Standpipe and Sprinkler Operations

Standpipe and Sprinkler Operations

PART 4-Conclusion

All material for this series of articles is taken from the Nassau County, N. Y., Fire Training Manual. Prepared by Battalion Chief Thomas D. Ryan, FDNY (ret.), it is produced here through the courtesy of the Nassau County Vocational and Educational Extension Board, Charles R. Wallendorf, director; James C. Rogers, chief fire training instructor.

BESIDES the post indicator and O.S. & Y. valves which normally control the flow of water in a sprinkler system, two special types of valves are found in automatic systems. Dry pipe systems are quite similar to wet pipe systems with the exception that, in the former, the lines are kept full of air until a head opens. The dry pipe valve (Figure 27) is then operated, charging the entire system with water and sounding a local alarm or in some cases transmitting the alarm to a supervisory service which then notifies the fire department. In some occupancies (schools, hospitals, etc.) the alarm is directly transmitted to the fire department. Details of a typical drv pipe installation arc shown in Figure 28.

The dry pipe valve is designed so that, in the normal position, the valve will hold a clapper or seat (D) open.

Figure 28

The water then rushes into the sprinkler system and out the sprinkler head. At the same time it passes into the outlets at (L) and (M), actuating the alarm device and accelerator or exhauster.

When fire conditions indicate the system should be shut down, the supply may be closed off at an individual O.S. & Y. valve on an individual floor or at the main valve shown in the open position (stem out). In this latter move, the drain valve should be opened so that the remaining water in the system beyond the valve will not have to be discharged and possibly cause additional water damage. Fire fighters may then work in comfort under the opened heads. Before the main supply valve is again opened, the drain valve must be closed, the dry pipe valve reset, air pressure built up in the system by the compressor and the alarm system drained and placed once more in its normal position ready to operate.

One objection to the use of a dry pipe system is the loss of time between the opening of a sprinkler head and the issuance of water, an interval made necessary to permit the escape of the compressed air content of the sprinkler pipes. The problem is overcome by the installation of quickopening devices and by proper attention to the maintenance of these devices. There are two general types, accelerators and exhausters. In the first type, when a sprinkler opens and air pressure drops 1 or 2 pounds, the diaphragm (F) (figure 27) becomes unbalanced. This forces open a valve which permits the air pressure in the system to enter the intermediate chamber of the differential valve, and the valve trips. In the exhauster type, the diaphragm causes a larger valve to open and the air in the system discharges to atmosphere through an outlet. Air pressure in the system is thus reduced until the dry pipe valve itself trips.

Both dry and wet pipe systems are commonly equipped with means of sounding an alarm upon the opening of a head and the flow of water past the valve proper. One type employs a flexible vane or paddle in the waterway which activates a water motor gong on the outside of the building. Other types sound an electric gong inside the building when water pressure actuates an electric switch at the alarm valve (Figure 29). Some installations employ both types and also notify a supervisory agency, such as ADT or other service.

Figure 29

The water pressure from public mains is variable and so it becomes necessary to provide means of counteracting the effects of water hammer and momentary surges in water pressure to prevent the transmission of false alarms. Retard devices are installed between the alarm check valve and the water motor gong or pressure switch (Figure 30). By such means, in cases of momentary surges, the action of the water is retarded for several seconds to provide time for the clapper of the alarm check valve (Figure 29) to reseat and cut off the water from reaching the alarm activator. This necessary time interval in many cases prevents the alarm being sounded due to a common water main fluctuation.

If a fire actually opens one or more sprinkler heads, the flow of water lifts the main clapper off its seat and opens the auxiliary valve so that water quickly fills the retard chamber and contacts the electric circuit closer, sending the alarm to the office, throughout the building or to distant points. At the same time, the water may activate the water motor gong and sound the alarm inside or outside the building.

