What Are the Most Common Solenoid Problems?

Electromagnetic valve (Electromagnetic valve) is an industrial device controlled by electromagnetics. It is an automatic basic component used to control fluids. Used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. The solenoid valve can be used with different circuits to achieve the desired control, and the accuracy and flexibility of the control can be guaranteed. There are many kinds of solenoid valves. Different solenoid valves play a role in different positions of the control system. The most commonly used are check valves, safety valves, directional control valves, speed regulating valves, etc.

Chinese name: The electromagnetic valve
Foreign name: electromagnetic valve
Affiliated industry: Industrial control, industry

main feature: Safe, convenient, versatile, versatile
Common types: Check valve, safety valve, directional control valve, etc.
Selection principle: Applicability, reliability, safety, economy

Working principle of solenoid valve

There is a closed cavity in the solenoid valve, and there are through holes in different positions. Each hole is connected to a different oil pipe. The middle of the cavity is a piston. On both sides are two electromagnets. Side, by controlling the movement of the valve body to open or close different drain holes, and the oil inlet is always open, hydraulic oil will enter different drain pipes, and then the piston of the cylinder is pushed by the pressure of the oil, the piston in turn Drive the piston rod, and the piston rod drives the mechanical device. In this way, the movement of the electromagnet is controlled to control the mechanical movement. ^[1]

The main classification of solenoid valve

1. The solenoid valve is divided into three categories in principle:

Direct-acting solenoid valve

Principle: When power is applied, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, the spring presses the closing member on the valve seat, and the valve closes.

Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm.

Step-by-step direct-acting solenoid valve

Principle: It is a combination of direct-acting and pilot-operated principle. When there is no pressure difference between the inlet and the outlet, after the power is turned on, the electromagnetic force directly lifts the pilot small valve and the main valve closing part upwards, and the valve opens. When the inlet and outlet reach the starting pressure difference, after power is applied, the electromagnetic force pilots the small valve. The pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber decreases, so the main valve is pushed upward by the pressure difference. When the power is off, the pilot valve uses a spring. Force or media pressure pushes the closing piece and moves down to close the valve.

Features: It can operate at zero pressure difference, vacuum, high pressure, but the power is large, and it must be installed horizontally.

Pilot operated solenoid valve

Principle: When power is applied, the electromagnetic force opens the pilot hole, and the pressure in the upper chamber rapidly decreases. A pressure difference between the upper and lower parts is formed around the closing member. The fluid pressure pushes the closing member to move upward and the valve opens. When the power is off, the spring force opens the pilot. The hole is closed, and the inlet pressure quickly passes through the bypass hole to form a low-to-high pressure difference around the valve closing member. The fluid pressure pushes the closing member to move downward and close the valve.

Features: The upper limit of the fluid pressure range can be arbitrarily installed (customized) but must meet the fluid pressure differential conditions.

2. The difference between the valve structure and material and the principle of the solenoid valve is divided into six sub-categories: direct-acting diaphragm structure, step-wise direct-acting diaphragm structure, pilot diaphragm structure, direct-acting piston structure Step by step direct acting piston structure, pilot piston structure.

3. Solenoid valve is classified according to function: water solenoid valve, steam solenoid valve, refrigeration solenoid valve, low temperature solenoid valve, gas solenoid valve, fire solenoid valve, ammonia solenoid valve, gas solenoid valve, liquid solenoid valve, miniature solenoid valve, Pulse solenoid valve, hydraulic solenoid valve normally open solenoid valve, oil solenoid valve, DC solenoid valve, high pressure solenoid valve, explosion-proof solenoid valve, etc.

Selection of solenoid valve

Selection basis of solenoid valve

The selection of solenoid valve should first follow the four principles of safety, reliability, applicability, and economy, followed by the on-site working conditions in six aspects (that is, pipeline parameters, fluid parameters, pressure parameters, electrical parameters, operating methods, For special requirements).

Selection basis:

1. Select the solenoid valve according to the pipeline parameters: diameter specification (ie DN), interface method

1) Determine the size of the diameter (DN) according to the on-site pipe diameter or flow requirements;

2) Interface mode, generally> DN50 should choose flange interface, DN50 can choose freely according to user needs.

