Safety:
1. Corrosive medium: plastic king solenoid valve and all stainless steel should be used; for strong corrosive medium, isolation diaphragm type must be selected. For neutral medium, it is also advisable to choose a solenoid valve with copper alloy as the valve housing material, otherwise, rust will often fall off in the valve housing, especially in occasions where the action is not frequent. Ammonia valves cannot be made of copper.
2. Explosive environment: products with corresponding explosion-proof grade must be selected, and waterproof and dust-proof varieties should be selected for outdoor installation or dusty places.
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 medium temperature, otherwise the coil will burn out and the seal will age, 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, use a multi-function solenoid valve; when the diameter is less than 15mm, use a high-viscosity solenoid valve.
4) When the cleanliness of the medium is not high, a recoil filter valve should be installed in front of the solenoid valve. When the pressure is low, a direct-acting diaphragm solenoid valve can be selected;
5) If the medium is directional and does not allow backflow, two-way circulation 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 the medium flow direction and the pipeline connection method;
2) Select the nominal diameter according to the flow rate and the Kv value of the valve, or the inner diameter of the pipe;
3) Working pressure difference: If the minimum working pressure difference is above 0.04Mpa, the indirect pilot type can be selected; if the minimum working pressure difference is close to or less than zero, the direct-acting or step-by-step direct type must be selected.
3. Environmental conditions
1) The maximum and minimum 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., a waterproof solenoid valve should be selected;
3) Special varieties, such as marine solenoid valves, should be selected when there are frequent vibrations, bumps and impacts in the environment;
4) For use in corrosive or explosive environments, priority should be given to the corrosion-resistant type according to safety requirements;
5) If the environmental space is restricted, a multi-function solenoid valve must be selected, as it eliminates the need for a bypass and three manual valves and facilitates online maintenance.
4. Power supply conditions
1) According to the type of power supply, AC and DC solenoid valves are selected respectively. Generally speaking, AC power is easy to access;
2) For voltage specifications, give priority to AC220V or DC24V;
3) The power supply voltage fluctuation is usually +%10%.-15% for AC, and ±%10 is allowed for DC. If it exceeds the 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. When the capacity is insufficient, the indirect pilot solenoid valve should be preferred.
5. Control accuracy
1) Ordinary solenoid valves only have two positions: on and off. When the control accuracy is high and the parameters are stable, a multi-position solenoid valve needs to be selected;
2) Action time: refers to the time from when the electrical signal is turned on or off to the completion of the main valve action;
3) Leakage volume: The leakage volume value given on the sample is a commonly used economic level.
Reliability:
1. Working life, this item is not included in the factory test items, but is a type test item. In order to ensure the quality, famous brand products from regular manufacturers should be selected.
2. Working system: long-term working system, repeated short-time working system and short-time working system. For the situation that the valve is opened for a long time and only closed for a short time, it is advisable to choose a normally open solenoid valve.
3. Working frequency: When the operating frequency is required to be high, the structure should be a direct-acting solenoid valve, and the power supply should be AC.
4. Action reliability
Strictly speaking, this test has not been officially included in the professional standards of China's solenoid valves. In order to ensure the quality, brand-name products from regular manufacturers should be selected. In some occasions, the number of actions is not many, but the reliability requirements are very high, such as fire protection, emergency protection, etc., and must not be taken lightly. Especially important, should also take two consecutive double insurance.
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 price of the product, but also its function and quality, as well as the cost of installation and maintenance and other accessories.
More importantly, the cost of a solenoid valve in the entire automatic control system is very small in the entire automatic control system and even in the production line.
