This is called a Normally Closed (NC) valve.Ī Normally Open (NO) valve works the opposite way: it has a different construction so that the orifice is open when the solenoid is not powered. This opens the orifice so that the medium can flow through. An electric coil is positioned around the plunger.Īs soon as the coil is electrical energized, a magnetic field is created which pulls the plunger up towards the center of the coil. The plunger is made of a ferromagnetic material. The medium flows through a small orifice which can be closed off by a plunger with a rubber gasket on the bottom.Ī small spring holds the plunger down to close the valve. Direct operated solenoid valves:ĭirect operated (direct acting) solenoid valves have the most simple working principle. Solenoid valves can be categorized into different groups of operation. For more information about valve symbols and circuit functions, please visit the page about valve symbols. The examples show a 2/2-way Normally Open (NO) valve, a 2/2-way Normally Closed (NC) valve and a 3/2-way Normally Closed valve. The arrows in the box show the flow direction between the valve ports. The circuit function of a valve is symbolized in two rectangular boxes for the de-energized state (right side, visualized by ) and energized state (left). Below are some examples of the most common circuit functions. The circuit function can be expressed in a symbol.

More ports or combinations of valves in a single construction are possible. 3/2 way valves can have different functions such as normally closed, normally open, diverting or universal. A 2/2 way valve can be ‘normally closed’ (closed in de-energized state) or ‘normally open’ (open in de-energized state).Ī 3/2 way valve has three ports and two positions and can therefore switch between two circuits. The specific purpose of a solenoid valve is expressed by its circuit function.Ī 2/2 way valve has two ports (inlet and outlet) and two positions (open or closed). Solenoid valves are used to close, dose, distribute or mix the flow of gas or liquid in a pipe. “A solenoid valve is an electromechanical actuated valve to control the flow of liquids and gases.” Circuit Functions of Solenoid Valves

Electric solenoid valve fuel gas moped