The fire sprinkler system is one of the basic types of defense mechanisms in place against fire. Sprinkler systems are mandatory nowadays. The occupancy areas in the building can be classified according to the type of fire risk. It is classified as a light hazard, medium hazard & high hazard area. The sprinklers should be designed according to the type of hazard the area belongs to.
The design of water supply systems, piping, fire pumps, and sprinklers should be as per the NFPA standards. Sprinkler installation should be done as per the manufacturer’s recommendation. The contractor should make sure that all the materials installed should meet the project specifications. The installation of fire protection systems along with piping should be done under the supervision of a fire system engineer.
In this document, the main focus is on working with the wet sprinkler system.
Water Supply System
The main water line is the primary source of water supply. Underground piping is done as per the NFPA and project code UPVC Class 5 pipes are commonly used for underground piping. Underground pipes should be flushed properly before the tie in connection with the existing main water line. The pipes should be flushed with sweet water until all the debris is removed. The water must be crystal clear. The underground tie in point should be inside a valve chamber. They must have proper access for maintenance purposes. The tie in connection has a butterfly valve and a check valve is provided to prevent any reverse water flow to the mainline. The tie in connection is made at the entry point of the building. Underground Piping should be done only with the approved utility drawing. Infrastructure works are carried out by experienced personnel.
Tie in connection is a connection of an existing pipe with a new one. Tie in connection has valves, adaptors, couplings for joining existing pipes with a new connection.
Flushing is a process of pumping water at selected velocity and pressure to remove scales, rust, and any other debris in the piping system.
Tanks are commonly kept at an elevated level and the capacity of the tank is designed as per the project specifications. Tanks are designed and constructed as per NFPA 22.
The pipes should be cleaned for removal of dirt and then painted with red oxide primer paint. The second coat will be the red color as per the project specification. The above-ground pipes should be made of black steel or GI. The Pipes must be a seamless type or ERW as per project specifications. ( ASTM A53 GRB).The wall thickness of pipes is schedule 40 or 80 as per the project requirement. Pipes of diameter up to 2 inches are threading and above 2 inches are usually welded or grooved. Pipe risers are vertical pipe main lines carrying water to all floors. The pipe risers are normally passing through mechanical shafts. Proper rigid supports should be provided to the risers.
Each pipe is supported by clevis clamps, u bolts, and hanger supports. The supports are spaced as per the specification. Bigger diameter pipes are supported using an angle bar or c channel. Vertical pipe risers in the shaft must be provided with rigid supports. Hanger supports are installed at an average spacing of 4.5 meters for the feeder main pipe. Supports are compulsory at locations having direction change.
Also, read – How the VESDA System Works?
Pipes and fittings are welded to make a joint. A welding joint is finished in 3 stages
The welded joints are normally checked by non-destructive testing methods ( NDT).
Grooving is a process in which two pipes are grooved at the ends using a grooving machine. A rubber gasket is fitted over two ends of pipe and coupling is screwed together at ends with nuts and bolts. Grooved fittings are easy and fast to install. It eliminates the chance of fire hazards which are normally associated with welding works. The pipe coupling’s bolts and nuts should be tightened with a socket wrench. Grooved piping reduces the mechanical stress in piping
Fully erected pipes along with riser connection should be hydro tested for any leakages. Pipes are pressurized for a period of 2 hrs for finding out any leakages
The test pressure is1.5 times the working pressure. Calibrated pressure gauges must be used during the test procedure. A pressure test should be conducted using only a sweet water source. Non-potable water cannot be used for testing the fire line.
The system is checked for a maximum pressure of 200 psi. Leaks are detected visually or by monitoring the pressure drop. In case of any leakages, the pressure will be released for doing rework. The system is pressurized using a manifold with facilities for drain & pressure gauges installed on it. Hydrotest is one of the most important stages of the piping system.
The alarm check valve is a check valve having an alarm port. Its main function is generating an alarm. The clapper of the check valve is fully closed during the normal operating cycle. The body of the check valve is made of ductile iron and the seat ring is bronze.
