What is the selection principle of solenoid valve?

Selection principles
safety:
1. Corrosive media: plastic king solenoid valve and all stainless steel should be selected; for strongly corrosive media, isolation diaphragm type must be used. For the neutral medium, the solenoid valve with copper alloy as the material of the valve shell should also be selected. Otherwise, rust debris often falls off in the valve shell, especially in the occasion of infrequent movement. The valve for ammonia cannot use copper.
2. Explosive environment: The corresponding explosion-proof products must be selected. Waterproof and dustproof products should be selected for outdoor installation or dusty occasions.
3. The nominal pressure of the solenoid valve should exceed the maximum working pressure in the pipe.
applicability:
1. Medium characteristics
1) Different types of solenoid valves are selected for gas, liquid or mixed state;
2) Products with different specifications of medium temperature, otherwise the coil will burn out and the seals will be aged, which will seriously affect the service life;
3) Medium viscosity, usually below 50cSt. If it exceeds this value, when the diameter is greater than 15mm, a multi-function solenoid valve is used; when the diameter is less than 15mm, a high viscosity solenoid valve is used.
4) When the cleanliness of the medium is not high, a recoil filter valve should be equipped in front of the solenoid valve. When the pressure is low, a direct-acting diaphragm solenoid valve can be used;
5) If the medium is directional and does not allow reverse flow, bidirectional flow is required;
6) The medium temperature should be selected within the allowable range of the solenoid valve.
2. Pipeline parameters
1) Select the valve port and model according to the requirements of medium flow direction and pipeline connection;
2) The nominal diameter is selected according to the flow rate and the Kv value of the valve, or the same as the inner diameter of the pipeline;
3) Working pressure difference: the minimum working pressure difference above 0.04Mpa is optional indirect pilot; the minimum working pressure difference is close to or less than zero must use direct-acting or step-by-step direct type.
3. Environmental conditions
1) The maximum and minimum temperature of the environment should be selected within the allowable range;
2) In the environment where the relative humidity is high and there are water drops and rain, waterproof solenoid valves should be selected;
3) In the environment where vibration, bumps and impacts are frequent, special varieties should be selected, such as marine solenoid valves;
4) Use in corrosive or explosive environments should preferentially select corrosion-resistant type according to safety requirements;
5) If the environmental space is restricted, a multi-function solenoid valve is required, because it eliminates the bypass and three manual valves and is convenient for online maintenance.
4. Power conditions
1) According to the type of power supply, select AC and DC solenoid valves respectively. Generally speaking, the AC power supply is convenient;
2) Use AC220V.DC24V as the priority for voltage specifications;
3) Fluctuation of power supply voltage usually selects +%10%.-15% for AC, and DC allows about ±%10. If it is out of tolerance, voltage stabilization measures must be taken;
4) The rated current and power consumption should be selected according to the power supply capacity. It should be noted that the VA value is higher during AC starting, and the indirect pilot solenoid valve should be preferred when the capacity is insufficient.
5. Control accuracy
1) Ordinary solenoid valves have only two positions, open and closed. When high control accuracy and parameter requirements are stable, multiple solenoid valves are required;
2) Action time: refers to the time when the electrical signal is turned on or off to the completion of the action of the main valve;
3) Leakage: The leakage value given on the sample is a commonly used economic grade.
reliability:
1. Working life, this item is not included in the factory test items, it is a type test item. In order to ensure the quality, we should choose the brand-name products of regular manufacturers.
2. Working system: divided into long-term working system, repeated short-time working system and short-time working system. For the case where the valve is opened for a long time and only closed for a short time, the normally open solenoid valve should be used.
3. Working frequency: When the operating frequency is high, the structure should be preferably direct-acting solenoid valve, and the power source is preferably AC.
4. Action reliability
Strictly speaking, this test has not been officially listed in China's solenoid valve professional standards, in order to ensure quality should choose the brand-name products of regular manufacturers. In some occasions, the number of actions is not very high, but the requirements for reliability are very high, such as fire protection, emergency protection, etc., which must not be taken lightly. It is particularly important to take two dual insurances.
Economical:
It is one of the selected scales, but it must be economical on the basis of safety, applicability, and reliability.
Economy is not only the selling price of the product, but also the priority of its function and quality, as well as the cost of installation, maintenance and other accessories.
More importantly, the cost of a solenoid valve in the entire automatic control system, the entire automatic control system and even the production line is very small. If you want to make a small choice and make a mistake, the damage group is huge.