2. Select the solenoid valve according to the fluid parameters: material, temperature group

1) Corrosive fluid: Corrosion-resistant solenoid valve and all stainless steel should be selected; Ultra-clean fluid for food: Food-grade stainless steel solenoid valve should be selected;

2) High-temperature fluids: select solenoid valves made of high-temperature-resistant electrical materials and sealing materials, and choose piston-type structures;

3) fluid state: gas state, liquid state or mixed state, especially when the diameter is larger than DN25, it must be distinguished;

4) Fluid viscosity: Generally, it can be arbitrarily selected below 50cSt. If it exceeds this value, a high viscosity solenoid valve should be used.

3. Select the solenoid valve according to the pressure parameter: principle and structure variety

1) Nominal pressure: This parameter has the same meaning as other common valves, and is determined according to the nominal pressure of the pipeline;

2) Working pressure: If the working pressure is low, you must use the direct-acting or step-wise direct-acting principle; when the minimum working pressure difference is above 0.04Mpa, direct-acting, step-wise direct-acting, and pilot-type can be used.

4. Electrical selection: AC220V and DC24 should be preferred for voltage specifications.

5. Choose according to the length of continuous working time: normally closed, normally open, or continuous power

1) When the solenoid valve needs to be opened for a long time and lasts longer than it is closed, the normally open type should be selected;

2) If the opening time is short or the opening and closing time is not long, select the normally closed type;

3) However, some working conditions for safety protection, such as furnace and kiln flame monitoring, cannot be selected as normally open, and should be selected for long-term power supply.

6. Select auxiliary functions according to environmental requirements: explosion-proof, non-return, manual, waterproof fog, water spray, diving.

Selection principle of solenoid valve

safety:

1. Corrosive media: Plastic King solenoid valves and all stainless steel should be used; for strongly corrosive media, isolation diaphragm type must be used. For neutral media, it is also appropriate to choose a solenoid valve with copper alloy as the material of the valve housing. Otherwise, rust debris will often fall off in the valve housing, especially in occasions where the action is not frequent. For ammonia valves, copper cannot be used.

2. Explosive environment: The corresponding explosion-proof products must be selected. Waterproof and dustproof varieties 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.Media characteristics

1) Different types of solenoid valves are used in the gas, liquid or mixed state;

2) Products with different media temperatures, otherwise the coils will burn out and the seals will age, which will seriously affect the service life;

3) Medium viscosity, usually below 50 cSt. If this value is exceeded, a multi-function solenoid valve is used when the diameter is greater than 15mm; a high-viscosity solenoid valve is used when the diameter is less than 15mm.

4) When the medium cleanliness 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 selected;

5) If the medium is directional and does not allow reverse flow, two-way circulation is required;

6) The medium temperature should be selected within the allowable range of the solenoid valve.

2.Pipe 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 valve Kv value, or choose the same diameter as the pipe;

3) Working pressure difference: the minimum working pressure difference above 0.04Mpa is optional with indirect pilot type; the minimum working pressure difference is close to or less than zero must be selected directly or stepwise direct type.

3. Environmental conditions

1) The maximum and minimum temperature of the environment should be selected within the allowable range;

2) When the environment has high relative humidity and there are drops of water and rain, etc., a waterproof solenoid valve should be selected;

3) Special varieties such as marine solenoid valves should be selected in the environment where there are often vibrations, bumps and shocks;

4) For use in corrosive or explosive environments, the corrosion-resistant type should be selected according to safety requirements;

5) If the environmental space is limited, a multi-function solenoid valve is required because it eliminates the bypass and three manual valves and facilitates online maintenance.

4.Power conditions

1) AC and DC solenoid valves are selected according to the type of power supply. Generally, AC power supply is easy to access;

2) AC220V.DC24V is preferred as the voltage specification;

3) Power supply voltage fluctuations usually use +% 10% .- 15% for AC, DC allowance is 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 when the AC is started. When the capacity is insufficient, the indirect pilot solenoid valve should be preferentially selected.

