Do two five-way solenoid valves with dual control require a holding valve?

A pressure holding valve is not required. Two five-way solenoid valves with dual control can keep the butterfly valve in a specific position, eliminating the need for an additional holding valve. .

With FL, you don’t even need a gas tank.

Whether a hold-back valve is needed for the pneumatic cut-off butterfly valve FL with an air tank, and in a system that uses a two-position five-way solenoid valve for dual control of the air supply, depends on the specific application requirements and system design. The main function of a position holding valve is to maintain the position of the pneumatic actuator unchanged in the event of a gas supply failure or loss of power to the solenoid valve, thereby ensuring stable valve operation. It can prevent the valve from opening or closing accidentally, thereby enhancing the safety and reliability of the system. Here are some factors to consider when determining whether a position holding valve is needed: Process requirements: If the manufacturing process imposes strict demands on the valve’s position, for example, if it is necessary to ensure that the valve remains in a specific position during certain critical operations or emergency situations, then a position holding valve may be essential. Safety considerations: If the security of the system is of paramount importance, and accidental operation of the valve could lead to danger or losses, a check valve can provide additional safety protection. Gas supply stability: If the gas supply is unstable, temporary pressure drops or interruptions may occur. A holding valve can help maintain the position of the valve until the gas supply returns to normal. Solenoid valve reliability: Two-position five-way solenoid valves generally have good reliability, but in some cases they may fail or lose power. A holdback valve can serve as a protection in such situations. System complexity and cost: Adding a check valve increases the system’s complexity and cost. Therefore, it is necessary to take into comprehensive account the overall requirements of the system as well as its economic viability. If it is decided to use a retention valve, the appropriate type and specifications for the application should be selected, and proper installation and calibration must be ensured. In addition, the position control valve should also be regularly inspected and maintained to ensure its proper operation. Whether a retention valve is ultimately needed should be determined based on the specific circumstances. If high requirements are placed on the system’s safety and reliability, or if it is crucial for the process to maintain a specific valve position, then using a positioning valve may be a wise choice. It is recommended to have further discussions and consultations with a professional pneumatic system engineer or supplier before making a decision.

There are two types of shut-off valves. One type is driven by a 2/3 way solenoid valve; when powered, the cylinder of this shut-off valve is connected to the instrument air, which pushes the cylinder to overcome the force of the return spring in order to open (or close) the shut-off valve. When there is no power supply, the solenoid valve releases the air in the cylinder, and under the action of the return spring, the shut-off valve returns to its original position. For a gas-on valve, it is reset to the closed state; for a gas-off valve, it is reset to the open state. Another approach is to use a three-way or five-way solenoid valve for actuation; the cylinder of the shut-off valve has two air inlets – one for opening the valve and the other for closing it. No return spring is required in this case, so unlike the previous method, there is no risk of the valve returning to its original position in the event of a loss of signal or air supply. When the signal to open the valve is ON, the solenoid valve is activated, allowing air to enter the cylinder and open the valve opening, while the valve closing opening is emptied. When the shutdown signal is ON, it allows the port of the cylinder’s valve to be emptied, while allowing air to enter through the valve’s closed port. This requires two digital output points. When the open valve and close valve signals are OFF, the valve maintains its current state. Another feature is that the switch signal does not need to remain active continuously; once the signal indicating that it is in the open or closed position is ON, the signal for opening, closing, or shutting off the valve can be sent.