Global’s third party mill, kiln & girth gear risk assessments are focused on avoiding catastrophic failures; providing risk improvement solutions, improved reliability, reduced maintenance costs, increased asset availability, and enhanced safety.

Global’s process provides a concise insight for the maintenance team and insurance industry on the level of exposure being presented by any operation relating to girth gear teeth.

We pride ourselves on being able to provide realistic and tailored risk improvement solutions to assist our customers’ businesses through reducing the cost of risk associated with gear teeth failure events.

In summary:

  • Can reduce downtime for mill gear inspections by over 50%.
  • Provides Risk Improvement Solutions, Reliability and Asset Optimization.
  • Provides more equipment availability.
  • Global’s process satisfies insurance requirements.
Girth Gear Inspection - Broken Tooth
Utilizing the Global Process can dramatically minimize the chance of failures like these
Girth Gear Inspection - Broken Tooth

Physical Asset Management

Acquisition

  • Quality assurance documentation, Audits, including specifications for critical manufacturing procedures and inspections

Commissioning

  • Commissioning support, contractor technical review
  • Power transmissions including
  • Girth gear and pinion installation oversight
  • Gearboxes
  • All critical fasteners and structural mill components

Logistic Support:

  • Resource support plans, total cost of ownership.
  • Training programs
  • Consultation and optimization of insurance spend, maintenance spend, and sparing costs

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

Acquisition and Commissioning; Fixed Plant

Engineering Support:

  • Third-party gear engineering, design, installation, risk assessments, inspections, pinion alignments and maintenance audit and full FMEA audits on large scale trunnion and roller supported mill and kiln drives
  • We can perform gear ratings for current and replacement gear sets, provide support for procurement, and provide complete gear and pinion installation
  • QA/QC support for all critical mill components, girth gears, pinions, shells, heads, trunnions

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.

Preventative maintenance tasks, tied to specific failure modes.

  • Proper alignment.
  • Contamination exclusion and removal. (GF 460EP Flushing Lubricant)
  • 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.

Support Fixed Plant

ASTM E2905 – Standard Practice for Examination of Mill and Kiln Girth Gear Teeth — Predictive Maintenance Process

  • Eddy Current Array (ECA) and ACFM are the two electromagnetic methods that are the basis of ASTM E2905
  • 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
  • ASTM E2905 is the only standard available today that specifically addresses inspection of girth gear teeth
  • Our database of girth gear failure modes is extensive which allows us to get to the root cause quickly
Gear tooth crack visualized with Eddy Current Array
Gear tooth crack visualized with Eddy Current Array
Crack on a Gear Flank

Diagram: Gear Flank Potential Failures and Failure Mode Relationships

A typical NDT company will detect porosity, Inclusions & cracks deep in the structure, using Phased Array. These processes miss the surface where critical failures typically start.

Gear tooth potential failures and failure mode relationships
Gear tooth potential failures and failure mode relationships

Risk Assessment Model

This approach provides a complete gear set inspection beyond just identifying cracks

Our on-site risk assessment model, as per AGMA 1010 F-14, is able to provide a comparative measurement of loss probability and consequence. Our extensive database of gear teeth failure modes enables us to provide root cause analysis effectively.

Girth Gear Tooth Condition Assessment
This approach provides a complete gear set inspection beyond just identifying cracks

Our girth gear inspection, which includes scanning 100% of both the drive side and the non-drive side flank and root, provides the asset owner a complete non-destructive test of the integrity of the mill gear teeth in accordance with ASTM E2905.

There are two electromagnetic methods that are the basis of ASTM E2905: Eddy Current Array (ECA) – for detection of surface defects and Alternating Current Field Measurement (ACFM) for sizing of any cracks found.

Onsite data analysis for immediate results. If critical indications are found, immediate action can be taken to mitigate operating risk.

If crack mapping is required, we use Phased Array Ultrasonics.

