Troubleshooting

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Troubleshooting
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Leading Causes of Belt Failure

• Improper Tensioning
• Misalignment
• Improper Equipment (damaged pulleys)
• Abrasive Conditions
• Unusual Loading Cycles
• Operating Temperature

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Belt Failure Modes
Rapid V-Belt Wear
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V-Belt Drive Troubleshooting Guide
Symptom 1 Rapid V-Belt Wear
PROBABLE CAUSE
ACTION
Rubbing belt guard. Sheave misalignment. Worn or
damaged sheave grooves. Wrong belt cross section
or type. Sheave diameter too small. Improper
V-belt installation. Overloaded drive. Belts
improperly stored. Mismatched belts. Replacing
one belt. V-belt slipping.
Check guard clearance. Correct sheave
alignment. Check, replace sheaves. Check
dimensions, replace belt. Use larger diameter
sheave. Replace belts (do not pry belts). Reduce
load. Use new set of V-Belts. Replace with
matched set. Replace complete set. Increase
tension.
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Belt Failure Modes
Side Wall Damage
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V-Belt Drive Troubleshooting Guide
Symptom 2 V-Belts Turned Over in Sheave Groove
PROBABLE CAUSE
ACTION
Broken cords in V-belts,belts pried over
sheaves. Overloaded drive. Defective cord
construction in V-belt. Impulse loads.
Determine how belt was installed (Replace belts,
do not pry belts over sheaves). Reduce
loads. Check for narrow spot in belt,replace
belts. Use banded V-belts orspring-loaded idlers.
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Belt Failure Modes
Glazed or burnt sidewall
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V-Belt Drive Troubleshooting Guide
Symptom 3 V-Belt Slippage
PROBABLE CAUSE
ACTION
Lack of tension. Overloaded drive. Sheave worn,
belt bottomingin groove (Shiny sheavegroove
bottom). Sheave grooves too wide,belts
bottoming in grooves. Oily drive conditions.
Increase tension. Reduce loads. Replace
sheave. Use belt with larger cross sectionor
replace sheave. Correct the unnecessary oil
orgrease condition.
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V-Belt Drive Troubleshooting Guide
Symptom 4 V-Belt Squeal
PROBABLE CAUSE
ACTION
Lack of tension. Overloaded drive. Insufficient
arc of contact.
Increase tension. Reduce loads. Increase center
distancebetween sheaves.

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• Belt Failure Modes

Cracked Belt
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V-Belt Drive Troubleshooting Guide
Symptom 5 Cracked V-Belts
PROBABLE CAUSE
ACTION
Belt slippage. Excessive heat.
Increase belt tension. Provide adequate
ventilation and check belt tension.

