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Solenoid valves are workhorses in the world of fluid control. These clever devices use electricity to manage the flow of liquids and gases. In this blog we will learn How Solenoid Valve Works?
At the heart of a solenoid valve there is a special kind of electromagnet called a solenoid. This coil of wire wraps around a movable metal rod, known as a plunger. When an electric current is sent through the coil, it generates a magnetic field. This invisible force acts like a powerful magnet, pulling the plunger upwards.
This upward pull opens a passage within the valve, allowing the liquid or gas to flow through. When no electricity is supplied, the magnetic field disappears, and a spring pushes the plunger back down, sealing the passage and stopping the flow.
In simple words, imagine a switch that uses electricity to control a liquid or gas pipeline. That’s the basic idea behind a solenoid valve!
Solenoid valves consist of two main components: solenoid and valve body.
The solenoid acts like an electromagnetic switch. It has a coil of wire wrapped around a central iron core, called a plunger. When the coil is inactive and no electricity is flowing, the plunger remains in its usual position. This position determines whether the valve is normally open or normally closed depending on the valve design.
When electricity passes through the coil, an electromagnetic field is generated. This magnetic field pulls the plunger upwards.
This upward movement of the plunger opens a designated passage within the valve body, called the orifice. With the orifice open, the path is clear for the liquid or gas (often referred to as media) to flow through the valve.
Where are solenoid valves used?
• Industrial automation: Solenoid valves are extensively used in various industrial processes for controlling the flow of fluids such as water, air, oil, gas, steam, and chemicals.
• HVAC systems: They are employed in heating, ventilation, and air conditioning systems to regulate the flow of refrigerants and fluids, controlling temperature and humidity levels.
• Automotive industry: Solenoid valves are integral components in vehicle systems, including transmission systems, fuel systems, engine control, and emissions control.
• Medical equipment: They are utilized in medical devices and equipment for controlling the flow of gases and liquids in applications such as anesthesia machines, dialysis machines, and laboratory equipment.
• Water treatment and irrigation: Solenoid valves are used in water treatment plants, irrigation systems, and plumbing applications for controlling the flow of water and other fluids.
• Aerospace and aviation: They are used in aircraft and spacecraft systems for various functions, including fuel control, hydraulic systems, and pneumatic systems.
• Household appliances: Solenoid valves are found in everyday appliances such as washing machines, dishwashers, refrigerators, and coffee machines for controlling the flow of water, detergents, and other fluids.
• Fire suppression systems: Solenoid valves are utilized in fire suppression systems to control the release of fire extinguishing agents such as water, foam, and gas.
Types of Solenoid Valves
Direct Acting Solenoid Valve
The direct-acting solenoid valve is usually used for small flow-rate jobs. Here’s how it works:
• When electricity flows through the coil, it makes a magnetic field that pulls the plunger upward. This opens a hole, letting the liquid or gas flow through.
• The size of the hole (called the orifice) determines how much pressure and flow the valve can handle. That’s why it’s best for low-flow situations.
• This type of valve doesn’t need any pressure to work, so it can even handle situations with no pressure or negative pressure.
Indirect Acting Solenoid Valve
Indirect Acting also called as Servo or Pilot Operated Solenoid Valves. They works a bit differently:
• It relies on a small pressure difference between the inlet and outlet to open and close.
• Sometimes called servo-operated or pilot operated, it typically needs at least a 0.5 bar pressure difference to function.
• There’s a rubber membrane between the inlet and outlet ports. Normally, a plunger blocks a low-pressure port above the membrane.
• When the solenoid is activated, it opens an orifice, causing a pressure drop across the membrane. This lifts the membrane, allowing the medium to flow from the inlet to the outlet.
• This setup acts like an amplifier, allowing a small solenoid to control a large flow. That’s why it’s used for managing high flow rates.
Semi-Direct Acting Solenoid Valve
The semi-direct acting solenoid valve combines features from both direct and indirect-acting types, making it versatile:
• It can work even when there’s no pressure and can handle high flow rates.
• Its design closely resembles that of the indirect-acting valve, with a rubber membrane and pressure chambers.
• The key difference is that the solenoid plunger is directly linked to the membrane. When the solenoid activates, the plunger lifts, allowing material to flow. This action also opens a smaller secondary orifice in the membrane, creating a pressure drop above it, which lifts the membrane further.
• By blending features from both direct and indirect types, the semi-direct acting valve can operate under zero pressure conditions and manage significant flow rates.
Selection Criteria of Solenoid Valve
1. Type of Solenoid Valve: Select between 2-way or 3-way based on your application needs.
2. Housing Material: Select material (like brass or stainless steel) based on the medium’s chemical properties and temperature.
3. Seal Material: Choose seal materials (like NBR, EPDM, FKM, or PTFE) based on the medium’s chemical properties and temperature.
4. Operating Voltage: Decide between AC or DC operating voltages based on your power supply availability.
5. Valve Function: Choose between normally open or normally closed based on your application, with normally open being the most common.
6. Operating Type: Consider direct-acting, indirect-acting, or semi-direct acting types based on your requirements.
7. Temperature: Ensure the valve material can withstand the minimum and maximum temperatures of its installation environment.
8. Response Time: Direct-acting solenoid valves generally have quicker response times compared to indirect-acting or semi-direct acting ones.
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