Global’s third-party girth gear specialist team conducts gear inspections and risk assessments based on the inspection recommendations outlined in the annex of AGMA 6014. Our inspection process will provide the customer with a complete non-destructive test of the integrity of the mill gear teeth in accordance with ASTM E2905 (Eddy Current Array). Eddy Current Array is a key word for searching. Learn more at: https://global-pam.com

1. Mill and Kiln Drivetrains
Asset Management
Condition Assessment for Asset Reliability, Risk Management and Optimization

2. Topics of Discussion
• Introductions
• Global Physical Asset Management Overview
• Physical Asset Management Support for Mills and Kilns
• Girth Gear Failure Modes per AGMA 1010
• RCM Approach to Managing Girth Gears
• Girth Gear Reliability & Failure Analysis
• Contingency Planning
• NDT Methods Used for Mill Gearing
• Introduction – ASTM E2905
• Girth Gear Cleaning
• Conclusion
• Review a Inspection Report
• Questions

3. Tom Shumka-President
• Tom is the President of Global PAM and has been involved in the
mining sector since 1976.
• Tom sits on the Sub-Committee for ASTM E7.07 (Electromagnetics)
and ASTM E7.10 (Specialized NDT Methods). Tom authored ASTM
E2905 – Electromagnetic Methods for Mill and Kiln Gear Teeth
Inspections.
William Quinn - Gearing Engineer
• Will is a mechanical engineer, specializing in open gearing. Will’s
expertise is in the engineering, design, manufacture, installation,
inspection and maintenance of large girth gear systems.
• Will previously held various engineering and business development
roles in Falk’s Mill Products division of Rexnord.
Jason Shumka-E2905 Specialist
• Jason has been performing open gear drive teeth inspections as per
ASTM E2905 for 10 years. No one in North and South America has
more knowledge and experience in this standard than Jason. Jason
holds Level II Certification in Eddy Current & Phased Array
Ultrasonics.

4. • Global PAM is a leader in advanced Non Destructive Examination (NDE)
techniques within the mining industry.
• We combine our knowledge and ingenuity to develop innovative solutions
to match the unique needs of our customers.
• Rotating Equipment & Machinery Integrity Specialists
• Our technicians and engineers are experts in both non destructive
testing techniques but also the design, procurement, maintenance,
and operation of mill and kiln girth gear drive trains, shells, heads,
trunnions, riding rings, and rollers. This approach enables us to offer
complete solutions to our customers asset management needs.
• General NDT work
• Many of our clients in the mining industry chose us as their preferred
vendor for all NDT work in addition to our specialties.
Company Overview

5. Acquisition and Commissioning
• AGMA ratings and drive train design, manufacturing, and instillation
• Quality assurance documentation, including critical manufacturing
procedures and standards for major mechanical parts girth gears, pinions,
mill shells, heads and trunnions.
• Manufacturer audits, and oversight during critical inspections and
documentation signoff prior to shipment of goods.
• Installation crew oversight, installation verification.
Commissioning
• Girth gear and pinion installation oversight.
• Proper installation procedures are followed
• All critical steps are documented and available for future reference.
• Proven methods for aligning girth gear and pinions rapidly with minimal
shimming iterations.
Physical Asset Management Support for
Mills and Kilns

6. Logistic Support
• Resource support plans, total cost of ownership.
• Training programs
• Optimization of insurance spend, maintenance spend, and sparing costs.
Operation and Maintenance:
• RCM approach to maintenance, and audits of existing maintenance plans
• Preventative maintenance tasks, tied to specific failure modes.
• Predictive maintenance tasks, to detect potential failures.
• Girth Gear Inspections per ASTM E-2905
• Structural Inspections, Shells, Heads, Trunnions, Rollers, Riding Rings
• Operational inspection tasks and intervals
• One time or engineering changes can be implemented where the
probability of failure and consequences of failure are deemed
unacceptable.
Physical Asset Management Support for
Mills and Kilns

