Selection basis
The selection of solenoid valves should first follow the four principles of safety, reliability, applicability and economy, and then be selected according to six field working conditions (namely, pipeline parameters, fluid parameters, pressure parameters, electrical parameters, action modes and special requirements).
1. Select the size (DN) and interface mode of the solenoid valve according to the pipeline parameters.
1. Determine the diameter (DN) according to the on-site pipeline internal diameter or flow requirements.
2. Interface mode: generally, flange interface should be selected for > DN50, and ≤DN50 can be freely selected according to user's needs.
2. Select the material and temperature group of the solenoid valve according to the fluid parameters.
1, corrosive fluid: corrosion-resistant electromagnetic valve and all stainless steel should be selected; Edible ultra-clean fluid: food-grade stainless steel solenoid valve should be selected.
2. High-temperature fluid: The electromagnetic valve shall be made of high-temperature resistant electrical materials and sealing materials, and the piston structure type shall be selected.
3. Fluid state: large to gaseous, liquid or mixed state, especially when the ordered diameter is larger than DN25, it must be distinguished.
4. Fluid viscosity: generally, below 50cSt can be selected. If it exceeds this value, a high-viscosity solenoid valve should be selected.
3. Selection of solenoid valve according to pressure parameters: principle and structural changes.
1. Nominal pressure: This parameter has the same meaning as other general valves and is determined according to the nominal pressure of the pipeline.
2. Working pressure: If the working pressure is low, you must choose the principle of direct action or step-by-step direct action; When the minimum working pressure difference is above 0.04Mpa, direct-acting type, step-by-step direct-acting type and pilot type can be selected.
Fourth, electrical selection: it is more convenient to give priority to AC220V and DC24 for voltage specifications.
5. Choose according to the length of continuous working time: normally closed, normally open or continuously energized.
1. When the solenoid valve needs to be opened for a long time and the duration is redundant, the normally open type should be selected.
2. If the opening time is short or the opening and closing time is short, select the normally closed type.
3. However, some working conditions used for safety protection, such as furnace flame monitoring, can't be turned on often, and should be charged for a long time.
According to environmental requirements, auxiliary functions are selected: explosion-proof, inspection, manual, fog-proof, water shower and diving.
1. explosive environment: electromagnetic valves with corresponding explosion-proof grades must be selected (our company has: d II BT4, d II CT5, Ex m I/II T4).
2. When the fluid in the pipeline flows backwards, we can choose OK7 1-N and OK72-N series solenoid valves with check function.
3. When it is necessary to manually operate the solenoid valve on site, we can choose OK7 1-S and OK72-S series solenoid valves with manual function.
4. Waterproof and dustproof varieties (protection grade IP54 or above) should be selected for outdoor installation or dusty occasions.
5. Fountain must use submersible solenoid valve (protection level is above IP68).
Matters needing attention in type selection
One: Applicability
The fluid in the pipeline must be consistent with the calibration medium in the selected solenoid valve series model.
The oil temperature must be lower than the calibration temperature of the selected solenoid valve.
The allowable liquid viscosity of solenoid valve is generally below 20CST, and it should be indicated if it is greater than 20CST.
When the working pressure difference and the highest pressure difference of the pipeline are less than 0.04MPa, ZS, 2W, ZQDF, ZCM series and other direct-acting and step-by-step direct-acting types should be selected. When the minimum working pressure difference is greater than 0.04MPa, the pilot solenoid valve can be selected; The maximum working pressure difference should be less than the maximum calibration pressure of the solenoid valve; Generally, solenoid valves work in one direction, so pay attention to whether there is reverse pressure difference, if there is a check valve.
When the fluid cleanliness is not high, a filter should be installed in front of the solenoid valve. Generally speaking, solenoid valves require better cleanliness of the medium.
Pay attention to the flow aperture and nozzle aperture; Solenoid valves are generally controlled by only two switches; If conditions permit, please install the bypass pipe to facilitate maintenance; When there is water hammer phenomenon, the opening and closing time adjustment of solenoid valve should be customized.
Pay attention to the influence of ambient temperature on solenoid valve.
The power supply current and power consumption should be selected according to the output capacity, and the power supply voltage is generally allowed to be around 10%. It must be noted that the VA value is high at AC startup.
Second, reliability.
Solenoid valves are divided into normally closed type and normally open type; Generally choose normally closed type, power on and power off; However, when the opening time is long and the closing time is short, the normally open type should be selected.
Life test, the factory generally belongs to the type test project, to be exact, there is no professional standard for solenoid valves in China, so we should be careful in choosing solenoid valve manufacturers.
When the action time is short and the frequency is high, the direct action type is generally selected, and the fast series is selected for large caliber.
Third, safety.
Generally, solenoid valves are not waterproof, so please choose waterproof type when conditions do not allow, and the manufacturer can customize it.
The highest calibrated nominal pressure of solenoid valve must exceed the highest pressure in the pipeline, otherwise the service life will be shortened or other unexpected situations will occur.
All stainless steel shall be used as corrosive liquid, and SLF solenoid valve shall be used as strong corrosive liquid.
In explosive environment, corresponding explosion-proof products must be selected.
Fourth, the economy
Generally, there are many solenoid valves that can be used, but the most economical product should be selected on the basis of satisfying the above three points.
Select the focus of the solenoid valve.
