What is a balanced valve and what are the benefits of this type of design?
A balanced valve design means that the internal forces from pressure are equal. The forces from air pressure that open the valves are equal to the forces from air pressure that close the valves. In engineering school, engineers are taught to draw a “free body diagram” of the part in question and then apply all forces to that “free body.” With a balanced valve design, the forces from the pressure will be equal in both directions.
Now when the engineer works on the design of a balanced valve he does not need to be concerned with how the internal pressures will affect the shifting of the valve. On a two-position single solenoid spring return valve, this allows him to design a spring that is just large enough to close the valve so that it does not leak and then design a solenoid strong enough to overcome that spring and open the valve. He is not concerned about overcoming pressure forces so he can design a lighter spring and use a lower watt solenoid.
As a direct acting balanced design, this valve can be used with vacuum, low pressure or high pressure and the valve will shift the same each time – no matter what port the pressure, or vacuum, is applied. It can operate normally open, normally closed, as a selector or as a diverter and that is what makes it a "Universal Valve." This multi-purpose valve is versatile for many different types of applications across many industries.
An application where a balanced valve would beneficial is when a customer wants a selector function that first pumps up a chamber to positive pressure, then shifts the valve to pull the chamber to vacuum. Both pressure and vacuum can be on the same valve.
Another might be a high-pressure application using an unbalanced valve that needs a stronger coil. This would require a high wattage coil, increasing the energy use and heat generation. The balanced solenoid valve design would offer a cost-savings to the overall application because it doesn’t need to overcome the internal pressures since they are equal.
Humphrey Products manufactures “Balanced Direct Acting Solenoid” universal valves. Visit the 153/193 Balanced Solenoid Valve Series to learn more about this technology and how it could work with your application.