Introduction to the principle of solenoid valve selection
safety:
1. Corrosive medium: Plastic King solenoid valve and all stainless steel should be used; for strong corrosive medium, isolation diaphragm type must be used. Neutral medium, it is also advisable to use copper alloy as the solenoid valve of the valve shell material. Otherwise, the rust will often fall off in the valve shell, especially in occasions with infrequent movement. Ammonia valves cannot be made of copper.
2. Explosive environment: The corresponding explosion-proof grade products must be selected. For outdoor installation or dusty occasions, waterproof and dustproof varieties should be used.
3. The nominal pressure of the solenoid valve should exceed the maximum working pressure in the pipe.
applicability:
1, media characteristics
1) Different types of solenoid valves are selected for the gas, liquid or mixed state;
2) The medium temperature is different in specifications, otherwise the
coil will burn out and the seal will age, which will seriously affect the life expectancy;
3) The viscosity of the medium is usually below 50 cSt. If this value is exceeded, the multi-function solenoid valve is used when the dia
meter is larger than 15 mm; the high-viscosity solenoid valve is used when the dia
meter is less than 15 mm.
4) When the medium cleanliness is not high, the backwash
filter valve should be installed in front of the solenoid valve. When the pressure is low, the direct-acting diaphragm type solenoid valve can be used.
5) If the medium is directional and does not allow backflow, it needs to be circulated in both directions;
6) The medium temperature should be selected within the allowable range of the solenoid valve.
2, pipeline para
meters
1) Select the valve port and model according to the flow direction requirements and pipe connection method;
2) The nominal dia
meter is selected according to the flow rate and the valve Kv value, and the inner dia
meter of the pipe can also be selected;
3) Working pressure difference: The minimum working pressure difference is above 0.04Mpa, which is optional indirect pilot type; the minimum working pressure difference is close to or less than zero, you must use direct-acting or step-by-step direct type.
3. Environmental conditions
1) The highest and lowest temperatures of the environment should be selected within the allowable range;
2) When the relative humidity in the environment is high and there are water droplets and rain, etc., the waterproof solenoid valve should be selected;
3) Special vibrations, bumps and impacts should be selected in the environment, such as marine solenoid valves;
4) In the case of corrosive or explosive environment, the corrosion resistant type should be selected according to the 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 facilitates online maintenance.
4, power conditions
1) According to the type of power supply, AC and DC solenoid valves are used respectively. Generally, AC power is convenient to use;
2) Use the AC220V.DC24V as much as possible for the voltage specification;
3) The fluctuation of the power supply voltage is usually +%10%.-15% for AC and ±10% for DC. If it is too poor, it must be stabilized.
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 when the AC starts, and the indirect-lead solenoid valve should be preferred when the capacity is insufficient.
5. Control accuracy
1) The ordinary solenoid valve can only open and close two positions. When the control precision is high and the para
meter requirements are stable, multiple solenoid valves should be selected.
2) Action time: refers to the time when the electrical signal is turned on or off to the main valve action completion time;
3) Leakage: The amount of leakage given on the sample is the common economic rating.
reliability:
1. Working life, this item is not included in the factory test project and belongs to the type test project. In order to ensure the quality, we should choose the famous brand products of regular manufacturers.
2. Work system: divided into long-term work system, repeated short-time work system and short-term work system. For long-time valve opening only when the time is closed, the normally open solenoid valve should be used.
3. Working frequency: When the operating frequency is high, the structure should be a direct-acting solenoid valve, and the power supply should be preferred.
4, motion reliability
Strictly speaking, this test has not been officially listed in China's professional standards for solenoid valves. In order to ensure quality, brand-name products of regular manufacturers should be selected. In some occasions, there are not many movements, but the reliability requirements are very high, such as fire protection, emergency protection, etc., should not be taken lightly. Of particular importance, two pairs of dual insurance should also be used.
Economical:
It is one of the scales chosen, but it must be based on a safe, applicable, and reliable economy.
Economics is not only the price of the product, but also the cost and quality of the product, as well as the cost of installing repairs and other accessories.
More importantly, the cost of a solenoid valve in the entire automatic control system in the entire automatic control system and even in the production line is negligible. If the coup is small and cheap, the damage caused by the wrong selection is huge.