Backflush valve is a 4-step valve designed for the change of eluent flow in the packed column and for blowoff of heavy components from the entry of the column back into detector. The valve is attached to the lower panel (bottom) of the module, meanwhile taking the temperature of column thermostat. Two upper fittings (see pic.) serve for column connection, two other ones are connected to evaporator and detector.
Photo: Gas scheme of backflush valve
Backflush valve can be automated. Valve drive consists of gear reducer with position sensor located on motor shaft.