chapter 6.ppt

Fire Detection and Suppression

Chapter 6

Sprinkler Systems

Sprinkler Systems6-2

Effectiveness of Sprinkler Systems

• 96 percent reliable when installed and maintained properly

• Insurance carrier report, 1984–1987— Sprinkler systems controlled 98 percent of fires

— One sprinkler controlled 29 percent of fires

— Ten or fewer sprinklers controlled 75 percent of fires


Reasons for Installing Sprinklers

• Code requirements

• Insurance incentives

• General fire protection of life and property

• Building design flexibility


Applicable Standards

• NFPA 13, Standard for the Installation of Sprinkler Systems

• NFPA 13D, Standard for the Installation of Sprinkler Systems in One-and Two-Family Dwellings and Mobile Homes

• NFPA 13R, Standard for the Installation of Sprinkler Systems in Residential Occupancies up to Four Stories in Height

(Continued)


Applicable Standards (cont.)

• NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems

• Underwriters Laboratories

• Insurance carriers


Components of Sprinkler Systems

• Sprinklers

• Piping

• Valves

• Fire department connections


Sprinklers

• Sense the fire, react to that sense, and then deliver the water to the fire area

• Heat-sensitive device— Fusible link

— Frangible bulb

• Temperature ratings: determined by maximum air temperature expected at level of the sprinkler under normal conditions

(Continued)


Sprinklers (cont.)• Sprinkler Response Time

— Inevitable delay

— Response time index (RTI)

• Deflector Component— Forms discharge pattern

— Basic configurations– Upright

– Pendant

– Sidewall

– Water spray nozzle(Continued)


Sprinklers (cont.)

• Early Suppression Fast Response Sprinklers— Thermal Sensitivity

— Actual Delivered Density

— Deflector design and discharge orifice


Sprinkler System Piping

• Materials— Steel

— Copper tubing

— Galvanized

— Plastic(Continued)


Sprinkler System Piping (cont.)

• Functions (Fig. 6.16)— Water supply main

— System riser

— Sprig-up

— Riser

— Feed main

— Cross main

— Branch line


Valves

• Control valves— Indicating/nonindicating

– Outside screw and yoke (OS&Y) (Fig 6.18)

– Post indicator valve (PIV) (Fig 6.19)

– Wall post indicator valve (WPIV) (Fig 6.20)

– Indicating butterfly valve (Fig. 6.21)(Continued)


Valves

• Control valves (cont.)— Mechanism

– Gate (Fig 6.22)

– Butterfly (Fig. 6.23)

– Ball

— Security– Chain/locks

– Electric supervision(Continued)


Valves (cont.)

• Operating valves— Check valves (Figs. 6.24 and 6.25)

— Automatic drain valves

— Globe valves

— Stop or cock valves


Fire Department Connections

• Number and sizes of connections (Fig. 6.29)

• Check valve

• Location relative to main supply valve— Single-riser systems

— Multiple-riser systems


Types of Sprinkler Systems

• Wet-pipe sprinkler system (Fig. 6.31)— Alarm check valve (Fig. 6.33)

— Waterflow indicator (Fig 6.34)

— Local and fire department notification systems

— Antifreeze systems (Fig. 6.38)(Continued)


Types of Sprinkler Systems (cont.)

• Dry-pipe sprinkler system (Fig. 6.39)— Dry-pipe valves

— Quick-opening devices– Accelerator (Fig. 6.42)

– Exhauster (Fig. 6.43)

— Operational sequence1. Heat from a fire causes the sprinkler to activate.

2. Pressurized air contained in the piping begins to flow through the open sprinkler.

(Continued)



• Dry-pipe sprinkler system — Operational sequence (cont.)

3. After a slight drop in air pressure, the quick-opening device (if present) activates to accelerate the removal of air from the piping.

4. Once the air pressure is reduced sufficiently, the dry-pipe valve trips open. The interior clapper is held in the open position by a latch.

(Continued)



• Dry-pipe sprinkler system — Operational sequence (cont.)

