1. Enhancing Conveyor Performance and
Reliability by Condition Monitoring
R.Suryanarayanan 1
, suryan237@gmail.com
1
Department of Mechanical Engineering, M S Ramaiah Institute of Technology, Bangalore
Abstract: Belt Conveyor systems are known for
transport of bulk material from one machine to another
machine for the required processing operation .The
performance and reliability of the conveyor system
depends upon the conveyor components like idlers,
pulleys and belt. The spatially distributed idlers of a
conveyor require regular maintenance. An idler failure
can cause belt damage, unplanned downtime and lost
production. The present method of maintenance
involves in manual inspection of idlers, this method does
not provide the data on health condition of all idlers
simultaneously and it is unreliable as it requires highly
experienced and skilled personnel. Hence a
Methodology is being proposed for monitoring the
condition of the conveyor idlers to enable an effective
overall performance by reducing the downtime by
adopting an effective Predictive Maintenance for these
components.
Keywords: Belt Conveyor, Idlers, Downtime, Preventive
Maintenance, Predictive Maintenance, Condition
Monitoring
I. INTRODUCTION
Conveyor systems form the streamline for
transportation for materials from one work station to
another work station. Belt conveyors are capable of
transferring materials over a large distance. Failure of
conveyor system can cause serious problems like
unscheduled downtime, fire accidents, unwanted
maintenance costs etc in Plants or Mines. Belt
Conveyor systems have three main components, Belt,
Idlers and Pulleys. These three components require
continuous monitoring .This paper suggests a
methodology for continuous monitoring of Idlers.
Idlers are rotating components used to support the
conveyor belt between the pulleys and the load
carried on the belt. Idlers are spatially distributed
components. Idlers mainly consist of Rollers and
frames. The number of idler rolls depends upon the
troughing angle. The Pipe conveyor has six rollers in
an idler. The Idler roller consists of roll shell, shaft,
and bearings.
• An idler failure in a conveyor system under
high belt speed or handling abrasive
materials the roll shell may wear out to form
a sharp knife edge which causes severe
damage to the belt.
• Bearing damage in idler rolls can cause
unplanned downtimes in the Plant or Mines.
• Conveyor downtime due to idler problems is
3 hrs/week with 40-70 idler failures.
Fig 1 Pipe Conveyor
Predictive maintenance technique is used to monitor
the conveyor idlers [1].
This technique involves in
predicting the failure of an idler [2]
. This work is done
with the help of Condition monitoring [3]
. Thermo-
graphy and Sound monitoring techniques are the
Condition monitoring methods which are used to
monitor the idlers continuously and predict the idler
failure [4]
. Thermo-graphy technique measures the
temperature of the idler roller bearing [5]
. Sound
monitoring technique uses acoustic enveloping and
the ultrasound to predict the idler failures [6]
. Thus
Predictive maintenance with condition monitoring
can be adopted to prevent unplanned downtime, belt
damage and fire accidents in the Plant/Mine [7]
.
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
47

2. II. EXISTING CONVEYOR SYSTEM
PARAMETERS
The Pipe conveyor transfers the ‘High grade coal
‘from harbor to the thermal power plant over a
distance of 4337 m. The pipe conveyor system is the
world’s largest pipe conveyor in terms of capacity.
The operating hours is 24 hrs/day. The conveying
rate is 4000 tph . The probable annual operation is
6000 hrs/day.
Table 1: Conveyor Design Parameters
Nominal Pipe
Diameter
650 mm
Nominal Belt
Speed
6 m/s
Belt width 2400
mm
Idler diameter 165 mm
Pipe roller pitch 2 m
Table 2 : Idler Parameters
Minimum Bearing Life 40000 hrs
Bearing type Std Deep groove ball
bearing
Face length 500 mm
Selected shaft diameter 40 mm
Shaft modulus 2.1x105
N/ mm2
Number of Idlers
( Carrying and Return)
25800 idlers / 2150
modules
III. EXISTING MAINTENANCE PRACTICE
Preventive maintenance technique is the most
common method of maintenance, it is also
known as the ‘Traditional method’. This
technique requires highly experienced and
skilled labor for detecting the idler failure. The
idler bearing failure is detected after a loud
audible noise. To replace the idlers, the relevant
conveyor must be stopped and isolated for safety
purposes. In case of Pipe conveyor, the pipe
diameter is reduced with strips and the belt is
pulled with chain block away from the rollers to
be replaced.
Fig 2 Damaged Idlers
Now damaged rollers can be replaced by removing
the bolts of the rollers and the bracket. This method is
unreliable when large number of idlers is found
defective.
Fig 3 Replacing of the damaged idler
From Fig 3 we can see the amount of risk involved
by the worker in replacing the damaged idler. The
idler replacement time can be 30-60 min. For
replacing the damaged idler, the conveyor must be
stopped. By considering the high risk factor and the
number of accidents caused due to such activity,
alternate solutions are being suggested.
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
48

