First, applicability
The fluid in the line must match the medium calibrated in the selected solenoid valve series.
The temperature of the fluid must be less than the calibration temperature of the solenoid valve selected.
Solenoid valves allow liquid viscosity to be generally below 20 CST, and greater than 20 CST should be noted.
Working pressure difference, the maximum pressure difference of the pipeline should be less than 0.04MPa, such as ZS, 2W, ZQDF, ZCM series and other direct-acting and step-by-step direct-acting type; when the minimum working pressure difference is greater than 0.04MPa, the pilot type can be used. Differential) Solenoid valve; the maximum working pressure difference should be less than the maximum calibration pressure of the solenoid valve; the general solenoid valve is one-way work, so pay attention to whether there is a back pressure difference, if there is a check valve installed.
When the fluid cleanliness is not high, the filter should be installed in front of the solenoid valve.
The valve requires good cleanliness for the media.
Pay attention to the flow aperture and the diameter of the nozzle; the solenoid valve is generally only controlled by the two-position switch; if necessary, please install the bypass tube for easy maintenance; when there is water hammer, customize the opening and closing time of the solenoid valve.
Pay attention to the influence of ambient temperature on the solenoid valve
The power supply current and power consumption should be selected according to the output capacity. The power supply voltage is generally allowed to be ±10%. It must be noted that the VA value is higher when the AC starts.
Second, reliability
The solenoid valve is divided into two types: normally closed and normally open; generally, the normally closed type is used, the power is turned on, and the power is turned off; but when the opening time is long, the normally open type is selected when the closing time is short. Life test, the factory is generally a type test project, to be exact, there is no professional standard for solenoid valves in China, so the choice of solenoid valve manufacturers is cautious. When the action time is short and the frequency is high, the direct motion type is generally selected, and the large diameter is selected as the fast series.
Third, security
Generally, the solenoid valve is not waterproof. When the conditions are not allowed, please choose waterproof type, the factory can be customized. The highest nominal pressure of the solenoid valve must exceed the maximum pressure in the pipeline, otherwise the service life will be shortened or other accidents will occur. Corrosive liquids should be selected from all stainless steel type, and strong corrosive fluids should be selected from plastic king (SLF) solenoid valves. Explosive environments must use the corresponding explosion-proof products.
Fourth, economic
There are many solenoid valves that can be used universally, but the most economical products should be selected on the basis of meeting the above three points.
The structural principle of the solenoid valve
One: direct-acting solenoid valve
There are two types of normally closed and normally open. When the normally closed type is powered off, it is in a closed state. When the coil is energized, an electromagnetic force is generated, so that the moving iron core overcomes the spring force and opens the valve directly with the static iron core, and the medium is in a path; when the coil is de-energized, the electromagnetic force disappears, and the moving iron disappears. The core is reset under the action of the spring force, and the valve port is directly closed, and the medium is blocked. The structure is simple, the action is reliable, and it works normally under zero pressure difference and micro vacuum. The normally open type is just the opposite. Such as solenoid valves smaller than φ6 flow path. (Figure 1 is a typical structure diagram)
Second, step-by-step direct-acting solenoid valve
The valve adopts one-time opening and two-opening in one, and the main valve and the pilot valve step by step to directly open the main valve port by electromagnetic force and pressure difference. When the coil is energized, an electromagnetic force is generated to cause the moving iron core and the static iron core to be sucked, the pilot valve port is opened and the pilot valve port is disposed on the main valve port, and the moving iron core is connected with the main valve core, and the main valve is connected at this time. The pressure of the chamber is unloaded through the pilot valve port, and the main spool is moved upwards under the action of the pressure difference and the electromagnetic force to open the main valve medium circulation. When the coil is de-energized, the electromagnetic force disappears. At this time, the moving iron core closes the pilot valve hole under the action of its own weight and spring force. At this time, the medium enters the upper cavity of the main valve core in the balance hole, so that the pressure in the upper chamber rises. The main valve is closed under the action of spring return and pressure, and the medium is interrupted. The structure is reasonable, the action is reliable, and the work is reliable when the pressure is zero. Such as: ZQDF, ZS, 2W and so on. (Figure 2 is a typical structure diagram)
Third, indirect pilot solenoid valve
The series of solenoid valves are composed of a combination of a pilot valve and a main spool to form a passage; the normally closed type is closed when not energized. When the coil is energized, the generated magnetic force causes the moving iron core and the static iron core to be sucked, the pilot valve opening is opened, and the medium flows to the outlet. At this time, the pressure in the upper chamber of the main spool is reduced, lower than the pressure on the inlet side, forming a pressure difference against the spring. The resistance moves with it upwards, reaching the purpose of opening the main valve port and circulating the medium. When the coil is de-energized, the magnetic force disappears, and the moving iron core is reset to close the pilot port under the action of the spring force. At this time, the medium flows in from the balance hole, the pressure in the upper chamber of the main spool increases, and moves downward under the action of the spring force. Close the main valve port. The normally open principle is just the opposite. Such as: SLA, DF (φ15 or more caliber), ZCZ and so on. (Figure 3 is a typical structure diagram)