Girth Gearing Asset Management Structure NDT Methods Used on Gearing ASTM E2905 Inspection Practice Girth Gear Cleaning Learn more at: https://global-pam.com

1. Mill & Kiln Gear Asset Management

2. Topics of Discussion
• Girth Gearing Asset Management Structure
• NDT Methods Used on Gearing
• ASTM E2905 Inspection Practice
• Girth Gear Cleaning
• Questions

3. Acquisition
• AGMA ratings and design verification, manufacturing, and
instillation drawings.
• Quality assurance documentation, including specifications for
critical manufacturing procedures and inspections.
• Manufacturer audits, and witness during critical inspections.
• Quality 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.
Logistic Support:
• Resource support plans, total cost of ownership.
• Training programs
• Consultation and optimization of insurance spend, maintenance
spend, and sparing costs.

4. Operation and Maintenance:
• RCM approach to maintenance, and audits of existing maintenance
plans
• Field Service
• Girth gear installation oversight
• Pinion installation oversight.
• Pinion alignments to the girth gear.
• Determining pinion adjustments based on temperatures.
• Training with site millwrights on installation procedures.
• Preventative maintenance tasks, tied to specific failure modes.
• Proper alignment
• Contamination exclusion and removal (Cleansolv)
• Monitoring and maintaining alignment (IR Systems)
• Predictive maintenance tasks, to detect potential failures.
• Inspections per ASTM E-2905
• Open Gear split joint and structure inspections
• Operational inspection tasks and intervals
• Design or Engineering changes are prescribed where the probability
of failure and consequences of failure are deemed unacceptable.

5. End of Life
• Provide inspections and recommendations on suitability for girth 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.

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

7.  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

8. 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

9. 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

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

11. Reliability and Inspection:
• ECA and ACFM are the two electromagnetic methods that are the
basis of ASTM E2905 – (Examination of Mill and Kiln Girth Gear
Teeth—Electromagnetic Methods).
• ECA is the most advanced inspection method for 100% surface
coverage for the detection of surface defects on the addendum,
dedendum and root of the drive side and non-drive side of the
gear flank.
• For any cracks found, we use Alternating Current Field
Measurement (ACFM) for length and depth or Phased Array
Ultrasonics; if the crack is deep.
• ASTM E2905 is the only standard available today that specifically
addresses inspection of girth gear teeth.

12. Magnetic Particle Inspection – MPI Wet & Dry
• Utilizes magnetic particles dry or suspended in a fluid and a
magnetic yoke to detect indications including cracks.
• Surface must be free of lubricant, deposits and wiped dry 10-
12 hours or rinsed.
• Typical in service inspections take to 24 – 36 hours.
• Hand written reports.

13. Dye Penetrant Inspection – LPI
• Utilizes a penetrating dye and developer to detect
cracks
• Surface must be free of lubricant, deposits and wiped
dry 10-12 hours or rinsed.
• Typical in service inspections take to 24 – 36 hours.
• Hand written reports.
• Difficult to separate common
failure modes from critical cracks
especially on gears which may be
subject to extensive macropitting.

14. 0
Eddy Current Single Coil Scan Method:
Eddy Current single coil probe must be moved rapidly across the
gear tooth flank to cover entire tooth surface.
Eddy Current Single Coil
Probe
Eddy Current
Single Coil
Path
ASTM E2905
Multiple (Array)
coil Path
• Relies on inspector interpretation
vs

15. Ultrasonic Testing (UT)
• Employs high energy sound to find and characterize defects inside of
an object.
• Due to gear tooth geometry this method cannot be used as a 100%
tooth inspection as parts of the tooth will be missed.
• Probe contact points must be clean from debris, and couplet must be
used.
• Data is not recorded.

16. Phased Array Ultrasonic Testing (PAUT)
• Utilizes an array of ultrasonic transducers pulsed in a desired manner
to allow a wider area to be inspected than traditional ultrasonic
inspections.
• Has a significant blind spot close to the transducer and in the tooth
addendum.
• Has a blind spot in the root where fatigue cracking can occur.
• Requires a flat well machined gear tooth topland when inspected
through the topland; does not work on teeth with thin, burred or
damaged toplands.
• Scan data is not saved for future reference.
• Is a poor primary crack detection method; not recommended for gear
tooth surface examination; AGMA 919 – Part 1.
• Cannot provide 100% surface coverage
of the addendum, dedendum and root.

17. PAUT Coverage on a gear flank Probe coverage of tooth centre
Probe coverage missing critical surface area Probe coverage missing critical surface area
Crack Detected
Crack Initiation Not Detected

18. ASTM E2905 Inspection Practice
Eddy Current is not the same as Eddy Current Array!

19. 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.

20. Example Crack Detected with ASTM E2905 Method

21. Crack found in the root
that could not be visualized. C-Scan image of figure on the
left
• Looking at the left figure, a clean root, using E2905 as the inspection
standard, reveals a critical crack. The crack is well illustrated in the center
figure. This crack could not be visualized.
• In the right figure, the crack in the left figure, could not be visualized because
of the presence of lubricant in the root nor could it be detected using various
NDT methods.
This root cannot be inspected because of
the presence of lubricant

22. • Photographic and thermal images are taken prior to shutting the equipment down.
Any significant contact pattern issues, vibrations, temperature differentials, or
concerning conditions are noted.
• The gear set is thoroughly flushed using Cleansolv HF EP in the last 1 hour of
operation during grind out.
•
• Access to the mill gear teeth is made available by removing a section of guard.
• Each tooth is scanned with the appropriate probe using Eddy Current Array in
accordance with ASTM E2905. This is the primary defect detection method. A
visual inspection also occurs identifying failure modes per AGMA 1010-F14.
• As defects are found they are further inspected with magnetic particle to verify
the defect, if it is a crack the length and depth are determined by ACFM.
Inspecting a large girth gear
Inspection process

23. The different inspection areas between E2905 and UT
Comparison of Coverage between E2905 and UT
E2905 Probe
Ultrasonic Transducer
E2905 Inspection Area
• Ultrasonic’ s are very good at detecting indications at depth but
misses the most highly stressed area where gear failure modes
develop. This is a inadequate primary detection method.
• Eddy Current Array is very sensitive to surface and near surface
indications where gearing failure modes develop.

24. 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.

25. The Ease of Girth Gear Cleaning
Girth gear cleaning is needed to remove contamination and lubricant
buildup on mill ring gears prior to inspection. This is accomplished by
cleaning the ring gear while in production minimizing downtime.
• The actual time of cleaning a ring gear is under an hour.
• There is no need to wipe the gear teeth down after by hand to
remove residue as in Magnetic Particle, Dye Penetrant inspections
and Ultrasonics inspections.
• The ability to fully visualize the gear teeth is critical for a true gear
inspection.
Clean Gear Flank and RootRoot filled with hardened Lubricant

26. Cleaning Process
• Spray Cleansolv HF EP through the inspection door 1
hour before shutdown; during grind out.
• Cleaning is typically completed in under I hour.
• No rinsing or wiping is required if using Eddy Current
Array inspection method (ASTM E2905).
• Clean flanks and roots allow for a complete visual in
accordance to AGMA 1010 and 100% coverage using
Eddy Current Array.

27. Risk Improvement Solutions, Reliability,
and Asset Optimization
Questions?
Key Management Team
Tom Shumka William Quinn Jason Shumka
Global PAM Global-PAM Global-PAM
President Dir. Engineer, Mill Products ASTM E2905 Specialist
1-(480) 407-9949 1-(262)-744-0373 1-(403)-651-8568
Tom@global-pam.com Will@global-pam.com Jason@global-pam.com