OS&Y gate valves are installed before the alarm check valve. There should be a minimum gap maintained between the valves as per the manufacturer’s recommendation. Tamper switch should be installed on the handle of the OS&Y gate valve. The tamper switch is an electromechanical device connected to valves to sense the partial opening or closing of a valve. It has an actuating unit.
The retard chamber body is constructed of cast iron. They are specifically listed to use in the wet pipe sprinkler system. It is designed to operate for a working pressure of 175 psi. Due to fluctuating water supplies, there is a chance of false alarm. The main function of the retard chamber is to detect the false alarm. Retard chambers can absorb the Pressure surge from the mainline. It allows the pressure switch to operate in an actual alarm condition.
During a fire, water flows through the alarm port, and the clapper of the check valve will be opened and water flows to the alarm line which in turn creates a bell. Strainers should be installed before the gong to prevent the entering of debris. The strainer prevents the gong from getting clogged.
Pressure switches are installed above the retard chamber. It only activates if the pressure goes above the retard set pressure. It will break the circuit and sends a signal to the main fire alarm control Panel
Vane type flow switches are most commonly used. The flow switch senses the water flow and gives an alert signal to the fire alarm control panel (FACP).
Alarm Check Valve Working Sequence
When there is a drop in pressure due to fire, water flows through the alarm check valve, and the alarm port will be opened. There will be a sudden increase in the pressure at the inlet and once the pressure gauge reads 6 psi pressure switch trips. The pressure switch is installed approximately 24 inches above the retard chamber. There is an automatic drain on the line to drain the water and bring the pressure back to zero.if the water is not properly drained from the retard chamber, it cannot prevent a false alarm.
On the left side of the alarm valve, there is a bypass line with a check valve and gauges. A small amount of water will flow through this line in case of a pressure increase in the mainline, which protects the check valve clapper from wear and tear. There are two gauges one at suction and another at the discharge end. In case of fire, once the heat crosses the designed temperature of the sprinkler, it breaks causing the flow of water through the alarm check valve. The pressure switch sends a signal to the fire alarm panel which in turn activates the fire pump controller and the pumps will start in sequence to resist the fire.
All the valves installed in the fire fighting system should be UL Listed & FM approved.
UL Listed: Underwriters Laboratories is an organization responsible for testing and certifying fire-related items.
FM Approved: FM approvals confirm research and testing of products to the highest degree of safety and prevention of any property loss.
Floor Control or Zone Control Valve Assembly
After the alarm check valve assembly connection is installed, the vertical pipe enters inside the building. Each floor should have a zone control valve assembly. This separates the fire area into small distribution zones.FCVA consists of gate valves, inspectors test & drain valve, and water flow switch. A vane-type of flow switch is used for this purpose. Inspectors test & drain valves have 2 operating ball valves,1 sight glass through which water flow can be seen. Inspectors test & drain valves are used to check the working of water motor gong. The test and drain valves are opened to make a pressure drop and the inspection team can check for the alarm. The contractor should select the best fabricators, welders, technicians, electricians, and foreman for the installation of piping and the valve assemblies.
Fire Department Connection
Fire department connection or siamese connection has 2 inlet sources for the fire department to hook up and supply water inside the building in case of fire. It should be installed in areas where the fire department has easy access. It is one of the supplementary sources for the automatic sprinkler system. The installation of Fire department connections should have a check valve to prevent the backflow of water. The normal size of the fire department connection is 4x4x2/12 inches. In case of fire, the fire department team will reach the site and the O&M Contractor must send the qualified fire and safety team to assist them.
Water Flow Switch
Water flow switches act as an interface between fire suppression and fire alarm. Flow switch senses the flow of water and activates an alarm. It is an electromechanical device. There are a plastic vane and paddle which is installed by making a hole in the pipe. Once the water flow is more than 10 Gallons/minute, the vane triggers a signal and alarm starts ringing
Pressure Switch
The pressure switch senses the change of pressure in the system. Once the pressure reaches the set point pressure, the circuit will be cut off. Then it will give a signal to the fire alarm control panel.
