预作用系统在伺应状态时系统侧管网充以一定压力的气体，其主要功能是监测管网的密封性是否完好。控制系统一般由电磁阀、控制柜和火灾报警系统组成。消防控制室接到探测器发出的火灾信号后，通过控制柜打开电磁阀，从而打开预作用系统，压力水充满管网，同时发出报警信号，待火灾进一步发展使喷头爆破时，才喷水灭火，如果探测器发生误报，预作用系统开启，系统侧管网充水，但没有喷头爆破，所以不会喷水，从而避免了水渍损失。在控制管路上设有紧急手动开关，用于联动失效时，手启动预作用系统。监测气压为 0.03-0.05MPa。当系统气压低于 0.02MPa时，由压力开关发出故障报警信号，提醒维修管网。

本预作用装置的配置，是在雨淋阀组件上安装同一通径的止回阀，在止回阀应预注一定量的底水，用于封闭管网，保持气压。

Pre-action system filling with certain pressure gas in the system side pipe network in ready condition mainly function is to supervise whether pipe network is air tightness or not. The controlling system is generally made up by magnetic valve, control cabinet and fire alarm system. When the fire control room receives fire signal sent by the detector, the magnetic valve will be open through the control cabinet, hence starts the pre-action system, fills the pipe network with pressure water and sends alerting signal, and then sprays water until the fire explode the sprayer. In case of wrongly alarm of the detector, the pre-action system open and fill the pipe network with pressure water, as long as there is no explosion of sprayer, the water will be saved and thus avoid loss of water logging. Emergency hand switch is equipped on the tube of control valve to start manual pre-action system in case failure of linkage. The monitoring pressure is 0.03-0.05MPa. When the system pressure is lower than 0.02Mpa, the pressure switch will send failure alarm signal to warn that the pipe network need to maintenance. The pre-action valve installation is to install a same diameter check valve on the assembly component of deluge alarm valve, and a certain amount of water shall be pre-grout to close the pipe network and keep pressure.