Fire Protection Engineering: Sprinkler Systems - Term Paper Example

Name of Student Student’s number Institution Course Code Instructor’s name Date Introduction Fire tragedies have occurred in recent times and they have resulted in huge losses arising from damage of property or even loss of life. If most of these fires had been detected and stopped at their earlier stages, then the damage could have been reduced drastically or even the fire put off completely. Sprinkler systems help control fires in the earliest stages hence limiting the spread of damage to a small area while reducing disruptions to in operations and, most important reducing loss of life. Therefore, a fire sprinkler system is among the most vital safety features that should be installed in a building (NFPA, 2003). However, in order to guarantee optimal performance, sprinkler systems ought to be properly installed and maintained regularly (Jones, 2008). A sprinkler system that is defective or that is not properly installed may have a lot of negative impacts such as causing substantial damage to water due to leaking when there is no fire failing when a fire occurs. It is therefore very important to ensure that the sprinkler systems are installed correctly and functioning properly. This can be achieved by regular maintenance and testing which helps identify the damaged sprinkler systems (NFPA, 2003). This report addresses sprinkler systems and how they should be installed in a building in order to reduce loss of life and damage to property in the event of a fire outbreak. Overview of sprinkler systems Fire sprinkler systems consist of a water supply system that provides sufficient flow rate and pressure to a water distribution and piping system where sprinklers are connected. Initially, sprinkler systems were designed for use in large commercial buildings and factories but nowadays, the uses has spread to homes and small buildings since they have proved to be very beneficial and are also available at a cost effective price. Sprinkler systems are of 2 main types; wet pipe and dry pipe systems. Both of them are connected to a source of water. Control valves are used to control regulate the amount of water entering the system and they help in turning off the water supply during service and maintenance. Both systems also use a grid work of smaller pipes which cover ceiling and are connected to the main source of water by use of a riser. Sprinkler heads are fitted individually onto this grid work and at predetermined levels so as to cover the whole floor area. The heads can also be positioned in areas where fires may start without been noticed (Bromann, 2001). (a) Wet pipe systems In this type of system, the pipes that are the simplest and the most often used are permanently filled with water. The advantage of wet pipe systems is that they pose no major delay in performance in the event of a fire outbreak. Water escapes immediately after the sprinkler heads open. These systems are mostly used in buildings that require a fast acting system for the safety of life and property. The main limitation of using wet pipe systems is that it cannot be utilized in areas subjected to freezing temperatures since it contains standing water. The frozen are mostly as a result of inadequate heating, for example during the winter season, and it may result in breakage of pipes (Smith et al, 1994). Protecting wet pipe systems In order to protect wet pipe systems form freezing, a thorough inspection of a facility should be carried out especially during and throughout the winter season (Cote, 2003). The staff in charge of maintenance should: i) Examine all pipes and ensure that they are heated adequately to prevent them from freezing (Smith et al, 1994). ii) Inspect the whole facility thoroughly to ensure that there are no cold air leaks e.g. around door and window frames, through the roof and other external doors. iii) Ensure that windows and doors are tightly shut and checked at regular intervals during seasons of prevalent cold weather. iv) Ensure that the inside room and the sprinkler system main control room temperature is maintained at above 4 degrees Celcius. The temperature should be checked daily during severe cold seasons. v) Have access to vacant rooms in order to carry cold weather checks. vi) Display the emergency contact details of the maintenance provider of the fire sprinkler system at the main fire panel. (b) Dry pipe systems In these sprinkler systems, the pipe network is filled with compressed air as a replacement for water. The pressurized air holds the control valves closed and also prevents water from entering the system. Once the valve on the sprinkler heads open, air escapes and this result in reduction of pressure inside the system hence drawing more water into the pipes, then through the open valves in the sprinkler heads. Problems associated with dry pipe systems The main advantage of dry pipe systems is that they do not contain standing water and are therefore not subjected to freezing (Smith et al, 1994). They are mostly used in places where pipes can easily freeze. However, dry pipes systems may freeze as a result of poor maintenance and poor system design. For example, a fracture or a break in the pipe network may cause the air pressure to drop hence causing the main valve to open and let water to flow out of the pipes. Another disadvantage, during a fire outbreak, they take a long time before the water is released. Protecting dry pipes systems Several methods can be used to ensure a problem-free operation