Fire Hose Cabinet (FHC)
Fire hose cabinet is fire-resisting equipment that consists of a fire hose or a fire hose reel. Besides that, an outlet and valves are provided to connect the inlet water pipe.FHC are of different types such as surface mounted, semi-recessed, and fully recessed types. It is installed on the wall. The height of the top of the cabinet shall be between 1.5 to 2 meters. A threaded landing valve is available inside the FHC. Fire hoses are made of synthetic rubber, Polyurethane, and other polymeric materials.FHC comes with fire extinguishers inside it as per the selected model.
Fire hose reels are made of red molded synthetic fiber covered with polyester. The cabinet body is made of stainless steel or aluminum as per project specifications.
During the time of the fire, the trained person has to pull out the reel for 2 to 3 meters and open the valve and control the discharge nozzle to discharge water efficiently. A minimum of 2 persons is required for this operation. They have to place it in the correct position to discharge the water towards the fire area.
Fire Nozzles
Fire hose nozzles are connected to the fire hose and the main purpose of the nozzle is to give proper direction and discharge of water towards the fire. The main functions of nozzles are to control flow and to provide reachability. Different types of fire nozzles are
The nozzle depends on water flow, water pumps, and hoses to determine what nozzle can achieve. The nozzle cannot create a flow.
Fire Pumps
Fire pumps form an integral part of automatic fire suppression systems. Fire pumps are installed in designated pump rooms. The system pressure drops when 2 or more sprinklers are broken due to fire, the pressure in the line decreases, and the fire pump gets started.
Fire pumps are installed along with vibration isolators. Vibration isolators help in reducing vibration and stress. Each fire pump is delivered along with a fire pump controller. The fire pump controller contains switches, relays, and circuit breakers. The fire pump controller is linked with the main fire alarm control panel.
Jockey Pump forms an integral portion of the fire pump’s control system. A jockey pump is used to maintain pressure inside the piping system. Jockey pumps are pressure maintenance Pumps. They are designed to keep the pressure at an elevated level and when the system is not in usage so that the main pump won’t start and jockey pumps help to maintain line pressure. This increases the efficiency and longevity of main fire pumps. In case of leaks, pressure drops slowly and jockey pumps will be able to maintain line pressure. If there is a drastic drop in pressure main fire water pumps will start. In case of fire, if the main pump starts directly, pressure in the system goes up and the pressurized water can damage the entire system. The jockey pumps maintain a minimum pressure in the line so that the main pumps work smoothly without damaging the network. Centrifugal pumps are preferred.
The electrical fire pump takes water from the underground mainline or from the tank or reservoir and pressurizes the system. Centrifugal pumps are the most common type of pump used in fire fighting. Water from the mainline enters the pump through an inlet and discharges outwardly through the impeller. The electrical fire pump controller receives signals from pressure switches, alarm valves, and thus by detecting the signals, the controller starts the electrical fire pump.
The pump has a rated suction and discharges pressures. High rise building can use 2 electrical pumps to achieve the required pressure
Diesel pumps are preferred if the pump room is located outside the building. Electrical fire pumps can be located inside the building but it is difficult to accommodate diesel pumps inside the building. Diesel pumps will be activated only in case of an electrical failure. Diesel pump installation is more costly. They require additional fuel storage tanks and a well-maintained exhaust system.
Hook up connection means connecting a pipe network with necessary fittings, valves & accessories to the equipment. Suction and discharge side connections of the pump are made using a flexible connector. The suction side and discharge side of the pump consists of flanged ends. Proper flange selection for connecting pipes must be decided only by trained fire system engineers. The flanged ends of the pumps are ANSI OR DIN. The procured flanges should be proper to connect with the pump and holes of the flanges should match each other. The suction side of the pump should have an OS&Y gate valve and a strainer to remove dust from entering the pump. Strainers must be cleaned periodically. The discharge side connection consists of the OS&Y gate valve, check valve to prevent backflow, and PRV ( Pressure reducing valve). Flow meters are installed for testing purposes. There should be a test and drain line installed. While doing testing and commissioning of the pump the main discharge valves to the building will be closed and the developed discharge pressure will be drained to the nearest drain point through the test & drain line. The testing & commissioning of the pump should be done by the manufacturer in the presence of the client and the contractor. Pressure gauges are installed at the suction and discharge side of the pump.
