What is a Solenoid Valve?
Using an electrical coil and a plunger, a solenoid valve operates using an electromechanical actuator. The solenoid valve controlle an electrical signal. Solenoid valves can produc in two ways. Normally, they are open and normally closed. AC or DC electricity is use to operate the solenoid (electrical coil). Batteries, generators, or rectifiers provide DC power. An AC supply is use to derive from AC mains voltage through a transformer.
What is the purpose of a solenoid valve?
An application uses a solenoid valve to open, close, mix, or divert liquids and gases. Industrial and domestic applications of solenoid valves are diverse. Solenoid valves use for a variety of applications, including standard process valves, overpressure protection systems, emergency stop valves, and fluid control in fire system valves. A solenoid valve has a very fast response time compared to traditional valves. Among the most common applications are:
- The refrigerant flows reverse solenoid valves in refrigeration systems during the summer and heat during the winter.
- Compressors use solenoid valves to discharge the compressor during the starting phase to reduce engine torque.
- For automatic control purposes, solenoid valves use in irrigation systems.
- Water flow is the control of solenoid valves in washing machines and dishwashers.
- Solenoid valves control air pressure in air conditioning systems.
- A solenoid valve use in automatic locking systems for door locks.
- Water, soap, and chemicals control solenoid valves in car washes and industrial cleaning equipment.
- Solenoid valves are often use to control the inflow and outflow of water in water tanks.
- In dental and medical equipment, solenoid valves control pressure, flow, and fluid direction.
The workings of a solenoid valve
The plunger (E) compose of an electromagnetically inductive coil (A) around an iron core. In its resting state, it will either be normally open (NO) or normally closed (NC). During the de-energized phase, a normally open valve remains open while a normally closed valve remains closed. A solenoid coil is an energy when current flows through it, creating a magnetic field that attracts the plunger. As a result, the plunger moves by overpowering the spring (D). A normally closed solenoid valve opens the orifice by lifting the plunger, allowing the media to flow through. For normally open solenoid valves, the plunger moves downward and the seal (F) blocks the orifice, preventing media from flowing through.
The solenoid valves control the flow of liquids and gases automatically. Increasingly, they use a variety of plants and equipment. The designs can customize to meet the needs of a particular application.
Types of Solenoid Valves
There are three types of solenoid valves based on the number of pipe connections.
- Solenoid valves with two ways of operation
- Solenoid valves with three ways
- Solenoid valves with four ways of operation
Solenoid valves with two ways of operation
An inlet and outlet piping connection share a two-way solenoid valve, as its name suggests. Two types can distinguish.
- Normally closed construction: Valve closes when de-energized and opens when energized.
- Solenoid valves with normally open construction close when energy and open when de-energy.
A three-way solenoid valve
A three-way solenoid valve has three pipe connections and two orifices. One orifice is open when the other is close, and vice versa. It is common to use three-way solenoid valves to apply pressure to and exhaust pressure from a diaphragm valve or a single-acting cylinder. Three modes of operation are available:
A normal close valve has a pressure port that closes when the valve is de-energy, and an exhaust port that connects to the cylinder port when the valve is energy. A close exhaust port and a close pressure port connect when the valve is energy.
Normally open valves have the pressure port connect to the cylinder port when they are de-energy. The valve’s pressure port closes when it is energy, while its cylinder port connects to its exhaust port.
Valve construction with universal connections: This type can install normally close or normally open. Additionally, the valve can connect to select one or two ports or divert flow between ports. Aira Euro Automation is the leading solenoid valve supplier in Zambia. We offer various industrial valves.
Solenoid valves with four directions
Double-acting cylinders operate four-way solenoid valves. Solenoid valves of this type have four or five pipe connections; one pressure, two cylinders, and one or two exhausts. One valve position connects the pressure to the cylinder port, the other to the exhaust port. At the cylinder connections, pressure and exhaust revers in the other valve position.
The solenoid valves are classified according to their functions
- Solenoid valves for general purposes
- Shut-off valves for safety and
- Valve for process control
A general-purpose solenoid valve controls the flow of fluid by opening or closing normally. These valves, however, do not function as safety valves.
To prevent unsafe fluid delivery, safety shut-off valves normally close “on” or “off” valves that operate by safety control devices. Concerning its normally closed port, a multiple port valve can function as a safety shut-off valve.
Normal use to control flammable gases, these solenoid valves do not work reliably as safety shut-off valves.
Also, read “Different Types of Solenoid Valves”
Following the working methodology, solenoid valves are classified into four groups:
- Solenoid valves with direct action
- Solenoid valves operated by pilots
- Solenoids that operate under pressure
- Solenoid valves that operate by air
Solenoid valves with direct action
An orifice of a normal close valve or an orifice of a normally open valve is directly open or closes a direct-acting solenoid valve. A valve’s opening force depends on its orifice size and fluid pressure.
Solenoid valves operated by pilots
A pilot and a smaller orifice include in this type of solenoid valve. Their operation is based on line pressure. Upon activation of the solenoid, the pilot orifice opens and releases the pressure from the top of the piston or diaphragm to the valve outlet. By creating an unbalanced pressure, the line pressure lifts the piston of the diaphragm off the main orifice and opens the valve.
The solenoid unplugs de-energizing it, and a seal create applying full line pressure to the piston or diaphragm. Construction can divide into two types:
Solenoid valve operated by pressure
Solenoid valves of this type use diaphragm or piston operation. Operating pressure controls the opening or closing of the main valve using a 3-way or 4-way solenoid pilot.
Solenoid valve selection
Choosing a solenoid valve is not an easy task. When selecting a solenoid valve for a particular application, several physical and operational factors must consider. Here are a few of these parameters:
In the same way as the pressure mentioned above, the following temperature shoul be known:
- Temperatures at minimum, maximum, and normal
- The temperature of the maximum fluid
During solenoid valve selection, the viscosity of the flowing fluid at the operating temperature is also an important parameter.
Time to respond:
A solenoid valve’s response time is how long it takes for the valve to move from an open to a close position. A solenoid valve’s response time varies with its size. Also, it depends on the type of electrical supply, fluids handling, temperature, pressure, and pressure drop.
Solenoid valve types:
A 2-way or 3-way solenoid valves is require the application requirements. Consider whether a direct, indirect, or semi-direct operating solenoid valve need for the specific application.
Material of the solenoid valve housing:
Valve housing materials determin by the chemical properties and temperature of the flowing media and the environment. Solenoid valves housings are commonly make of brass, stainless steel, PVC, and polyamide.
Solenoid Valve Sizing
Under-size and over-size solenoid valves can cause a variety of undesirable effects, so selecting the right size and type is crucial. Solenoid valves sizing takes into account the following factors:
- Control of minimum and maximum flows.
- The minimum and maximum pressure differential across the solenoid valves
- Fluid-specific gravity, temperature, and viscosity.
- Pipe diameters at the inlet and outlet.
- Voltage supply.
Flow rate determines the optimal size of solenoid valves, which in turn determines the flow factor (kV).