18
Air Handling Unit
Installation, Operation, and Maintenance Manual
April 2021
i) Do not open “8V” sheaves more than 8 ½ turns
j) Tighten BOTH locking screws “A” in the outer
locking ring to 100-110 LB-IN.
k) Verify sheave alignment, replace belts and apply
sufficient belt tension to prevent slippage.
Figure 12-1.
Single-Groove Variable-Pitch Key-Type Sheaves –
Figure 12-2
a) Loosen setscrews “Y” and “C” in moving parts
of sheave and pull out external key “E”. (This
key projects a small amount to provide a grip for
removing.
b) Adjust sheave pitch diameter for desired speed
by opening moving parts by half or full turns
from closed position. Do not open more than
five full turns for “A” belts or six full turns for “B”
belts.
c) Replace external key “E” and tighten set screw
“Y” over key and set screw “C” into keyway in
fixed half of the sheave. Wrench torque 110 in.
lbs. min – 130 in. lbs. max.
d) Verify sheave alignment, install belts and adjust
belt tension. (Do not force belts over grooves.)
e) Future adjustments should be made by
loosening the belt tension and increasing or
decreasing the pitch diameter of the sheave
by half or full turns as required. Readjust belt
tension before starting drive.
f) Be sure that all keys are in place and that all
set screws are torqued properly before starting
drive. Check set screws and belt tension after 24
hours of service.
Figure 12-2.
Key “E” projects to provide a
grip for removing.
Do not operate sheave with
flange projecting beyond the
hub end.
Two-Groove Variable-Pitch Key-Type Sheaves –
Figure 12-3
Each flange of the sheave has a small notch on the
O.D. of the flange. This mark is located directly over
the keyway on the two adjustable flanges and over
one of the keyways on the non-adjustable (center)
flange. To obtain proper adjustments:
a) Loosen setscrews “Y” in moving parts of sheave
and pull out external key “E”. (This key projects a
small amount to provide a grip for removing.)
b) Tighten both adjustable flanges to their fully
closed position.
c) Locate the file mark over the keyway on the
center flange.
d) Open each adjustable flange until its notch is
adjacent to the notch on the center flange. Be
certain that neither adjustable flange is opened
more than one full turn.
e) From the position obtained in step 4, open each
adjustable flange the same number of full or
half turns until the desired flange spacing is
obtained. Do not open more than five full turns
for “A” belts or six full turns for “B” belts.
f) Replace external key “E” and tighten setscrews
“Y” over key. Wrench torque 110 in. lbs. min. –
130 in. lbs. max.
g) Verify sheave alignment, install belts and adjust
belt tension (Do not force belts over flanges).
h) Future adjustments should be made by
loosening the belt tension and increasing or
decreasing the pitch diameter of the sheave
by half or full turns as required. Readjust belt
tension before starting drive.
i) Two groove sheaves must have both halves
adjusted by the same number of turns from the
position established in step 4 to insure the same
pitch diameter.
j) Be sure that all keys are in place and that all
set screws are torqued properly before starting
drive. Check set screws and belt tension after 24
hours of service.
Figure 12-3.
Key “E” projects to provide a
grip for removing.
Do not operate sheave with
flange projecting beyond the
hub end.