Fire Sprinklers
Fire sprinkler systems are connected with the pipe system. Water is discharged through the deflectors of sprinklers in all the directions. Type of sprinklers commonly used
Pendent sprinklers are installed below the pipelines and the water discharged by the sprinkler head is directed downward against a deflector. The pendant sprinklers are installed in areas where there is a false ceiling. Sprinkler head contains glycerine based liquid and it has a designed temperature.
Sprinklers shouldn’t be installed in areas where there is an obstruction like beams or other structures. As per NFPA 13, the gap between the deflector of the sprinkler and top of storage must be at least 18 inches. Sprinkler spacing requirements should be as per the NFPA 13.
The spacing of sprinklers depends upon the occupancy hazard that area belongs
Light hazard areas
Light hazard areas are commonly offices, universities, schools, hospitals, restaurants & theaters. The maximum spacing of sprinklers is 4.5 Meters.
Ordinary hazard areas
Ordinary hazard areas are commonly workshops, wooden work areas, Parking areas, and Bakeries. The maximum spacing of sprinklers is 4.5 meters.
Extra hazard areas
Extra hazard areas are commonly painting workshops, chemical Labs & workshops. The maximum spacing of sprinklers is 3.7 Meters.
Upright Sprinkler
Upright sprinklers are installed upwards and the deflector is pointing upwards. The water spray pattern is domed. Upright sprinklers are used in areas having no false ceiling.
Sidewall Sprinkler
Whenever there is limited access to the ceiling, sidewall sprinklers are preferred. They are installed horizontally on the wall. Mainly they are seen used in bedrooms of apartments and flats.
Corrosion-Resistant Sprinkler
Corrosion-resistant sprinklers are used in areas exposed to chemicals, moisture, or other corrosive vapors.
From the mainline using fittings like tees, elbows and threadolets branch pipe can be installed. From this branch pipe, a small pipe riser is connected with the sprinkler.
Sprinkler numbers as per riser size ( NFPA 13)
25mm pipe: 2 sprinklers
32mm pipe: 3 sprinklers
40mm pipe: 5 sprinklers
50mm pipe: 8 – 10 sprinklers
65mm pipe: 15 sprinklers
Plenum Area: Plenum space is an area that can provide air circulation for the heating & ventilation system.
After all connections of piping including sprinkler, valves, and pump headers are finished, the fire fighting pipes should be tagged. Mechanical tagging is very important as there will be different utilities passing through the same area.
The main aim of a wet suppression system is to resist the fire by discharging high-pressure water. When there is an outbreak of fire, the temperature in the area goes up. Once the heat will reach the designed temperature of the sprinkler, the bulb breaks, and water starts to flow through the sprinklers. This will result in a pressure decrease in the system. The same time water from the mainline starts flowing through the alarm check valve. Due to the pressure of the water, the clapper of the check valve opens. The water flows through the gong and it starts producing the mechanical bell which will inform a case of an emergency in the building to the occupants. The emergency response team should act fastly. The pressure switch which is installed above the retard chamber will pass a signal to the main fire alarm control panel. The FACP, in turn, will give a signal to the pump controller.
Initially, the jockey pump controller will start the jockey pump to maintain the system pressure for a little time. If the main pump starts initially the immediate rise in the pressure can make the system unstable. Once the set point pressure is reached the jockey pump will be automatically turned off. The second stage of operation starts with the main electrical fire pump controller giving the signal to start the electrical fire pump. This will discharge high-pressure water into the building to suppress the fire. In case of power failure, the diesel pump will immediately start to suppress the fire.
Q1. What is an experience certificate, and why is it important? A. An experience certificate…
Q1. What is a course certificate? A course certificate is an official document issued upon…
Q1. What is an experience certificate, and why is it important? An experience certificate is…
Q1. What are the optical fiber & LAN networking job opportunities available in Bengaluru? A.…
If you're looking to break into the world of digital marketing, Kerala there are a…
Today, technology is evolving at the speed of light, and maybe this could be one…