Figure 30

Temperature ratings

Automatic sprinklers have various temperature ratings which approximate the temperatures at which they will operate in a heated atmosphere. Where high heats are maintained, such as over boilers, over ovens and in drying rooms, a higher degree head must be used than in an ordinary occupancy. If high-degree heads are used where not required, i.e., in an ordinary atmosphere, the value of the sprinkler protection is materially reduced. The difference between the various heads, as to their ratings, is not only indicated on them but they may also be identified by colors. The table lists the ratings of the various heads, operating temperatures and distinctive colors. All heads which fuse at a fire should be replaced by those of duplicate ratings. If responding units do not have replacement heads, such can usually be procured from the owner or building superintendent.

Sprinkler heads are made of metal, screwed into the piping at standard intervals and generally have a ½-inch opening. The disc or seat of the sprinkler head is held in place (preventing the escape of water) by a strut or two levers inserted between the seat and the top of the yoke. Most frequently the strut is of metal, consisting of two or more pieces held together with fusible solder (Figure 31). Many types, however, use as a strut a quartz bulb which expands and breaks under heat or a solid chemical held in a cylinder which disintegrates by heat action.

Figure 31

When constructed, the struts or levers are set in place under compression and are released when the fusible device operates from the heat of the fire. The disc is released from the ⅛inch openings and water flows out under pressure. The force of the water against the deflector of the head breaks it into a heavy spray, part of which passes through the openings in the deflector to hit the ceiling and part is deflected downward.

To find a sprinkler control valve and to close it may take considerable time. If the fused heads are few in number, they may be closed by using a pole shut-off, sprinkler tongs (Figure 32), or a wooden wedge inserted in the ruptured head.

Figure 32

Discharges and head pressures

The exact amount of water being discharged from a system depends on the number of heads open, the type of head, and the pressures maintained on them. For most systems approximate discharges may be calculated by the following method:

Discharge in gallons per minute 1/2 the pressure in pounds at the head + 15.

The following table presents discharges at pressures up to 100 pounds at the head:

Based on the above, it may be seen that a 1,000-gpm pumper can effectively supply at most 50 heads at a minimum pressure of 15 pounds. A 750-gpm pumper can only supply about 35 heads. Each head will effectively cover 80 to 100 square feet of floor area.

Recommended engine pressures

Exact computations of engine pressures are impractical on the fire ground, due to required information on such factors as the number and type of heads opened, and the number, length and size oi the supply lines to the Siamese. In cases where the pumper is located near the fire building, most authorities recommend a pump pressure of 100 pounds be maintained, particularly on older systems, where there is always the danger of part of the system bursting if excessive pressures are built up on the pumper.

Supplying Siamese connection

The recommended number of supply lines and the method of hooking up to a Siamese is the same for both systems (see Figure 16, July 1963 issue of FIRE ENGINEEIUNG). If the system is automatic and already charged from another source (gravity tank, pressure tank, fire pump or connection to a public main), the pressure on the pumper side of the check valve in the Siamese connection (Figure 26, August 1963 issue of Fire Engineering) must exceed the pressure on the other side before the check will swing open and allow the pumper to actually feed the standpipe or sprinkler system. This also means that the engine pressure must he sufficient to close the check valve beneath the gravity tank on the roof, or on the discharge side of the pressure tank, fire pump, or street main. It is important that a pumper actually discharge some water and not pump continually against a closed check valve. In such cases the water in the pump will heat up considerably and possibly damage the packing or other parts of the pump. As such, this water is unsuitable for auxiliary cooling purposes, with the result that the oil in the engine may heat up to the point where the motor may burn out. A simple solution to this problem is to keep a bleeder valve (drain) open on one of the discharge gates so that a small stream of water spills to the ground and insures complete circulation.

