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NOTE: Avoid 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
(.45 of absolute pressure) where available, and
select connected equipment using resultant pressure
on downstream side of valve. List calculated Cv and
flow rate in schedules (not manufacturer's listed
Cv) to allow bidders to personally select valves.
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2.3.1
Valve Assembly
Valves shall have stainless steel stems and stuffing boxes with extended
necks to clear the piping insulation. Valve bodies shall be designed for
not less than 862 kPa (gage) 125 psig working pressure or 150 percent of
the system operating pressure, whichever is greater. Maximum rated shutoff
pressure of the valve shall exceed the rated deadhead pressure of the pump
that supplies it. Valve leakage rating shall be 0.01 percent of rated Cv
for soft-seated valves and 0.05 percent for metal-to-metal seated valves.
Class 125 copper alloy valve bodies and Class 150 steel or stainless steel
valves shall conform to ASME B16.5 as a minimum. Components of cast iron
valves shall conform to ASTM A 126 Class B or C as a minimum.
2.3.2
Butterfly Valve Assembly
Butterfly valves shall be threaded lug type suitable for dead-end service,
and for modulation to the fully closed position, with carbon steel bodies
or cast iron Class 125 and noncorrosive discs, stainless steel shafts
supported by bearings, and EPDM seats suitable for temperatures from minus
29 degrees to plus 121 degrees C. 20 degrees to plus 250 degrees F. Valves
shall have a manual means of operation independent of the actuator.
2.3.3
Two-Way Valves
Two-way modulating valves shall have equal percentage characteristics.
2.3.4
Three-Way Valves
Three-way valves shall provide constant total flow throughout full plug
travel.
2.3.5
Duct-Coil and Terminal-Unit-Coil Valves
Control valves with either flare-type or solder-type ends shall be provided
for duct or terminal-unit coils. Flare nuts shall be provided for each
flare-type end valve.
2.3.6
Valves for Chilled Water, Condenser Water, and Glycol Service
ASME B16.1. Bodies for valves 50 mm 2 inches and smaller shall be brass or
bronze, with threaded-end or union-end connections.
Bodies for valves from
65 mm 2.5 inches and larger shall be cast iron. Bodies for valves 65 mm
2.5 inches and larger shall have flanged-end connections. Internal valve
trim shall be brass or bronze except that valve stems may be Type 316
stainless steel. Water valves shall be sized for a [21 kPa] [3 psi]
SECTION 15901N
Page 17
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