We also include an onsite assessment as per AGMA 1010-F14 of the failure modes present, if any, their severity, and how these might impact the operational function of the mill.

All this satisfying maintenance, reliability and insurance requirements.

Mill Gear Inspection Deliverables & Benefits

Deliverables

  • We provide a complete non-destructive examination of the integrity of the mill gear teeth in accordance with ASTM E2905, for macro-pitting and cracking
  • We can clean a girth gear set in under 1 hour and inspect the same in under 9 hours; saving valuable downtime and increasing production revenue
  • We also provide an onsite failure analysis as per AGMA 1010-F14 of the failure modes present, if any, their severity, and how these might impact the operational function of the mill
  • The final report provides a concise insight for the maintenance team and insurance industry on the level of exposure being presented by any operation relating to girth gear teeth

Benefits

  • Creating a girth gear asset management program would deliver consistency, efficiency and standardization.
  • We have compiled 12 years of data of gear failure modes in an electronic format. This helps us find the root cause quickly.
  • Providing a complete girth gear asset management program.
  • Scheduled inspections and maintenance recommendations.
  • The program will provide the ability to accurately forecast demand for components in the future.
  • Enhance the lifecycle of critical assets.
  • Provide electronic reports that can be archived for future reference.

The Importance of Girth Gear Flushing

Contamination is often a significant contributor to gear tooth failures.

Flushing Process as per ASTM E2905

  • Girth gear flushing is needed to remove contamination and lubricant buildup on mill girth gears when contamination is present, particularly when liner bolts fail, and slurry enters the gear guard
  • Flushing prior to inspection is necessary to enable a proper ASTM E2905 and visual inspection in accordance with AGMA 1010
Root filled with hardened lubricant
Root filled with hardened lubricant
Clean gear flank and root
Clean gear flank and root
Broken Gear Tooth Contamination in Guard
Broken Gear Tooth - Contamination in Guard
Lubricant Contamination
Lubricant Contamination

GF 460EP Flushing Lubricant

GF 460EP is a unique Flushing Lubricant for open gear flushing applications; designed to remove contamination and lubricant buildup on girth gear flanks and pinions prior to inspection or any related maintenance procedures.

  • Annually flushing contamination out of the gear set is an excellent preventative maintenance program.
  • Excellent for flushing out Slurry Ingres
  • Girth Gear Cleaning in accordance to ASTM E2905 Appendix X2
  • Necessary for AGMA 1010 Inspection
GF 460EP Flushing Lubricant Technical Data
FZG Scuffing Load Capacity – ASTM D5182 – Pass Load Stage>14
Viscosity – ASTM D445 – Viscosity 40°C (cSt)3.7
Base Oil Viscosity @ 40°C (cSt)486.76
Flash Point – ASTM D0092A212°F
Volatile Organic Compounds (VOC’s) – ASTM E18680.56%
VOC g/L4.69
Shipped as Non-Regulated under DOT, TDG, IATA, and IMDG

Advanced Pinion Monitoring Program

  • The autonomous predicative maintenance solution for monitoring mill pinion condition in real time.
    • Visual condition is monitored on programable intervals
    • Thermal imaging on programable intervals
    • Continuous temperature monitoring
  • Mobile application available
    • Photographs, thermal images, and data available
  • Data is archived for recall
  • Inspection doors do not need to be opened, eliminating safety concerns.

Failure modes addressed

  • Misalignment
  • Wear/abrasion
  • Scuffing/adhesive abrasion
  • Macro-pitting and Spalling
  • Fractured pinion tooth

Determining Root Cause Through Visual Vibration Program

Motion Amplification Technology:

  • Motion Amplification® is an exciting technology that allows a vibration analyst to see minute amounts of machine movement that would ordinarily be invisible to the naked eye.
  • The results lend themselves to a visualization of the movement. We can measure and quantify any structural assets that a camera can see.
  • Motion Amplification is a proprietary video processing algorithm that detects subtle movement then increases that movement to a level visible to the naked eye which enhances the understanding of the components and interrelationships creating the motion.
  • Traditional vibration monitoring equipment and strain gauges still are useful in diagnosing concerns with Machinery and structures. Motion Amplification is excellent technology to finding the root cause of an issue.

