1. InfraMation 2007 Proceedings ITC 121A 2007-06-27
Hennie Matthee
Diagnostic Engineering Thermographer ITC LEV III, South Africa, Sishen, Kumba Iron Ore Ltd.
Maintenance managers are seeking to optimize the value of their existing equipment by extending
equipment life and reducing maintenance cost. All plants contain literally thousands of low-speed bearings
that are virtually impossible to inspect cost effectively using vibration monitoring. Conveyor systems like
idlers, however, are quite easy to inspect with thermography. Idlers that fail have a direct influence on
production. The inspection technique is simply to compare similar bearings while the system is under load.
The benefits are significant. In potentially flammable environments, there may be a reduction in fire
hazards. Certainly, there will be more focused and cost-effective maintenance. System wide, there will
probably be a reduction in the power required to drive the machine.
Sishen Mine (Kumba Iron Ore) was asked to do an Infrared inspection at SAPO (South African Port
Operations) Saldanha since the problems experienced there have a direct impact on the mine. These
conditions are unique in Saldanha. The temperature variations, regular rainfall, wind and seawater spray are
the main factors contributing to high rate of corrosion on equipment. The major defects currently experienced
on the idlers are the collapse of bearing ends and corrosion. Two companies due to their competitive price
and their willingness to manufacture the rollers according to present specifications of Saldanha supply the
rollers in use. By using Thermal inspections the best idler for these conditions could be determined.
Conveyor Belt specifications:
Garlands consisting of five rollers
Belt speed 4m/s
Capacity of 6000 – 7000 t/h
Idler spacing 1.5m trough and 3m return idlers
Bulk factor 2.75 x volume
Description – iron ore (-27mm to +.2mm)
The main inspection was done on all the conveyor drives, substations, conveyor equipment, hydraulic
systems and the tippler.
The first inspection indicated that there were major problems on the conveyor idlers. The problems SAPO is
currently experiencing are the misalignment of the conveyor belts and the continuous replacement of idlers.
The inspection was to determine the reason for the deterioration of the current rollers, recommendations on
how to solve the problem and help with necessary modifications.
The hotspots detected on the idler bearings were between 27 degree Celsius and 290 degree Celsius at
normal load conditions. The amount of problems detected was more than 400 garlands consisting out of five
idlers per garland. Most of the problems were detected on the blue idlers with yellow outer seals. It was clear
that there is a problem with the idlers. The defects were reported to the Quality Manager at SAPO. The
garlands were schedule to be changed at the next maintenance window.
Infrared images of the some of the problems.

2. InfraMation 2007 Proceedings ITC 121A 2007-06-27
5.8°C
33.9°C
10
20
30
AR01
5.0°C
45.2°C
10
20
30
40
AR01
AR02
SP01
Figure 1. Figure 2
1. Thermogram of idler 49.4°C.
2. Thermagram of idlers SP01 15.2°C AR01: max 50.9°C, AR02:max108.3°C.
To monitor the newly installed idlers a follow up inspection was scheduled. On the next IR inspection the hot
spots were still high on the new installed idlers. The Examiners of SAPO informed us that the some of the
new idlers failed between 2 - 13 days in operation. One of the idlers was inspected to determine the cause of
failure. It was clear that the bearing failed. Probable causes of failure can be excessive belt tension,
overloading, improper lubrication, under designed idlers, misalignment of idler or structure, eccentric or out of
balance idler, quality of the idler.
One of the new installed idlers
5.0°C
45.2°C
10
20
30
40
AR01
AR02
AR03
AR04
Figure 1.
1. Thermogram of idler AR01:max 103°C, AR02: max 40.7°C, AR03: max 38.6°C, AR04: max 31.1°C.

