Its working principle is that in case of fire, the temperature-sensitive smoke fire detector installed in the protected area sends out fire alarm and other signals. After receiving the alarm signal, the fire alarm controller or fire control center sends an instruction to open the electromagnetic valve on the deluge valve, so that the deluge valve is opened, and the pressure water flows into the pipe network on the system side, becoming a wet spraying system. At the same time, the hydraulic alarm bell complains, the pressure switch action is fed back to the control center to show that the pipeline is full of water, and the fire pump is started.
At this time, the closed nozzle installed on the pipeline has not been released and will not spray water. People can still take the initiative to take appropriate actions, and the person in charge will put out the fire, thus avoiding the losses caused by water damage caused by sprinkler action. If the fire can't be controlled and continues to develop, the closed nozzle glass ball will spray water and the water pump will start automatically.
After the fire extinguishing, the electromagnetic valve should be closed to close the deluge valve, and the water in the pipeline should be removed, so that the inflation pressure of the system can be kept within the range of 0.03-0.05MPa, and the quasi-working state can be restored.
Extended data:
Pre-action alarm valves are generally installed in places where water is needed to extinguish fire, but water spraying is not allowed unless it is caused by fire. Such as libraries, archives, museums, valuables storage rooms, computer rooms, etc.
The pipeline on the side of pre-action alarm valve system is usually filled with low-pressure compressed air, which has the characteristics of dry system and can meet the needs of installing automatic sprinkler system in cold areas.
The pre-action system is to combine the automatic fire detection and alarm technology with the automatic sprinkler system, and install closed nozzles in the system. When there is no fire, the pipeline of the system is usually filled with low-pressure air or nitrogen for monitoring, so the system has the characteristics of dry system.
Key points of construction and installation
The main feed water signal butterfly valve, deluge valve and dry alarm valve of 1) system should be installed vertically in the control room near the protected area, and the temperature of the control room should not be lower than 4℃ to avoid the failure of the whole system due to the freezing of water in the low-temperature diaphragm cavity.
2) When installing, put the diaphragm valve group into the flange of the water source pipeline, and put the gasket. After tightening the flange bolts, put the gasket at the outlet of the diaphragm valve, with the same installation specifications and 90-degree elbow, and tighten the bolts. And then connected with the system pipe network. Open a hole in the straight pipe section of the upper mouth of the dry alarm valve and connect it with a 3/4 "pipe. It is connected with air maintenance components such as low-voltage switch, air compressor and electric contact pressure gauge.
3) Floor drains shall be set at the drainage places such as system drain valves, solenoid valves, manual quick-open valves, hydraulic alarms, water replenishing funnels, etc., and the discharged water shall be discharged into sewers respectively.
4) Install pressure switch, solenoid valve, signal butterfly valve lead-out wire and air maintenance equipment on deluge valve, and connect the low-voltage switch and lead-out wire of electric contact pressure gauge with the loop of fire control center respectively.
5) The hydraulic alarm bell shall be installed near deluge valve or in public passages and duty rooms, with a pipe diameter of 20mm, an alarm pipeline length of less than 20m and a height of no more than 5m from the alarm valve.
6) After the installation, turn the deluge valve anti-reset handwheel to the anti-reset lock position, and the red dot on the handwheel is aligned with the lock position of the sign, so that the system is in a quasi-working state.
References:
Baidu encyclopedia-pre-acting alarm valve