Frick AcuAir Manual Download

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210.100-IOM (JUL 2018)

Page 44

ACUAIR

HYGIENIC AIR UNITS

MAINTENANCE

INSPECTING V-BELTS AND SHEAVES

Before a new set of V-belts are installed, inspect the condition
of the sheaves. Dirty or rusty sheaves impair the drive's

efficiency and abrade the belts, which result in premature

failure. (See Figure 51)

Inspect and clean sheaves; replace worn or damaged sheaves-
Worn sheave grooves are one of the principal causes of
premature belt failure.

• Clean dirty, dusty, or rusty sheaves. Feel sheave grooves

(wear gloves or use a rag) for nicks or burrs, and file them

smooth.

• Belts should ride in sheave grooves so that the top of the

belt is just above the highest point of the sheave. If the
grooves are worn to the point where the belt bottoms out
(a clue: check for shiny groove bottoms), the belts will slip
and burn.

• If the groove walls are “dished out,” the bottom corners

of the belt will quickly wear off and cause rapid failure.
Check groove wear by sight, touch, or with a groove gauge.

If grooves are “dished out” 1/32" or more - replace the

sheaves.

DISHING

ORIGINAL

GROOVE

“DISHING” OF GROOVE SIDEWALLS

SHORTENS BELT LIFE

LOW RIDING BELTS

INDICATE WORN GROOVES

BELTS SHOULD

RIDE LIKE THIS

Figure 51 – Sheave Inspection

Inspect

Sheave Alignment

NOTICE

An incorrectly aligned sheave can substantially shorten
belt life or overload blower and motor bearings, short

ening their life expectancy. A belt tensioned too tightly
can overload the motor electrically, causing nuisance
tripping of the motor overloads and/or motor failure and/
or shaft failure.

Sheave adjustment should be verified by placing a straight

edge across the sheave faces so that it touches all four points

of contact. Ordinarily, a misalignment of more than one-half of
one degree (one-eighth inch in one foot) will adversely affect
belt life. Improper sheave alignment produces uneven wear on
one side of the belt, causes the belt to roll over in the sheave
or throws all the load on one side of the belt, stretching or
breaking the cords on that side.

After the proper operating tension has been applied to the
belts, verify the following:

• Parallel position of the sheave shafts.
• Correct alignment of sheave grooves.
Sheave alignment and parallelism of shafts is very important.
Proper alignment helps equalize the load across the entire belt
width, thereby reducing wear and extending belt life. Figure
52 shows how to align a synchronous drive properly using a
straightedge (A) or a piece of string (B).

After aligning the sheaves, verify the rigidity of the supporting
framework. Shafts should be well supported to prevent
distortion and a resulting change in the center distance under
load. Do not use spring-loaded or weighted idlers.

Alignment Using A Straightedge (Preferred)

Place a straightedge against the outer edge of the sheaves.
Figure 52

(A) shows the four points where the straight edge

should touch the sheaves. The straight edge should cross the
sheaves at the widest possible part of the sheave.

Alignment Using A String

Tie a string around either shaft and pull it around and across
the outer edge of both sheaves. Figure 52 (B) shows how the
string should touch four points when the drive is properly
aligned.

Belt Replacement

Always replace belts as a matched set. Used belts will always
be longer because of stretcthing and new belts should never
be installed singly on a matched drive.

Follow the steps below to replace belts:

1. Release the tension on the belts by loosening the adjusting

nuts on the fan motor.

2. Remove old belts and verify the sheave alignment with a

straight edge.

3. Install the new belts on the sheave.

CAUTION

Never place the belts on the sheaves by using a screw

driver to pry the belt over the rim of the sheave.

TENSIONING V-BELTS AND SHEAVES

General Rules Of Tensioning:

1. Correct belt tensioning data is located on “V-belt Drive
Kit Label”, which is mounted on inside of fan access door.