5.Control accuracy

1) Ordinary solenoid valve has only two positions, on and off. When high control accuracy is required and parameters are required to be stable, a multi-position solenoid valve is required.

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: The leakage value given on the sample is a common 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 famous brand products of regular manufacturers.

2. Working system: There are three types of long-term working system, repeated short-time working system and short-time working system. For long-term valve opening and only short-term closing, a normally open solenoid valve should be used.

3. Working frequency: When the action frequency is high, the structure should be a direct-acting solenoid valve, and the power supply should be AC.

4. Motion reliability

Strictly speaking, this test has not been formally listed in China's professional standards for solenoid valves. In order to ensure the quality, it should choose the famous brand products of regular manufacturers. In some occasions, the number of actions is not high, but the reliability requirements are very high, such as fire protection, emergency protection, etc., must not be taken lightly. It is particularly important to take two double 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 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 and even the production line is very small. If you choose small and cheap, the damage will be huge.

Attention of solenoid valve installation

1. When installing, pay attention to the arrow on the valve body should be consistent with the flow direction of the medium. Do not install in a place with direct dripping or splashing water. The solenoid valve should be installed vertically upwards;

2. The solenoid valve should ensure normal operation within the fluctuation range of 15% -10% of the rated voltage;

3. After the solenoid valve is installed, there must be no reverse pressure difference in the pipeline. And it needs to be powered on several times so that it can be officially put into use after it is at the proper temperature;

4. Clean the pipeline thoroughly before installing the solenoid valve. The incoming medium should be free of impurities. Filter is installed before the valve;

5. When the solenoid valve fails or is cleaned, a bypass device should be installed to ensure the system continues to run.

Solenoid valve troubleshooting

Solenoid valve does not work after power on

Check if the power wiring is bad reconnect and connect the connector

Different kinds of solenoid valves (34 photos)

Check if the power supply voltage is within the ± working range- adjust to the normal position range

Whether the coil is de-soldered re-solder

Coil short-circuit Replace coil

Is the working pressure difference inappropriate? Adjust the pressure difference or replace the appropriate solenoid valve

Fluid temperature is too high Replace proportional solenoid valve

The main valve core and moving iron core of the solenoid valve are stuck due to impurities clean, if the seal is damaged, replace the seal and install a filter

The viscosity of the liquid is too high, the frequency is too high and the life has reached Replace the product

Solenoid valve cannot be closed

The seal of the main spool or iron core is damaged replace the seal

Is the fluid temperature and viscosity too high? Replace the solenoid valve

Foreign matter enters the solenoid valve or moving iron core clean

Spring life has reached or deformed replace

Throttle balance hole blocked clean in time

The operating frequency is too high or the life has expired change product or update product

Other situations of solenoid valve

Internal leakage check whether the seal is damaged and the spring is not well assembled

External leakage Loose connection or broken seal Tighten screws or replace seal

There is noise when power is on The solid parts on the head are loose and tightened. The voltage fluctuation is not within the allowable range. Adjust the voltage. Impurities or unevenness on the iron core suction surface, clean or replace in time.

Solenoid valve sealing material

There are currently three most commonly used sealing materials for solenoid valves.

NBR nitrile butadiene rubber Solenoid valve NBR nitrile butadiene rubber

It is made from butadiene and acrylonitrile through emulsion polymerization. Nitrile rubber is mainly produced by low-temperature emulsion polymerization. It has excellent oil resistance, high wear resistance, good heat resistance, and strong adhesion. Its disadvantages are poor low temperature resistance, poor ozone resistance, poor electrical properties and slightly lower elasticity.

In addition, it also has good water resistance, air tightness and excellent adhesion properties. It is widely used in the production of various oil-resistant rubber products, a variety of oil-resistant gaskets, gaskets, sleeves, flexible packaging, soft hoses, printing and dyeing rubber rollers, cable adhesive materials, etc., and has become essential in the automotive, aviation, petroleum, copying and other industries. Elastic material.