3. IV. PREDICTIVE MAINTENANCE WITH
CONDITION MONITORING
In predictive maintenance the components are being
monitored until irregular factors are discovered. In
general one waits until a maintenance opportunity
arises. Condition monitoring is a process of
monitoring a parameter or condition in machinery to
identify a significant change which is indicative of a
developing fault. Predictive maintenance with
condition monitoring has the ability to pick up the
signals usually referred as ‘signatures’. In case of
idler rolls the signatures are temperature and
vibration. In specific vibration is referred to the
‘bearing tones’ and temperature is ‘Hot bearings’ [8]
.
By analyzing either the temperature or bearing tones
of an idler we can predict its failure [9]
.
V. THE PROPOSED SOLUTIONS
The proposed solutions are aimed at reducing the
downtime of the conveyor system by monitoring the
condition of the idlers.
Fig 4 P-F Curve
The existing maintenance activities are carried out
after the point ‘F’ which indicates the Failure. With
respect to the graph (Fig 1) the Predictive
maintenance technique carries out the maintenance
activity in the P-F interval with the help of condition
monitoring. At point P the fault is identified.
The solutions are based upon the condition
monitoring principle. The solutions are:
1. Thermo-grapghy
2. Bearing Sound Monitoring
3. Smart Idlers
4. Automated Maintenance Systems
1 Thermo-graphy
Thermo-graphy is a the technique of using Infra-Red
cameras to monitor the idlers on the conveyor. The
temperature of the idler is monitored in this process.
The output is fed to the Central control room which
monitors the Conveyor system. On rise of idler
temperature than its idler by 15-20 Celsius, the roller
can be tagged for replacement.
Fig 5 Infra Red Monitoring of Idlers (Mine in
Queensland, Australia)
The advantage of thermo-graphy method is that this
system can easily be integrated into the Control
systems like SCADA or PLC . The modules for such
technique can be added to the Control software. The
tagged idler is identified by the onsite maintenance
personnel who carry out the replacement of the faulty
idler. Many Australian ore and coal mines have
installed this facility and they have proven successful
in terms of increased reliability.
2 Sound Monitoring Systems
Sound monitoring systems uses the help of acoustics
and ultrasonic signals to detect the faulty idlers. In
this technique “the bearing tones” are analyzed.
There are two portable equipments available in
market which help in detecting the faulty idlers. SKF
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
49

4. Idler sound monitoring kit and UE systems
Ultraprobe 10000 are the two available equipments.
The SKF idler sound monitoring kit works on the
principle of acoustic enveloping technique. This
equipment is user friendly. The SKF system consists
of Microphone, Micro log analyzer and hears phones.
As the equipment is hand held device, the
maintenance engineer listens to the idler sound
through the microphone. The collected sound is
analyzed by the micro log analyzer and gives the
output in the form of colored lights. Red light
indicates the bad idler, Yellow light indicates to the
suspicion idler and the Green light indicates the good
idler.
Fig 6 SKF Idler Sound Monitor kit
This device helps workers in detecting faulty idlers
which helps in avoiding belt damage. The worker can
detect the faulty idlers from a distance of 3m . This
device can also detect the idlers on the far side of the
belt and there is no need to walk on both sides.
Fig 7 Micro log analyzer
The other equipment is the UE Ultraprobe 10000.
This equipment uses the ultrasonic sound for
condition monitoring of conveyor idlers (Autar,
2008) . Ultraprobe 10000 is multipurpose device , its
also used to check steam traps, identify electrical
emissions and finding compressed air leaks . This
device is hand held equipment; the operator listens
and record to the bearing sound .. The operator stores
the data in the device. This data can be transferred to
the Data Management and Spectral analysis software,
where the recorded data is analyzed
Fig 8 Ultraprobe 10000
The spectral analysis software uses the Fast Fourier
Transform to analyze the recorded sound and the
output is given in the form of the ‘Sound images’.
Fig 9 Sound Image
3 SMART Idlers
SMART Idlers are different from the conventional
idlers. These idlers have sensors incorporated in
them. Sensors like RFID and Temperature are used.
These sensors help in monitoring the conveyor
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
50

