In light of the difficulties the Philadelphia Fire Department encountered while attempting to use the standpipe system at the One Meridian Plaza fire on February 23-24, 1991, fire departments should inspect and understand the operation of each standpipe system in their jurisdiction. This way, you can familiarize yourself with each standpipe system and know that it will operate properly during suppression operations. All officers and firefighters should be familiar with how standpipe systems are engineered and what combination of devices—pumps, piping, and valving—is used to ensure that useful operating pressures arcavailable in all parts of an occupancy.
Standpipe systems provide a largediameter, metal “water main,” permanently installed in a building, to which firefighters can connect hoselines for firefighting operations when distances or height precludes efficient stretching of attack lines directly from a pumper. Standpipes are found not only in vertical occupancies but also in structures that are low in height but cover a vast amount of area. Examples are steel mills, automotive assembly plants, shopping malls, subways, warehouses, and oil refineries. Standpipe systems containing 1 1/2inch connections in predominantly horizontal occupancies may be supplied from the sprinkler system piping, and because overcoming or controlling head pressure due to height is not a factor, their use should pose no unusual problems for firefighters.
Most problems fire departments encounter when operating from standpipe systems occur in high-rise occupancies because of the need to generate and control the high-system pressure required to deliver water to great heights. The standpipe system must be provided with some means to overcome head pressure in order to deliver water at an effective firefighting pressure to the upper floors. This can be accomplished with city main pressure alone if that pressure is high enough and the building is only a few stories tall. The most common practice is to supply the system with building fire pumps, either alone or in series.
Built-in fire protection systems are designed by fire protection engineers who calculate incoming city water main pressure, friction loss in piping, pressure loss due to height, and pressures needed on each floor to generate effective firefighting streams. Most systems can be engineered to meet NFPA 14 (the most commonly used standard), the standards contained within various national or state building codes, or standards adopted by individual jurisdictions. In many designs, these codes are only a starting point. Many times the written standards are modified to fit special or individual conditions. For example, trade-offs may be made, most often to reduce system cost, by compartmentizing floor space to reduce waterflow requirements or to utilize highsystem pressures to eliminate the expense of extra risers (the large water main that is installed vertically in a building), valving, and pumps. Each system is unique to its building, and probably the vast majority of installed systems do not conform exactly to code. Expect the unexpected, therefore, when working with standpipe systems, especially if you are not the authority having jurisdiction over system design and construction. Experience has shown that even similar buildings in the same project may have entirely different fire protection systems, emphasizing the importance of inspecting each system.
Class I. Class I systems provide 2 Viinch connections for heavy streams and are designed solely for use by trained fire suppression personnel. The hose outlets generally are located in “protected” areas such as stairwells and in most cases are not provided with hose.
Class II. These systems provide outlets with only 1 1/2-inch connections and are intended for use by building occupants. They are installed complete with racks or reels, hose, and nozzles. It is possible for fire departments to remove the attached hose and stretch their own lines from Class II connections. However, remember that Class II connections will flow less than Class I or Class III systems. These should be located so that all portions of a building are 130 feet from a hose-rack station.
Class III. Class III service combines the elements of Class I and Class II systems, providing a 1 1/2-inch hoseline as well as a separate 2 1/2-inch valve for fire department use. Some older Class III systems provide a 2 1/2-inch outlet to which a 2 1/2-inch firefighting line is connected. Depending on the code followed for design, both connections may be located inside a fire-resistant stairwell or the hose racks may be located inside the fire occupancy and the 2 1/2-inch fire department floor hose valve located in the stairwell.
Class I and Class III standpipe systems usually are rated for total water supplies for 500 gpm from any one riser and 250 gpm for each additional riser, and the total gallonage is not to exceed 2,500 gpm. Class II systems require 100 gpm per outlet.
When inspecting standpipeequipped buildings it is important to note the class of service installed in each occupancy, including any combinations. For example, in the One Meridian Plaza building, the Class 1 standpipe system supplied both the sprinkler systems installed on a number of floors as well as the stairway hose valves. A Class II system also was provided, which drew its supply from the domestic water system. (Domestic water pumps are not as reliable as fire pumps because they are not required to have such carefully designed prime movers.) Remember, most standpipe systems and all highrise systems that supply sprinklers provide some type of water-flow alarm. If a Class II system is supplied from the domestic water mains, unless the cabinet door is wired into the alarm system, no water-flow alarm will be received if the line is stretched by occupants to extinguish a fire. Of main concern to suppression forces is how each individual standpipe system is supplied with water.