Nitrile rubber has excellent oil resistance, its oil resistance is second only to polysulfide rubber and fluorine rubber, and it has abrasion resistance and air tightness. The disadvantage of nitrile rubber is that it is not resistant to ozone and aromatic, halogenated hydrocarbons, ketones and ester solvents, and is not suitable for insulating materials.

The main purpose

Nitrile rubber is mainly used to make oil-resistant products, such as oil-resistant pipes, tapes, rubber diaphragms and large oil sacs. It is often used to make various oil-resistant molded products, such as O-rings, oil seals, leather bowls, diaphragms, valves, bellows It is also used to make rubber sheets and wear-resistant parts.

EPDM Solenoid valve EPDM EPDM rubber

EPDM rubber is a terpolymer of ethylene, propylene, and non-conjugated diene. Commercial production began in 1963. Annual consumption worldwide is 800,000 tons. The main feature of EPDM is its superior resistance to oxidation, ozone and erosion. Since EPDM rubber belongs to the polyolefin family, it has excellent vulcanization properties. Among all rubbers, EPDM has the lowest specific gravity. It can absorb a large amount of fillers and oils without affecting the characteristics. Therefore, a low-cost rubber compound can be produced.

Molecular structure and characteristics : EPDM is a terpolymer of ethylene, propylene and non-conjugated diene. Diene has a special structure, and only one of the two bonds can be copolymerized. The unsaturated double bond is mainly used as a crosslink. The other unsaturated one will not become the polymer backbone, but only the side chains. The main polymer chains of EPDM are fully saturated. This property makes EPDM resistant to heat, light, oxygen, and especially ozone. EPDM is essentially non-polar, resistant to polar solutions and chemicals, low water absorption, and good insulation properties.

Features

1. Low density and high filling property;

2, aging resistance;

3. Corrosion resistance;

4. Water vapor resistance;

5. Resistance to overheating water;

6. Electrical performance;

7, flexibility;

8. Adhesiveness.

VITON FKM) Solenoid valve VITON fluorine rubber (FKM)

There are various types of fluorine-containing rubber in the molecule, depending on the fluorine content, that is, the structure of the monomer. The hexafluoride-based fluorine rubber has higher temperature resistance than silicone rubber, chemical resistance, and resistance to most oils and solvents (ketones, esters). (Except for other types), weather resistance and ozone resistance are good, but cold resistance is poor; generally used in automobiles, motorcycles and other products, seals in chemical plants, the use temperature range -20 ~ 260 , when the use of low temperature requirements There are low-temperature-resistant types that can be applied to -40 ° C, but the price is higher.

The main differences between solenoid valves

The difference between solenoid valve and solenoid valve

The solenoid valve is a magnetic coil that generates magnetic force after the solenoid coil is energized to overcome the pressure of the spring to drive the valve core. The solenoid coil has a simple structure and a low price, and can only be switched.

The electric valve is driven by a motor to drive the valve core, and the electric valve is divided into a shut-off valve and a regulating valve. The shut-off valve is a two-position operation, that is, fully open and fully closed. The regulating valve is equipped with an electric valve positioner on it, and the valve is dynamically stabilized in one position through closed-loop adjustment.

Comparison of use of solenoid valve and solenoid valve

Solenoid valve: used for on-off control of liquid and gas pipelines, it is two-position DO control. Generally used for the control of small pipelines.

Electric valve: It is used for analog quantity adjustment of pipeline medium flow of liquid, gas and wind system. It is AI control. In the control of large valves and wind systems, electric valves can also be used for two-position switch control.

Solenoid valve: It can only be used as a switching value. It is DO control and can only be used for small pipeline control. It is common in pipelines of DN50 and below.

Electric valve: It can have AI feedback signal and can be controlled by DO or AO. It is more commonly found in large pipes and dampers.

1. Switch form:

The solenoid valve is driven by the coil and can only be opened or closed, and the action time when switching is short.

The drive of electric valve is generally driven by a motor. It takes a certain amount of time to complete the opening or closing action and can be adjusted.

2. Nature of work:

The solenoid valve generally has a small flow coefficient and a small working pressure difference. For example, a 25-port solenoid valve has a much smaller flow coefficient than a 15-port electric ball valve. The solenoid valve is driven by the electromagnetic coil, which is relatively easy to be damaged by voltage shock. Equivalent to the role of a switch, that is, on and off.