Display board provided by American District Telegraph Co. permits instruction in sprinkler and fire detection system supervision as well as methods of alarm transmission. Chief Hagers (right) points out detector unit as Assistant Chief Robert Hopkins looks on in Nassau County Training Center classroom

Miscellaneous information

  1. Whether or not the check valve beyond the Siamese connection is actually open in a standpipe or sprinkler system may readily be determined by the following method:
    1. Working with caution, slowly close or partially close the discharge gate(s) of the pumper supplying the Siamese. If the check valve is open (pumper actually supplying the water), the engine pressure on a positive-displacement pumper will go up, the motor will start to labor and slow down, and the relief valve will open.
    2. On a centrifugal pumper under the same conditions, the engine pressure will rise slightly until the relief valve opens and the passage of water through it can be heard. The engine speed will also start to increase (load partially or completely off it) to the point where the motor governor controls it.
    3. In addition, on both types if the water output is considerable, the intake gage on the pumper will show an increase in intake pressure as gate(s) are closed.
    4. If either type pumper is not actually putting water into the system (check closed), there will be no change in pump pressure or motor speed when the gate is closed.
  2. In addition to the method of calculating engine pressures required in standpipe operations, as explained previously, some authorities recommend this method which is adequate for most operations in which supply lines to the Siamese are short and a solid stream type of nozzle is used on the line: Required engine pressure = 100 pounds + 5 pounds per story.
  3. In standpipe operations where riser water supply is from a gravity tank or a weak water main, it is inadvisable to use l 1/2-inch lines or fog nozzles on floors immediately below the roof as the pressure on the riser outlet will not be sufficient to overcome friction losses in the small hose nor give required pressure on fog nozzles.

NBFU recommendations

Studies of large-loss fires in sprinkler-protected buildings show that fire departments should follow the suggestions below to most effectively use sprinkler systems as a fire control and extinguishment tool:

  1. Fire departments should have a list of all sprinkler-protected buildings in the area which they protect. Each officer should be familiar with at least those buildings in his district to which he responds on first alarms.
  2. Sketches should be prepared showing the locations of alarm valves, control valves and fire department connections. Officers should be familiar with this data on buildings in their district.
  3. Fire departments should have information on the available water supply such as: How many pumpers can be used in addition to those supplying the fire department sprinkler connections; is there a water supply separate from that supplying the sprinkler system that can be used; is there a nearby surface water supply, such as a pond, from which pumpers can draft water?
  4. Fire department connections for sprinkler and standpipe systems should be inspected at regular intervals by the fire department to assure that caps can be readily removed, that threads are in good condition, and that the connection is otherwise ready for use and threads match those of the fire department.
  5. One of the first-alarm engine companies responding to a fire in a sprinkler-protected building should stretch two 2 ½-inch lines to the fire department connection.
  6. Fire departments should impress responsible personnel of sprinkler-protected buildings that once sprinklers have operated as a result of fire, the system should not be shut off before the fire department arrives.
  7. Extreme caution should be exercised by officers when ordering sprinkler systems shut off. A shut-off should be made only after a thorough check reveals the fire is out and will not rekindle. The fireman ordered to close the control valve should remain at the valve so that it can be opened without delay if needed.

When a shut-off is made by the fire department, someone should be left at the valve until the sprinklers can be replaced and the water supply restored. If the system cannot be put back into service, watch service should be maintained on each floor, in addition to the man at the control valve, until all danger is past.

Standpipe and Sprinkler Operations

Standpipe and Sprinkler Operations

PART 3-Sprinkler Systems

All material for this series of articles is taken from the Nassau County, N. Y., Fire Training Manual. Prepared by Battalion Chief Thomas D. Ryan, FDNY (ret.), it is produced here through the courtesy of the Nassau County Vocational and Educational Extension Board, Charles R. Wallendorf, director; James C. Rogers, chief fire training instructor.

SPRINKLERS are installed in various occupancies under requirements of law or voluntarily for protection of a building or its contents. From the standpoint of fire fighting, these systems are of great value because of the extinguishment which they perform without aid by the fire fighter, and also because the fire is attacked in its incipiency, thereby reducing the number of major fires to be fought. They are also of value when the building in which they are installed is threatened by fire in a neighboring building.

