Why Not Learn Basic Solenoid Valve Operation?

Update:18 Nov 2021

To understand the theory and benefits of hit and hold electrical control, we must first have a basic understanding of direct acting Steam Solenoid Valve design and operation. A typical direct acting solenoid valve is comprised of the following sub-components:

Insulated copper coil
Pole, flux bracket, flux bushing, armature
Plunger seal, stem, o-ring, body


Note: Iron core/solenoid components are shown in blue. Pneumatic components are in green and the return spring is orange.

The Benefits of Using "Hit and Hold" Electrical Control on Direct Acting Solenoid Valve_Direct Acting Solenoid Valve_Parker Precision Fluidics

When an electrical potential is applied to the coil and current flows through the copper conductor, the coil component transforms into a magnet or solenoid. The magnetic field generated from the solenoid is then captured and directed through the iron core components of the valve as illustrated in figure 2.

Figure-2: Magnetic field captured and directed through iron core components

The Benefits of Using "Hit and Hold" Electrical Control on Direct Acting Solenoid Valves_Magnetic-Field_Parker Precision Fluidics

As the magnetic field is established, opposing magnetic poles are formed between the armature and pole subcomponents as illustrated in figure 3. (Also illustrated are the lines of magnetic force, or flux density, connecting the poles in green and blue).

Figure-3: Magnetic pole locations

The Benefits of Using "Hit and Hold" Electrical Control on Direct Acting Solenoid Valves

The resulting magnetic force generated between these components is inversely proportional to the distance squared between the two components as illustrated in Figure-4. This distance is referred to as the magnetic gap.

Figure-4: Magnetic force on the armature

The Benefits of Using "Hit and Hold" Electrical Control on Direct Acting Solenoid Valves_Magnetic Force on armature_Parker Precision Fluidics

When the magnetic force on the armature exceeds the installed load of the return spring, (and any supplemental pneumatic differential force), the armature will actuate/move to contact the pole as illustrated in Figure-5. Specific to the 2-way/2-position solenoid valve illustrated in Figure-5, once the actuation occurs, the fluidic path is opened between the valve ports.

Figure-5: Actuated valve state (open fluidic path)

The Benefits of Using "Hit and Hold" Electrical Control on Direct Solenoid Valves_Actuated valve state_Parker Precision Fluidics

To close the fluidic path and return the valve to a normally closed state, the voltage source is removed/disconnected from the coil. Once the power source is removed, the magnetic field collapses, and the spring returns the armature to the normally closed position.

It is important to understand that solenoid valves are current-driven devices where the magnetic field strength of the solenoid is proportional to the amount of current traveling through the coil. Therefore, the two-valve states described above, (actuation and drop-out), will ultimately be defined by the effective current traveling through the coil.

Now that you have an understanding of the basic solenoid valve operation, read the second part of this three blog series titled: Capitalizing on Valve Mechanics. This second part gives an in-depth understanding of how these principles tie into reducing consumption and heat generation within the solenoid valve.