Electric valve is generally driven by a motor, which is more resistant to voltage shock. Solenoid valves are quick-opening and quick-closing. They are generally used in small flows and pressures, where electric switching is required where the switching frequency is high. The opening degree of the electric valve can be controlled, and the states are open, closed, half-open and half-closed. The flow rate of the medium in the pipeline can be controlled, but the solenoid valve cannot meet this requirement.

The solenoid valve can be reset when the power is off. The electric valve needs a reset device for this function.

3. Applicable technology:

The solenoid valve is suitable for some special process requirements, such as leakage, special fluid media, etc., and the price is more expensive.

Electric valves are generally used for regulation, and there are also switching values, such as the end of a fan coil.

Main features of solenoid valve

1. The external leakage is blocked, the internal leakage is easy to control, and it is safe to use

Internal and external leaks are a threat to safety. Other automatic control valves usually extend the valve stem, and the rotation or movement of the valve core is controlled by electric, pneumatic and hydraulic actuators. This must solve the problem of external leakage of the long-term action valve stem dynamic seal; only the solenoid valve is completed by the electromagnetic force acting on the iron core sealed in the magnetic insulation sleeve of the electric regulating valve, and there is no dynamic seal, so the leakage is easy to be blocked . Electric valve torque control is not easy, it is easy to cause internal leakage, and even break the stem head; the structure of the solenoid valve is easy to control internal leakage until it reaches zero. Therefore, the use of solenoid valves is particularly safe, especially suitable for corrosive, toxic or high and low temperature media.

2, the system is simple, it will be connected to the computer, the price is low

The solenoid valve itself has a simple structure and a low price, and is easier to install and maintain than other types of actuators such as regulating valves. What is more remarkable is that the automatic control system is much simpler and the price is much lower. Since the solenoid valve is controlled by a switch signal, it is very convenient to connect with the industrial computer. In today's era of popularization of computers and sharply lower prices, the advantages of solenoid valves are even more obvious.

3. Express action, small power, lightweight

The solenoid valve response time can be as short as a few milliseconds, and even pilot operated solenoid valves can be controlled within tens of milliseconds. Due to its own circuit, it is more sensitive than other automatic control valves. Properly designed solenoid valve coils have very low power consumption and are energy-saving products. They can also trigger the action and automatically maintain the valve position, which usually consumes no power at all. The small size of the solenoid valve not only saves space, but also is light and beautiful.

4, the adjustment accuracy is limited, the applicable medium is limited

The solenoid valve usually only has two states of opening and closing. The valve core can only be at two extreme positions and cannot be continuously adjusted, so the adjustment accuracy is also limited to a certain extent.

The solenoid valve has high requirements on the cleanliness of the medium, and granular media cannot be used. If it is an impurity, it must be filtered first. In addition, viscous media cannot be used, and the viscosity range of media for specific products is relatively narrow.

5.Various models and widely used

Although the solenoid valve has inherent disadvantages, its advantages are still very prominent, so it is designed into a variety of products to meet various needs and has a wide range of uses. The advancement of solenoid valve technology also revolves around how to overcome the inherent deficiencies and how to make better use of the inherent advantages.

Related regulations of solenoid valve

1. Product selection points

1) The main control parameters of the solenoid valve are diameter, design nominal pressure, medium temperature range, and interface size.

2) Solenoid valve is used to open and close the valve with an electromagnet. It is usually used in two-position control with a diameter of less than 40mm. It is especially used to connect, cut off or switch the gas and liquid circuits.

3) The sealing performance of the valve is one of the main indicators for evaluating the quality of the valve. The sealing performance of the valve mainly includes two aspects, namely internal leakage and external leakage. Internal leakage refers to the degree of sealing between the valve seat and the closing member against the medium. External leakage refers to the leakage of the valve stem packing part, the leakage of the middle mouth gasket part and the leakage of the valve body due to casting defects. Leakage is not allowed.

