at 748 mm 29.92 inches of mercury and 0 degrees C0 degrees C 32 degrees F.
The air filter gage shall be provided for measuring resistance in mm In.W.G.
to air flow through the air filter. The gage shall be of the inclined
tube differential type equipped with three-way angle type valve for venting
to atmosphere. The case shall be of corrosion resisting material and shall
have dial with gradations. It shall be provided with necessary lengths of
6 m 1/4 inch copper or aluminum tubing, two static pressure taps, two
toggle bolt mounting assemblies, and two additional bottles of red gage oil.
3.3.5.2
Butterfly Valve
Butterfly valve and operators shall conform to AWWA C504, except as
modified herein, and shall have rubber seats which are recess-mounted and
clamped into the valve body. Each valve shall be shop-tested for leakage
with the disc in the horizontal plane, with zero pressure downstream, and
with an upstream gage pressure of 345 kPa 50 psig, all in accordance with
testing requirements of AWWA C504 for butterfly valves. The upper surface
of the disc shall be visible and covered with a pool of water. Air
pressure as stated shall be applied to the lower face of the closed disc
for a period of 5 minutes, during which period there shall be no indication
of leakage past the valve disc as revealed in the form of bubbles in the
water pool on top of the disc. Valve operator shall be hand-wheel, lever,
or chain operated.
a.
Valve Body: Valve body shall be constructed of close-grained cast
iron conforming to ASTM A 126, Class B, with integrally cast hubs
for shaft bearing housing of the through boss-type. Permanently
self-lubricating body bushings shall be provided and shall be
sized to withstand bearing loads. A stuffing box of liberal
dimensions shall be provided at the operator end of the vane
shaft, arranged so that the packing can be replaced by removing
the bronze follower without removing the operator.
b.
Discs: Discs shall be positively secured to the shaft with keys
and/or pins of Type 316 stainless steel. Seating edge of the disc
shall contact the seat in the body for full 6.28 rad 360 degrees
without penetration of the seating surface by the shaft. Discs
for valves with rubber seat mounted in the body shall be of a
symmetrical one-piece cast design of alloy cast-iron (14 percent
nickel, 6 percent copper, 2 1/2 percent chromium) with no external
ribs. Discs for valves with rubber seat mounted on the disc shall
be cast iron conforming to Class 40.
c.
Valve Shaft: Valve shaft shall be of Type 304 stainless steel and
designed for both torsional and shearing stresses when the valve
is operated under its greatest dynamic or seating torque.
3.3.5.3
Pressure Relief and Unloading Valve
A pressure relief and unloading valve shall be provided for each positive
displacement blower in the air piping on the discharge side and shall
perform the dual function of pressure relief and unloading the blower for
start-up. The valve shall have a cast-iron body with integral valve seat,
cast-iron disc, and steel spring for pressure setting. Valve shall be
furnished for a pressure setting of not more than 10 percent above maximum
operating pressure, but shall also have an operating nut or wheel for field
adjustment of pressure setting. Pipe connection shall be flanged or
screwed.
SECTION 11375N
Page 105
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