maintenance. Fans shall be suitable for continuous operation at full or
part load. The fans and their ducts, flow-regulating devices and dampers
shall be coordinated to give an installation which will be capable of
operation without excessive vibration, fan noise, or air or gas vibrations.
This satisfactory performance shall be maintained throughout the entire
load range of the fans including operation at minimum flow settings with
cold air. Fans over 19 kW 25 hp shall be two-bearing design with rotor
suspended between bearings with no overhung wheels.
2.11.4.1
Fan Housing
Provide split housing so the rotor is accessible and removable for normal
maintenance without disconnecting the housing from the inlet or outlet
ducts or foundation and without moving the motor. Shape the housing for
maximum streamline flow from inlet to outlet. Construct from mild steel
plate. Brace with structural steel welded to the housing and designed for
sufficient strength to prevent warping and excessive vibration under
operating conditions. Provide with gas-tight inspection doors. Provide
with inlet and outlet connections of structural angle flanges for welding
to similar flanges on the ductwork with bolts provided and used for
alignment only, or for connections to similar flanges on the ductwork by
means of gaskets and bolts. Bolts shall be spaced not more than 65 mm 2
1/2 inches apart. Provide with a 50 mm 2 inch drain pipe connection welded
to the lowest point of the fan scroll. Provide nipple and cap. Housing
will be supported from a concrete base. Housing shall be designed so a
minimum distance of 600 mm 24 inches will exist between the bottom of the
housing and the foundation to permit application of insulation and access
to the housing drain connection. Shop paint fan housings in accordance
with the specifications for painting of the ductwork to which they connect.
2.11.4.2
Fan Rotors and Shafts
**************************************************************************
NOTE: Rotors shall be balanced statically and
dynamically so that vibration displacement at the
bearings measured on the shaft at full load and full
speed with a clean rotor will not exceed the
following.
Maximum Vibration
Rotor Speed, rpm
Displacement, mm
Up to 600 ................. 0.051
600 to 900 ................ 0.038
Above 900 ................. 0.025
Maximum Vibration
Rotor Speed, rpm
Displacement, Inches
Up to 600 ................. 0.0020
600 to 900 ................ 0.0015
Above 900 ................. 0.0010
Weight adjustment for balancing shall be by either
the addition or the removal of metal.
**************************************************************************
Fan rotors shall be designed and constructed to keep stresses from rotation
SECTION 15864N
Page 76
Previous Page