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V-Belt Drive Troubleshooting Guide
Symptom 6 Repeated V-Belt Fracture
PROBABLE CAUSE
ACTION
Shock loads. Heavy starting loads. Improper
V-belt installation,belts pried over sheaves.
Increase V-belt tension.Heavier drive may be
required. Increase V-belt tension.Heavier drive
may be required Determine how belt was
installed.(Replace belts, do not pry beltsover
sheaves.)
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Troubleshooting Guide
Symptom 7 Flat Belt Drive Operating Improperly
PROBABLE CAUSE
ACTION
Belt slippage. Pulley with excessive
crown. Center Distance too long. Slippage on flat
pulleys. Excessive shock loads.
Increase belt tension. Remove excessive
crown. Use shorter center distance. Use
V-Belts. Use V-Belts.
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Synchronous Troubleshooting Guide
Symptom 8 Synchronous Belt Noise or Vibration
PROBABLE CAUSE
ACTION
Misaligned drive. Incorrect belt tension. Belt
speed too high. Incorrect belt profile for
sprocket. Sprocket diameter too small. Overloaded
drive.
Correct drive alignment. Adjust tension to
recommended value. Redesign drive.. Use proper
belt/sprocket combination. Redesign drive using
larger diameter sprockets. Reduce the load.
Heavier drive may be required.
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Synchronous Troubleshooting Guide
Symptom 9 Synchronous Belt Edge Wear
PROBABLE CAUSE
ACTION
Sprocket flange damaged. Belt too wide. Belt
tension too low. Improper tracking. Belt rubbing
drive guard.
Replace the sprocket. Use proper width belt or
sprocket. Adjust belt tension to recommended
values. Correct drive alignment. Check guard
clearance.
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Synchronous Troubleshooting Guide
Symptom 10 Synchronous Belt Tensile Break
PROBABLE CAUSE
ACTION
Shock loads. Improper belt handling or
storage. Forcing belt onto drive during
installation. Debris or foreign object in drive.
Redesign drive. Store in original package. Do not
crimp. Do not pry belt over sprockets. Remove
debris and check guard.
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Troubleshooting Synchronous Drives
Normal Failure Mode The end of the useful life of
a synchronous belt is most often
characterized by even tooth fabric wear and
eventually, tooth separation. Any other type of
belt failure could be an indication that there
are other problems present within the drive.
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Troubleshooting Synchronous Drives
Noise Noise can be an issue with synchronous belt
drives. The noise created by a drive increases
with the belt speed. To minimize noise make sure
the drive is aligned and tensioned properly.
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Troubleshooting Synchronous Drives
Sprocket Wear Sprocket wear can have a great
impact on belt wear. When unusual belt wear
occurs, the first step is to inspect the
sprockets. Excessive tooth wear is obvious with
visual inspection. Use a pi tape to evaluate
sprocket wear. The best sprocket material for
minimizing wear is gray cast or ductile iron. A
softer material may wear more quickly. Abrasive
environments, drive misalignment, and improper
tensioning can lead to rapid belt and sprocket
wear.
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Troubleshooting Synchronous Drives
Sprocket Misalignment The leading symptoms of
belt misalignment are excessive edge wear
(exposing or fraying the tensile cord), running
off the flange, snub breaking (in a stair step
pattern) and excessive drive noise. If sprockets
are verified to be in alignment and problems
persist, frame and bearing supports should be
checked for rigidity. The frame may be flexing
during operation, causing drive misalignment.
Proper Parallel Horizontal Vertical
(Off-Set) Angular Angular (Pigeon-Toed)
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Troubleshooting Synchronous Drives
Excessive Tension Excessive tension of a
synchronous drive will cause premature belt
failure due to wear and high tooth stress. The
noise level of a synchronous belt drive will
increase considerably if the belt is
over-tensioned. Excessive tension produces
fabric wear between the belt teeth exposing the
tensile cord and wearing of the sprocket teeth.
If tooth shear, snub break, or tooth jump occurs
under correct tension, the drive may be
under-designed.
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Troubleshooting Synchronous Drives
Under-Tensioning Under-tensioning is the most
common cause of belt failure. It can cause
premature belt wear, tooth jump and belt failure.
Belt wear is characterized by fabric wear on the
tooth flank which can accumulate material between
the teeth. Jumping can cause tooth shear and
tensile cord breakage. Tooth jump or ratcheting
occurs when the belt teeth climb up and out of
the sprocket grooves. The most obvious indication
of tooth jump is a machine gun like sound.
Although there may be no visible evidence of
damage, the capabilities of the belt are likely
destroyed after tooth jump.
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Troubleshooting Synchronous Drives
Non-Rigid Frame A less common cause of belt
failure is a non-rigid frame which allows the
center distance to vary when a load is applied.
The supporting structure should be checked for
rigidity to make sure the shafts are not
deflecting during periods of peak loading and
causing tooth jump.
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Troubleshooting Synchronous Drives
Overloaded Drive Severe overload conditions can
cause fabric and sprocket wear on the pressure
surfaces, belt tooth shear, snub break, tooth
jump and a resulting increase in noise level.
These conditions generally force a drive
re-design to provide additional capacity. A wider
belt will sometimes accomplish this.
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Troubleshooting Synchronous Drives

