2.3.2.8
Valves for Steam Service
Entire bodies for valves 40 mm 1 1/2 inches and smaller shall be brass or
bronze, with threaded or union ends. Bodies for valves from 50 to 80 mm 2
to 3 inches inclusive shall be of brass, bronze, or iron.
Bodies for
valves 100 mm 4 inches and larger shall be iron. Bodies for 50 mm 2 inch
valves shall have threaded ends. Provide bodies for valves 65 mm 2 1/2
inches and larger shall with flanged-end connections. Steam valves shall
be sized for [103 kPa (gage)] [15 psig] [_____] inlet steam pressure with a
maximum [90 kPa] [13 psi] [_____] differential through the valve at rated
flow, except as indicated otherwise.
2.3.2.9
Valves for High Temperature Hot Water Service
Valves for high temperature hot water service above 121 degrees C 250
Degrees F. Valve bodies shall conform to ASME B16.34 Class 300. Valve and
actuator combination shall be normally closed. Bodies shall be carbon
steel, globe type with welded ends on valves 25 mm 1 inch and larger.
Valves smaller than 25 mm 1 inch shall have socket-weld ends. Packing
shall be virgin polytetrafluoroethylene (PTFE).
Internal valve trim shall
be Type 316 stainless steel. Water valves shall be sized for a [21 kPa] [3
psi] [_____] through the valve at rated flow, except as indicated
otherwise. Select valve flow coefficient (Cv) for an actual pressure drop
not less than 50 percent or greater than 125 percent of the design pressure
drop at design flow.
2.3.3
Actuators
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NOTE: Indicate on drawings and in sequence of
operation, the normal position of each actuator
without power or control signal. Select normal
position with regard to power loss, freezing,
moisture damage, and smoke or fire transmission.
Indicate power return actuators where necessary for
actuator timing and process requirements, or where
rapid valve or damper opening or closing would be
hazardous. Indicate spring return for actuators
where normal position, but not timing, is required.
Spring return closed is often desirable for steam
actuators. Indicate requirements for standby or
emergency power for actuators and devices
controlling the actuators.
Indicate on drawings when a coordinated action is
required. For example, coordinated action may be
required when one control output may control both
the hot water valve (3 - 7 psig or 4 to 10 ma) and
the chilled water valve (8 - 13 psig or 12 to 18 ma).
Note: Electric actuators are generally preferable
to pneumatic actuators for reduced maintenance,
quality of control, and integration into DDC.
Pneumatic actuators should be used in hazardous
areas. They may be used in the retrofit of existing
systems that use pneumatic actuators and costs
prevent total actuator replacement.. In general,
pneumatic actuation of large valves (greater than 4
inch), large dampers (greater than 9 sq. ft.), and
SECTION 15910N
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