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Solenoid Valve Supplier
info@atosolenoidvalves.com3 Types of Solenoid Valves
The solenoid valve is an industrial tool for electromagnetic control. As an automatic basic element used to control the liquids, the solenoid valve has advantages, including steady performance, firmness, durability, high sensitivity, etc. It is usually applied to the heating system, compressed air technology, industrial automation, swimming pool, fire-sprinkling system, washing machine, dental equipment, vehicle washing system and irrigation system. The solenoid valve can be divided into three different operation types in working principle.
Direct-acting solenoid valve
The direct-acting solenoid valve follows the simplest working principle. When the medium flows into the solenoid valve through one hole, the middle is sealed by the plunger, the bottom has the rubber gasket, and a small spring fixes the plunger downwards to close off the valve. The plunger is made up of the iron magnetic materials, and the electric coil circles the plunger for positioning.
Once the coil is powered on, the magnetic field is generated, and the magnetic power lifts the plunger upward from the valve seat. Open the valve to allow the medium to flow by. When it is powered off, the electromagnetic power disappears, and the spring will press the plunger downward onto the valve seat, and the valve turns off. This is known as the normally-closed solenoid valve. The normally-open solenoid valve acts the other way around. It has a different structure, which can facilitate opening of the hole before electrification of the solenoid valve. When the solenoid valve is started, the hole will turn off. The maximum working pressure and flowing speed are directly connected with the hole diameter and the magnetic power of the solenoid valve. Therefore, the solenoid valve of this operation type is applicable to a relatively small flowing speed.
Direct-acting solenoid valves do not require minimum operating pressure or pressure difference, so they can be used under zero pressure to maximum allowable pressure, but the diameter generally does not exceed 25 mm.
Pilot-operated solenoid valve
The pilot-operated solenoid valve makes use of the pressure differential of the medium on the valve terminal to start and close the valve. Here, the minimum pressure differential is required. The exit and entrance of the pilot-operated solenoid valve are separated by the rubber membrane. The membrane has small holes, which can allow the medium to flow to the upper compartment. The upper pressure of the membrane and the supporting spring can ensure the valve to be closed. The cavity above the membrane is connected to the low-pressure terminal via the small passage. This connection is blocked in the switch-off position via the solenoid. The diameter of the pilot hole is larger than the hole diameter in the membrane.
When the solenoid valve is powered on, the pilot hope is opened, which results in the decreasing pressure above the membrane. Because of the pressure differential on two sides of the membrane, the membrane is lifted and the medium can flow from the entrance to the exit. The extra pressure chamber above the membrane serves as an amplifier. Therefore, the small solenoid can still control the large flow.
This kind of solenoid valve just has one flowing direction and can be applied to conditions satisfying the fluid pressure differential, such as the irrigation system, shower or car-washing system.
Semi-direct opearted solenoid valve
The semi-direct operated solenoid valve is a combination of the direct-action type and the pilot-operated type. When there is no pressure difference between the entrance and exit, the magnetic force, after powering on, can directly lift closure members of pilot small valves and main valves in turn, and the valve opens. When the entrance and the exit reaches the starting pressure differential, the magnetic force, after powering on, lifts up the pressure of the pilot small valve and the main valve lower cavity, and the upper cavity pressure drops. The pressure differential is made use of to push the main valve upward. When there is no power supply, the pilot valve makes use of the spring force or the medium pressure to push the closure members and move them downwards to close off the valve. Therefore, semi-direct operated solenoid valve can operate under the zero-pressure condition, and can control a relatively large flowing speed.
Direct-acting solenoid valve
The direct-acting solenoid valve follows the simplest working principle. When the medium flows into the solenoid valve through one hole, the middle is sealed by the plunger, the bottom has the rubber gasket, and a small spring fixes the plunger downwards to close off the valve. The plunger is made up of the iron magnetic materials, and the electric coil circles the plunger for positioning.
Once the coil is powered on, the magnetic field is generated, and the magnetic power lifts the plunger upward from the valve seat. Open the valve to allow the medium to flow by. When it is powered off, the electromagnetic power disappears, and the spring will press the plunger downward onto the valve seat, and the valve turns off. This is known as the normally-closed solenoid valve. The normally-open solenoid valve acts the other way around. It has a different structure, which can facilitate opening of the hole before electrification of the solenoid valve. When the solenoid valve is started, the hole will turn off. The maximum working pressure and flowing speed are directly connected with the hole diameter and the magnetic power of the solenoid valve. Therefore, the solenoid valve of this operation type is applicable to a relatively small flowing speed.
Direct-acting solenoid valves do not require minimum operating pressure or pressure difference, so they can be used under zero pressure to maximum allowable pressure, but the diameter generally does not exceed 25 mm.
Pilot-operated solenoid valve
The pilot-operated solenoid valve makes use of the pressure differential of the medium on the valve terminal to start and close the valve. Here, the minimum pressure differential is required. The exit and entrance of the pilot-operated solenoid valve are separated by the rubber membrane. The membrane has small holes, which can allow the medium to flow to the upper compartment. The upper pressure of the membrane and the supporting spring can ensure the valve to be closed. The cavity above the membrane is connected to the low-pressure terminal via the small passage. This connection is blocked in the switch-off position via the solenoid. The diameter of the pilot hole is larger than the hole diameter in the membrane.
When the solenoid valve is powered on, the pilot hope is opened, which results in the decreasing pressure above the membrane. Because of the pressure differential on two sides of the membrane, the membrane is lifted and the medium can flow from the entrance to the exit. The extra pressure chamber above the membrane serves as an amplifier. Therefore, the small solenoid can still control the large flow.
This kind of solenoid valve just has one flowing direction and can be applied to conditions satisfying the fluid pressure differential, such as the irrigation system, shower or car-washing system.
Semi-direct opearted solenoid valve
The semi-direct operated solenoid valve is a combination of the direct-action type and the pilot-operated type. When there is no pressure difference between the entrance and exit, the magnetic force, after powering on, can directly lift closure members of pilot small valves and main valves in turn, and the valve opens. When the entrance and the exit reaches the starting pressure differential, the magnetic force, after powering on, lifts up the pressure of the pilot small valve and the main valve lower cavity, and the upper cavity pressure drops. The pressure differential is made use of to push the main valve upward. When there is no power supply, the pilot valve makes use of the spring force or the medium pressure to push the closure members and move them downwards to close off the valve. Therefore, semi-direct operated solenoid valve can operate under the zero-pressure condition, and can control a relatively large flowing speed.
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