7. End of Life
• Provide a procedure for inspection and verification on suitability for open
gear and pinion flipping.
• Provide a framework and decision making process for replacement gears.
• Assess alternative solutions to scrapping old gearing, dependent on
condition and structure.
Physical Asset Management Support for
Mills and Kilns

8. Girth Gear Potential Failure Modes AGMA
1010-F14
Gear failure modes are classified into 7 Classes
1.Wear
2.Scuffing
3.Plastic Deformation
4.Hertzian Fatigue
5.Cracking (Hardening Cracks, Grinding Damage,
Rim Cracks) all related to manufacturing not
operation.
6.Fracture
7.Bending Fatigue

9. Wear-Abrasion
Abrasive wear is the removal or displacement of material along
the tooth flank due to the presence of hard particles. These
particles can come from external sources such as slurry, dust,
contamination, or may be self-generated hard metal fragments
from other failure modes such as macropitting or scuffing.
The tooth profile is most affected resulting in poor mesh action
and localized overloading.

10. Wear-Abrasion Severe
Often severe wear will progress to macropitting as contact stresses
increase from localized overloading

11. Scuffing
Scuffing is a severe form of adhesive wear caused by the transfer of
material from one tooth surface to another due to microwelding and
tearing. Scuffing occurs when the lubricant film cannot completely
separate the metal surfaces. Machining marks are removed and deeper
craters are observed. In the severe form surface temperatures may
become significantly elevated causing localized metallurgical changes to
occur. Proper lubricant and lubrication is the best prevention.

12. Scuffing
Severe scuffing can initiate flank cracks!!
Flank cracks from severe
scuffing

13. Plastic Deformation-Indentation
Indention is caused by hard foreign material that becomes trapped
between mating teeth, causing an indentation in the tooth surface.
The area around the indentations is typically raised from plastic
deformation of the metal.

14. Plastic Deformation
Cold Flow, Tip to Root Interference, Tight Mesh
The topland of this gear is completely rounded from plastic
deformation where the gear is in tight mesh with the pinion and
experiencing tip to root interference.

15. Plastic Deformation
Cold Flow, Tip to Root Interference, Tight
Mesh
Significant edge burrs have
developed form the tight
mesh condition

16. Hertzian Fatigue-Macropitting
Macropitting forms when small fatigue cracks initiate at
or near the surface and propagate for a short distance
before breaching the surface and breaking out a small
piece of material.

17. Hertzian Fatigue-Spalling
Spalling occurs when
macropits form, then grow is
size and coalesce into larger
cavity’s on the gear tooth
surface. asperities and high
pressures from variations in
manufacturing tolerances.
This form of macropitting
quickly stops once the load
redistributes. The image
adjacent is a gearbox gear,
showing spalling across the
entire face.

18. Hertzian Fatigue-Spalling
Spalling can be easily
identified from stop action
photographs of pinion teeth.
This is a severe failure mode
which can quickly lead to
tooth cracking and fracture.

19. Bending Fatigue
When a tooth is overloaded, it can
be exceed its fatigue limit.
- Stage 1, Crack initiation (plastic
deformation occurs at stress
concentrations leading to
microscopic
cracks);
- Stage 2, Crack propagation (cracks
grow perpendicular to maximum
tensile stress);
- Stage 3, Fracture (when a crack
grows large enough, it causes sudden
fracture).

20. Bending Fatigue
When a tooth is overloaded, it
can exceed its fatigue limit.
Here rippling is a sign of
overloading from misalignment.
The Crack shown here has
propagated to the tooth
boundary’s and will fracture
soon.
- Stage 2, Crack propagation
(cracks grow perpendicular to
maximum tensile stress);
- Adjacent tooth loading occurs
in helical gears with over 1.0
Axial overlap and sets
designed with a proper
amount of involute overlap.

21. Bending Fatigue and Fracture
When a tooth is overloaded, it
can exceed its fatigue limit.
Here rippling is a sign of
overloading from
misalignment. The Crack
shown here has propagated to
the tooth boundary's and
caused a section of tooth to
fracture.
- Stage 3, Fracture (when a
crack grows large enough, it
causes sudden fracture).

