Fire Extinguishing Standpipe & Sprinkler Systems PDF

Fire Extinguishing OBJECTIVE • Chapter 5 3 Describe the types, layout, and operation of standpipe and sprinkler systems. STANDPIPE SYSTEMS Standpipe systems are used in buildings over 3 stories (14 metres) in height. This is the practical limit for firefighters to couple hoses together from a p...

Fire Extinguishing OBJECTIVE • Chapter 5 3 Describe the types, layout, and operation of standpipe and sprinkler systems. STANDPIPE SYSTEMS Standpipe systems are used in buildings over 3 stories (14 metres) in height. This is the practical limit for firefighters to couple hoses together from a pumper truck at street level, and up the stairways to the floor where the fire is located. Standpipes allow firefighters, and in some cases, building occupants, the ability to fight fire using a fire hose connected to a standpipe. The standpipe may also be used to supply water to the sprinlder system. If the standpipe only has hose connections, it must be at least DN 100 (4" NPS). If the standpipe also supplies sprinlder systems, it must be at least DN 150 (6" NPS). The standpipe rises to all floors, usually through a stairwell or a pipe chase. At each floor, there is a provision for fire hose connection. The firefighters can connect the hoses to one of the valve outlets on the standpipe to access the firefighting water supply. It is best practice to use the standpipe connections on the floor below the fire, and approach the fire from below. Fighting a fire from above is like approaching a fire through a chimney: heat and smoke rise. This is not a recommended way to fight a fire. Newer buildings have stairwell pressurization fans to keep the stairwell exits clear of smoke for people leaving the building. This also minimizes the chimney effect. There are three classes of standpipe systems: Class 1: These standpipe systems have 65 mm (2.5 inches) hoses and hose connections, to accommodate the larger hoses used by firefighters. When pressurized, these larger hoses can be difficult to control. Only those who have been trained in their use should handle them. Class I systems are usually installed in stairwells. Class II: These systems have 40 mm (1.5 inch) hoses and hose connections. These are smaller and easier for building occupants to handle. Subject to local authority, 25 mm (1 inch) hoses and hose connections may be used in Class II service for light hazard occupations. Class II systems are usually found in rooms with wall-mounted firehose cabinets, located to be readily available to the personnel in the area. Note that training is required for these types of hoses. Class III: Class III standpipes combine Class I and Class II hose fittings. In other words, Class III standpipes have both 40 mm (1.5 inch) and 65 mm (2.5 inch) hose connections. 4th Class Edition 3 • Part A 5-15 Unit A-4 • Introduction to Plant and Fire Safety Provincial and local authorities govern the fire acts, codes, and regulations for the installation and use of fire systems. The number and location of standpipes and equipment depends on the use, occupancy, and construction of the facility. The standpipe risers are usually located in non-combustible, fire- rated stairwells. If it is not possible to locate all standpipes in stairwells, additional standpipes may be located in pipe shafts at the building interior column locations. There should be at least one 65 mm hose connection on the roof for each standpipe. Power Engineers should know the location of the standpipes and their fire department connections, to provide valuable information to responding firefighters. Fire Zones for Standpipes New plants and buildings are built to current building and fire codes. Included in the codes are requirements for fire separations, or zones, within the building or plant. These zones must have suitable walls, floors, and ceilings to prevent fire from spreading for a specified period of time. This allows occupants time to get out, and fire fighters time to contain a fire before it moves to other areas of the building or plant. The usual zone separations are by floor - each floor being its own zone - with fire doors protecting the stairwells. If the floor area is large, there may be fire walls on each floor, to further separate the zones. Each zone will have access to firefighting equipment and a standpipe system. These zones will also have sprinlder systems. Hose stations must be installed so that all places in each building zone are within 9 metres of a nozzle. The nozzle must not have more than 30 metres of hose. If the smaller NPS 25 mm hose is installed, then all portions of each zone of a building must be within 6 metres of a hose, as the smaller hoses do not have the high flow capacity of the larger size hoses. 5-16 -ss-E-dition-3-• P -a- rt-A---------------------::; :;::--------------------------4th- C- la Fire Extinguishing • Chapter 5 Types of Standpipe Systems There are seven basic standpipe systems, as defined by NFPA 14- Standard for the Installation of Standpipe and Hose Systems. 