The simplest of all systems, a manual or dry-pipe system consists of a dry pipe that runs from ground level (or below) to the roof with hose outlet valves on each floor. It can be supplied by a building fire pump, fire department connections, or a combination.
A manual system may or may not have a dry pipe clapper valve, which is held closed by compressed air. This air is placed under pressure within a standpipe system and holds the clapper valve closed until the system is vented when a hose valve is opened. When the air pressure drops, water flows, causing pressure switches to close, activating the fire pump and transmitting the alarm. In some systems, the fire pump is activated by pull stations near each floor hose outlet. Some systems installed in parking garages or other locations prone to tampering may utilize a combination of supervisory air and a pull station. Dry-pipe systems normally do not have hose installed on the floor valve outlets, as they are intended solely for fire department use and should be marked as such with a sign. Some dry-pipe systems are carried wet—the pipes are filled with water to reduce time to charge the system, but it is not under pressure.
Dry-pipe operations. The first-due engine company connects supply lines into the fire department Siamese connection and pumps the pressure necessary to provide the fire floor with water at a usable pressure. It must be remembered that a single typical fire department pumper may be able to provide usable pressures only to about the 30th floor. If the building is higher, building pumps must be available to boost the pressure. Building pumps supplying drypipe systems can have automatic starters, activated by the reduction in supervisory air pressure, but many must be started manually by the activation of pull stations or by the building engineer. When inspecting such a system, all firefighters should be shown how to manually activate the pumps in case the building engineer is unavailable. This information should be recorded on a preplan sheet and be available to all applicable suppression companies.
Two major problems can affect the proper operation of dry-pipe systems. The first is safely vented compressed air. As a dry pipe is charged with water, air trapped in the system above the supply point will be compressed as the water column rises. If hose is connected at the point of operation and the floor valve is opened, compressed air, sometimes under hundreds of pounds of pressure, will be vented, which can cause the hose to burst or the nozzle to become uncontrollable. Depending on the design of the system and the distance from the supply point, it may take quite a bit of time to get water to the point of operation. All this time, compressed air will be roaring out of the hose outlet, making communications difficult To avoid this, vent compressed air two or three floors below the point of operation as engine companies are connecting lines and preparing for operation. When water is obtained at the lower outlets, the valve on the operating floor can be “cracked” to vent air until water reaches the valve. The valve then can be operated normally.
A second problem with dry-pipe systems is that a number of floor valves may be open due to lack of inspection or vandalism. Water may pour from open valves remote from the point of operation of hoselines. Additional crews may have to be assigned to check the system from top to bottom to close these valves, which can delay firefighting operations.
Except in areas prone to freezing or vandalism, dry-pipe standpipe systems are relatively rare in new highrise installations. Today dry-pipe systems are installed mostly in parking garages, unheated occupancies, and cold-storage facilities. Conversion to wet-pipe systems is common, especially when buildings containing drypipe systems are retrofitted with sprinklers. The Class I standpipe system installed in the One Meridian Plaza building was a converted drypipe system.
Wet-pipe systems are standpipe systems that are kept charged at full system operating pressure—in theory, instantly providing firefighting water at any outlet.
Water supply. In many older systems, especially in large cities, wetpipe standpipes are supplied from a gravity tank on the roof. These systems are calculated to provide for about 30 minutes of use before the tank is drained and the system has to be supplemented by fire department pumpers.
Most new systems are the wet-pipe type, supplied by building fire pumps usually located in the basement or at grade in a pumphouse in the case of horizontal standpipe systems. These pumps can be either electricor diesel-driven (older installations may have pumps driven by natural gas or gasoline engines). Many installations have a combination of pumps driven by both electric motors and diesel engines. Building fire pumps usually take their suction from the city water mains, although in earthquake-prone areas they may take suction from a reservoir filled by city mains.
It is important to determine suction sources when inspecting wet-pipe systems. At the First Interstate fire in Los Angeles, engine companies pumped into a Siamese connection they thought directly fed a standpipe riser, only to discover later that it supplied water to refill a suction reservoir.
