Self-acting control valve

The main difference between the fail-close and fail-open types of self-acting control valves lies in the mechanism used to control the opening and closing of the valve: 1. **Fail-close**: When the input signal or supply pressure is absent or insufficient, the force of the spring causes the valve to close. In other words, the valve will close automatically in the absence of a control signal. 2. **Fail-open type**: Conversely, when the input signal or supply pressure fails or is insufficient, the valve opens due to the force of the spring. That is, the valve will open automatically when the control signal fails. The choice between a closed-type or open-type valve usually depends on the safety requirements of the process. For example, in scenarios where it is necessary to ensure that the system stops flowing in the event of a failure of the control signal, a pressure-acting type is chosen ； In scenarios where it is necessary to ensure that the fluid can continue to flow in case of a loss of control, the push-type is chosen. .

It’s the air on/off valve. It is a pressure-operated valve; it remains closed when there is no pressure or no signal. Air shut-off valve: the valve remains in the open position when there is no air or no signal. If it is a steam valve, production cannot proceed properly in the absence of instrument air; the steam supply must be shut off, so a normally open valve should be selected. If they are the inlet and outlet valves for the cooling water used to cool the reactor, in the event of a power or gas outage, these two valves need to remain open to ensure production safety; therefore, gas-operated shut-off valves should be chosen.