What Are Solenoid Valves?

Nicholson steam trap

A valve is any device that is used for halting or controlling the flow of a liquid, gas, or other material through a pipe, passage, inlet, or outlet. Without these hinged lids or other movable parts that close or modify the passage, many of the modern conveniences that we take for granted would overheat, or completely quit working.
A solenoid valve is a valve that is operated electromechanically. The valve is controlled by an electric current through a solenoid, a type of electric conductor. in the case of a two-port valve, for example, the flow is switched on or off. In a three-port valve, on the other hand, the outflow is switched between two different outlet ports.
Because a solenoid valve is electronically operated, it can be is used to control the flow of liquids or gases in a positive, fully-closed or fully-open mode. These types of valves are commonly used to replace a manual valve whenever remote control is needed.
While steam trap valves are merely a hinged escape for temperature controlled air, a solenoid valve is operated by opening and closing an orifice in the valve body that permits or prevents flow through the valve. A plunging device is used to open or close the sleeve tube by energizing the coil. The bottom of most solenoid valve plungers contains a reliable sealing material, which closes off the the opening in the body, thus stopping the flow through the valve.
All solenoid valves are assembled with a coil, plunger, and sleeve assembly. In a normally closed solenoid valve it is the plunger return spring which holds the plunger flat against the the opening, preventing flow through the valve. When the coil is energized, or on, a magnetic field is produced which raises the plunger and allows flow through the valve. In normally opened solenoid valves, when the coil is energized, the plunger seals the orifice, completely stopping flow through the valve.
Thermostatic valves, on the other hand, can be used to blend hot water with cold water to ensure a constant, safe shower and bath water temperature. Without this valve, accidental scalding would be more likely.
In the case of all of these valves, regular maintenance and testing is necessary. In steam systems that have not been maintained for three to five years, for example, between 15% and 30% of the installed steam trap parts may have failed. Many steam products are subject to rust and corrosion, but in systems with a regularly scheduled maintenance program, leaking valves should account for less than 5% of the steam trap population. While old, inefficient solenoid valves can produce $8,000 in waste annually, quality equipment and programs can reduce losses to less than 1%.