1. Automatic Dry Standpipe: A standpipe system permanently attached to a water supply (municipal or otherwise) capable of supplying the standpipe system water demand at all times. This system is charged with compressed air or nitrogen. Upon release of the compressed gas, a dry pipe valve opens, allowing water to flow into the piping system and out of the opened hose valve. The release of compressed gas is caused by the opening of a standpipe hose valve. If a fire requires fire department participation, a pumper engine will connect to a nearby street hydrant, and supply water into the standpipe system through the fire department connection, which features a "Y" piece so that two sources can feed the standpipe system from the exterior of the building. See Figure 13. 2. Automatic Wet Standpipe: A standpipe system containing water at all times that is attached to a water supply (municipal or otherwise) capable of supplying the standpipe system water demand at all times. An automatic wet standpipe provides immediate water flow upon opening a valve at a hose connection. A "Y" connection can also be provided on a wet standpipe system, so the fire department can hook up and supply the system. 3. Combined Standpipe System: A standpipe system that supplies water to both the hose connections and an automatic sprinkler system. 4. Manual Dry Standpipe: A standpipe system with no permanently connected water supply. It relies exclusively on external fire department connections to supply the water. The installed piping is completely dry, and terminates outside the building with a fire department connection. 5. Manual Wet Standpipe: A standpipe system that contains a water charge, but is not hooked up to a permanent water supply. This system relies solely on the connection outside the building by the Fire Department. 6. Semi-Automatic Dry Standpipe: A standpipe system that is permanently attached to a water supply (municipal or otherwise) capable of supplying the standpipe system water demand at all times, through a control device such as a deluge valve, that must be activated by another device before the valve opens and allows water into the system. 7. Wet Standpipe System: A standpipe system that contains water at all times and does not depend on any other controls to allow water to flow to the system. I Figure 13 - Fire Department Connection -------------------------"' 4th Class Edition 3 • Part A Z 5-17 Unit A-4 • Introduction to Plant and Fire Safety ==================== ================== SPRINKLER SYSTEMS The NFPA 13 - Standard for the Installation of Sprinkler Systems is adopted by the National Fire Code of Canada. This standard provides the necessary requirements and specific guidance with respect to the design, layout, and installation of sprinlder systems. There are four basic types of sprinkler systems: 1. Wet pipe 2. Dry pipe 3. Preaction 4. Deluge Wet Pipe Sprinkler Systems Wet pipe sprinkler systems are the most common. They are the easiest to design, and the simplest to maintain. Wet pipe sprinkler systems contain water under pressure, and are piped to headers that have rows of sprinkler heads. When a sprinkler head is exposed to heat and rises to a predetermined temperature (presumably due to fire), a small liquid filled bulb or metal fusible link in the sprinkler head breaks and water flows to extinguish the fire. Wet pipe systems are used when the temperature of the protected area is maintained at or above 4°C, to prevent freezing of the system. Wet pipe systems are typically found in office buildings, stores, hotels, schools, and health facilities. They are intended to provide coverage for general use facilities. Figure 14- Sprinkler Head Plug Fusible Link Deflector Plate (a) (b) The sprinkler head shown in Figure 14(a) has a thermally activated glass bulb that contains a blue-coloured liquid. (The colour of the liquid indicates that this sprinkler activates at between l20°C and 150°C.) The bulb holds a valve mechanism shut. At a predetermined temperature, the bulb pops open, due to the volumetric expansion of the liquid in the bulb. This allows water to flow out and extinguish the fire. Sprinkler head liquid bulbs have different colours that correspond to their activation temperatures. These temperatures range from 38°C to 329°C. Figure 14(b) is a ceiling mounted fusible link sprinkler head. When the temperature increases, the soldered link melts, and the plug opens. Water then flows out and the deflector plate spreads it over the fire. 5-18 s-------------------------4th Class Edition 3 • Part A Fire Extinguishing • Chapter 5 Dry Pipe Sprinkler Systems When the temperature in an environment is subject to freezing temperatures or maintained below 4oc, dry pipe sprinkler systems are installed. The water in this type of system has a supply valve (called a "dry pipe valve") held closed with air pressure. The sprinkler piping is pressurized with compressed air to at least 275 kPa, in order to hold the dry pipe valve closed. A small air compressor keeps the sprinlder system piping pressurized in the event of a small air leak. The compressor does not have the capacity to maintain the system air pressure if a sprinkler head is activated. Like wet sprinkler systems, dry pipe systems have sprinlder heads that pop open at a predetermined temperature. When a sprinlder head opens, it first releases air. When the piping system air pressure drops, the dry pipe valve opens wide, and quicldy fills the entire sprinlder system with water. The water flows from the