• Girth Gear

2 Gear Tooth Area Showing One Pass CoverageGirth gear asset management is a difficult but critical task at many mine sites, cement plants, lime plants, and paper mills. Mill and Kiln shutdowns are always very costly and girth gearing lead times are long, but large girth gears and pinions are very expensive and thus spare inventory time and inventory quantity need to be kept low. In order to manage these assets many sites employ condition based monitoring techniques which require periodic inspection and assessment.

Our gear engineering team often conducts gear inspections and risk assessments based on the inspection recommendations outlined in the annex of AGMA 6014. Part of this inspection is a visual and photographic inspection of the teeth, recording damage in accordance with the terminology outlined in AGMA 1010-F14. With the introduction of ASTM E2905 an improved cleaning and tooth inspection method is available that quickly detects and accurately maps surface breaking indications and cracks on gear teeth. Inspections per ASTM E2905 are powerful standalone inspections, but when combined with classic inspections per the inspection recommendations in AGMA 6014 the result is a complete snapshot of the girth gear system’s condition. Cleaning and inspection times for a 10m mill gear drive is seven hours.

Inspections per ASTM E2905, penetrate just below the surface of ferrous materials to accurately detect cracking, macro-pitting, and subsurface precursor macro-pitting damage. The inspection probe covers the entire tooth height from tip to root and when scanned covers the entire tooth flank in a fraction of the time of traditional tooth flank inspections requiring less downtime. The output of a scan is a three dimensional color map which is read live to quickly identify significant indications or cracks, each scan is also archived for later retrieval and analysis. While conducting the scans we are also conducting a visual inspection identifying, categorizing, and characterizing tooth surface indications, cracks, and distress. When an indication of significance is identified by E2905 it is then accurately sized; visualized using MPI; and documented through photography. Accurately sizing significant indications or cracks utilizing E2905 enables operational impact analysis and damage monitoring. The recorded scans are also useful in establishing baseline tooth condition and through consecutive inspections monitoring wear and damage trends.

Combining E2905 into our inspections has enabled us to refine our girth gear risk assessments and add clarity to our asset management recommendations helping our customers make informed condition based decisions.

Insurance companies have now accepted this standard. E2905 is recognized in AGMA 919-1-A14 Condition Monitoring as an accepted method for gear inspection. This practice standardizes the cleaning and use of this non-destructive testing approach for large girth gear and pinion inspections, delivering consistency, efficiency and standardization, a service valued worldwide.

pdfGirth Gear Asset Management 2016