Siebe MK-6800 SERIES Pneumatic Valve Actuator

Siebe MK-6800 Series Pneumatic Valve Actuator is a pre-owned proportional, linear pneumatic actuator designed to drive VB-series globe valves in HVAC and industrial control applications. It uses compressed air to position valve stems with proportional control and features a 50 square inch piston area, enabling robust actuation for typical valve trims; a linkage kit is included to connect the actuator to the valve stem. The unit uses a standard 1/4 inch NPT air inlet and is available in several MK-6800 variants, including spring-return configurations; for example, the MK-6821 variant specifies 8-13 PSIG actuation with spring return and linear motion. This actuator family is documented as compatible with VB valve families (VB-11 and VB-9XXX series) and is referenced in Schneider Electric/Invensys product literature, including linkage interfaces. The MK-6800 lineage traces through Schneider Electric’s data sheets and catalogs, connecting to legacy Barber Colman/MK actuation components used in HVAC controls and process-valve assemblies.