large numbers of valves and dampers may be more cost
effective than using electric actuators. Include
the cost of the air compressor, power, air
distribution, and operation and maintenance in the
life cycle cost analysis to justify pneumatic over
electric actuation.
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2.3.3.1
Electric Actuators
Provide direct drive electric actuators for all control applications,
except where indicated otherwise. When operated at rated voltage, each
actuator shall be capable of delivering torque required for continuous
uniform motion and shall have end switch to limit travel, or shall
withstand continuous stalling without damage. Actuators shall function
properly with range of 85 to 110 percent of line voltage.
Provide gears manufactured from steel, copper alloy, fiber, or reinforced
nylon. Provide hardened steel running shafts in sleeve bearing of copper
alloy, hardened steel, nylon, or ball bearing. Provide two-position
actuators of the single direction, spring return, or reversing type.
Provide proportioning actuators capable of stopping at all points in the
cycle and starting in either direction, from any point.
Provide reversing and proportioning actuators with limit switches to limit
travel in either direction unless operator is stall type. Actuators shall
have a simple switch for reversing direction, and a button to disengage
clutch for manual adjustments. Provide reversible shaded pole, split
capacitor, synchronous, or steper type electric motors.
2.3.3.2
Provide piston or diaphragm type actuator, where indicated with full range
or split range springs to provide required sequence specified and fail safe
operation.
2.3.4
Output Signal Conversion
2.3.4.1
Electronic to Pneumatic Transducer
Electronic to pneumatic transducer shall convert 4 to 20 mA or 0 to 10 VDC
digital controller output signal to a proportional 0 to 20 psig pressure
signal (operator scaleable). Accuracy shall be 1.0 percent or better.
Linearity shall be 0.1 percent. Transducer shall have feedback circuit
that converts pneumatic signal to a proportional 4 to 20 mA or 0 to 10 VDC
signal.
2.3.4.2
Pneumatic to Electronic Pressure Transducer
Pneumatic to electronic transducer shall convert 0 to 20 psig signal to a
proportional 4 to 20 mA or 0 to 10 VDC signal (operator scaleable). Supply
voltage shall be 24 VDC. Accuracy shall be 1.0 percent or better.
Linearity shall be 0.1 percent.
SECTION 15910N
Page 44
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