of dry pipe systems. These are: (i) Regular inspection and maintenance of leaks if any. (ii) Dual valves that have been installed at the systems’ low points should be checked weekly so as to make sure that they are free from water. (iii) Ensuring that the air valve and the air compressor are located in a cool and dry area so as to prevent moisture from entering the system. (iv) Ensuring that the main control valves and the fire pump are situated in an area with adequate heating, that is where the temperature is above 4 degrees Celcius. Other types of sprinkler systems include; deluge systems, pre-action systems, foam water sprinkler systems, water spray and water mist systems. The system’s internal pressure and the diameter of the pipes should be calculated to ensure that a sufficient supply of water will be present at any given time while also considering the size of the building and the occupancy (Ward, 2005). Most sprinkler systems incorporate a tiny valve that holds back water (wet pipe system) or compressed air (Dry pipe system). The valve is usually held shut by glass bulb that is filled with a heat sensitive liquid. Hot gases from the fire causes the valves to open and hence allowing water to flow onto a deflector plate, and then onto the fire. Sprinkler heads are activated by heat and therefore no water can be released to areas where the fire has not started yet since the sprinklers activate one by one as required. Failure of sprinkler systems Fire sprinkler systems have had a reputation of effectiveness and reliability over time especially when designed, installed and maintained properly. Installers expect them to lie dormant for some time and respond efficiently in the event of a fire outbreak. However, there are instances when sprinkler systems fail to operate as per the expectations. The failure in operation may be as a result of a few factors as discussed in this section. Manufacturing defects rarely lead to failure of sprinkler systems. According to a sprinkler leakage report by the Canadian Conservation Institute, the chances of a fire sprinkler system opening accidentally due to defects has been estimated at not more than 1 in every 16 million (2002).In most situations, sprinkler systems fail due to poor installation, improper maintenance or physical damage that may have been prevented. The following are other causes of failure in sprinkler systems: (i) Accidental heating which causes activation of the sprinkler heads. It mostly occurs as a result of installing heads near sources of heat such as heating vents. (ii) Sprinkler heads may be activated as a result of pipes being damaged by impact of equipment such as ladders and forklifts (Brannigan, 2007). (iii) Rust and corrosion may both weaken pipes and sprinkler heads resulting in water discharge. (iv) The sprinkler system may be damaged during construction and renovation work. (v) Inadequate insulation of pipes can result in freezing and rapture of pipes especially during the winter periods and this may make a sprinkler system become inoperable. (vi) Vandalism of pipes and sprinkler heads. In the event of failure of a sprinkler system due to damage or frozen pipes leading to discharge of water, the following are the steps that should be carried out to prevent further damage: (i) The main control valve of the system should be shut off so as to avert further water damage. Staff and maintenance workers should be well trained on how to carry out this procedure. (ii) Contact the local fire department or a sprinkler maintenance company immediately. (iii) Move all property to an unaffected part of the property to avoid further loss. Areas that are unsafe should also be avoided. (iv) Incase of frozen sprinkler pipes, do not use an open flame or a heat source to thaw it out but instead contact the sprinkler service and maintenance company immediately. (v) In case of frozen pipes, ensure that the maintenance company examines the entire sprinkler system for leaking heads, split pipes and cracked fittings before reconnecting the system. Sprinkler Systems Design and Installation Sprinkler fitting and installation involves installing, inspecting, testing, and certification of sprinkler systems in different types of structures. As discussed earlier, sprinkler systems consist of a fire suppression piping with either water, air antifreeze etc. They are designed for the purpose of suppressing or controlling fire. Control mode sprinklers help control the release of heat from a building hence preventing it from collapsing and pre- wet the surrounding combustible products to prevent the fire from spreading. Therefore, fire sprinkler systems should be designed, installed and maintained properly so as to ensure effective performance (Brannigan, 2007). After installation of sprinkler systems, it is then essential for a commissioning certificate to be issued. The certification provides the highest possible assurances and offers a high level of quality, safety and reliability. Nowadays, most sprinkler systems are designed using the approach of area and density. Firstly, the use and contents of the building are analyzed so as to identify the level of the fire hazard (Cote, 1997). Classification is done according to the level of hazard. Buildings may be classified as light, ordinary or extra hazard. After the hazard classification has been determined, the design area and density are determined by referencing tables in the NFPA (National Fire Protection Association) standards (NFPA, 2003). The design density is usually a measurement