Sprinkler systems may be found in: Factories, institutions, schools, theaters, hospitals, hotels, flammables stored or used, garages, oil cloth or linoleum manufacturing, pyroxylin plastics stored or used, large undivided floor areas, duct systems for commercial kitchen ranges, transformer vaults, or any occupancy where large numbers of people work or congregate. Particularly where water is used in the form of fog or spray, as from a sprinkler head, many old taboos such as “oil and water don’t mix” and “never use water on hot metal or electrical equipment” have been dispelled. Except for chemicals which react violently with water, and where water might cause a boil-over in an oil tank, there are few cases in which water cannot be used effectively for fire extinguishment.

Value of sprinkler systems

Essentially an automatic sprinkler installation is comprised of a system of pipes erected at or near the ceiling on each story of a building and connected through controlling valves to one or more sources of water supply At intervals in the pipework sprinkler heads are placed which embody a device whereby a rise in temperature to a predetermined limit causes the sprinkler to open and water to be discharged in the form of spray over a given area (Figure 19). The heads are so spaced that if more than one head opens, the area sprayed by each overlaps that of the adjacent one.

Nassau County Training Center demonstration sprinkler system designed by Chief James C. Rogers. Hose connected to Siamese permits operation exactly as building system

Photo by James Heffernan

In many installations the operation of one or more heads leads to the opening of a valve, thus causing an alarm bell to ring and draw attention to the condition. The fire department responds and supplements the automatic action of the sprinkler system, making sure all pockets of fire are out.

The performance of sprinklers shows that they either extinguish or hold in check 96 per cent of the fires in premises which are so equipped. The 4 per cent failures are due to a variety of causes, such as explosions, closed valves, freeze-ups, and failure of water supply. Many of the so-called sprinkler failures have been due to premature closing of the main valve. After one or more heads opened and apparently extinguished the fire, the water supply was cut off to prevent further damage. The fire which had continued to smolder in a hidden place, burst out again and gained headway. Without sprinkler protection it grew to large proportions, possibly opening a large number of heads. The supply valve was then reopened but the large number of open heads caused a pressure drop and a less effective flow . Sprinkler systems are designed to check an incipient fire and not to cope with one that has gotten out of control.

Figure 19Figure 20 Figure 21Figure 22Figure 23

Types of sprinkler systems

Sprinkler systems are classed according to the following categories:

  1. Automatic Wet Pipe Systems (Figure 20): Installed in buildings where heat is maintained during cold weather. The piping is full of water, always under pressure, so that it is discharged immediately when any head is fused.
  2. Automatic Dry Pipe Systems (Figure 21): Found in buildings which are not heated, or may not be heated in some portions, and there is danger of damage to the system due to freezing. The pipes are filled with air, either compressed or at atmospheric pressure and water supply to the heads is controlled by a dry pipe valve. In some cases a separate dry system is installed in an unheated area of a building and the rest of the system is wet.
  3. Nonautomatic Systems (Figure 22): Those in which all pipes are normally maintained dry and water is supplied, when necessary, by pumping into the Siamese connection. At times some of these systems are supplied by manual operation of a control valve. The nonautomatic types of sprinkler systems include:
    1. Exterior exposure sprinklers (or window sprinklers), using opentype sprinkler heads to form an external water curtain down the walls of a building
    2. Perforated pipe systems, consisting of single lines of pipe drilled at intervals for water discharge, and intended to protect basement areas which are difficult of access in fire operations
    3. Open fixed spray nozzles or distributor nozzle systems for transformer vaults and similar areas
    4. Foam supply systems for protection of special hazardous occupancies into which a foam mixture is pumped or into which water is supplied to augment that required by foam mixing apparatus inside the yard or building

Special types of sprinkler systems

There are many special types of automatic sprinkler systems, among which may be found one of the following or a combination of two or more of them in one occupancy:

Deluge Systems: May be a system of open sprinklers, or a combination of open and closed sprinklers, controlled by a quick-opening mechanical or hydraulic valve (deluge valve), the latter operated by automatic heat-responsive devices, by manual control, or otherwise. The purpose of this type of system is to wet down all at once an entire area in which a fire may originate, by admitting water to open sprinklers, rather than by using automatic sprinklers that would open independently, as the fire spreads. This system is actuated by the rate of rise of heat within a given space and is used in rooms of a very dangerous occupancy, such as explosives manufacturing, film manufacturing, film cutting and packing, lacquer mixing and coating operations; also in airplane hangars and assembly plants where ceilings are unusually high and ordinary sprinklers would not open due to high drafts.