First, security:
1, corrosive medium: plastic solenoid valve and all stainless steel should be selected; For highly corrosive media, isolation diaphragm type must be selected. For example, CD-F. Z3CF is the neutral medium, and it is also advisable to use copper alloy as the valve housing material for the solenoid valve, otherwise rust will often fall off in the valve housing, especially when 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 dustproof varieties should be selected for outdoor installation or dusty occasions.
3. The nominal pressure of the solenoid valve shall exceed the maximum working pressure in the pipeline.
Second, the applicability:
1. Dielectric properties
(1) Choose different kinds of solenoid valves for gas, liquid or mixed state, such as ZQDF for air, ZQDF-Y for liquid and ZQDF-2 (or -3) for steam, otherwise it is easy to cause misoperation. ZDF series multifunctional solenoid valves can communicate gas and liquid. It is best to inform the state of the media at an appropriate time, so that the installation user does not have to adjust the mode.
(2) Products with different specifications of medium temperature, otherwise the coil will be burned and the seal will be aged, which will seriously affect the service life.
(3) The viscosity of the medium is usually less than 50 centistokes. If it exceeds this value and the diameter is greater than 15mm, ZDF series multi-function solenoid valves are specially ordered. Order high viscosity solenoid valve with diameter less than15 mm.
(4) When the cleanliness of the medium is not high, a backwashing filter valve should be installed in front of the solenoid valve. For example, when the pressure is low, the direct-acting diaphragm solenoid valve can be used as CD-P.
(5) If the medium is in directional circulation, reverse flow is not allowed, and ZDF-N and ZQDF-N only need bidirectional circulation, please put forward special requirements. 1.6 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 mode. For example, when switching from one pipeline to two pipelines, CA5 and Z3F are selected for small diameter, and ZDF-Z 1/2 is selected for medium diameter or large diameter. Another example is to control the confluence of two pipelines, please choose ZDF-Z2/ 1 and so on.
(2) Select the nominal diameter according to the flow rate and valve Kv value, or select the same pipe diameter. Please note that some manufacturers have not marked the Kv value, and the size of the valve hole is often smaller than the pipe diameter of the interface. Do not covet low prices and delay work.
(3) Working pressure difference
When 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, direct-acting or step-by-step direct-acting must be selected.
3. Environmental conditions
(1) The maximum and minimum ambient temperatures should be selected within the allowable range, and special orders should be made in case of deviation.
(2) When the relative humidity of the environment is high and there are water drops and rain, a waterproof solenoid valve should be selected.
(3) For vibration, bumps, shocks and other occasions in the environment, special varieties, such as marine electromagnetic valves, should be selected.
(4) In corrosive or explosive environment, according to safety requirements, corrosion resistance should be given priority.
(5) If the environmental space is limited, please choose the multi-function solenoid valve, because it saves the bypass and three manual valves, which is convenient for online maintenance.
4. Power supply conditions
(1) According to the type of power supply, select AC and DC solenoid valves respectively. Generally speaking, AC power supply is easier to access.
(2) AC 220 volts. DC24V is preferred as far as possible for voltage specification.
(3) The AC voltage fluctuation is usually +% 10%. -15%, and the DC voltage is allowed to be around +/- 10. In case of out-of-tolerance, voltage stabilizing measures should be taken or special ordering requirements should be put forward.
(4) The rated current and power consumption should be selected according to the power supply capacity. Attention should be paid to high VA value when AC starts, and indirect solenoid valve should be preferred when capacity is insufficient.
5. Control accuracy
(1) The ordinary solenoid valve has only two positions. Please choose a multi-position solenoid valve under the condition of high control accuracy and stable parameters. Z3CF three-position normally open solenoid valve, with three flows: slightly open, fully open and fully closed;
ZDF-Z11The combined multi-function solenoid valve has four flows: full open, large open, small open and full open.
(2) Action time: refers to the time when the electric signal is turned on or off until the action of the main valve is completed. Only the multifunctional solenoid valve patented by our company can adjust the opening and closing time respectively, which can not only meet the control accuracy requirements, but also prevent water hammer damage.
(3) leakage
The leakage value given on the sample is a common economic grade. If the price is too high, please make a special order.
Third, reliability:
1, service life, which is not included in the ex-factory test item, belongs to the type test item. In order to ensure the quality, we should choose the famous brand products of regular manufacturers.
2. Working system: There are three types of working system: long-term working system, repeated short-term working system and short-term working system. The company's conventional products are long-term working system, that is, the coil is allowed to be charged for a long time. When the valve is open for a long time and closed only for a short time, the normally open solenoid valve should be selected. It can be used as a special order to reduce power consumption when it is used in short-term working system and large batch.
3. Working frequency: When the working frequency is required to be high, the direct-acting solenoid valve should be the first choice in structure, and the AC power supply should be the first choice.
4, action reliability
Strictly speaking, this test has not been formally included in the professional standard of solenoid valves in China, so we should choose the famous brand products of regular manufacturers to ensure the quality. On some occasions, there are not many actions, but the reliability is high, such as fire fighting and emergency protection, which must not be taken lightly. Above all, you should also bring two pairs of insurance.
Fourth, the economy:
It is one of the standards, but it must be economical on the basis of safety, applicability and reliability.
Economy is not only the price of the product, but also the function and quality of the product and the cost of installation, maintenance and other accessories.
More importantly, the cost of a solenoid valve in the whole automatic control system, in the whole automatic control system, and even in the production line is very small, because the harm caused by greedy and cheap selection is huge.