22. Sample Failure History Tooth Cracking
• A gear in South America was installed March 29, 2015
• A complete gear inspection was conducted March 31, 2015 only
minor casting indications found.
• 31 cracks were found October 16, 2016, 18 months later.
• 45 cracked teeth were present by January 11, 2017
• Our recommendation for Inspection intervals of a year is generally
sufficient to catch crack formation.
• in this case severe scuffing initiated the cracks on odd numbered
teeth 39, even numbered teeth 6. The common factor between the
pinion and gear teeth was two.

23. Sample Failure Event:
• Cracks formed in the pinion which caused a section of tooth to
break off and run through the gear mesh.
• This incident forced this pinion off its foundation along with a rapid
coupling failure. This caused the mill to stop rotating, thus failing to
fulfill its function.
Fractured Teeth
Failed Coupling

24. Failure Event:
• The initial fractures occurred from bending fatigue caused by
misalignment.
• The gear contains an impact mark from the tooth section as
well as a cracked tooth at one of the joints.
• The mill was down for and extended period for foundation
repairs and gear and pinion assembly replacement.
• On the following slide, we show the following failure modes
before ultimately failing.
• With regular inspections many of these failure modes could
have been detected far enough in advance to take action and
prevent the ultimate failure of the drivetrain.

25. Failure Modes:
• Misalignment: Detectable with lubricant contact checks with
photographs or stroboscopic inspections, pinion mesh
temperature deviations, and vibration analysis.
• Tooth Cracking: Detectable with inspections per ASTM E2905
and vibration analysis
• Single Tooth Fracture: Detectable with lubricant contact checks
with photographs or stroboscopic inspections, pinion mesh
temperature deviations, and vibration analysis.
• Multiple Tooth Fracture with Fracture Piece Entering Mesh
(Ultimate Failure): Pinion does not transmit torque as the
coupling has failed along with multiple teeth.
• Gear: The gear has a fractured tooth near the split joint between
stations 4-5 with an indentation from the impact of the tooth
fragment.

26. Tooth Fracture Photographs

27. Introduction - Girth Gear Reliability and Failure Analysis
• Global PAM’s third-party gear engineering team specializes in reliability
consulting for gear driven mills. When a site determines that its mills are
not meeting its expectations in its current operating context an RCM review
plan in compliance with SAE JA1011 can be facilitated and conducted for
each of the mills using industry best practice methods, manufacturer
recommendations, and information from maintenance and operations.
• Our approach to failure analysis is also combined with RCM to
systematically determine the root cause of failure, develop proper
maintenance tasks, and or engineering changes to reduce the probability
and or consequence of functional failure if the failure is ongoing. And after
a failure has occurred to determine the corrective actions needs to prevent
future failures from the failure mode identified.

28. RCM Approach ( 7 Basic Questions)
1. Each girth gear system needs its functions and desired standard of
performance clearly identified, in its present operating context.
2. Determine how the gear system can fail to fulfill its functions
3. Determine the causes of each functional failure (failure modes).
4. Determine what happens when each failure occurs (failure effects).
5. Classify the consequences of failure (failure consequences).
6. Determine what should be performed to predict or prevent each failure (tasks
and task intervals).
7. Determine if other failure management strategies may be more effective (one-
time changes).

29. FIGURE1: Reliability-Centered Maintenance (RCM) Handbook, United States Navy,
Complex Asset Failure Patterns

30. Girth Gear RCM High Level
Girth Gear System Function
• To rotate a cylindrical drum by transferring and increasing torque from a high
speed shaft to a low speed girth gear operating 95% uptime 8300 hours/year.
Girth Gear Functional Failures
• Gear cannot transfer torque.
• Pinion cannot transfer torque.
Failure Modes:
• Structure failure
• Joint failure
• Tooth fracture (predominant mode)
Failure Effects from Tooth Fracture:
• When a tooth fractures the effects can include high vibrations, loud noises as
the broken section comes through mesh, additional teeth break from impact of
the broken section. The gear and pinion will likely need to be replaced.