5. Water enters the intermediate chamber of the dry-pipe valve. This automatically forces the automatic drip valve closed and begins the flow of water through alarm-signaling equipment.

6. Water flows through the entire piping system and is discharged through the open sprinkler.

(Continued)



• Deluge sprinkler system— Design and purpose

— Operation– Electrical

– Pneumatic

– Hydraulic(Continued)



• Deluge sprinkler system (cont.)— Operational sequence

1. A product-of-combustion (heat, smoke, or flame) detector senses the presence of a fire condition, or an individual in the area discovers a fire in progress.

2. The fire detection system sends a signal to the deluge valve, causing the valve to open, or the individual who discovers the fire manually trips the deluge valve.

(Continued)



• Deluge sprinkler system— Operational sequence (cont.)

3. As water enters the deluge valve and the piping, a pressure switch is activated that transmits an alarm either locally or to a supervising station. A water motor gong (if present) is activated.

4. Water flows through all open sprinklers simultaneously.

(Continued)



• Preaction sprinkler system— Mechanisms

– Single-interlock

– Non-interlock

– Double-interlock(Continued)



• Preaction sprinkler system (cont.)— Operational sequence

1. Product-of-combustion (heat, smoke, or flame) detector senses presence of fire condition.

2. Fire detection system sends signal to preaction valve, causing valve to open.

3. Sensors in piping system detect flow of water into system and trigger waterflow fire alarm.

4. When level of heat at a sprinkler reaches appropriate temperature, sprinkler opens and water flows through orifice.


Sprinkler Systems for Industrial Storage Occupancies

• High fuel loads

• High loss potential— Large undivided areas

— Large concentration of value in a single fire area

— Very high stockpiling with narrow aisles (Continued)


Sprinkler Systems for Industrial Storage Occupancies (cont.)• Classification of commodities

— Classes

Class I: Generally noncombustible, stored on wooden pallets in ordinary packaging

Class II: Noncombustible commodity, packaged in wooden crates or multi-layered cardboard cartons

Class III: Commodities made of combustible materials such as wood, paper, or certain plastics, irrespective of pallets or packaging

(Continued)


Sprinkler Systems for Industrial Storage Occupancies

• Classification of commodities— Classes (cont.)

Class IV: Meets one of the following criteria:1. Constructed of Group B plastics.

2. Consists of free-flowing Group A plastics.

3. Contains an appreciable amount of Group A plastics. Remaining materials may be wood, metal, paper, natural or synthetic fibers, or Groups B & C plastics.

Plastics: Groups A, B, and C

— Determining the classification


Inspecting and Testing Sprinkler Systems

• Preinspection procedures— Review records of prior inspections and identify

make, model, and type of equipment, and area protected by the system.

— Wear appropriate clothing for dirty locations such as attics and basements. Protective clothing may be necessary for certain manufacturing areas.

(Continued)



• Preinspection procedures (cont.)— Obtain permission from the plant management

before performing any inspection.

— Never personally or physically operate, adjust, manipulate, alter, or handle any sprinkler devices or equipment during situations other than emergencies or planned training sessions.

— If equipment is electronically supervised, plant personnel should notify alarm-monitoring organization before and after testing. (Continued)


Inspecting and Testing Sprinkler Systems (cont.)

• Sprinklers— Signs of weakness

— Obstructions

— Extra sprinklers

• Sprinkler piping, hangers, and seismic braces

(Continued)



• Changes in building occupancy— What are the sprinkler system design criteria?

— Has a change in the occupancy occurred?

— Have combustibles been added that will contribute to a greater fire load or a more rapid fire spread?

— Have alterations caused a need for the reconfiguration of sprinklers?

(Continued)



• Inspecting and testing wet-pipe sprinkler systems— Inspections

– Valves

– Sprinklers

– Piping

– Water supply

(Continued)



• Inspecting and testing wet-pipe sprinkler systems (cont.) — Acceptance tests

– Flushing of underground connections

– Hydrostatic tests

— Wet-pipe system testing– Alarm test

– Waterflow alarm test

– Main drain test (Continued)



• Inspecting and testing dry-pipe sprinkler systems— Inspection points

– All indicating control valves open and properly supervised.