of the volume of water per square foot of the floor area that must be applied to the area under design (Cote, 1997). After determining the design area, calculations are carried out to prove that the design can effectively deliver the required volume of water over the required area. The calculations also account for all the pressure lost or gained between the source of water supply and the sprinklers expected to operate in the design area (Cote, 2003). In residential places, sprinklers are designed mainly to protect the occupants and the structure from fire. Most of them are designed to suppress a fire while at the same time allow the occupants of the building to safely exit the structure. Although fire sprinklers are designed to protect damage to property, there is always a secondary consideration. Sprinkler systems in residential structures are omitted from balconies, bathrooms, attics and garages since a fire outbreak in these areas would affect the escape routes of the occupants (Ward, 2005). When installing sprinklers, it should be ensured that the sprinklers are located in an open space area without any obstacles to the spray pattern. According to the rack storage fire tests, sprinklers work most effectively with clearances of 18-inches (Robert, 1985). Therefore, there should be an 18 inch clearance between the top of storage and the ceiling sprinkler deflectors. Installations of sprinklers should be done below a flat and horizontal ceiling construction using approved one-step cement. Listed hangers can also be used for sprinkler piping mounted onto the ceiling wall directly (Puchovsky, 1999). In Light Hazard pendent sprinklers, maximum quick response temperature is rated at 77 degrees Celcius. The deflectors should be within 203 mm (8 inches) from the ceiling with the maximum distance between the sprinklers not exceeding 15 feet (4.57 mm). The piping will be mounted directly onto the ceiling. For light hazard horizontal side wall sprinklers, the quick response temperature is listed as 93 degrees Celcius maximum. The deflectors should be installed 12 inches (304 mm) away from the ceiling and 6 inches (4.27 mm) away from the side wall. The piping shall be installed directly onto the sidewall (Bromann, 2001). Light Hazard Upright Sprinklers should have the deflectors installed 4 inches from the ceiling with a maximum distance of 15 feet between the sprinklers. The maximum distance between the ceiling and the centre line of the main pipe should not exceed 8 inches. The distance between the closest hanger and the centerline of the sprinkler should be 3 inches (Puchovsky, 1999). Design for the OH3 fire sprinkler system The OH3 (ordinary hazard group 3) sprinkler system should be designed and installed with a water source with sufficient capacity to provide the required flow rate while at the same time ensuring that the sprinklers remain in operation for a minimum of 60 minutes (Cote, 1997). The water supply could be from the town’s mains, pressure tanks and storage tanks (Bromann, 2001). The design for an OH3 system should for 5mm/min discharge over a total area of 216 square meters as required by the European standard (Puchovsky, 1999). The project design will be as shown below. Calculations Compartment 1 Total area = (35 * 20) meters = 700 square meters Area covered by each sprinkler = 216 square meters Number of required sprinklers = 700 / 216 = approx. 4 Volume of water required = (5 * 60) * (4 * 216) = 259.2 cubic meters. Distance between sprinklers and side wall = 6 mm Compartment 2 Total area = (17 * 25) meters = 425 square meters Area covered by each sprinkler = 216 square meters Number of required sprinklers = 425 / 216 = approx. 2 Volume of water required = (5 * 60) * (2 * 216) = 129.6 cubic meters. Total volume of water required = 129.6 + 259.2 = 388.8 cubic meters. Conclusion Fire sprinklers can be of a great significance in reducing losses in the event of a fire tragedy. A malfunction in the sprinkler system may have very many undesirable effects on a structure when a fire breaks out (Jones, 2008). This may be in the form of destruction of property, loss of life and interruptions in operations. Sprinkler system malfunctioning can be avoided through proper design, installation, service, and maintenance of the fire sprinkler systems. It is therefore vital to engage qualified personnel to handle the design and installation work (Jones, 2008). References Brannigan, F, Corbett, G, 2007, Brannigans Building and Construction for the Fire Service, , Jones & Barlette Learning, Sudbury, Massachusetts. Bromann, M, 2001, The design and layout of fire sprinkler systems, CRC press, Florida. Canadian Conservation Institute, 2002, National Fire Code, Regulation of Fire Safety, Viewed on 29th April 29, 2012 www.cci-icc.go.ca/cci/notes/html/2-8-eng.aspx Cote, A, 1997, Fire protection Handbook, National Fire Protection Association, Massachusetts. Cote, A, 2003, Operation of Fire Protection Systems, Jones & Barlette Learning, Sudbury, Massachusetts. Jones, A, 2008, Fire Protection Systems, Cengage Learning, Stamford. National Fire Protection Association, 2003, Standard for the Installation of Sprinkler Systems, Viewed on 29th April 29, 2012 Puchovsky, M, 1999, Automatic Sprinkler Systems Handbook, National Fire Protection Association, Massachusetts. Smith, C, et al., 1994, Private Fire Protection and Detection, Fire Protection Publications, Oklahoma State University. Ward, M, 2005, Fire Officer: Principles and Practice, Jones & Barlette Learning, Sudbury, Massachusetts. Read More