31. Girth Gear Bending Fatigue Failures

32.  P=Potential Failure
 Is an identifiable condition which indicates that a functional failure is either
about to occur or in the process of occurring.
 F=Functional Failure
 The asset fails to fulfill the indented function.
SAE JA1012 Revised AUG 2011
Failure Patterns the P-F Interval
FIGURE 5: Complex Asset Failure Patterns

33. Classical View of Gear and Pinion Failure Rates
FIGURE 2: Gear Failure
Rate
FIGURE 3: Pinion Failure
Rate

34. Contributions to Failure
FIGURE 4: Contributions to Failure

35. Tooth Fracture
Wear (teeth become
thin, crack)
Severe abrasion
Severe adhesion (Scuffing)
Plastic deformation
(crack formation)
Indentation
Cold flow
Tip-to-root interference
Tight mesh
Hertzian fatigue (crack
origination)
Severe progressive
macropitting
Spalling
Cracking
Hardening cracks
Grinding damage
Rim Cracks
Bending fatigue cracks
Low-cycle fatigue cracks
High-cycle bending
fatigue cracks
Gear tooth potential failures and failure mode relationships
Visual
Inspection
Proper Design
and
Manufacturing
Detectable with
ASTM E2905

36. Girth Gear Failures
Failure Effect Consequence:
The fracture of gear teeth has evident operational consequences. This failure
mode results in extended downtime while the gear and pinion are replaced. If a
spare is not available the downtime can be catastrophic.
What needs to be done to predict or prevent failure from tooth fracture:
On condition tasks need to be implemented to check for potential failures
(crack formation, severe wear, and spalling), in order to avoid the
consequences of a broken tooth.
• Inspections of the gear teeth are necessary to detect crack
formation, spalling, severe wear and other potential failures!
• These inspections must be done at intervals less than the P-F
interval! Experience has shown that the time between crack
formation and tooth fracture is often longer than 1 year.
• Regular visual/stroboscopic/photographic inspections, thermal
imaging, vibration analysis, and lubrication analysis are also
necessary.
Determine if one-time engineering or system changes are necessary:
• This will depend on the operating context of a particular gear.

37. FMEA
(FAILURE MODES AND EFFECTS ANALYSIS)
• The failure modes and effects are traditionally
analyzed by performing a FMEA analysis.
• For each functional failure the causes (modes) of
failure are identified.
• For each mode the effects are listed

38. FAILURE MODES (CAUSES)
• An event which is reasonably likely to cause a functional failure.
• Need to be addressed at the same level that the system will be
maintained
• Should included failure modes that have happened, are being
prevented, and others reasonably likely to occur, this should
include design errors and human error.

39. FAILURE EFFECTS
• What would happen if the failure mode and functional failure
occurred
• Effects descriptions include all the information needed to
evaluate the consequences.
• What evidence is there that the failure has occurred
• What physical damage is caused
• Does the failure injure or kill someone, or effect the
environment
• Does the failure have an impact on production or operations
• What does it take to restore the function after the failure.

40. FAILURE CONSEQUENCES
• The assessment of failure mode consequences is done as if no
specific task is currently being done to anticipate, prevent, or
detect the failure.
• The consequences of every failure mode is categorized
• First we determine if it is an evident (detectable) failure mode or
a hidden failure mode.
• Second we determine if it has safety and/or environmental
consequences
• Third we determine if it has operational consequences or simple
economic consequences

41. Severe Spalling AGMA 1010-F14
Contingency Planning
Severe Wear and Fracture
Gear Tooth Crack Initiation <5mm

42. Contingency Planning
What are the risks of tooth fracture?
• Broken segment wraps around and goes through mesh, the mill or kiln
may jump the foundation. This can damage the footing, foundation,
trunnion bearings or rollers, the cost of lost production and repairs can
easily exceed $10M in mineral processing circuits.
• Load is now concentrated in a smaller area increasing stress resulting in
complete tooth loss and loss of torque transmission.
• Load sharing with surrounding teeth decreases resulting in additional
fractured teeth and loss of torque transmission.
• Vibrations increase causing damage to the bearing elements.
• Mill head bolts break distorting and damaging the mill shell

