 6 centrifugal pumps, driven by direct connected induction motors as shown in Figure 79 of the interior of the South Street Station. Each pump was guaranteed to deliver 3,000 gallons of water per minute at 300 pounds pressure, and at the acceptance tests did deliver an average of 3,600 gallons per minute, a total of 43,000 gallons for both stations. The delivery is proportionately greater at low pressures, and reaches a total of about 62,000 gallons per minute at 200 pounds pressure and 66,000 gallons at 150 pounds. Fresh water is used, unless in case of emergency, as it causes less damage to stock than salt water, and also because it has less effect on the pipes, and apparatus of the system. The range of pressure on the high pressure system is from 125 to 300 pounds. Pressure is not kept up at all times, but when a fire alarm comes in from the district covered by the system the pumps are started and pressure raised to 125 pounds. This takes less than one minute, so that the water is always ready before the fire department has a Tine connected to the hydrant and ready for use.
The pumps can operate only at one speed, regardless of the discharge or pressure desired. Their normal rate of speed is. 740 r.p.m., and this is the speed they attain when started at any alarm. The regulation of pressure and discharge is arranged for by the use of relief valves, which are nothing more than churn valves, and which divert the water from the discharge pipe back to the intake side of the pump. While this churning of the water may cause a slight rise in temperature, there is little danger of any damage to the pump resulting, for the flow of water through the pump is well capable of keeping the temperature down.
Should the high pressure pumps fall down, it is possible to connect fire boats to the system by means of hose lines and maintain satisfactory streams, although the supply would be limited. In Brooklyn special hydrants have been installed to facilitate connecting up by fireboats. while in Manhattan any high pressure hydrant is suitable for connecting up by the boats. Relative to this point, it may be mentioned that it makes little difference where the boats are connected to the system, for the pipes of the system are always filled up to the level of the hydrants, and the loss by friction for the maximum length of the system has been found to be less than 5 pounds. Thus a boat giving 150 pounds hydrant pressure at one end of the system could be expected to give at least 145 pounds at the other end, provided the. other end i? fit the same level. There will likely be, of course, considerable loss by friction in the lines of hose leading from trie boats to the hydrants. A point which should be borne in mind by an officer in ordering a fireboat to connect up to the high pressure system is to send a hose company to the dock where the boat or boats are to land and have the lines ready to attach to the boat or boats on their arrival.
The equipment of the upper station of Brooklyn consists of three centrifugal pumps and of the lower, five pumps, or a total of eight. They are built up in 60-pound stages. Each pump has five stages and is therefore capable of producing 300 pounds pressure. The upper station is only supplied with fresh water, and should the supply give out the lower station could supply the territory of the upper station as far as the supply would go. The fresh water supply for the Brooklyn and Coney Island stations is taken from Ridgewood Reservoir. The lower station has also a supply of salt water available, as has also the Coney Island Station.
The Coney Island Station is equipped with three sets of piston pumps, three in a set. They are driven by three 170 horse-power gas engines, and the gas is supplied by the solitary gas company operating in that district, so that in case of accident to this gas plant, the pumping station would be put out of service. The pumps are capable of delivering 1,500 gallons of water per minute per set under a pressure of 150 pounds. The total capacity of the three sets is 4,500 gallons at 150 pounds. The principle of operation of the pumps is very similar to that of the old Amoskeag steam fire engine pump. The Coney Island Station has two 12-inch supply lines from the Ridgewood Reservoir, and an alternate 20-inch intake line extending out into Coney Island Creek to supply salt water. While this system has a liberal supply of hydrants placed along the principal thoroughfares, and also two large stationary turret pipes with 4-inch barrels, the capacity of the pumps at the station is sorely inadequate to serve as protection for this highly inflammable section in its entirety. A pressure of 60 pounds is maintained on the system at all times.
The precautions taken to insure the dependability of the pumping stations and the reliability of operation includes pumping stations of fireproof construction throughout, protected against exposure fires and located outside the conflagration zone as shown by the illustration of the South street station (figure 80), duplicate mains from the pumping stations in the gridiron system and automatic relief and pressure-regulating valves at each station; power for operating the pumps supplied from five different power stations of the New York Edison Company, with duplicate sets of underground cables to each pumping station. To make the electric supply still more reliable, the Edison Company has made contracts with the Interborough Rapid Transit Company of New York and the Brooklyn Rapid Transit Company and the Brooklyn Heights Railway Company of Brooklyn to furnish power in case of emergency. Besides these, the company also maintains a turbine engine ready to operate in case the other sources should fail. As mentioned before, the Coney Island station is dependent solely upon the one source of power, i. e., the gas company supplying gas to that neighborhood. Should this source of fuel supply fail, the plant would be compelled to shut down. The system would thus be useless, for it would be impracticable for the fire boats to get sufficiently near in time to supply the system.
(To be continued.)