06-06
4.
Provide an air flow control and balancing valve in the
exhaust air stream side to ensure constant air flow
through the exhaust air system.
5.
Coordinate the following accessories with the hood
manufacturer.
I.
Air tight damper on the exhaust side to isolate the
hood for service and maintenance.
II.
Air Monitoring Device: To sound an audible and
visible alarm at the hood and at the central ECC in
the event the flow varies more than plus or minus
5% of the normal value.
III.Air Flow Switch: Provide an air flow switch to sound
an alarm in the event of an interruption in exhaust
fan operation.
6. H14, Perchloric Acid Hoods: The perchloric acid hoods require
dedicated exhaust systems with the following requirements:
a. The exhaust air quantities (m3/min) (CFM) and pressure drops (Pa)
(Inch of Water Gage) for H14 hoods are listed below in Table 3.5.
Table 3.5
SIZE
MILLIMETERS
EXHAUST
PRESSURE DROP
1200 (48")
29 (1030)
156 (0.625")
---------------------------------------------
1500 (60")
38 (1355)
125 (0.50")
---------------------------------------------
1800 (72")
47 (1680)
187 (0.75")
---------------------------------------------
2400 (96")
66 (2355)
187 (0.75")
---------------------------------------------
b. Provide stainless steel (type 316) welded construction ductwork,
acid resistant metallic fan or metallic fan covered with inorganic
(polyurethane) coating, and explosion proof motor.
c. The ductwork shall be short, straight, and with minimum horizontal
runs, manifolds, and sharp turns.
The exhaust discharge shall
terminate by using a vertical discharge cap which extends well
above the roof eddy zone.
d. Coordinate cold water make-up connections and electrical power
supply for heat tracing requirements with other trades for the
washdown cycle for hood and ductwork.
e. Provide local (visible and audible) and central (Engineering
Control Center - ECC) alarms indicating status and failure.
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