43. Contingency Planning
What is the plan if a crack, severe spalling, severe wear, or fracture is found
on a ring gear?
Crack: A crack of any size is a critical potential failure that will eventually
result in tooth fracture.
• Ensure a spare gear is available onsite, order one if one is not present.
• Have a gearing expert assess the crack size, orientation, and determine the
risk of fracture in a given timeframe.
• Determine risk level and coordinate plan accordingly
• High risk- Immediate action
• Moderate-Low risk
• Regular crack size monitoring, visual/stroboscopic/photographic
inspections, vibration monitoring, and thermal imaging will enable the site
monitor prorogation and detect additional failures.

44. • Typically, cracks develop from macropitting, severe wear, or fatigue cracks on
or very near the gear tooth surface.
• Casting imperfections can serve as crack initiation sites but are rarely the
root cause of the crack. These types of cracks are rare as internal tooth
stresses are relatively low compared to those near the tooth surface.
• If a crack initiates at an internal imperfection they tend to propagate towards
the surface, once the crack nears or breaches the surface detection and
action can be taken.
• Any casting imperfections in the casting should identified by the
manufacturer’s Quality Control Program with UT per the requirements for
Grade M2 materials from AGMA 6014-B15 before the gear leaves the plant.
Material Imperfections porosity and shrinkage

45. Contingency Planning
Gear Flipping
• When the decision is made to flip a gear, a complete inspection per
ASTM E2905 is needed to check for any cracks in the teeth or
structure.
• If tooth or structure cracking is found flipping should be reconsidered
and new gearing used.
• The split blocks need a thorough inspection.
• A new set of mounting and split hardware must be ordered
• Remove the old hardware without damaging the split blocks, avoid
gas cutting.
• Once off the mill all components should undergo a thorough
cleaning.
• Use a new pinion to mesh with the gear and set the pinion with root
clearance NOT backlash.

46. Decision Matrix Sample
Assumptions for model: Gear is in good
condition, and operating with a flat
conditional probability of failure.
MTBF Ideal set from
fatigue cracking Use
Design Life
219,000
MTBF Spare gearset, from
bending fatigue cracking.
Gear has 2 serious defects
which could pose risk to
cracking and tooth fracture.
60,000
Probability Failure from tooth
fracture in any 5 Year Interval,
assume exponential law of
distribution, good condition gear.
18%
Downtime
Cost/Day 500,000$
Decision
Probability of tooth
fracture after action
1 Year Gear Cost Installation Cost Installation Days
Holding Cost, Inventory Cost
(Estimated 20% per Year) 5 Year
Estimated Hold
Extended Downtime Risk
30 days downtime % *
Probability of tooth
fracture operating for 1
year.
Significant
Risk Days
downtime
Expected
Value Total Cost
Overall
Expected
Value
Order new spare gear, 1 installation, and
8 days of Installation. Extended
downtime risk factor 20%
4% 1,000,000$ 300,000$ 8 $1,000,000.0 0.78% $117,631.7 $5,300,000 $1,325,448
Order new spare gear, 1 installation, and
8 days of Installation. Extended
downtime risk factor 10% with regular
inspections.
4% 1,000,000$ 300,000$ 8 $1,000,000.0 0.39% $58,815.8 $5,300,000 $1,266,632
Install onsite spare gear, then order new
spare gear. 1 installation, and 8 days of
downtime. Extended downtime risk
factor 20%
13.6% 1,000,000$ 300,000$ 8 $75,000.0 2.72% $407,526.9 $5,375,000 $1,212,679
Install onsite spare gear, then order new
spare gear. 1 installation, and 8 days of
downtime. Extended downtime risk
factor 10% with additional regular
inspections.
13.6% 1,000,000$ 300,000$ 8 $75,000.0 1.36% $203,763.4 $5,375,000 $1,008,916
Decision Tree for Contingency If Gear Tooth Cracks

