Solenoid Valve Basics

In just about every application where the flow of air, water, oil, gas, or any other fluid needs to be stopped or started a solenoid valve is incorporated into the piping system.

Here is a list of common questions that need to be addressed to properly start the selection of your solenoid valve needs.

Valve Type         2-way, 3-way, 4-way

Operation           Normally Open, Normally Closed, Universal

Pipe Size              Pipe size or flow requirements

Media                    Fluid to be controlled (what’s going through valve)

Pressure              Minimum and Maximum operating pressure

Temperature    Minimum and Maximum fluid and ambient temperature

Voltage                   Voltage and frequency to be used

Extras                      Special seals, special seats, manual reset, explosion proof, etc.

Since most of the day by day uses of solenoid valves are 2-way/ 2-position let’s look at the above questions closer.

Operation           This the most misunderstood question. Normally Open simply put means that when the valve is not energized (no power to coil) the valve is open allowing the media to pass through the valve.  When the Normally Open valve is energized (power to coil) the Normally Open valve will shut down not allowing media to pass through the valve. The Normally Closed valve is of course opposite to the Normally Open valve. When the Normally Closed valve is not energized the valve will not allow media to flow through the valve. When the Normally Closed valve is energized the valve will open to allow media to flow.

Pipe Size             Most all valves are listed by pipe size and Cv rating along with the valve’s orifice size. Notice that the smaller the orifice size is on a solenoid valve that the Cv rating is reduced.  So what Cv do you need? Here is a “rule of thumb”. Cv = 50% of the gpm flow through a valve based on a 2-5 psi pressure drop between the inlet and outlet of the valve. So by way of example if you need 10 gpm of water to supply your need to some equipment with a 2-5 psi pressure drop the solenoid’s Cv factor would be 5.

Media                   Most common of media type for solenoid valves is air, water, gas, steam, or oil.

Pressure              Maximum Operating Pressure Differential (M.O.P.D.) The maximum operating pressure differential refers to the maximum difference in pressure between the inlet and the outlet, against which the solenoid can safely operate the valve. If the pressure at the valve OUTLET is not known, it is safest to regard SUPPLY pressure as the M.O.P.D. Minimum Operating Pressure Differential  is that which is required to OPEN the valve and keep it open. 2-way way solenoids with a floating piston or diaphragm, the valve will start to close below the minimum operating differential pressure.

Temperature     The normal limitation of 32 degrees F (O degrees C) is advisable for any valve that might contain moisture (water Vapor). Where freezing water is not a factor, minimum ambience as low as 0 degrees F (-18 degrees C) can be tolerated. Special constructions are available for lower temperature ratings. Maximum ambient temperature is usually controlled by the UL listing for the coil insulation available for the valve.

Voltage                  There are various coil voltages available for solenoids to meet your needs.  Please remember when asking for valves to state if the voltage is AC or DC and whether 50 or 60 cycles.

Stromquist and Company is proud to service your needs for solenoid valves by ASCO, GC Valve, and Honeywell. Let us help you pick the right solenoid valve for your needs by calling us at 1-800-241-9471 or 1-800-638-7828.