DAMPER ACTUATOR (MOTOR) Damper actuators position automatic dampers via a control pressure entering the damper actuator through the air connection. The air pressure is distributed evenly over the face of the diaphragm, exerting a total force on the diaphragm cup, which transfers that force to the shaft. The spring resists the force generated by the air pressure, returning the actuator to its normal position when air pressure is removed. Damper actuators have a spring range (throttling range). The spring range on an actuator’s specification sheet is based on the actuator with no load. An actuator with a spring range of 8 PSIG to 13 PSIG will start to move at 8 PSIG and reach the end of its stroke at 13 PSIG. There are many spring ranges with the most common being 8# to 13#, 5# to 10#, 3# to 7#, 2# to 12#, 3# to 13# and 10# to 15#. Some Barber Colman and some older Powers damper actuators allow shifting of the spring range via an adjusting nut, which has the shaft running through its middle. The diaphragms are normally replaceable, but not always. Springs in pneumatic actuators can be potentially very dangerous; therefore, you should respect the power stored in the spring while disassembling an actuator. When replacing a diaphragm, remove air pressure from the actuator and then back off the actuator housing nuts just enough to separate the actuator housing cap from the actuator housing. Push on the actuator housing with your hand giving you a sense of the power of the spring. If this is difficult to push, take appropriate steps to protect yourself replacing the actuator housing bolts, one at a time, with longer bolts and nuts for adjustment. Do not apply air pressure higher than recommended by the manufacturer, as you may: -1- damage the actuator -2- injure or kill yourself or others ACTUATOR ACTUATOR HOUSING HOUSING BOLT DIAPHRAGM CUP (4 TO 8 TYPICAL) SPRING RETENTION NUT SHAFT AIR CONNECTION ACTUATOR HOUSING CAP RETURN SPRING DIAPHRAGM 2.10
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