47. Task Intervals and Timing After FMEA Review
ASSET Condition Factor TASK DESRIPTION INTERVAL (hours) Standard INTERVAL (hours) Condition TASK DURATION
Girth Gear 8
Remove residue around girth gear split joints, check joint opening and rims step with feeler gauges. If opening in the cold state is
greater than 0.076 mm and or the rim step is greater than 0.038 mm consult manufacturer or industry expert. Visually inspect the
structure for cracks two windows on either side. Use ACFM to detect cracking below painted structure.
8760 4380 4
Girth Gear 8
Annual girth Gear Inspection per ASTM E2905 with visual inspection. The visual inspection should be conducted by a gearing expert to
identify the failure modes present per AGMA 1010-F14.
8760 4380 10
Girth Gear 5
Conduct root clearance measurements between the pinion topland and the root of the gear teeth, compare side to side and
average. Compare average to previous measurements and as installed measurements. Check the foundation bolts for proper torque.
8760 8760 3
Girth Gear 5
Check gear spray patterns, ensure proper nozzles and coverage
4380 4380 1
Girth Gear 8
Visual inspection of gearing elements stopped spot inspection of 2 teeth each element
reference AGMA 1010-F14 to identify failure modes present.
8760 4380 2
Girth Gear 8
Stroboscopic inspection while running
Check pinion teeth for
even lubricant film
scuffing
severe macropitting
spalling
tooth fracture 24 12 0.25
Girth Gear 8
Stop action photograph inspection of the pinions while running
compare against previous photographs for changes in
lubricant film
macropitting coverage
wear patterns
730 168 0.25
Girth Gear 8
Pinion Temperature Montoring
Temperature differential from end to end should be set to alarm and interlock
Temperature differential alarm needs to be set If differential greater than 15 °F [8 °C] the pinion should be aligned at the next
convenient opportunity.
Temperature differential interlock needs to be set If differential greater than 30 °F [17 °C] the mill should be shutdown and an
alignment conducted.
Additional alarms can be set on the max temperature from any given sensor if the emmisivity is properly calcualted
168 or Continuous if
online system, with
alarm and shutdown
levels mentioned 24 0.25
Girth Gear N/A
Girth Gear Contingency Plan Action Items
a. Option 1: Coordinate plan with OEM and manufacturer holding blanks on the plan, ensure OEM has manufacturing drawings for
the gears. Please varify that Hoffmann has drawings for Ball Mill #1, 2, and the regrind mill gears.
b. Option 2: Coordinate with manufacturer holding blanks to reverse engineer all the gears.
c. Option 3: Compile QA/QC plan for manufacturing and distribute to OEM/Manufacturer.
d. Option 4: Manage additional lead time risk with annual girth gear inspections, gear must be ordered if critical failure modes develp.
One time task N/A 16
Girth Gear 8
Vibration analysis on pinion bearings in vertical horizontal and axial directions.
• AGMA 6000 Class A vibration limits 13 mm/s alarm above this, investigate vibration source. Some mills may operate normally at
vibrations higher than this but the trend needs to be established.
730 365 2
F° C° F° C°
Mill T A to C 15 8 30 17
Temp A to B 20 11 30 17
Temp B to C 20 11 30 17
Pinion Temp A, B or C 200 93 220 104
ALARM SHUTDOWN

48. Inspection Methods
• Magnetic Particle (MT) - ASTM E709
• Dye Penetrant (LT) - ASTM E1417
• Eddy Current (ET) – ASTM E309
• Ultrasonics (UT) - ASTM A609
• Phased Array Ultrasonics (PAUT) ASTM 2700
• ASTM E2905 Eddy Current Array (ECA) / Alternating Current Field
Measurement (ACFM)

49. ASTM E2905 Introduction
• Defines an electromagnetic method for the detection of surface breaking
defects including cracks and macropitting in the addendum, dedendum, and
root area of girth gear teeth.. Scuffing and wear patterns can also be
visualized through the C-Scans.
• Two electromagnetic methods that are the basis of this standard:
• Eddy Current Array (ECA) – Electromagnetic method for detection of defects.
Probes are designed to cover the entire profile including the tooth root
ensuring 100% tooth coverage.
• Alternating Current Field Measurement (ACFM) for sizing of any cracks
found.
• A visual inspection is also utilized, characterizing failure modes present on
the teeth, wear patterns, and identifying alignment issues.

