Size a girth gear.

01Mill configuration

02Site, duty & lubrication inputs

These drive the lubricant selection in section 07. Temperature and application method are hard gates; the rest are weighted preferences.

03Gear sizing result

04Method, step by step

The report and CSV carry your current live values. Nothing you type here leaves the browser.

05Drive topology and AGMA checks

PASSFail = outside an AGMA / manufacturing limit or below target SF. Check = outside typical or published practice; review before proceeding.

06Benchmark comparison

Published gear sets [8, 9] with stated geometry. Your design point is overlaid.

Interpolation basis: transmitted torque governs face width more than mill diameter [8, 9]; no single published F = f(D) exists. The 5.0 m cement ball set [4] states no face width, so it is listed but excluded from the weighting.

07Whitmore lubricant recommendation

From the same inputs. The gates, weights and scores are shown in full below.

Temperature and application feasibility are hard gates (1 = feasible, 0 = excluded). Weights: surface repair 100 · bath, filterable fluid 50 · bath, other fluid 15 · manual or drip, tacky grease 5 · wash-off, tenacious film 30 · wash-off, non-emulsifying grease 10 · transparent film 20 · TCLP-safe 20 · OEM approval match 25. A small tie-break favours the earlier row. Held = the preference would apply, but its backing record is pending datasheet verification — sections 09 and 14 carry the records.

'n/s' = not stated in the document set. MillGuard (high-viscosity petroleum-resin fluid) and Surtac 2000 are also in the open-gear line — TDS on request; information only, not scored.

Figures are from the Whitmore document set of 2 June 2026, pending datasheet checks. Confirm against current Whitmore TDS at quote.

Case OEM match

No OEM approval requirement set.

Recommended initial spray-cycle interval

5–15 min — Envirolube XE Extreme is a fluid. Reference bands and the application-rate basis: section 10 [E2, E8].

08Consumption, energy & cost in use

Asphaltic reference against the recommended Whitmore product. Cost rows stay blank until you enter the rates and prices. The decision metric is cost per operating hour, not price per kilogram. A premium non-asphaltic can cost several times an asphaltic per kilogram and still be cheaper in service. Consumption falls to a fifth or a tenth in the documented field cases [E1].

Energy saving — specific grinding energy

The paper's headline effect. The 2015 South African gold-mine trial was independently assessed at −4.03% specific grinding energy [E5]. CMD reproduced it three ways from raw SCADA: −3.92% aggregate, −5.2% by daily means (p = 0.024), −4.4% by ANCOVA [E1]. Field references place the effect in a 3–16% band [E1].

09Disclaimer & terms of use

10Technical evidence — energy, wear & OEM requirements

Sourced from the published conference paper [E1]. Evidence is labelled by tier: independently reanalysed, independently published, third-party reported, and vendor reported. Only the 2015 South African gold-mine energy result has been reanalysed from raw data.

Download the conference paper (PDF)

DANIEL, M.J., DANIEL, K. and DAVIES, L. (2026). Technical conference paper, 12 pp. CMD Consulting Pty Ltd, Brisbane, and Whitmore Manufacturing LLC, Rockwall, Texas. Name, company and email first.

Laboratory wear — FZG, ISO 14635-3 (setting A/2.8/50)

The comparison products stay anonymised by number, as the paper publishes them. Envirolube XE Extreme Heavy passed the full >12 load stages, then an extended 30-hour test with the original crosshatch machining pattern still clearly visible. Third-party testing reported a 66% reduction in friction and wear overall [E1, E3].

Field and laboratory evidence

Read together, the mill energy effect clusters in a ≈3–16% band with the best-verified single number at ≈4%. The larger and more certain effect everywhere is the 70–90% reduction in lubricant consumption, measured directly and not confounded by ore or throughput. General lubrication literature documents a 5–15% power reduction from lubricant and reliability upgrades; this mill-specific evidence sits at the conservative end of that band, and is measured rather than asserted [E1, E7].

OEM minimum requirements — cited record [E2]

The OEM's open-gear guideline sets the bar a mill lubricant must clear before it is considered, and asks for proof in similar service. Viscosity is graded to the working environment temperature, not the mill temperature — which is why this tool takes site ambient minimum and maximum rather than gear temperature.

Legacy asphaltic against the modern non-asphaltic approach

The move from Type I to Type II is the change every field case above has in common [E1, E2].

How the savings arise — physical mechanisms

1. 01Higher film strength and EP capacity. Moving from a ≈20–25 lb Timken asphaltic to a ≈70 lb non-asphaltic with four-ball weld > 800 kgf keeps mating flanks separated under shock and slow-speed boundary contact, cutting the metal-to-metal friction that both wears teeth and wastes drive power [E1].
2. 02Direct friction reduction. Third-party testing measured a 66% reduction in friction and wear against the comparison. Lower friction in the mesh is, directly, lower parasitic power draw at constant ore load [E1, E3].
3. 03Flank smoothing in service (planishing). The additive package deforms surface asperities with minimal wear, flattening the tooth surface instead of abrasively removing metal. A smoother flank raises the specific film thickness and lowers friction — and removes the need for a separate abrasive run-in compound on new or re-toothed gears [E1, E6].
4. 04Stable, non-hardening film. Spent product does not harden or build up in the tooth roots, so the film stays uniform between spray cycles. Asphaltics can starve the contact if solvent has not evaporated, or build up and misdistribute load [E1].
5. 05Lower operating temperature. Reduced friction shows up as lower pinion and flank temperature — field cases report 10–30 °C reductions — which slows oxidation and extends gear and oil life [E1].
6. 06Dramatically lower consumption. A tenacious non-asphaltic film that resists water wash-off and does not need frequent replacement cuts application rate by 70–90% in the field cases: the fastest and most certain saving, and the one that offsets the unit-price premium [E1].

