We will be working with pneumatics instead of hydraulics for several reasons. While both systems follow the same basic principles, pneumatics use gases, which can be compressed, unlike liquids used in hydraulics. Additionally, pneumatic systems are cleaner and more accessible—after all, a small release of air (mainly oxygen and nitrogen) isn’t a concern.​

3. Pneumatic Solenoid Valve Symbols and Wiring Diagram
Figure 5: Pneumatic solenoid valve in pneumatic system. 3.1 Pneumatic Solenoid Valve Symbols There are 2 boxes in the picture below, representing “2 positions”, and there are 5 ports, referring to “5 ways”, that is, the 2-position 5-way. The red box on the left indicates the state of the solenoid valve when de-energized, and the arrow indicates the air flow direction, while the green box on the right indicates the air flow direction when the solenoid valve energized.


Figure 6: 2-position 5-way pneumatic solenoid valve symbol.

P: Air inlet
R1: Air exhaust port
R2: Air exhaust port
A: Cylinder air inlet 1
B: Cylinder air inlet 2 3.2 Pneumatic Solenoid Valve Wiring Diagram The power supply for the solenoid valve is 12V, 24V, etc., and the wiring diagram is as follows. Pay attention to the positive and negative poles of the power supply wiring, and reverse connection will cause the valve to not work.


Figure 7: Solenoid valve wiring diagram. 4. Pneumatic Solenoid Valve Types 4.1 According to the Working Principle Pneumatic solenoid valves can be divided into two types: direct-acting and indirect-acting (pilot-operated).

Direct-acting solenoid valve: It is composed of valve core, coil, spring, etc. When the coil is energized, the magnetic field force generated directly drives the valve core to move without pilot air flow. It has simple structure and reliable action, but requires larger drive current.

Indirect-acting solenoid valve: It consists of two parts: main valve and pilot valve. The pilot valve controls the action of the main valve. When the coil is energized, the pilot valve opens or closes, and makes the main valve core operate to control the opening or closing of the air channel. Pilot-operated solenoid valve requires smaller drive current and has higher control accuracy. 4.2 According to the Number of “Positions” and “Ways” Pneumatic solenoid valves can be divided into: 2-position 2-way, 2-position 3-way, 2-position 5-way, 3-position 5-way, etc.

The number of “positions” and “ways” of solenoid valves refers to that of working states of the solenoid valve (2 or 3 working positions) and that of ports in the valve body (including the number of air inlets, air outlets and air exhaust ports). Among them, "positions" indicates how many working states the valve has, and "ways" indicates the total number of ports on the solenoid valve body.

For example, a two-position two-way solenoid valve has two working states (the coil is de-energized, and the coil is energized). It has 1 air inlet, 1 air outlet, and no air exhaust port.


Figure 8: Two-position two-way solenoid valve. 4.3 According to Operation Type Pneumatic solenoid valves can be divided into: normally open (NO) and normally closed (NC).

When the normally closed solenoid valve loses power, the solenoid valve is shut off, the air outlet is not connected to the air inlet, and there is no air in the air outlet; when the power is on, the solenoid valve is opened, the air outlet is connected to the air inlet, and there is air in the air outlet.

When the normally open solenoid valve loses power, the solenoid valve is opened, the air outlet is connected to the air inlet, and there is air in the air outlet; when the power is on, the solenoid valve is shut off, the air outlet is not connected to the air inlet, and there is no air in the air outlet. 5. How to Properly Clean Pneumatic Solenoid Valves Preparation Work before Cleaning
1. Disconnect the pneumatic solenoid valve from the power and air source, and remove it;
2. Check whether the appearance of the pneumatic solenoid valve is damaged or corroded. If necessary, replace the corresponding parts in time;
3. Prepare cleaning fluid. Generally alcohol or cleaning agent can be used;
4. Prepare tools: brush, clean cloth or paper towel, cleaner, etc.

Cleaning Steps
1. Remove pneumatic solenoid valve;
2. Soak the pneumatic solenoid valve with a cleaning agent. Do not let the cleaning agent enter the coil to avoid affecting the valve service life;
3. Use a soft brush to gently scrub the surface of the pneumatic solenoid valve. Do not use a hard brush to avoid damaging the surface of the valve body;
4. For some stubborn stains, you can use a cleaner to clean them, but pay attention to controlling the pressure of the nozzle to avoid excessive pressure from damaging the valve body;
5. Use a clean cloth or paper towel to dry the pneumatic solenoid valve to avoid oxidation caused by moisture residue;
6. Carry out assembly, inspection and testing to ensure the normal operation of the pneumatic solenoid valve.


Figure 9: Pneumatic solenoid valve connected to other components.

Precautions
1. When cleaning the pneumatic solenoid valve, be careful to prevent cleaning agent from entering the coil and causing short circuit or oxidation;
2. When using a cleaner for cleaning, pay attention to controlling the pressure of the nozzle to prevent damage to the valve body;
3. When reinstalling the pneumatic solenoid valve after cleaning, pay attention to the installation position and connection method of each component to ensure that it is correct;
4. Regular cleaning of the pneumatic solenoid valve can effectively extend the service life and avoid failures caused by long-term use.

In short, the correct cleaning method is of great significance for the maintenance of pneumatic solenoid valves. We hope the above steps can help you to keep your pneumatic solenoid valve in the best working condition. 6. Things to Note When Selecting Pneumatic Solenoid Valves 1. Working Medium: Determine the working medium of the pneumatic solenoid valve according to actual needs, such as air, nitrogen, etc.

2. Working Temperature: Determine the working temperature of the pneumatic solenoid valve according to actual needs to ensure its normal operation.

3. Working Pressure: Determine the working pressure of the pneumatic solenoid valve according to actual needs to ensure its normal operation.

4. Installation Method: Determine the installation method of the pneumatic solenoid valve according to actual needs, such as pipeline connection, flange connection, etc.

5. Brand and Specifications: Choose a reliable pneumatic solenoid valve brand and specifications on the market to ensure its performance and stability.

6. Energy Saving and Environmental Protection: On the premise of meeting functional requirements, try to choose a pneumatic solenoid valve with high energy efficiency and environmental protection.

7. Maintenance: Regularly inspect and maintain the pneumatic solenoid valve to extend its service life.

8. Training and Operation: Operators need professional training to ensure that they can correctly use and maintain pneumatic solenoid valves.

In short, the pneumatic solenoid valve, as an important fluid control component, plays an important role in industrial automation and process control. Understanding its structure, working principle, types, cleaning and selection precautions will help to better apply and maintain pneumatic solenoid valves, and improve production efficiency and equipment reliability.