• Excessive Shock Loads / Start-Up Loads
• Some applications are not conducive to
  synchronous belt drives
• Use special consideration on drives with
  excessive or extreme shock loads or start-up
  loads - Some drives may require soft start
• Positive drive engagement and the high modulus
  cord (low-stretch) make synchronous belts less
  tolerant of severe shock loads than v-belts which
  allow slippage
• If you require the characteristics of
  synchronous belts in a shock load application,
  an RPP Panther synchronous belt is your best
  choice in these situations

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Troubleshooting Environmental Problems
Belt Deterioration The synchronous belt can
deteriorate when operated in caustic or acidic
atmospheres, environments saturated with vapors
from hydrocarbon solvents, and ambient
temperatures above 185F or less than -30F.
Specially constructed belts may provide
satisfactory service in a number of applications
not suitable for stock belts.
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Troubleshooting Environmental Problems
Excessive Heat Carlisle standard rubber
construction synchronous belts are compounded
for moderate resistance to heat and should give
adequate service life under normal conditions.
The operating limits of a standard construction
synchronous belt range from a minimum of -32F to
200F ambient temperature (230F intermittently).
Polyurethane synchronous belts are only capable
of 185F.
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Troubleshooting Environmental Problems

• Environments with Excessive Debris
• Synchronous belts should not be used in
  environments where excessive debris is present
• Debris can be more damaging to a synchronous
  belt drive than to a v-belt drive, which has a
  tendency to eject debris from the sheave grooves
  as the drive operates
• Large debris trapped between a synchronous belt
  and pulley will destroy belt tensile cords or
  drive hardware
• Small debris will become compacted in the pulley
  groove, forcing the belt to ride out away from
  the pulley and lead to belt failure by destroying
  the tensile member

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Troubleshooting Environmental Problems

• Environments with Excessive Debris (cont.)
• Exposure of synchronous belts to oil and other
  lubricants should be minimized
• Oil and petroleum distillates may alter the belt
  polymers and adhesion systems
• Care must be taken to provide adequate shielding
  on drives where debris or contaminants are likely
• Completely enclosing a synchronous belt drive
  may be acceptable. Synchronous belts generate
  less heat than v-belts. Air circulation around
  the drive is not a critical consideration except
  in extremely high temperature environments.

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Synchronous Belt Storage
The quality of a Carlisle Belt is not considered
to change significantly within eight years, when
stored properly under normal conditions. Normal
conditions can be defined as temperature below
85F and relative humidity of 70 or less with no
exposure to direct sunlight. Beyond eight years,
assuming normal storage, a decrease in service
life of approximately 10 per year can be
expected. For belts not stored under normal
conditions, the actual reduction in shelf life is
difficult to measure due to lack of precise data
and an infinite number of variables involved.
When belts are stored under abnormal conditions,
conservatism is recommended in estimating shelf
life. Improper or prolonged storage can reduce
service life considerably.
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Synchronous Belt Storage
Like V-belts, synchronous belts may be stored on
pins or saddles with precautions taken to avoid
distortion. However, belts of this type up to
approximately 120 inches are normally shipped in
a nested configuration and it is recommended
that the belts be stored in this manner as well.
Nests are formed by laying a belt on its side on
a flat surface and placing as many belts inside
the first belt as possible without undue force.
When the nests are tight and are stacked with
each rotated 180 from the one below, they may be
stacked without damage. Belts of this type over
approximately 120 inches may be rolled up and
tied for shipment. These rolls may be stacked for
easy storage. Care should be taken to avoid small
bend radii which could damage the belts.
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U.S. Customer Service 866-773-2926
Canada 866-797-2358
www.CarlisleBelts.com info_at_CarlisleBelts.com