– Air pressure readings correspond to previously recorded readings.

– The ball-drip valve moves freely and allows trapped water to seep out of the fire department connection.

(Continued)



• Inspecting and testing dry-pipe sprinkler systems— Inspection points (cont.)

– Velocity drip valve beneath intermediate chamber is free to move and allow trapped water to seep out.

– Fire department connection threads unobstructed, in good condition, and caps in place with gaskets intact. Identification signs in place and readable.

– Any drum drips are drained to eliminate the moisture trapped in the low areas of the system.

(Continued)




– During freezing weather, dry-pipe valve enclosure heating device keeps dry-pipe valve temperature at or above 40° F (4° C).

– Priming water at correct level.

NOTE: If the system is equipped with a quick-opening device, opening the priming water test line could trip the system.

(Continued)




– The system’s air pressure is maintained at 15 to 20 psi (105 kPa to 140 kPa) above the trip point, and no air leaks are indicated by a rapid or steady air loss. If inspectors note excessive air pressure, they should have the system drained down.

– The system air compressor is approved for sprinkler system use, well maintained, operable, and of sufficient size.

(Continued)



• Inspecting and testing dry-pipe sprinkler systems (cont.)— Acceptance tests

– Flushing of underground connections

– Hydrostatic tests

— Dry-pipe system testing– Main drain test

– Trip test

(Continued)



• Inspecting and testing deluge and preaction sprinkler systems— Main drain and alarm tests

— Trip test


Restoring Sprinkler Systems

• General guidelines— For safety reasons when practical, one fire

company may be left on the scene to verify restoration of the system.

— A chief officer may continue to recheck the occupancy until the system is restored.

— Responsibility for the building’s welfare may be turned over to the occupant or a responsible agent of the occupant.

(Continued)


Restoring Sprinkler Systems

• General guidelines (cont.)— Sprinklers that have activated must be replaced

with identical sprinklers if at all possible.

• Restoring wet-pipe sprinkler systems

• Restoring dry-pipe sprinkler systems

• Restoring deluge and preaction sprinkler systems


Sprinkler System Impairment Control

• Planned interruptions— Maintenance

— Testing

— Building renovation

• Unplanned interruptions — Frozen pipes

— Broken pipes

— Equipment failures(Continued)


Sprinkler System Impairment Control (cont.)

• Fire safety measures when sprinkler system impairment occurs may include:— Fire guards

— Suspension of hazardous operations

— Additional manual equipment


Residential Sprinkler Systems

• Standards— NFPA 13D, Standard for the Installation of

Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes

— NFPA 13R, Standard for the Installation of Sprinkler Systems in Residential Occupancies Up To and Including Four Stories in Height

(Continued)


Residential Sprinkler Systems (cont.)

• Residential modifications— Residential sprinklers were designed to be fast

response.

— Water supply requirements were reduced to levels appropriate for life safety.

— Areas of coverage for sprinklers were adjusted based on sprinkler design and typical residential fire loads.

(Continued)



• Residential modifications (cont.)— Alarms were made simpler and more realistic for

residential applications and smoke detectors may also be used for notification.

— Valve arrangements were made so that they would be unobtrusive in a common residence.

— Sprinklers are designed to discharge water high on the walls.

(Continued)



• Residential sprinklers versus conventional sprinklers— Speed of operation

— Distribution pattern

• Residential sprinkler piping(Continued)



• Water supply and flow rate requirements— 18 gpm (68 L/min) for any single sprinkler. If

there are two or more sprinklers, each requires 13 gpm (49 L/min) as a maximum required water supply. In addition, the water supply needs only to supply this flow rate for 10 minutes

(Continued)



• Water supply and flow rate requirements (cont.)— For larger multiple dwellings, the designed flow

rates are greater. NFPA 13R requires 18 gpm (68 L/min) for a single sprinkler and not less than 13 gpm (49 L/min) to a maximum of four sprinklers. The water supply for these larger buildings is required to supply the sprinklers for 30 minutes.

chapter 6.ppt

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