Draft Fans

supplier shall submit to the Contracting Officer satisfactory evidence that

the fan furnished meets the requirements of AMCA 210. Acceptable evidence

of meeting the requirements of this standard will be the AMCA Certified

Rating Seal or a certified inspection report from an independent testing

laboratory indicating that the fan conforms to the requirements of AMCA 210.

Fans shall be centrifugal with backward curved blades or radial tip

blades. Each fan shall be sized for operation at an elevation of [_____]

meters feet, with an output volume and equipment, leaks, and temperature

and elevation corrections for a dirty boiler with worst ambient conditions,

all at full combustion. In addition, fan sizing shall include margins of

10 percent excess volume against a 21 percent static pressure and air

temperature 22 degrees C 40 degrees F above operating temperature. Induced

draft fans shall be designed for handling hot flue gas at the maximum

boiler outlet temperature adjusted for boiler surface fouling. Fans shall

be of the [single] [or] [double] width centrifugal type. [When the fan is

a double-width centrifugal type, it shall have a double inlet.] The

direction of fan rotation shall be [clockwise] [or] [counterclockwise] as

determined from the drive side of the fan. The direction of discharge

shall be [top horizontal] [top angular down] [down blast] [bottom angular

down] [top angular up] [up blast] [bottom angular up] [or] [bottom

horizontal]. The position of inlet box shall be [45] [90] [135] [180]

[225] [270] [315] [or] [360]. The fans shall have a static efficiency of

not less than 0 percent in standard air at best efficiency point. Fan

wheel shall be constructed of [steel] [or] [aluminum]. The shaft shall be

turned, ground, and polished. The fan wheel and shaft assembly shall be

balanced statically and dynamically. The complete rotating assembly of the

fan shall be dynamically balanced within the limits of the following

formula:

Vibration displacement

-

1.620

__________________________

mills-peak-to-peak

revolutions per minute

Noise levels for fans shall not exceed 85 dBA at a 914.4 mm 3 foot station.

The fan housing shall be carbon steel of a nominal thickness not less than

that selected in Table I.

TABLE I

HOUSING GAUGES

Nominal fan diameter

Sides

Scroll in inches

____________________________________________________________________________

up to 23

3.42 mm (10 gauge)

24-27

4.55 mm (7 gauge)

73-over

6.35 mm (1/4 inch)

TABLE I

HOUSING GAUGES

Nominal fan diameter

Sides

Scroll in inches

____________________________________________________________________________

up to 23

10 gauge

24-27

7 gauge

73-over

1/4 inch

Scroll and sideplate joints shall be continuously welded. The housing

shall be reinforced with steel member to provide a rigid structure and to

SECTION 15846A

Page 32