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General FAQs
1. What is a solenoid valve?
A solenoid valve is an electrically operated valve that automatically opens or closes the flow of a fluid (air, water, oil, gas, or other fluids). It consists of a valve body and an electromagnetic coil that actuates the internal sealing element.
2. How does a solenoid valve work?
When the coil is energized, it generates a magnetic field that moves the plunger, opening or closing the fluid passage. When power is removed, a spring returns the plunger to its initial position.
3. What is the difference between a normally closed (NC) and a normally open (NO) solenoid valve?
• Normally Closed (NC): remains closed when not energized.
• Normally Open (NO): remains open when not energized.
The choice depends on the required behavior in case of power failure.
4. Which fluids can be used?
Solenoid valves can control:
• Water
• Compressed air
• Vacuum
• Neutral gases
• Oil
• Hot water
• Steam (with specific models)
• Chemical fluids compatible with the construction materials
Product Selection
5. How do I choose the correct solenoid valve?
You should know:
• type of fluid
• minimum and maximum pressure
• fluid temperature
• coil voltage
• connection size
• required flow rate
• body material
• seal material
• operating principle (direct acting or pilot operated)
6. Which body material should I choose?
• Brass → water, air, oils.
• Stainless steel → aggressive fluids, demineralized water, food and pharmaceutical industries.
• Plastic → chemicals and demineralized water.
7. Which seal material should I choose?
• NBR → air, water, oils.
• EPDM → hot water, low-pressure steam.
• FKM (Viton®) → oils and high temperatures.
• PTFE → aggressive chemicals
8. Which voltages are available?
The most common are:
• 12 VDC
• 24 VDC
• 24 VAC
• 110 VAC
• 230 VAC
Other voltages are available on request.
Installation
9. Can the solenoid valve be installed in any position?
Generally, it is recommended to install it with the coil facing upward. Some models can also operate in other positions, but the manufacturer’s instructions should be checked.
10. Is it important to respect the flow direction?
Yes. An arrow on the valve body indicates the correct installation direction.
If no arrow is present, connection numbers “1” and “2” indicate inlet and outlet.
11. Is it necessary to install a filter?
Yes. It is advisable to install a filter upstream of the solenoid valve to prevent impurities from affecting operation. The need for a filter depends on the cleanliness level of the fluid used.
12. Can the solenoid valve be installed outdoors?
Yes, provided that the coil has an adequate protection rating (for example IP65 or higher) and is protected from weather conditions.
Operation
13. What is the difference between direct acting and pilot operated (indirect acting)?
Direct acting solenoid valves operate even at zero pressure.
Pilot operated valves use fluid pressure for opening and require a minimum differential pressure.
14. What does minimum differential pressure mean?
It is the pressure difference between the inlet and outlet of the solenoid valve under both closed and open valve conditions.
15. Can a solenoid valve operate with vacuum?
Only certain models are designed for vacuum service. Please check the technical specifications in the catalog or contact our customer service at sales@r2g-fluidics.com
16. Does the coil get hot?
Yes. It is normal for the coil to reach relatively high temperatures during operation, and this does not necessarily indicate a malfunction.
Maintenance
17. How often should maintenance be performed?
It depends on the type of fluid and operating conditions. With clean fluids, maintenance is generally limited; with dirty fluids, periodic inspections are recommended.
18. Is it possible to replace only the coil?
In most models, yes, without replacing the valve body.
19. Are spare part kits available?
Yes. Kits including diaphragms, springs, seals, and other wear components are available.
20. What are the most common causes of malfunction?
The main causes are:
• impurities in the fluid
• incorrect voltage
• non-compliant pressure
• worn seals
• damaged coil
• incorrect installation
Compatibility
21. Can I use a water solenoid valve with compressed air?
Often yes, but compatibility with pressure, flow rate, and materials must be verified.
22. Are solenoid valves suitable for food applications?
Versions with materials compliant with food industry regulations are available.
23. Are ATEX versions available?
Yes. For potentially explosive atmospheres, solenoid valves with ATEX-certified coils are available.
Applications
24. In which industries are they used?
Solenoid valves are used in many industrial sectors, including:
• industrial automation
• pneumatic systems
• water treatment
• washing systems
• machine tools
• food industry
• chemical industry
• HVAC systems
• irrigation systems
• pharmaceutical industry.
25. Can they operate continuously (24/7)?
Yes. Solenoid valves designed for continuous duty (ED 100%) can remain energized permanently.
26. What does ED 100% mean?
It means the coil can remain continuously energized without time limitations, provided the operating conditions specified by the manufacturer are respected.
27. How do I calculate the correct orifice size?
The selection depends on:
• required flow rate
• available pressure
• allowable pressure drop
• type of fluid
• temperature
Correct sizing avoids pressure losses and unnecessary energy consumption.
28. How can I request technical support?
To receive support, it is helpful to provide:
• solenoid valve model
• fluid used
• pressure
• temperature
• coil voltage
• description of the problem
• any installation photos
Write to sales@r2g-fluidics.com
29. Can I request a customized solenoid valve?
Yes. Customized configurations can be manufactured by selecting materials, voltages, connections, seals, and accessories according to the application and required purchase volumes.
Problems and Troubleshooting
Why doesn’t my solenoid valve open?
Short answer
If the solenoid valve does not open, the most common causes are lack of electrical power, a faulty coil, insufficient pressure (in pilot-operated models), impurities blocking the internal mechanism, or incorrect installation.
Detailed explanation
Before replacing the solenoid valve, it is advisable to check:
• presence of the correct voltage at the coil terminals;
• matching between the supply voltage and the voltage indicated on the coil;
• presence of dirt or scale deposits;
• minimum pressure required by the installed model;
• correct orientation with respect to the flow direction.
Pilot-operated solenoid valves require a minimum differential pressure to operate. If the pressure is too low, the coil energizes but the valve remains closed.