The sprinkler system is developed based on the automatic sprinkler system. It is mainly used in places where the fire spreads quickly and is suitable for water but difficult to protect by automatic sprinkler systems. The fixed fire extinguishing system uses a fine water mist nozzle to decompose the water flow into fine water mist droplets under a certain water pressure, which is used for fire extinguishing or protection and cooling. The sprinkler system can not only extinguish solid, liquid, and electrical fires, but also provide protection and cooling for liquefied hydrocarbon storage tanks and other facilities or equipment with high fire hazards and difficult fire extinguishing. Widely used in petrochemical, electric power, metallurgy, and other industries. In recent years, the water spray fire extinguishing system has been popularized and applied in the brewing industry.
In addition, the protection objects of the sprinkler system include industrial facilities and equipment such as the electric power and petrochemical industry, which is different from the automatic sprinkler system.
Some Terms Related to Water Spray Fire Extinguishing Systems
- Water spray fire protection system
It is composed of a water source, water supply equipment, pipeline, deluge alarm valve (or electric control valve, pneumatic control valve), filter and water mist nozzle, etc., spraying water mist to the protected object for fire extinguishing or protective cooling system. - transfer pipe
A pipeline that detects fires using closed nozzles and transmits signals using changes in air pressure or water pressure. - application density
The amount of water sprayed by the system to the unit protection area per unit of time. - response time
From the start of the water supply facilities of the system to the time from the most unfavorable point in the system to the spraying of water mist from the water mist nozzle. - spray nozzle
Under certain pressure, the water flow can be decomposed into water droplets with a diameter of less than 1mm in the set area, and the nozzles can be sprayed according to the designed sprinkling shape. - effective range
When the nozzle sprays horizontally, the horizontal distance between the highest point of the water mist and the plane where the nozzle is located is perpendicular to the axis of the nozzle. - water spray cone
The cone is formed by the water mist within the effective range of the water mist nozzle. - deluge alarm valves unit
It is a device composed of a deluge alarm valve, solenoid valve, pressure switch, hydraulic alarm bell, pressure gauge, and supporting general valves.
What factors need to be considered in the design of a water spray fire extinguishing system?
The basic design parameters of the system should be determined according to the protection purpose and protection object.
The basic design parameters include design supply intensity, continuous spray time, protection area, working pressure of water mist nozzle, and system response time. Butterfly valve firefighting manufacturer The basic design parameters need to be selected according to the protection purpose of the water spray fire extinguishing system and the category of protection objects.
The working pressure of the water mist nozzle should not be less than 0.35MPa when it is used for fire extinguishing; it should not be less than 0.2MPa when it is used for protective cooling, but it should not be less than 0.15MPa for Class A, B, B, and C liquid storage tanks.
Sprinkler and piping arrangement
The number of water mist nozzles required for the protection object should be based on the design supply strength, protection area, and characteristics of the water mist nozzles. The arrangement of the nozzles should make the water mist directly spray to and cover the protection objects. If the requirements cannot be met, additional water mist nozzles should be added.
The safe net distance between water mist nozzles, pipelines and live (exposed) parts of electrical equipment should comply with current industry standards.
The distance between the water mist nozzle and the protected object shall not be greater than the effective range of the water mist nozzle.
The planar layout of the water mist nozzles can be rectangular or rhombus. When arranged in a rectangular shape, the distance between the water mist nozzles should not be greater than 1.4 times the radius of the water mist cone bottom of the water mist nozzles; when arranged in a diamond shape, the distance between the water mist nozzles should not be greater than 1.7 times the water mist nozzles The radius of the bottom circle of the water mist cone.
System Components of Water Spray Fire Extinguishing Systems
The selection of water mist nozzles should meet the following requirements:
- Centrifugal atomization water mist nozzles should be used to fight electrical fires;
- The water mist nozzles installed in indoor dusty places should be equipped with dustproof caps, and the water mist nozzles installed outdoors should be equipped with dustproof caps;
- Centrifugal atomization water mist nozzles should be equipped with columnar filters.
For systems with a response time not greater than 120s, a deluge alarm valve group should be installed, and the function and configuration of the deluge alarm valve group should meet the following requirements: - The deluge alarm valve group receiving the electric control signal should be able to be opened electrically, and the deluge alarm valve group receiving the transmission pipe signal should be able to be opened hydraulically or pneumatically;
- It should have remote manual control and on-site emergency mechanical start-up functions;
- The opening and closing status of the deluge alarm valve should be displayed on the control panel;
- It is advisable to drive the hydraulic alarm bell to alarm;
- Pressure gauges should be installed at the inlet and outlet of the deluge alarm valve;
- A flushable filter should be installed in front of the solenoid valve.
When the system water supply control valve adopts electric control valve or pneumatic control valve, it shall meet the following requirements: - It should be able to display the opening and closing status of the valve;
- It should have the function of receiving control signals to open and close the valve;
- The opening time of the valve should not be greater than 45s;
- It should be able to alarm when the valve fails, and display the cause of the failure;
- It should have the on-site emergency mechanical start function;
- When the valve is installed in the valve well, the stem of the valve should be lengthened, and the electric actuator should be higher than the top of the well;
- The pneumatic valve should be equipped with a reserve gas tank. The volume of the gas tank can be calculated according to the gas volume required to open and close all the pneumatic valves connected to the gas tank 3 times.