3. InfraMation 2007 Proceedings ITC 121A 2007-06-27
The controlled IR inspection indicates that the average working temperature of one idler supplier (B) under
load is between 8 and 12 degree Celsius. The average working temperature of the other supplier (A) is
between 27 and 170 degree Celsius.
One idler per supplier was cut open to see from its design what can be the cause of the temperature
differences.
Figure 1. Photo of idlers Figure 2. Bearing failure
Idler installed on 02-05-2002 Removed on 15-05-2002. Tonnage 747107 tonnes
5.5°C
133.9°C
20
40
60
80
100
120
AR01
AR02
11.6°C
48.1°C
20
30
40
SP01
SP02SP03
SP04
SP05
Figure 1. Thermogram of idlers Figure 2. Thermogram of idler Supplier A and. Supplier B
1. AR01 : max 166.3°C AR02 : max 67.2°C
2. Supplier A SP01: 52.1°C, SP02: 42.8°C, Supplier B SP03: 43.3°C, SP04: 19.7°C, SP05: 15.8°C
11.6°C
48.1°C
20
30
40
SP01
SP02
SP03
SP04
SP05
SP06
Figure 1. Thermogram of idlers. Supplier A and. Supplier B
Supplier A SP01: 63.0°C, SP02: 48.1°C Supplier B SP03: 16.8°C, SP04: 18.5°C, SP05: 19.8°C, SP06: 24.1°C

4. InfraMation 2007 Proceedings ITC 121A 2007-06-27
Bearing end cap
Seal arrangement
Seal
Figure 1. Photo of idler Supplier A Figure 2. Supplier B
1. 6203 Bearings Shaft 30mm Outer Seal
Figure 1. Photo of idler Supplier A Figure 2. Supplier B
Supplier A bearing end cap < 2mm Supplier B bearing end cap 4mm
Figure 1. Photo of idler Supplier A Figure 2. Supplier B
2. Supplier A no inner seal. Supplier B good inner seal

5. InfraMation 2007 Proceedings ITC 121A 2007-06-27
The main differences between the two suppliers were the outer seal, inner seal and the thickness of the
bearing cap. Supplier A use a cheap outer seal with no inner seal, supplier B uses a labyrinth outer seal and
an inner dust seal. Supplier A uses a no name brand bearing while supplier B uses SKF bearings. The
quality manager has addressed this problem and a modification was done on the bearings.
The bearing end caps of supplier A gives no support to the bearing under load conditions. This caused the
end cap to deform under load and misalign the bearings. The result of misalignment is overheating and
failure of the bearings.
Due to the variations in temperature, the air inside the idler heats up and cools down forming water inside the
idler. This water enters the bearing causing the bearing to fail because there is no inner seal.
Figure 1. Photo of Seal (no labyrinth seal)
Figure 1. Load on Garland

6. InfraMation 2007 Proceedings ITC 121A 2007-06-27
Thermography can be used to help choose the best idler and to detect design shortcomings. IR inspections
on conveyor equipment help SAPO Saldanha to determine the best idler supplier under their specific
conditions and redesign conveyor equipment to increase production and reduce maintenance costs.
The author wish to acknowledge the cooperation of South Africa Port Operations Maintenance personnel and
personnel at Sishen Kumba Iron Ore Company for there assistance. We are also grateful for the support of H
Rohloff (PTY) Ltd. Johannesburg South Africa who provided additional data and information for this paper.
Hennie is ITC certification Lev III Thermographer and has been using IR for 8 years. He was appointed at
Sishen mine on 1 January 1986. He was trained as a Fitter and turner and qualified in August 1990. He
achieved the following qualifications: National Higher diploma N6 Mechanical and National Higher diploma
N6 Electrical at Kathu College.
He has experience in the reconditioning of Hydraulic and Electrical equipment. He started at Diagnostic
Engineering in 1994. He implemented and developed standards for Balancing at Sishen mine. He was part
of the vibration section for 6 years where he was responsible for analyzing and reporting of all vibration
readings. He started the Thermal Infrared program in 1999.
Figure 1. Misaligned bearings due to load, shaft deflection and under design end caps