Direct Acting also known as poppet type solenoid valves will operate at zero pressure, they are a compact or miniature cost effective design. The magnetic core or armature is directly responsible for the ON OFF or open closed control of the solenoid valve as this rests over the orifice or flow path of the solenoid valve. Available in 2/2-way and 3/2-way versions with pressure ratings up to 200 Bar but will suffer a reduced flow
miniature series: AD6, AD8, AD10, AD12
Servo Assisted also known as pilot operated, floating diaphragm, floating piston and pilot assisted solenoid valves. These solenoid valves require a minimum pressure difference to operate i.e. a higher inlet pressure than outlet pressure (minimum pressure difference) which is typically 0.2 to 0.5 bar which is controlled via an internal pilot circuit to operate the open and close function of the solenoid valve. Brass pressure assisted solenoid valves are available in 2/2 way normally closed and normally open function with pressure ratings up to 200 Bar and typically offer good flow rates. Ideally suited for medium to high pressure applications and open to atmosphere general purpose systems.
Assisted Lift also known as Hung Diaphragm or Kick Pilot Solenoid Valves. These solenoid valves will operate from zero pressure differential offering good flow similar to a servo pressure assisted solenoid valves, however the diaphragm or piston is mechanically attached to the solenoid armature thus ensuring the valve opens fully regardless of pressure difference. These are ideally suited to closed loop and low pressure gravity fed systems where high flow is required combined with low differential pressures but are typically more expensive than servo assisted solenoid valves. These assisted operation brass solenoid valves are a reliable choice when minimum pressures are not known or if users what to ensure brass solenoid valve operation at all times.