Active and passive explosion-proof electrical devices

Active and passive explosion-proof electrical devices block the flame by the action of one component of the device, which is different from the industrial flame arrester's physical resistance to fire. On the other hand, industrial flame arresters are working at the moment of industrial production, and the resistance to fluid medium is large, while the main and passive flameproof devices only work when flameproof occurs, so they do not act on the fluid medium. With low resistance, some flameproof devices do not even produce any pressure loss. In addition, industrial explosion-proof electrical appliances are effective for pure gaseous media. For pipelines containing impurities (such as dust, condensables, etc.) in gases, main and passive flameproof devices should be selected.

The active (monitoring) flameproof device is a sensitive sensor that detects the flameproof signal and outputs the flameproof signal to the actuator after amplification. The flameproof device is controlled to spray the anti-explosive agent or close the valve so as to block the propagation of the flameproof flame. The passive flameproof device is a flameproof wave that pushes the valve or shutter of the flameproof device off to block the flame.

(I) Automatic fire extinguishing agent fire prevention device

Automatic fire extinguishing agent, also known as chemical flame arrester, it is an active flameproof barrier device, its structure shown in Figure 1. When flameproof occurs, the flameproof signal is detected by the flame detector. After the signal is amplified, the detonator of the outlet valve of the fire extinguishing agent tank is detonated, so that the fire extinguishing agent is sprayed to extinguish the flame propagated in the pipe, so that the flameproof is blocked. This kind of flame arrester is more suitable for pipelines conveying combustible dust, especially narrow pipelines, which can cut off the propagation of dust explosions at predetermined positions. The biggest advantage of this kind of flameproof device is that it does not close the pipeline so that the production operation can continue.

Fire extinguishing agents are often selected as fire extinguishing powders and their main component is ammonium phosphate. The working pressure of nitrogen in the fire extinguishing agent tank is 12MPa. Its connection to the piping is simple and can be installed at any angle. The working principle of quickly closing the gate valve is: When the probe receives the signal of the explosion-proof electrical appliance, the amplified signal blasts the valve of the gas storage tank, and the high-pressure gas is ejected to push the gate to quickly close the pipeline. This kind of gas tank that closes the valve quickly is opened by the detonator. Therefore, the reaction is faster and the valve closing time is shorter, up to 50 ms. However, in order to test its effectiveness in production, a destructive experiment is required. For this reason, a quick-close valve that uses a fast solenoid valve instead of a high-pressure gas as a power source has been widely used in industrial production.

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