50. • 100 % coverage of the Addendum, dedendum and root of the drive and
non-drive of the gear flank.

51. ASTM E2905 (Advantages):
 With 2 and 3D Dimensional Isometric
Displays, we can see the defects as it
is in the material.
 E2905 will display the actual
characteristics of the defects which
helps in quickly identifying failure
modes and reduces the potential for
errors.
Crack clearly identified on a gear flank
Pitting clearly identified on a gear flank
Software display of calibration block

52. Example Crack Detected with ASTM E2905 Method
• Picture on the left shows two cracks detected with ECA but could not be
visualized. MPI was used to visualize the cracks.
• Picture on the right shows the 2D & 3D displays. Notice the scuffing on the
top right.

53. Crack found in root that could not
be visualized
2D Display
3D Display
This root could not be inspected because
of the presence of lubricant
• Looking at the left picture, a clean root, using E2905 as the inspection standard,
reveals a critical crack shown in the 2D & 3D displays. This crack could not be
visualized.
• In right figure, the crack in the left picture could not be visualized or inspected
because of the presence of lubricant in the root.

54. Alternating Current Field Measurement (ACFM)
• ACFM is an electromagnetic technique for
detection and sizing of surface breaking cracks.
ASTM E2261.
• ACFM is significant for routine preventative
maintenance schedules to determine whether
crack growth is occurring.
• Rapid scanning using a hand-held probe.
• Reliable crack detection and sizing (length and
depth) up to 25mm.
• Dramatically reduces most cleaning requirements
with no need to clean to bare metal.
• Capable of inspection through thin metallic
coatings, or through non-conducting coatings up to
10mm thick.
• Full data storage for back-up, off-line view and
audit purposes.

55. Inspection Process
Step 1: Dynamic Inspection Prior to Cleaning (0.5 – 1.0 hours)
• Thermal imaging and video of the operating pinion, and gear.
• Stop action photographs of the operating pinion and gear teeth.
Thermal Imaging
Stop action photograph
showing the lubrication
film and the five points
to take the readings
from

56. Step 2: Gear Cleaning (1 hour or less)
• Cleaning the girth gear and pinion with Cleansolv HF EP.
• Removing built-up contaminated lubricant, allowing for an accurate
visual inspection as per AGMA 1010-F14 and to ensure an accurate scan
using Eddy Current Array probes.
• **Wiping and/or rinsing gear teeth not required for this process.
Clean Girth Gear and Pinion Access required – top portion of guard easily removed after cleaning

57. Step 3: ASTM E2905 and visual tooth Inspection with tooth condition report
based on AGMA 1010 (equipment must be shut down, locked out, inching
drive available, and guarding removed) (5-7 hours)
• Gear and Pinion Tooth Inspection per ASTM E2905. Scanning both the drive
side and the non-drive side flank and root of each tooth on the girth gear and
pinion; to identify cracks that may go unnoticed by visual inspection.
• Onsite data analysis for immediate results.
• As defects are found they are further inspected with magnetic particle to
illustrate the defect; if a crack is detected, the length and depth are sized by
ACFM.
• If required, Phased Array UT will be
utilized to map out a crack.
• Visual inspection of each tooth
identifying specific failure modes
per ANSI/AGMA 1010-F14.
Inspecting a large girth gear

58. Gear Tooth Assessment as per AGMA 1010

59. Where Ultrasonics Works as a Secondary Method for Gear Inspection
Crack on drive side of tooth flank
Red Line (cracks) Blue Line (June) Green Line (July)
• Surface cracks (red)
• UT measurement in June (blue)
• UT measurement in July
(green)
• This representation shows the
cracks have propagated deeper
in one month.