The pipeline before the deluge alarm valve should be equipped with a flushable filter, the filter screen should be made of corrosion-resistant metal material, and the basic size of the mesh should be 0.600mm ~ 0.710mm.
The water supply pipeline shall meet the following requirements: - The pipes between the filter and the deluge alarm valve and after the deluge alarm valve should be made of hot-dip galvanized steel pipes, stainless steel pipes, or copper pipes inside and outside; seamless steel pipes should be used for pipes that need to be bent;
- The working pressure of the pipeline should not exceed 1.6MPa;
- When the system pipeline adopts galvanized steel pipe, the nominal diameter should not be less than 25mm; when stainless steel pipe or copper pipe is used, the nominal diameter should not be less than 20mm;
- The system pipes should be connected by grooved pipe joints (clamps), flanges, or threaded buckles, and ordinary steel pipes can be welded;
- For grooved pipe joints (clamps), the material of the shell should be ductile iron with a grade not lower than QT 450-12;
- The grooved pipe joint (clamp) sealing ring and non-metallic flange gasket in the protection area should pass the dry burning test;
- A drain valve or sewage outlet should be set at the lower part of the pipeline.
Regulations on Water Supply in Water Spray Fire Extinguishing System
The water for the system can be supplied by the fire pool (tank), fire water tank, or natural water source, or it can be supplied by the stable high-pressure fire water supply system independently set up by the enterprise; the water volume of the system water source should meet the requirements of the maximum design flow rate and supply time of the system.
The fire pump room of the system should be built together with other water pump rooms and should comply with the current relevant national standards for fire pump rooms.
In severe cold and cold regions, antifreeze measures should be taken for parts of the system that may freeze.
When the system is equipped with two or more deluge alarm valves, an annular water supply pipe should be installed in front of the deluge alarm valves.
The inlet and outlet pipes of reinforced concrete fire pools should be equipped with waterproof casings, and flexible joints should be added for pipelines with vibration; the inlet and outlet pipe joints of combined fire pools should be connected by flanges.
The setting of fire pressure water supply equipment shall meet the following requirements:
- A check valve should be installed on the outlet pipe;
- Maintenance channels should be set up around, and the width should not be less than 0.7m;
- The distance from the top to the floor or the bottom of the beam should not be less than 0.6m.
The place where the water spray fire extinguishing system is installed should have drainage facilities.
The overflow pipe and drain pipe of the fire pool shall not be directly connected with the drainage system of production or domestic water, and the indirect drainage method shall be adopted.
Water pump
The water supply pump of the system should self-irrigate and divert water. When natural water is used for water supply, measures should be taken to prevent debris from clogging the suction port of the water pump. The water supply pressure of the system should meet the working pressure requirements of each component of the system within the corresponding design flow range, and measures to prevent system overpressure should be taken.
The system should be equipped with a spare pump whose working capacity should not be less than the water supply capacity of the largest pump.
There should be no less than two suction pipes for a group of fire pumps. When one of them is damaged, the rest of the suction pipes should be able to pass all the water; the suction pipes of the water supply pumps should be equipped with control valves.
For systems with ring-shaped pipes installed in front of the inlet of the deluge alarm valve, there should be no less than two outlet pipes for a group of water supply pumps; the outlet pipes should be equipped with control valves, check valves, and pressure gauges.
The fire pump shall be equipped with a test pump return pipe and an overpressure return pipe, and when conditions permit, the two may share a return pipe.
For fire pumps driven by diesel engines, the exhaust pipes of the diesel engines should lead to the outside.
Water supply control valve
The rain alarm valve group should be installed in a room with a temperature not lower than 4°C and drainage facilities. The deluge alarm valve installed indoors should be 1.2m away from the ground, the distance between the two sides and the wall should not be less than 0.5m, the distance between the front and the wall should not be less than 1.2m, and the distance between the protruding parts of the deluge alarm valve should not be less than 0.5m. Less than 0.5m.
Deluge alarm valves, electric control valves, and pneumatic control valves should be arranged close to the protected objects and convenient for safe operation by personnel.
The deluge alarm valve, electric control valve, pneumatic control valve and its pipelines installed outdoors in severe cold and cold areas should adopt heat tracing and heat preservation measures.
In places where the water spray test cannot be carried out, a discharge test detection device shall be installed on the main water supply pipe after the deluge alarm valve, and its water passing capacity shall be consistent with the system’s water passing capacity.
The hydraulic alarm bell should be installed on the outer wall near the public passage or duty room, and valves for inspection and testing should be installed. The deluge alarm valve and hydraulic alarm bell should be connected by a hot-dip galvanized steel pipe, and its nominal diameter should not be less than 20mm. When the nominal diameter is 20mm, its length should not be greater than 20m.
Water pump adapter
The system installed indoors should be equipped with a water pump adapter.
The quantity of water pump joints should be determined according to the design flow rate of the system, and the flow rate of a single water pump joint should be calculated according to 10L/s~15L/s.
The water pump adapter shall be set on the sidewalk or the section where non-motorized vehicles can easily approach, and the distance from the outdoor fire hydrant or fire pool should be 15m~40m.
The wall-type fire pump adapter should be 0.7m away from the ground, and the net distance from the door, window, and opening on the wall should not be less than 2.0m, and should not be installed under the glass curtain wall.
The distance between the water inlet of the underground fire pump adapter and the bottom surface of the manhole cover should not be greater than 0.4m, and should not be smaller than the radius of the manhole cover, and waterproof and drainage measures should be taken in the well of the underground fire water pump adapter.
