operating temperature range of minus 40 degrees C to 93 degrees C
40 degrees F to 200 degrees F. Dampers shall be rated at not less
than 10 m/s 2000 fpm air velocity. All blade-operating linkages
shall be within the frame so that blade-connecting devices within
the same damper section will not be located directly in the air
stream. Damper axles shall be 13 mm 0.5 inch (minimum) plated
steel rods supported in the damper frame by stainless steel or
bronze bearings. Blades mounted vertically shall be supported by
thrust bearings. Pressure drop through dampers shall not exceed
10 Pa gage at 5 m/s 0.04 inch water gage at 1000 fpm in the
wide-open position. Frames shall not be less than 50 mm 2 inches
in width. Dampers shall be tested in accordance with AMCA 500-D.
c.
Operating links external to dampers (such as crank arms,
connecting rods, and line shafting for transmitting motion from
damper actuators to dampers) shall withstand a load equal to twice
the maximum required damper-operating force. Rod lengths shall be
adjustable. Links shall be brass, bronze, zinc-coated steel, or
stainless steel. Moving parts in contact with one another shall
be of different materials. Working parts of joints and clevises
shall be brass, bronze, or stainless steel. Adjustments of crank
arms shall control the open and closed position of dampers.
2.3.2
Valves
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NOTE: Avoid the selection of oversized control
valves. Select valve Cv so that maximum pressure
drops are used within constraints of available
pressures, pipe velocities, economy of design, and
noise criteria. Select steam valves using critical
pressure drop (0.45 of absolute pressure) where
available, and select connected equipment using
resultant pressure on downstream side of valve.
Size water system for a minimum drop through control
valves of 21 kPa 3 psi and include in hydraulic
calculations. List calculated Cv in schedules (not
manufacturer's listed Cv) to allow bidders to
personally select valves.
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2.3.2.1
Valve Assembly
Valves shall have stainless steel stems. Valves shall be ANSI Class 125 or
ANSI Class 150, as required by the following pressure-temperature design
criteria: 150 percent of the system operating pressure at the system
operating temperature. Valve leakage rating shall be 0.01 percent of rated
Cv. Class 125 copper alloy valve bodies and Class 150 steel or stainless
steel valves shall conform to ASME B16.5 as a minimum. Cast iron valve
components shall conform to ASTM A 126 Class B or C as a minimum.
2.3.2.2
Butterfly Valve Assembly
Butterfly valves shall be threaded lug type suitable for dead-end service
and for modulation to the fully closed position, with noncorrosive discs,
stainless steel shafts supported by bearing, and EPDM seats suitable for
temperatures from minus 29 degrees C to plus 121 degrees C minus 20 degrees
F to plus 250 degrees F. Valves shall have a manual means of operation
independent of the actuator.
SECTION 15910N
Page 41
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