Preaction Systems: These are also of the rate-of-rise type and differ from the deluge systems in one main respect. All heads have fusible links on them and the alarm is given before the heat has risen enough to melt the fusible links of the heads and permit water to flow from them. These systems are designed to protect properties where there is danger of serious water damage, as could result from premature or accidental operation of a sprinkler or due to a break in the piping system. In this type of system the action of the heat-responsive device or thermostat releases the preaction valve, the water fills the piping system, and an alarm is given in advance of the fusing of the sprinkler heads.

Rate-of-Rise Systems: These consist of heat-actuated devices connected through air tubing to an automatic release. They operate in conjunction with lines of copper tubing passing around the room, with small copper balls inserted periodically in the lines. When the temperature within a room rises 15 degrees—or to whatever rise in degrees it may be set—the air in the copper ball expands, as does the air in the copper tubing, transmitting the alarm to an electrical switch which may accomplish any of the following: Announce the presence of a fire by sounding an alarm; prevent the spread of fire to adjoining rooms by closing communicating doors or openings; open vents to allow the escape of air pressure that could result from an explosion oroginating from the fire; discharge water or other fluids to extinguish the fire. The heat-actuated device is bulb-shaped metal (Figure 23) surrounded by a wire guard to protect it against mechanical injury.

Antifreeze Sprinkler Systems: These are installed in some freezing locations, such as cold storage rooms, truck loading docks, etc. The piping is normally filled with an antifreeze solution such as calcium chloride, glycerine or diethylene. At times these systems are small extensions from wet pipe systems, arranged with check valves and a trap so that the system water does not mix with the antifreeze solution. When a head opens, the antifreeze solution is lost and must therefore be replaced when the system is again placed in operation.

Figure 24Figure 25Figure 26

Water supply

Generally speaking, the methods of water supply for sprinkler systems are the same as those for standpipe systems. One, but in most cases at least two, of the following sources of supply are used: Connections to public mains, gravity tanks, pressure tanks, fire pumps or fire department Siamese connections.

As may be seen in Figures 20 and 21, when the supply is from a public water main, the entire system may be closed down by operating a control valve between the building and the water main. This valve may be located in a box which is recessed in the sidewalk, with its location indicated by a sign on a building nearby reading, “Shut-Off for Sprinkler System Located 6 Feet from This Sign” or similar instructions. This valve may require a special key to operate.

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The control valve may also be an upright post, known as a post indicator valve (Figure 24). The building or section of the building controlled by the valve is generally indicated by the post. The condition of this valve (open or closed) is shown through a tell-tale opening in the post. On some posts a padlock must first be opened or forced to release the operating wrench. On others an iron strap must first be released by cutting a riveted leather section.

Main supply valves may also be ol the O. S. & Y. type (outside stem and yoke) (Figure 25) and may be found just inside the building wall on the main riser, or outside in protected pits. The fire fighter can tell at a glance if the valve is open or shut, because the stem is all the way out when the valve is open and all the way in when it is closed. This type of valve is also used for control of supply for individual floors or separate valves may be installed to shut off certain sections of a floor. In many cases parts of a system which are subject to freezing are isolated by closing the O. S. & Y. valve and draining the pipes in cold weather.

Nearly all automatic and nonautomatic sprinkler systems are equipped with a fire department Siamese connection designed to permit attachment of lines from a pumper. This connection (Figure 26) is installed so that water supply may be furnished from outside sources in the event that the public water main connection or other source of supply is inadequate or out of service. After the standpipe system (if present) is supplied, one or more of the first lines should be laid to the Siamese. Care should be taken to see that the proper Siamese is selected for the needs of the operation, as those for standpipe systems, sprinkler systems, transformer vaults and other installations are alike in appearance. The exact purpose of each is indicated nearby or on the Siamese itself.