60. Preparation /
Inspection Times
Mag Particle /
Dye Penetrant
E2905
Cleaning 10-12 hours 1 hour
Inspection 20-30 hours 8 hours
Report Paper
Full Electronic
Archived Backup
Crack Sizing No Yes
Total Time for Cleaning
& Inspection
30 – 50 hours 8 hours
Compliant with E2905 No Yes
Comparison of E2905 to Magnetic Particle and Dye Penetrant Inspection Methods
Benefits of ASTM E2905 vs MPI / LPI

61. Eddy Current Array vs Phased Array Ultrasonics
Description ECA PAUT
100% surface coverage – addendum, dedendum, root Yes No
Has a significant blind spot from probe to inspection surface No Yes
Ability to identify wear patterns and surface fatigue associated
with gear failure modes
Yes No
Data can be archived for future reference Yes No
Sensitive to surface inspection Yes No
Recommended for gear tooth surface examination – AGMA 919 –
Part 1
Yes No
Compliant with ASTM E2905 – specifically for gear teeth
inspections
Yes No
Detects indications subsurface (casting defects etc.) No Yes
• Eddy Current Array is very sensitive to surface and near surface indications,
typically where gearing failure modes develop.
• PAUT is very good at detecting indications at depth, as a secondary
inspection; but misses the most highly stressed area where gear failure modes
develop. It is an inadequate primary detection method.

63. The Ease of Girth Gear Cleaning
Girth gear cleaning is required to remove contamination and lubricant buildup on
mill ring gears prior to inspection. This is accomplished by cleaning the gear set
while in production minimizing downtime.
 The actual time of cleaning a girth gear is under an hour.
 There is no need to wipe the gear teeth down after by hand when using ECA.
 The light oil left behind helps the probes glide along the tooth controlling liftoff.
 Gear Engineers utilize visual interpretation (AGMA 1010) to analyze the gear
teeth condition, such as contact patterns and wear patterns; hence, a clean gear
set is a must.
 Clear or translucent lubricants still require cleaning to conduct a thorough visual
inspection, as the lubricant can obstruct critical details on the tooth surface.

64. Root filled with hardened lubricant Clean gear flank and root
Why work with this? When you can have this!
Perfect for visual
inspection,
identifying failure
modes as per AGMA
1010 – ready in
under 1 hour

65. Clear, Synthetic Lubricants
• The clear lubricant sales representatives will advise; cleaning is not
required with our clear lubricant as you can see through it to visualize the
gear flanks; unless there is contamination present (below).
• Contamination is often a significant contributor to gear tooth failures.
• The ability to fully visualize gear teeth is critical for a true gear
inspection or audit.

66. Girth Gear & Pinion Temperatures During Cleaning
Pinion temperatures from pre-cleaning, to during cleaning, to finished cleaning
Girth gear temperatures from pre-cleaning, to during cleaning, to finished cleaning

67. Continuous Pinion Temperature Monitoring Program
• A common failure cause of gear driven mill systems is misalignment, which
in its most severe form can cause rapid tooth fatigue and fracture.
• The operating temperature profile of
girth gear pinions give an indication of
the pinion’s overall alignment with the
girth gear.
• High differential temperatures from end
to end indicate misalignment.
Pinion Temperature Profile
Global Inspections Installed System
on a Ball Mill

68. Conclusion
• Our comprehensive offering for mills and kilns enables us to work with sites
throughout the life cycle of their critical mechanical assets. Upfront we can
improve operational reliability with additional built in service factors in the
design phase, and proper installation and alignment during commissioning.
• During the operational phase our inspection process detects critical failure
modes early in their development. Having experts onsite conducting the
inspection enables us to act immediately when issues are found preventing
additional lost time due to unnecessary shutdowns. When an issue develops
we can quickly pull up archived data to assist with failure investigations.
• If the inspection detects critical failure modes such as cracks we can assist
with the sites decision on whether to flip, replace, or repair the set. Our
Decision matrix monetizes it for the site to aid in the decision based on the
options and their associated risks.
• Our offering when customized for a site allows them to optimize the
utilization and cost of ownership of their mill and kiln assets.