Servo-assisted pilot solenoids:

This principle uses a direct-acting plunger valve as the pilot valve and a flexible diaphragm as the seal for the main seat.  As soon as the pilot valve opens, the fluid chamber above the diaphragm is discharged.  The media pressure within the diaphragm raises the diaphragm and opens the valve so that the medium can flow. If the pilot valve is closed, the media pressure above the diaphragm builds up again through the small pilot tube/hole opening and the closing process is assisted by the closing spring.  Minimal differential pressure between the inlet and outlet is necessary for complete opening and closing.

For the SSSV5012 solenoid valve, the pressure drop at a flow rate of 200 lpm is approximately 0.12 bar (1.72 psi or 11.89 kPa). This value is calculated using the valve's Kv factor, which represents its flow capacity when fully open.

It is important to understand the difference between the valve's minimum operating pressure and the pressure drop during flow. The SSSV5012 is a pilot-assisted valve, which means it requires a minimum pressure differential (typically 0.5 bar) to open. This pressure differential is needed to power the valve's internal mechanism. However, once the valve is fully open and the fluid is flowing, the pressure drop is a separate characteristic determined by the flow rate and the valve's overall resistance, as reflected in its Kv value.

Application:
The main uses for these valves are clean liquid or gaseous media such as compressed air, water, hydraulic oils, etc.  The small pilot valve makes them less expensive than direct-acting valves for use with higher pressures and larger diameters.
Since pilot-controlled valves (also: servo-assisted valves) have only a small pressure equalisation hole in the diaphragm, up steam strainer is recommended.  Coil power requirements (amps) are lower than direct acting due to less force needed to open the valve.