A solenoid valve can be described as an electrically controlled electronic proportional valve. It is equip with the solenoid that comprises an electrical coil that has the ability to move a ferromagnetic center (plunger) at its center. In the resting position, the plunger is close by a tiny orifice. A current of electricity through the coil produces an electric field. The magnetic field creates an upwards force on the plunger, opening the orifice. This is the fundamental principle behind the process employe to close and open the pinch solenoid valve.
Working Principle:
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Direct-Acting:
Direct action (direct-controlled) solenoid valves are based on an easy working principle. In a normally closed valve without power, the plunger blocks the orifice using the seal of the valve. A spring forces the closure. In the event that power is applly, it generates an electromagnetic field that pulls the plunger up and overcomes the force of the spring. The orifice is open and lets the media flow through. A normally closed high quality pneumatic pinch valve includes the same components; however, it operates in a different manner.
The maximum operating pressure and stream rate are directly connect to the diameter of the orifice and the force that drives the electric pinch valve. Thus, a direct-acting solenoid electronic proportional valve is generally utilize for small flow rates. Solenoid valves that are operate by direct means have no pressure differential; therefore, they can be use from 0 bar to the maximum pressure that is allow.
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Indirect Acting:
Indirect acting solenoid valves (also called servo-operated or pilot operated) make use to measure the difference in pressure of the media across the valve’s inlet and outlet ports to open and shut the valve. This means that they generally require an initial pressure differential of about 0.5 bar. The ports for the inlet and outlet will be divide by a membrane of rubber, also known as a diaphragm. The membrane is fit with a tiny hole that allows the medium to flow to the upper compartment from the outlet. In the case of indirect-acting, normally closed solenoid valve pressure at the inlet (above that of the membrane) and the supporting spring over the membrane ensures that the valve stays shut. Small channels join the chamber that is above the membrane to the port with low pressure.
The valve seal and the plunger seal the connection. The diameter of the “pilot” orifice is larger than the diameter of the hole inside the membrane. When the pilot orifice activates the solenoid, it is open, which causes the membrane’s pressure to decrease. Due to the difference in pressure between the two surfaces, the membrane is raise, and the medium will flow from the port that is the inlet to the outlet port. However, it operates in the opposite manner. The pressure chamber that is above the membrane functions as an amplifier, which means even a tiny solenoid could manage a huge flow. An indirect solenoid electronic proportional valve can only be utilized for flow control in only one direction. Direct operate solenoid valves can be utilize in applications with the right pressure differential and an extremely high flow rate.
Solenoid Valve Features:
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Reduced Power From Electric Sources:
A brief current pulse is deliver to either open or close the valve, and the electric power is diminish enough to ensure it remains in its place. This saves energy.
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Latching:
Latching or pulse coil versions are a solution for users that require low-frequency switching. The proportional pneumatic valve is power by a brief electric pulse for the purpose of moving the plunger. A permanent magnetic field is utilize to keep the plunger in its current place without the need for a magnetic field or spring. This decreases the amount of power consumed and the development of heat within the valve.
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High Pressure:
The high-pressure electronic proportional valve models are developed to meet pressure requirements of up to 250 bar.
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Manual Override:
A manual override option can be add to provide more safety and comfort during commissioning, testing, and maintenance and in the event of an electrical interruption. In certain versions, the pinch pneumatic valve cannot be actuate electrically if the control manual is not lock.