5 Ways Solenoid Valves are Used

Solenoid valves are key parts of many systems in which the flow of material needs to be controlled remotely. This type of valve opens and closes in response to an electrical charge, so they are perfect for machinery and systems operated by control panels, or in automated systems. In this article, we will describe a few examples of solenoid valve uses, and the types of SV best suited to the application.

To name a few examples, solenoid valves are used in:

• Automated Irrigation/Sprinkler systems
• Air Compressor systems
• Electric Showers
• Drinks Dispensers
• Automatic Door Locking systems

In each of these systems, an electrical signal controls the valve, allowing simple, immediate and accurate control, and enabling programmable systems.

What is a Solenoid Valve?

A solenoid valve is an electromagnetically-operated gate used to control the flow of gasses and liquids in pressurised systems. The valve can be either “normally open” or “normally closed” and is moved from its normal position when the solenoid receives an electrical current. A solenoid is a coil of copper wire around a rod (or core, or plunger) of ferrous (iron-containing) metal. When electrical energy passes through the coil, it creates a magnetic field, moving the rod. When this happens, the rod opens or closes the valve, starting or stopping the flow of the medium (substances) through the system.

Working Principles: Direct Acting vs Pilot Operated Valves

There are two main types of solenoid valves: directly or pilot operated. In a direct-acting solenoid valve, the core or rod is the part which blocks the opening, sealing the valve. It is the simplest working principle and adequate for many systems.

Pilot-operated valves, on the other hand, are quite complex. They are also known as indirect-acting valves and rely on the pressure differential between the inlet and outlet ports. The rod of a pilot-operated valve moves when the coil is electrified and causes a rubber membrane or ‘diaphragm’ to open the orifice. To do this, there must be a minimum pressure differential of approximately 0.5 bar. between the inlet and outlet ports.

The diaphragm has a small opening, allowing the medium (water, gas, etc.) to flow from the inlet port into the upper compartment, where the diaphragm is supported by a spring.

The rod in the solenoid acts upon a pilot hole, a narrow opening which connects the upper compartment to the low-pressure port.

In the closed position, the rod closes this pilot hole, but in the open position, a small amount of the medium can flow through, causing the pressure above the diaphragm to drop.

This allows the spring to contract, lifting the diaphragm away from the main opening. The medium can then flow freely from the inlet port to the outlet port.

The engineers at Instrumentation Academy have made an informative video explaining with diagrams and simple terms how pilot-operated solenoid valves work.

For more information on 5 Ways Solenoid Valves are Used talk to Avalco Ltd