Knowledge Extension - Air Shutoff Valve

Knowledge Extension - Air Shutoff Valve

Some people ask why the pneumatic membrane regulating valve in the figure belongs to the air-tight type.

First, check the air inlet direction of the pneumatic film, which shows positive.

Second, look at the installation direction of the valve core, which is positive.

Pneumatic Actuator Valve

The pneumatic membrane air chamber inlet the air, pushing the diaphragm to presses down the six springs covered by it, thus pushing the valve rod to move downward. The valve rod is connected with the valve core, and the valve core is installed in the forward direction. Based on that, we know the air source flows to the closed position in the valve. Therefore, it is called an air shutoff valve. Failure leading to opening means that when the gas supply is interrupted due to construction or corrosion of the gas pipe, the valve is reset again under the reactive force of the spring and the valve then is in the fully open state.

How to use the air shutoff valve?

The question that how to use it is considered from a safety point of view, and this is a necessary precondition for selecting air on or off.

For examples, the steam drum, one of the core devices of the boiler, and a regulating valve used in the water supply system must be of gas-tight type. Why? For example, if the furnace is still burning while a sudden interruption of the air supply or power supply occurs, the water in the steam drum will be continuously heated. If the gas is used to open the regulating valve, the energy source will be cut off, and the valve will be closed. The steam drum will be dried up (dry burning) without water in minutes. This situation is very dangerous. It is impossible to deal with the faults of the regulating valve in a short time, which will lead to boiler shutdown accidents. Therefore, it is necessary to use shutoff valve to avoid dry burning or even shutdown. Although the energy is cut off, the regulating valve is in the fully open position, and the steam drum is continuously fed with water, it will not lead to a dry burning, and there is still time to deal with the faults of the regulating valve rather than stopping the furnace directly.

Through the above example, you must have a preliminary understanding of how to select the air-on and air-off regulating valves.