In most installations, water pressure is maintained in the system by the use of a small pump called a jockey pump. This pump compensates for small changes in system pressure caused by fluctuations in city pressure, leaking check valves, or temperature variations. If a floor hose valve is opened for firefighting, a drop in pressure, usually about 25 psi, will cause pressure switches to activate, automatically starting the building fire pumps.
Depending on the height of the building, fire pumps may be installed on upper floors. In Chicago’s 110story Sears Tower, a number of fire pumps are installed on the upper floors, taking their suction from large reservoirs filled by fire pumps on lower floors and by the domestic water system. By relaying water through a series of upper-floor fire pumps, enough pressure and volume are obtained for fire streams on upper floors.
The Chicago building code is unique in that it calls for standpipe systems to be split, or zoned, usually every 20 floors. Other codes call for 275to 400-foot zones, depending on system design. Standpipe systems that have larger zones, due to the high pressures needed, require pumps that will produce these pressures and pressure-regulating valves that will handle them. Water can be supplied to a zoned system either by a series of fire pumps installed on lower floors or by the use of relay reservoirs and booster pumps. Pipes called “express risers” are used to transport water nonstop from fire pumps on a lower floor to the set of floors each pump is designed to supply. This means that a pump in the basement may have to pump water at pressures from 400 to 600 psi in order to provide adequate working pressures on upper floors. Express risers that carry this water have no hose valves on the lower floors, eliminating the possibility of dangerous high pressures being available on those floors. Because of the relatively short height requirements mandated for each zone, zoned systems usually are provided with floor hose valves having no pressure-control devices.
Providing zoned systems, while ideal for fire department operations, is a very costly proposition. To overcome the high costs of providing fire protection water to the upper floor of high-rise buildings, many codes now allow for single-zone risers to service all floors by using a combination of high riser pressures along with devices designed to reduce operating pressures on lower floors.
In order to deliver water up a standpipe riser at usable pressure on the topmost floor (which is required by most standards to be only 65 psi at the valve outlet), the riser water pressure will be much higher at lower outlets than at upper outlets. In Class I and III systems, most codes specify a flow of 250 gpm delivered from each outlet at about 65 psi. In Class II systems, the flow requirement is usually 100 gpm also at 65 psi.
While not designated as a pressurecontrol device, the common floor hose valve often is used by suppression personnel to restrict flow, and thereby pressure, on hoselines. These valves have screw shutoffs and normally are rated to operate at system pressures between 100 and 300 psi. Although some standards call for devices to restrict outlet pressures to 100 psi in Class I systems, some codes, such as Chicago’s, specifically eliminate the requirement for restriction. Under these codes, pressures up to 175 psi may be encountered when operating from valves without restriding devices.
While opening or closing the valve to control pressure works when the water is flowing, when the nozzle is shut off the entire system pressure will build up beyond the hose valve, even if it is partially shut, and will be available at the nozzle when it is opened again. This method cannot control excessive pressures under noflow conditions unless the hose valve is completely shut off.
If riser pressures above 100 psi are encountered, most codes require that each floor hose valve outlet be provided with a method to reduce operating pressure to about 100 psi. Two classes of devices are available to automatically reduce outlet pressures to within standards: pressure reducers and pressure regulators.
Pressure-reducing devices. There are three common types of pressurereducing devices. One is a pressurerestricting disc, or orifice plate, which looks like a large washer with a small hole. It is inexpensive and commonly used in Class 11 and Class III hose-rack systems. If the only standpipe valve on a floor is connected to a Class II firstaid hose rack, the fire department will have to remove the first-aid hose as well as the pressure-reducing device before connecting the firefighting line. The second device is a removable pressure reducer. This unit normally is attached to a hose outlet by fire hose screw threads. It too should be removed if firefighters attach their own hoselines to a floor hose control valve.
A third device is on the valve itself. Some floor hose control valves are manufactured with stops that physically limit the distance the valve can be opened. On most of these valves, the device can be overridden by fire department personnel by removing a pin or fracturing a holding link, permitting the valve to be opened fully.
Remember that these pressure-reducing devices control pressure only under flow conditions. They will allow’ full system pressure to pressurize the hoseline when the nozzle is shut off, and they generally are specified for use on those systems where the riser pressure does not exceed 175 psi.
To design less costly systems, riser pressures higher than 175 psi are used to eliminate the expense of extra pumps and piping associated with zoned systems.