5. system 24x7. With this technology its easy monitor
and track idler failures, schedule maintenance and
more accurately manage stock inventories, all from
the comfort of the control desk. These idlers can also
be integrated with the Control systems like SCADA
or PLC with the help of Idler Management software
which is the add -on software for the control system.
Fig 10 CPS Vaeyron Smart Idler
Moreover the SMART idlers are light in weight when
compared to the conventional idlers. Once the faulty
idlers are detected, the replacement procedure begins.
The replacement is generally done by the use of
robots. These robots are specially designed to replace
the faulty idlers with the good ones . Some robots are
also capable of predicting the idler failure and then
simultaneously replacing the idlers. We shall discuss
these systems in the topic Automated Maintenance
systems.
COVE Engineering NSW, Australia has found
success with the SMART idlers. Vaeyron SMART
idlers are also proven successful by reducing the
overall cost related to the conventional idler.
Productivity Development Solutions NSW, Australia
have developed Idler Management software, through
which they achieved 50% reduction in idler delays
and Operating cost saving of estimated $1.5m pa. in
an underground coal mine in NSW Australia which
was having Idler delays due to shell damage at an
alarming rate to 181.5 hours per annum.
4 Automated Maintenance Systems
Automated Maintenance systems are specially
designed systems to perform the maintenance
operation. These systems are generally autonomous
robotic systems. These robots have customized end
effectors which are used to replace the damaged
idlers. These robots not only replace the idlers but
also predict the idler failure. With these robots the
downtime of the conveyor due to idler problem is
completely avoided. In case of an idler failure, the
conveyor must be stopped and the maintenance
activity is carried out. The Robotic systems are used
to monitor the conveyor system in underground coal
and ore mines.
In case of Overland conveyors Maintenance trolley is
used. These trolleys are used in conveyors which is
along the cross country. For automated maintenance
of the overland conveyor this maintenance trolley can
be modified with the help of a robot mounted on the
top of the trolley (S.S Kalidien , 2006). This system
is an autonomous system which is capable of
traversing over the steel structure of the pipe
conveyor. The faulty idlers are identified with the
help of laser vibrometers, which are fitted in the
trolley. The Robot is a customized pick and place
type with a specialized end effectors.
Fig 11 Automated Maintenance trolley
MARbot and Spidler are robotic systems which are
used to predict and replace the faulty idlers. These
systems can be used in underground coal/ore mines.
Roy Hill an iron ore mine in Western Australia are
using the robotic system and it has been a successful
implementation. In Roy Hill had loss of $300,000
every time due to idler roller change stoppage at
conveyors.
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
51

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International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
52

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International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
53

8. [14] Strategies for Automated Maintenance of
Belt Conveyor Systems Prof.dr.ir. Gabriel
Lodewijks DeIft University of Technology, the
Netherlands
[15]http://www.machineryautomation.com.au/mi
ning-2/materials-handling-mining/robotic-roller-
set-replacement/#.VSY-ZZOOLDc
[16] Condition Based Maintenance (CBM)
Through Vibration Spectrum Analysis for
Improving the Reliability of B-1 Conveyor
(DIVE542) Diagnosis of Fault through Vibration
Spectrum Analysis Technique, K.RaviRaju,
B.MadhavaVarma,N.RaviKumar
ISSN: 2278-3075, Volume-2, Issue-2,
January 2013 .
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.10 No.71 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
54