Solenoid valve is a two or three way industrial valve which is energized via AC or DC electrical power, and which controls the flow of various fluid lines. They are made of coil, core, tube and the body. The control of the flow line is provided by the movement of the core, which is generated by the electromagnetic force on the coil when it is energized. olenoid valves are divided into two groups as per their operating positions. The valves which open a closed line when the coil is energized are called Normally Closed (N.C.), and the valves which close an open line when the coil is energized are called Normally Open (N.O.)
When the coil is energized an electromagnetic force is generated and this force pulls the plunger to the fixed core. The plunger opens (Normally Closed type) or closes (Normally Closed type) the orifice through which the flow occures between valve inlet and outlet. At the surface at which the plunger faces the orifice is made leak-tightness is provided with the seal fitted on the plunger. Since this seal contacts with the fluid flowing through the valve it is extremely important to choose the correct sealing material. Direct action solenoid valves operate depending only on the coil force, so that they can operate even if the line pressure is 0 Bar. For the same reason operating pressure decreases as the orifice diameter increases. In GEVAX direct action solenoid valve series, the orifice ranges between 1,5 mm and 6 mm while the pressure changes between 0 and 40 Bar.
The plastic handle of cocking lever on top of the coil must be lifted upwards in or order to set the valve open for gas flow. Cocking lever moves down and gas flow orifice is closed when the valve receives an electric signal through the device (gas leakage detector, earthquake sensor etc.) that the valve is connected. The valve has to be manually re-setted via the cocking lever in order to oepn the gas flow line.
This type operates on the basis of creating two pressure chambers in the body with a diaphragm, and controlling the pressure difference between these two chambers. Once the fluid is applied, both sides (upper and lower sides) of the diaphragm are pressurized. Since the pressure on the upper side is bigger, the diaphragm closes the main flow orifice. In the normally closed pilot operated type, when the coil is energized the pilot orifice, which is connected with upper chamber, is opened to outlet; once the pressure balance on the diaphragm is spoilt, main flow orifice opens and flow occures. Because this type operates on the basis of pressure difference, the difference between inlet and outlet pressures of the valve must be minimum 0,5 Bar. If not, flow does not occure through the valve. Since solenoid valve does not operate as check valve the fluid flows back in case of backward pressure. In such cases it is necessary to install a check valve after the solenoid valve.
The maximum pressure difference between inlet and outlet of the valve when the valve is closed.
The minimum pressure difference between inlet and outlet of the valve when the valve is closed.
The pressure which is applied during test of solenoid valves. According to EN 12266-1:2003 if the test fluid is liquid, the test pressure shall be minimum of 1,5 times the allowable pressure at room temperature.
The temperature range at which the valve can normally operate.
- Coil is one of the most critical parts for the valve to have a long life cycle. It is very important to use correct protection and insulation coil according to the application. The voltage level and type (AC/DC) must be taken into consideration. GEVAX solenoid valves are provided with proven quality world-famous coils
- The minimum or maximum pressure levels of the line or the system is very important for the selection of appropriate valve. Inappropriate selection causes shorter life cycle.
- The specifications of the media to be applied must be considered. If not, internal valve parts may be subject to excessive corosion.
- Temperature of the media must be taken into account
- Solenoid valve must be fitted on the line in a way that the arrow on the body and the flow are in the same direction.
- Since solenoid valve does not operate as check valve the fluid flows back in case of backward pressure. In such cases it is necessary to install a check valve after the solenoid valve
- The line to fit the valve should be free of dirts and particles
An easy-to-understand code system is being used for GEVAX solenoid valves, which indicates the functional crtiterion playing role in valve selection. Details of code system is shown below: