Solenoid valves are magnetically operated valves. The are sometimes called electromechanical valves. The electrical part refers to the solenoid. The solenoid is a cylindrical coil of wire that, when energized, produces a magnetic field. This magnetic field is used to move the ferrous plunger, which directly or indirectly closes (or opens) the valve. There are several different classifications of solenoid valves, based on a few different parameters. The first is based on the acting mechanism: Direct Acting- Direct acting solenoid valves use the plunger to directly close the orifice (small opening). The are almost exclusively smaller valves, as larger direct acting valves would require a very large solenoid. These solenoid get pricey, so instead pilot operated solenoid valves are used. Pilot Operated- Pilot operated valves use the pressure of the fluid to close and seal the orifice. This allows for a larger orifice without a larger solenoid. The second type of classification is based on the resting state of the valve: Normally Closed (N.C.)- Normally closed valves are closed when at rest (unenergized). This is the more common of the valves. Normally Open (N.O.)- Normally open valves are open when at rest (unenergized). We offer a variety of solenoid valves of different sizes, materials, and acting mechanisms.