4) The main advantages of solenoid valves are small size, reliable operation, convenient maintenance and cheap price. When selecting, you need to pay attention to select the normally open or normally closed type according to the process requirements.

2. Points for construction and installation

1) The installation position and height of the valve must meet the design requirements of the port direction, and the connection should be firm and tight.

2) The valve must be visually inspected before installation. The nameplate of the valve should comply with the current national standard GB12220 "General Valve Mark".

3.Executive standards

Product Standards:

China solenoid valve product industry standard "Solenoid valve for industrial process control system (JB / T7352-2010)"

GB / T13927-92 "General valve pressure test"

JB / T8528-1997 "Technical conditions for ordinary valve electric devices"

GB12220-89 "General Valve Mark"

Engineering standards:

GB50243-2002 "Code for Construction Quality Acceptance of Ventilation and Air Conditioning Engineering"

GB50242-2002 "Code for Construction Water Quality Acceptance of Buildings and Heating Engineering"

Common types of solenoid valves

1, 2 position, 2 port universal valve

2.Hot water / steam valve

3-, 2-position, 3-port valve

4, 2 position 4 way valve

5, 2 position 5 port valve

6.Intrinsically safe explosion-proof solenoid valve

7, low power solenoid valve

8.Manual reset solenoid valve

9.Precision miniature valve

10.Valve position indicator

Solenoid valve common fault

The solenoid valve is composed of an electromagnetic coil and a magnetic core, and is a valve body containing one or several holes. When the coil is energized or de-energized, the operation of the magnetic core will cause the fluid to pass through the valve body or be cut off to achieve the purpose of changing the direction of the fluid. The electromagnetic part of the solenoid valve is composed of a fixed iron core, a moving iron core, a coil and the like; the valve body part is composed of a slide valve core, a slide valve sleeve, a spring base and the like. The solenoid coil is directly mounted on the valve body, and the valve body is enclosed in a sealed tube, forming a simple and compact combination. The solenoid valves we commonly use in production include two-position three-way, two-position four-way, and two-position five-way. Let's talk about the meaning of the two positions first: for the solenoid valve, it is live and de-energized, and for the valve being controlled, it is open and close.

The malfunction of the solenoid valve will directly affect the action of the switching valve and the regulating valve. The common malfunctions are that the solenoid valve does not operate. It should be checked from the following aspects:

1. The terminal of the solenoid valve is loose or the wire head is disconnected. The solenoid valve must not be electric, and the wire head can be tightened.

2. The solenoid valve coil is burned out. The solenoid valve wiring can be removed and measured with a multimeter. If it is open, the solenoid valve coil will burn out. The reason is that the coil is wet, causing poor insulation and magnetic leakage, which causes the current in the coil to be too large and burn out. Therefore, it is necessary to prevent rainwater from entering the solenoid valve. In addition, the spring is too hard, the reaction force is too large, the number of coil turns is too small, and the suction force is not enough to cause the coil to burn out. During emergency processing, the manual button on the coil can be turned from the "0" position to the "1" position during normal operation to make the valve open.

3. Solenoid valve jam: The clearance between the solenoid valve spool and the valve core is very small (less than 0.008mm), which is generally a single piece assembly. When mechanical impurities are brought in or the lubricant is too little, it is easy to jam. . The treatment method can be penetrated with a wire through a small hole in the head to make it rebound. The fundamental solution is to remove the solenoid valve, take out the valve core and the valve core sleeve, and clean it with CCI4, so that the valve core can move flexibly in the valve sleeve. When disassembling, pay attention to the assembly sequence of each component and the location of the external wiring, so that the reassembly and wiring are correct. Also check whether the injection hole of the lubricator is blocked and whether the lubricant is sufficient.

4. Air leakage: Air leakage will cause insufficient air pressure, making it difficult to open and close the compulsory valve, due to damage to the sealing gasket or the wear of the slide valve, resulting in blow-by of several cavities. When dealing with the failure of the solenoid valve of the switching system, you should choose an appropriate time to handle the solenoid valve when it is out of power. If the processing is not completed within a switching gap, you can pause the switching system and handle it calmly.