Some jurisdictions, especially on the West Coast, now are allowing a single riser to operate at pressures up to 600 psi. Imagine what would happen if a simple hose valve were opened on a lower floor, providing nozzle pressures of 600 psi on 1¾inch line. To safely handle these higher riser pressures, a new style of floor hose valve called a pressure-regulating valve commonly is used.
Pressure-regulating valve (PRV). This valve controls the outlet pressure under flow and no-flow conditions. This is accomplished by a floating valve seat, controlled by springs and balanced pressure discs. PRV operation is very similar to that of a pumper relief valve except that the PRV does not bypass excessive pressure—it controls it by automatically adjusting the size of the valve opening.
The PRV usually can be recognized by its size, as it normally is much larger (taller or larger in diameter) than a standard hose valve. It is avail-, able in two types: factory preset and adjustable.
Some pressure-regulating valves are preset at the factory to the pressure requirements designed and specified by fire protection engineers before the system is constructed. Since each valve is factory-set to a certain pressure, it will work properly only in the location for which it was set. If the piping contractor installs the wrong valve on the wrong floor during construction, abnormally low or high pressure output will result You must flow-test each installed valve on each floor to check tor proper operation of factory preset PRVs.
(Photos courtesy Potter-Roemer.)
(Photos courtesy of Elkhart Brass Mfg.)
(Photo courtesy of Potter-Roemer.)
- Set desired static outlet pressure (60 to 175 psi) on pressureindirating scale using special setting tool.
- The outlet pressure is controlled by the adjustable pressure spring. When outlet pressure reaches the setting, upward force in outlet pressure chamber closes the main piston.
- The static outlet pressure is not affected by changes in the inlet pressure. Inlet pressure exerts force on both upper and lower portion of main piston; since the two surfaces ore equal, no changes result.
- When outlet flow occurs, the pressure lessens in the outlet pressure chamber, allowing the moin piston to open, permitting flow from inlet side.
- The amount of flow determines the degree of opening. The increase of flow, or demand, decreases outlet pressure, causing the main piston to open further. Under full flow conditions, the main piston is fully open.
- The decrease of flow, or demond, increases the outlet pressure, causing the moin piston to close. Under no-flow condition, the main piston is fully closed when outlet pressure reaches static outlet setting.
- Loss of inlet pressure will activate the check device, preventing back flow.
(Photo courtesy of Elkhart Brass Mfg.)
The second type of PRV usually is set to the proper operating pressure on the job site. As with the preset type of PRV, these also must be tested individually to ensure proper adjustment. At the One Meridian Plaza fire, field-set PRVs were installed above the 12th floor. Investigation has determined that they were improperly adjusted, drastically reducing the pressure available to firefighters.
If a jurisdiction allows high pressures in a standpipe system, PRVs are necessary to prevent serious injury to firefighters. As with any other type of fire equipment, if properly specified, adjusted, and tested, PRVs—which first were installed about 15 years ago—will provide satisfactory service. The keys to the successful operation of PRV-equipped standpipe systems are first to determine that the system utilizes high pressures and PRVs and then to verify that the system is adjusted properly by flow-testing.
Since PRVs regulate pressure by sensing incoming pressure and then adjusting the valve opening to restrict the incoming pressure to the specified outlet pressure, it is important that the specified system pressure be maintained; if it is not, the valves will not function as designed.
For example, if 450 psi is the normal system riser pressure, and a building fire pump fails and the pressure is reduced to 100 psi, the PRVs will not be subject to enough pressure to open the pistons properly and may not be capable of supplying usable fire streams. A drop in riser operating pressure can be caused by a break in the line, a number of valves being opened on different floors for firefighting purposes, or pump failure due to mechanical malfunction or power outage.
Since all PRVs also are designed as check valves, they cannot be pumped into or supplied from hoselines from other risers. If the outside standpipe Siamese is damaged, many departments use hoselines to supply a standpipe system when connected with double female connections to hose outlets on lower floors. If this procedure is attemped with a PRV, the valve disc will be pushed against its seat, checking the backward water flow.
Depending on a system’s design, it is possible to find regular hose valves, pressure-reducing devices, and pressure-regulating valves installed on the same riser. Usually the lower the floor, the more sophisticated the pressure-control device becomes. Engineers use the three different valves to reduce costs and simplify the system. From a firefighting operations standpoint, the effectiveness of a system that uses different valves should be the same as a system that uses the same type of valve throughout, as long as the designed system operating pressure is maintained.
