Selection criteria:
1. Select the solenoid valve based on pipeline parameters: diameter specification (i.e. DN), interface method
1) Determine the diameter (DN) size according to the on-site pipeline inner diameter size or flow requirements;
2) Interface method, generally>DN50 requires flange interface, ≤ DN50 can be freely selected according to user needs.
2. Select the material and temperature group of the solenoid valve based on fluid parameters
1) Corrosive fluids: corrosion-resistant solenoid valves and all stainless steel should be selected; Edible ultra clean fluid: It is recommended to use food grade stainless steel solenoid valves;
2) High temperature fluid: It is necessary to choose electromagnetic valves made of high-temperature resistant electrical materials and sealing materials, and to choose piston type structures;
3) Fluid state: up to gaseous, liquid, or mixed state, especially when the diameter is greater than DN25, it must be distinguished;
4) Fluid viscosity: Usually below 50cSt, it can be freely selected. If it exceeds this value, a high viscosity solenoid valve should be used.
3. Selecting solenoid valves based on pressure parameters: principles and structural types
1) Nominal pressure: This parameter has the same meaning as other general valves and is determined based on the nominal pressure of the pipeline;
2) Work pressure: If the work pressure is low, the principle of direct action or step-by-step direct action must be selected; When the minimum working pressure difference is above 0.04Mpa, direct acting, step-by-step direct acting, and pilot operated can all be selected.
4. Electrical selection: The voltage specifications should preferably be AC220V or DC24, which are more convenient.
5. Choose based on the duration of continuous work: normally closed, normally open, or continuously powered on
1) When the solenoid valve needs to be opened for a long time and the duration exceeds the closing time, the normally open type should be selected;
2) If the opening time is short or the opening and closing time is not long, choose the normally closed type;
3) However, for some working conditions used for safety protection, such as furnace and kiln flame monitoring, the normally open type cannot be selected, and the long-term electrified type should be selected.
6. Select auxiliary functions according to environmental requirements: explosion-proof, check, manual, waterproof fog, water shower, and diving.
Selection principle
Security:
1. Corrosive media: Plastic king solenoid valves and all stainless steel should be selected; For strongly corrosive media, isolation membrane type must be selected. Neutral media, it is also advisable to use copper alloy as the valve shell material for solenoid valves, otherwise rust debris often falls off from the valve shell, especially in situations where the action is not frequent. Ammonia valves cannot use copper materials.
2. Explosive environment: Corresponding explosion-proof products must be selected, and waterproof and dustproof varieties should be selected for outdoor installation or in dusty environments.
3. The nominal pressure of the solenoid valve should exceed the maximum working pressure inside the pipe.
Applicability:
1. Medium characteristics
1) Select different types of solenoid valves for gas, liquid, or mixed states;
2) Products with different specifications and medium temperatures may cause the coil to burn out and the sealing components to age, seriously affecting their service life;
3) The viscosity of the medium is usually below 50cSt. If it exceeds this value and the diameter is greater than 15mm, use a multifunctional 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 backwash 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 flows in a directional manner and backflow is not allowed, it needs to flow in both directions;
6) The medium temperature should be selected within the allowable range of the solenoid valve.
2. Pipeline parameters
1) Select valve ports and models based on the requirements of medium flow direction and pipeline connection method;
2) Select the nominal diameter based on the flow rate and valve Kv value, or choose the same pipe inner diameter;
3) Working pressure difference: Indirect pilot type can be used when the minimum working pressure difference is above 0.04Mpa; For those with a minimum working pressure difference close to or less than zero, direct acting or step-by-step direct acting must be selected.
3. Environmental conditions
1) The maximum and minimum temperatures of the environment should be selected within the allowable range;
2) In environments with high relative humidity and water droplets and rain, waterproof solenoid valves should be selected;
3) Special varieties should be selected for situations where there are frequent vibrations, bumps, and impacts in the environment, such as marine solenoid valves;
4) When used in corrosive or explosive environments, priority should be given to selecting corrosion-resistant types according to safety requirements;
5) If the environmental space is limited, a multifunctional solenoid valve should be selected because it eliminates the need for a bypass and three manual valves, and is easy to maintain online.
4. Power supply conditions
1) Select AC and DC solenoid valves according to the type of power supply. Generally speaking, AC power supply is easy to access;
2) Voltage specifications should prioritize AC220V and DC24V as much as possible;
3) The fluctuation of power supply voltage is usually selected as% -15% for AC, and ± for DC. If it exceeds the tolerance, voltage stabilization measures must be taken;
4) The rated current and power consumption should be selected based on the power capacity. Attention should be paid to the high VA value during communication start-up, and indirect induction solenoid valves should be preferred when the capacity is insufficient.
5. Control accuracy
1) Ordinary solenoid valves only have two positions, on and off. When high control accuracy and stable parameter requirements are needed, multi position solenoid valves should be selected;
2) Action time: refers to the time from when the electrical signal is turned on or off to when the main valve action is completed;
3) Leakage rate: The leakage rate values given on the sample are commonly used economic levels.
Reliability:
1. The working life is not included in the factory test items, but belongs to the type test items. To ensure quality, branded products from reputable manufacturers should be selected.
2. Work system: divided into three types: long-term work system, repeated short-term work system, and short-term work system. For situations where the valve is open for a long time but only closed for a short time, it is advisable to use a normally open solenoid valve.
3. Working frequency: When the operating frequency requirement is high, the structure should preferably use a direct acting solenoid valve, and the power supply should preferably use AC.
4. Action reliability
Strictly speaking, this test has not yet been officially included in the professional standards of Chinese solenoid valves. To ensure quality, branded products from reputable manufacturers should be selected. In some situations where the number of actions is not high, but the reliability requirements are very high, such as fire protection, emergency protection, etc., we must not take it lightly. It is particularly important to adopt dual insurance for two consecutive uses.
Economy:
It is one of the selected scales, but it must be economical based on safety, applicability, and reliability.
Economy is not only about the price of the product, but also about prioritizing its functionality and quality, as well as the cost of installation, maintenance, and other accessories.
More importantly, the cost of a single solenoid valve in the entire control system and even in the production line is negligible. If one chooses the wrong one for the sake of small gains, it can cause huge damage to the group.