activated head as soon as it reaches that point in the piping system. Dry pipe installations are found in outside areas, cold storage warehouses, or anywhere freezing could occur. Preaction Systems Preaction sprinkler systems are categorized three ways: 1. Single-Interlock Systems 2. Non-Interlock Systems 3. Double-Interlock Systems Single-Interlock Systems The piping for single-interlock systems is similar to a dry pipe system. Typically, the system has compressed air or nitrogen in the lines, and an electrically operated preaction valve that must open before water flows into the sprinlder line. The preaction system is equipped with a supplemental detection system such as a smoke detector, heat detector or other sensing device. This supplemental detection system electrically opens the preaction valve. This charges the sprinlder line with water, malting it essentially a wet pipe system. If a sprinlder head is activated, water will immediately flow to suppress the fire. This is lmown as a single-interlock system. The sprinlder lines can be filled with water due to the detection system opening the preaction valve, even if the sprinlder head has not activated. The small amount of compressed air or nitrogen in the pipe is used to monitor system integrity. If the pipe develops a leak, air pressure will drop, and a low system pressure alarm will sound. However, the preaction valve stays closed until the detection system is activated. Non-Interlock Systems Non-interlock systems allow water into the sprinkler piping with either operation of the detection device or the activation of an automatic sprinlder head. Double- Interlock Systems In double-interlock systems, water is not admitted to the sprinlder piping until both the detection device and an automatic sprinkler head are activated. These systems are mostly found in lowtemperature applications, where water may cause sprinlder system pipes to freeze. Preaction systems are typically found in environments like museums, or facilities where water discharge is of major concern. They are also found in computer rooms or telecommunications facilities where an unintended discharge of water can do significant damage. 4th Class Edition 3 • Part A 5-19 Unit A-4 • Introduction to Plant and Fire Safety ============ ================== A double-interlock preaction system is shown in Figure 15. The Dry Pilot Actuator and the Solenoid Valve must both activate for the preaction valve to open. Figure 15- Double Interlock Preaction System Automatic Sprinklers System Shut-Off Valve ,...---- Check Valve Electric Detectors Air/Nitrogen Maintenance Device Fire Alarm Bell Water Motor Alarm Solenoid Valve / (normally closed) Electric Releasing Panel Electric Manual Control Station(s) Combined Dry Pipe Valve w/Double Interlock Trim Waterflow Pressure Alarm Switch -Water Pressure -Atmospheric Pressure D Air Pressure D Double Interlock Deluge Systems Deluge sprinkler systems deliver large amounts of water using non-automatic sprinlder heads. These sprinkler heads are not heat activated; they are always fully open. When water flows through the sprinlder line, all of the sprinlders on the piping system flow without delay. A deluge valve is used to control the system water supply. The sprinlder system pipe is at atmospheric pressure, since only open sprinlders are attached to it. Supply water is delivered upstream of the deluge valve. As in preaction systems, a supplemental detection system is located in the same area as the sprinlders. Upon activation of the supplemental detection system, the deluge valve is electrically opened, admitting water into the sprinlder system piping. As the water reaches the sprinklers, the water immediately discharges, and soaks the entire area. 5-20 7 S: E-- -----------------------4th Class Edition 3 • Part A Fire Extinguishing • Chapter 5 ======================================== Figure 16 shows a deluge valve for a power plant sprinlder system. Note the manual activation lever in the box on the right. Figure 16- Deluge Valve Installed in a Deluge System This system is appropriate for facilities that contain combustible or flammable liquids, warehouses full of paper, or other situations in which extensive fire damage is likely to occur over a short period of time. This system may also be used to provide fire separation between parts of a building or plant. Another use is to keep windows that separate building sections cool so they do not break during a fire. Some building have specialized automatic fire suppression systems that operate similar to sprinlder systems. These include: a) Kitchen fire suppression systems that spray Class K extinguishing agent on cooking equipment. b) C02 extinguishing systems that flood an area such as a gas turbine enclosure, smothering the fire, see figure 17. c) Other systems using extinguishing agents to extinguish electrical fires. While these are not usually identified as standpipe or sprinlder systems, they do utilize devices to direct and distribute the extinguishing agent over a specific area. -------------------------s 4th Class Edition 3 • Part A Z s-21 Unit A-4 • Introductionto Plant and Fire Safety Figure 17 - C02 Fire Suppression System for an Engine Room 5-22 <(------------------------------4 -th_ _C s_ s _E_d_ ft0_n _ _3_•_P_a_rt_A _