Siemens 331-4810 Damper Actuator, Pneumatic, Number 3, 2 3/8" Stroke, 8 to 13 psi, Front Mounting. Siemens Nos. 3, 4 and 6 Pneumatic Damper Actuators are heavy-duty, spring return actuators designed to drive large dampers and other applications requiring large diaphragm area and long stroke.
