a.
Valves for 125 pound class steel piping shall conform to the
following:
(1) Sizes 65 mm 2-1/2 inches and less, bronze:
MSS SP-80, Type
1, 2, or 3, Class 125.
(2) Sizes 80 mm 3 inches through 300 mm 12 inches, cast-iron:
MSS SP-85, Type III and Type IV, Class 125.
b.
Valves for 150 pound class steel piping shall conform to the
following:
(1) Sizes 65 mm 2-1/2 inches and less, bronze:
MSS SP-80, Type
1, 2, or 3, Class 150 minimum.
(2) Sizes 80 mm 3 inches through 600 mm 24 inches, steel:
ASME
B16.34, Class 150 minimum, flanged ends.
c.
Valves for system operating pressure greater than 1.4 MPa 200 psi
shall be suitable for specified operating conditions, but not less
than 300 pound class. Valves 50 mm 2 inch and smaller shall be
forged steel with socket welded ends. Valves 65 mm 2-1/2 inches
and larger shall be steel and shall have butt welded ends. Valves
shall have renewable flat metal seats.
2.26.7.4
Steam Pressure Reducing Valves
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NOTE: Single-seated valves should be used when a
dead-end shutoff of the steam is required. When a
thermostatically-controlled valve is installed after
and near the reducing valve in a manner to cut off
the passage of steam, the single-seated valve should
be used. Double-seated valves may be used where the
low (reduced) pressure lines will condense enough
steam to offset normal leakage through the valve.
Under conditions of widely varying initial pressure,
double-seated valves usually give closer control of
reduced pressure.
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Reducing valves designed for the working pressure shown, but not for less
than 1.4 MPa 200 psig, shall be provided wherever indicated or required.
Each reducing valve shall be adjusted to maintain the desired terminal
pressure, regardless of fluctuations in the initial pressure. The valves
shall be [single seated] [doubled seated], spring-loaded, quiet in
operation, and shall not stick internally. Pilot-operated valves or other
controllers using steam or compressed air for operating medium shall be
provided. Valves 65 mm 2-1/2 inches and larger shall be cast steel,
cast-iron, or semisteel as required for the steam pressure. Valves 50 mm 2
inches and smaller shall be bronze. Valve trim for iron body valves shall
be stainless steel, nickel copper, or other approved corrosion-resisting
material. All parts subject to wear shall be readily renewable. Valves
shall have seats and plugs faced with a cobalt-tungsten carbide mixture, or
made of heat-treated stainless steel or a high chromium steel designed to
resist erosion. Seat and plug facing shall have a Brinell hardness of not
less than 450. Each valve shall be installed with a strainer, a
three-valve bypass, and a safety relief valve as indicated. Where pressure
SECTION 15559A
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