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Provide air chambers and manual air vent valves as indicated at all high
points in the [HTW][MTW] system. Provide a 15 mm 1/2 inch vent line from
each air vent to the nearest drain. Vent lines shall be provided with two
15 mm 1/2 inch bar stock globe valves as
indicated.
2.1.7
Valves; Gate, Globe, Ball, Check, Angle, and Control
All valve materials shall conform to ASME B16.34. Valve bodies shall be
carbon or stainless steel (Type 304 or 316) with stainless steel trim. All
valves shall be Class 300. Ends shall be butt welding or raised face
flanged type conforming to ASME B16.34. Valve pressure and temperature
design values shall not be exceeded. The Contractor shall submit the
manufacturers recommended materials list for valves, packing, and gaskets
with certification that all meet the system design pressure @ maximum
operating temperature and the service as specified herein.
2.1.7.1
Globe type valves shall have outside screw and yoke with bolt bonnets, and
flat seats, but shall not be of the reversed-cup type. The stuffing boxes
shall be large and deep. Valves 50 mm 2 inches and larger shall have at
least six U or V type [teflon-impregnated braided asbestos] [_____] packing
rings, specifically designated as suitable for high-temperature water.
Valves smaller than 50 mm 2 inches shall have four or five rings. Spiral
or continuous packing will not be acceptable. A metal insert shall be
provided having proper clearance around the stem at the bottom of the
stuffing box and acting as a base for the packing materials. Packing
glands shall be furnished with liner of noncorrosive material and shall be
of one piece with not less than two bolts. Valves 32 mm 1 1/4 inches and
smaller need not have yokes or bolted screws and deep stuffing boxes.
Stems shall be provided with bevel above the disk for cutoff and repacking
valve under pressure when fully open. On the underside side of the bonnet
a pack-under-pressure bushing of stainless steel shall be provided. The
bushing shall be screwed into place.
2.1.7.2
Gate valves, wedge gate type, outside screw and yoke, valve body with
straight through ports without recesses except between seats to assure
minimum turbulence, erosion, and resistance to flow. The bonnet shall be
equipped with a bonnet bushing. The valves shall have a self-centering
male and female joint equipped with a gasket.
2.1.7.3
Temperature Control Valves
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NOTE: Provide valve operating conditions based upon
the type of control maintained at the central
heating plant for the distribution system, and the
arrangement of piping at the system terminal unit.
Three-way valves and balancing valves are not
recommended, nor any arrangement that may allow a
drop in temperature/pressure sufficient to cause
flash to steam. The delta P @ design load should
not be less than one half the available pressure
drop across the valve in order for the
SECTION 15184N
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