The mechanical smoke exhaust system consists of smoke-proof vertical wall, smoke outlet, smoke exhaust duct, smoke exhaust valve, smoke exhaust fire damper and smoke exhaust fan.

(1) Generally, the smoke outlet should be arranged in the center of the smoke-proof partition as far as possible, and the horizontal distance from the farthest point should not exceed 31m. The smoke outlet should be located on the ceiling or the wall near the ceiling, and the minimum horizontal distance between it and the adjacent edge of the nearby safety exit along the aisle direction is less than 15m. The smoke outlet is usually closed. When a fire breaks out, the automatic control system will open the smoke outlet, and the smoke will be discharged to the outside in time and quickly through the smoke outlet. The smoke outlet can also be used as an air supply outlet. The plate smoke outlet is composed of electromagnet, valve, microswitch and blade, as shown in Figure 3-23.

fig. 3-23 plate smoke exhaust port

The working principle of the plate smoke exhaust port is as follows:

1) Automatic opening: In case of fire, after the automatic opening device receives the electrical signal (DC 24V) input by the smoke (temperature) detector through the control panel or the remote control system, the electromagnet coil is energized, and the moving iron core is attracted, so that the ratchet and pawl are disengaged through lever action. Depending on the spring force on the valve body, The wire rope wound on the drum is released, so the blade is opened, and at the same time, the microswitch acts to cut off the power supply of the electromagnet, and the contact of the valve opening action display line is connected, and the signal is returned to the control panel, so that the smoke exhaust fan is linked.

2) Remote manual opening: In case of fire, the fluorescent plastic plate on the BSD operating device is manually opened, and the red button is pressed to open the valve.

3) manual reset: press the blue reset button on the BSD operating device to reset the pawl, insert the rocker into the insertion opening of the winding drum, and shake the rocker clockwise, so that the wire rope will be pulled back and wound on the drum until the smoke outlet is closed, and the microswitch will be reset.

(2) The smoke exhaust valve is applied to the air duct of the smoke exhaust system, which is usually closed. When a fire occurs, the smoke detector sends out a fire alarm signal, and the control center outputs a DC 24V power supply to open the smoke exhaust valve, so that smoke can be exhausted through the smoke exhaust port. As shown in figure 3-24.

figure 3-24 smoke exhaust valve

(3) smoke exhaust fire valve is a valve installed on the pipeline of smoke exhaust system or the suction inlet of fan, which has the functions of both smoke exhaust valve and smoke prevention valve, can meet the requirements of fire stability and fire integrity in a certain period of time, and has the function of fire prevention and smoke isolation.