Some people want to eliminate all types of pressure-reducing devices and pressure-regulating valves. To accomplish this, all high-pressure standpipe systems will have to be repiped and zoned to provide lower operating pressures. To eliminate high-pressure standpipe systems, the authority having jurisdiction will have to revise its codes and requirements. Chicago does not allow high-pressure riser systems. Los Angeles and many other West Coast cities do. Until codes are changed, departments must learn how to work PRVs and must insist that all such devices within their jurisdictions be flow-tested. The Los Angeles City Fire Department requires that all such devices be tested annually.
FIRE DEPARTMENT CONNECTIONS
All standpipe standards require that some type of fire department connection be provided to supply the system in case the normal water source fails. (In the case of dry-pipe systems, the fire department connection may be the only water source.) Note the location of all such connections on each system. Some buildings provide connections on all sides of the building facing the street but often hide the connections behind shrubbery or dumpsters. In a building with zoned riser systems, a number of fire department connections will be provided, and it is important that their destinations and system-operating pressures be clearly marked. In this way, enough pressure can be supplied to operate the system, which is extremely important in systems equipped with PRVs.
It is possible that a fire department connection may have to be supplied with pressures higher than the maximum 250 psi that can be easily supplied by standard fire department pumpers. The Boston Fire Department recently tested the standpipe system installed in the Prudential Tower and found that pressures of approximately 400 psi were needed to properly operate the PRVs installed in the building. This was easily accomplished by using two pumpers. The first took suction from a hydrant and discharged into the suction of the second pumper. The second pumper, with an intake pressure of 250 psi, then was capable of supplying 400 psi to the system Siamese. This type of series or relay pumping is necessary in many cases to supply proper operating pressures to high-pressure standpipe systems. Precautions must be taken not to exceed hose and fitting rated operating pressures.
To properly perform an inspection, walk the full length of a standpipe system, from the roof down, and check the following items:
- The roof connection. Usually this outlet can be easily flow-tested because the discharged water can be disposed of over the roofs edge.
- Locations of all doors leading from stairwells to the roof. Some stairwells, such as in One Meridian Plaza, terminate in a nest of catwalls, making it almost impossible to reach the roof from inside the building under fire conditions.
- Floor hose control valves. Check caps, reducers, proper threads, and side clearance; open and close them with the caps in place to test their operation. Also check the condition of valves and threads.
- Risers. Check and note the locations of any isolation valves. Isolation
- valves are designed to shut off a broken or damaged riser without taking the system completely out of service.
- The type of floor hose control valves. Note them along with the types of installed pressure-reducing or pressure-regulating devices.
- Doors to each floor. Try them. At One Meridian Plaza, it was found that doors were unlocked only on every third floor.
- The occupancies on each floor. Get a general idea of partitioning, fire loads, and floor layout. If there seems to be a large number of partitions or a complicated floor layout, measure distances from the standpipe outlets to far rooms to determine the amount of hose needed for attack operations. Remember that hoselines usually are connected to valves below the fire floor.
- Locations of all fire department Siamese connections. It is important to determine which risers each connection feeds and the distances to nearby hydrants. It may be wise to plan that pumpers supplying Siamese connections be located away from the building to protect the operators from falling debris.
- Closely inspect the Siamese connections for debris. They should be flushed as part of the annual inspection. Also check the swivels for proper operation and to see that they are
- provided with the proper fire department threads. Make certain that clappers are in place if the fire department connection feed is a manifold.
- Carefully inspect the building fire pump installations. Note locations of main and booster pumps. All firefighters should be shown how to start these pumps manually in case of pressure-switch failure.
- Determine each standpipe system ‘s operating pressure. This is extremely important to note if total failure of the building’s pumping system occurs and the fire department becomes the sole source of operational pressure.
- Become familiar with the other building systems. This includes elevator; smoke-control systems; electrical systems, including emergency power provisions; the alarm system; exit stair systems; and ventilating and air-conditioning systems.
It is extremely important for departments to begin a program of inspection and evaluation of each standpipe system in their jurisdiction to better formulate practical operating procedures.
A pitch-black, red-hot, smokey fire stair doorway is a lousy place to try to figure out how a PRV works or to discover that threads don’t match or that your hoseline is too short. The time to plan is long before the box is pulled.