Reverse Engineering Program – “you keep the drawings”

Reverse modeling refers to the process of analyzing the construction of a product when there are no design documents available from its original production. Reverse modeling serves many purposes including:

  • developing a similar or improved product/design
  • creating adapters or enclosures to the original product
  • reproducing an existing part
  • Customer keeps the drawings

Case Study: Practical approach to girth gear failures from tooth cracking

How all of this comes together to mitigate potential catastrophic failures

34′ X 20′ SAG Mill
Nameplate Mill Power (HP)17,000
Motor Power (HP) Max8,985
Face Width [mm]1,016
Mill Speed (RPM) Nominal10.3
Gear Ratio20.2
Mesh Per Revolution2.0
Operating Hours at First Detection35,345
Gear tooth load cycles43,686,420
SAG Mill

Detecting Cracks with ASTM E 2905 on 3/15/2016

  • A complete cleaning and girth gear inspection was conducted March 15, 2016 per ASTM E2905.
  • 4 Cracks were detected and relieved onsite. This is extremely important to stop or slow down the progression of any cracks found.
  • The prior inspection by Global personnel on June 2014 did not detect any cracking.
ToothTotal Crack Length [mm] on 3/15/2016
1867
11122
189254
22567
Crack Detection in Tooth 189
Crack Detection in Tooth 189
Crack Detection in Tooth 189
Crack Detection in Tooth 189
Mitigation Technique
Dykem Blue is used to monitor the contact in the vicinity of the crack.
Dykem Blue is used to monitor the contact in the vicinity of the crack.

Follow up Inspections

  • Monthly MPI of the surface
  • Monthly Conventional Ultrasonic Inspection of the Depth
  • Complete ASTM E2905 Inspection at 11 months, recommended every 4 months for compromised gearing.
Follow Up Inspection
Follow Up Inspection
Phased Array Ultrasonic Inspection to Map Depth [NOT for Crack Detection]
Phased Array Ultrasonic Inspection to Map Depth [NOT for Crack Detection] Phased Array Ultrasonics is beneficial as a secondary inspection method for mapping out cracks
This picture shows an excellent representation of crack mapping using PAUT. We can track growth and orientation of the crack over a period.
This picture shows an excellent representation of crack mapping using PAUT. We can track growth and orientation of the crack over a period.

Additional Cracking Found on 2/15/2017

ToothTotal Crack Length [mm]
1867
6628
7419
7919
10713
11151
13036
189306
22582
253166

Surface Crack Lengths Over Time

Surface Crack Length [mm]
Tooth3/15/20164/13/20165/3/20166/7/20167/12/20168/9/20169/7/201610/12/201611/22/201612/14/20161/17/20172/15/20173/14/2017
1867676870707070707070707070
662828
741919
791919
1071313
11122514848484848484848515151
1303638
189254276286286286306306306306306306306306
22577777878787878828282828282
253166166
Surface Crack Lengths Over Time using PAUT
Surface Crack Lengths Over Time using PAUT

ASTM E2905 Inspection Interval Setting

  • Over 11-month time period, 6 additional cracks formed.
  • Original length of time between inspections was 21 months; then 4 cracks were identified
  • Annual Inspections would likely have caught the cracking earlier in its development allowing for crack mitigation at smaller sizes, elimination, or less expediting for replacement gearing

Girth Gear Replacement 4/15/2017

Global conducted all the QA/QC with the manufacturer to ensure the new gear met the appropriate specifications.

Global also conducted oversight of the new gear installation. Ensuring the gear was installed properly giving it the best chance to meet or exceed its design life of 25 years.

replacing the girth gear