Not monetised in section 08: the third-party-measured 66% reduction in friction and wear (FZG, ISO 14635-3), 10–30 °C lower operating temperature (≈30 °C pinion reduction in the STLE/TLT 2022 field test), +33% open-gear life reported at two cement plants, in-service flank smoothing that can replace an abrasive run-in step, no tooth-root clean-down, and a TCLP-safe waste stream. Reduced downtime and hazardous-waste disposal are additional credits that are harder to isolate [E1, E7].

11Basis of girth gear design

Girth gear and pinion sizing for tumbling mills is driven primarily by transmitted torque at the pitch circle — motor power divided by pitch-line velocity — rather than by mill diameter alone. Published dual-pinion installations at 12.7 and 20 MW cluster at face widths of 1,016–1,080 mm despite mill inside diameters from 7.3 to 12.2 m [8, 9]. No single published formula F = f(D) exists. Selection should follow AGMA rating practice using connected motor power, mill speed, module, duty factor, and material data [16].

Load path and AGMA 6114 basis

ANSI/AGMA 6114-B15 [16] rates cylindrical shell- and trunnion-supported equipment (grinding mills, kilns) on connected motor nameplate power including service factor. Tangential load on the girth gear pitch circle is:

Pitch-line velocity is v = π · d_p · n / 60, with girth pitch diameter typically ≈ 1.05 × shell ID. Limits include v ≤ 10.16 m/s and module 8–50 mm [16]. The published 20 MW gear design [8] uses a 25° pressure angle, 7.5° helix and 21 pinion teeth. It reports AGMA durability factors of 1.81–3.20 on 20 MW class gears.

Drive topology and aspect ratio

Industry boundaries from the literature review [1, 3]: single-pinion ring gear to ~9 MW total; dual pinion to ~18 MW; above that, gearless drives dominate. Mill speed is correlated empirically as n ≈ K / √D (K ≈ 32.3 for SAG and ball, 33.5 for AG), with a small reduction for long mills (high L/D). Aspect ratio affects filling and impact loading: AG mills use higher duty factors (Ka ≈ 1.35) than ball mills (Ka ≈ 1.25).

Face-width selection in this calculator

Recommended face width is the greater of two figures. (a) A load-based width for the target durability factor, scaled from the published pinion benchmark [8] (SF ≈ 2.75 at 1,325 N/mm). (b) Benchmark interpolation from the published gear sets [8, 9] at similar power and diameter. Results are rounded to 10 mm and capped at the upper manufacturing limit of 1,800 mm [8]. Published tooth widths at large low-speed dual-pinion plants have reached ~1.4 m [9]. A conservative reference limit of 1,250 mm is published as a practical maximum [live ref 9].

Reference constants & typical values

12Important caveats — MJD review, June 2026

• Linear load-intensity scaling for the durability factor is a screening approximation. AGMA pitting durability relates more closely to contact stress (∝ √load).
• Applying the published dual-pinion operating load intensity (≈1,050 N/mm) [9] to a design load (Wt × Ka) would imply face widths above 2,000 mm — inconsistent load bases, and not manufacturable.
• Reference [1] cites 42 ft / 38 MW as an upper aspirational figure. The largest installed 42 ft gearless drive is 28 MW [11].
• Critical speed convention. The site engine shows nc = 23.80 rpm (42% Cs) for the 34 ft example. That equals 76.6/√D with D in metres — the imperial constant applied to a metric diameter. With nc = 42.3/√D (m) the critical speed is 13.14 rpm and 10.0 rpm is ≈ 76% of critical. Because mill speed itself comes from n = K/√D, all downstream figures (v, Wt, F, SF) are effectively unchanged. Select the CMD workbook basis in section 01 to use 42.3/√D.
• Module / teeth rule. The site's module rule was not stated on the page; both bases now state theirs in sections 04 and 11. The CMD workbook uses a target-pinion-speed basis, which reproduces the site example exactly (38 mm, 286/21 T, 136 rpm) and gives 41–42 mm for the 20 MW [8] set. An override cell is provided.
• Benchmark band. The CMD workbook applies the published band only for dual pinion ≥ 10 MW total. Applying it to all cases, as the site engine does, returns ~1,000 mm faces for small single-pinion mills; on the workbook basis those are sized on load only.
• Lubricant flags. Envirolube and GearMate are both explicitly TCLP-safe: Whitmore state it twice on the Envirolube XE Extreme product page, and on the current GearMate PDS. Others are not stated. Grade rules and intermediate low-temperature limits (GearMate All-Season / Light / Heavy; SurStik Medium / Heavy) are assumptions between the stated end-points — confirm on the current Whitmore TDS.

Integrity precedes efficiency. The primary duty of a mill open-gear lubricant is to preserve the gear; efficiency is a secondary benefit. Any trial protocol must halt on an adverse gear indication (temperature, vibration, visual or oil analysis). Delivery and climate matter: sprayability, heat tracing and pump / nozzle selection must be engineered for the site's ambient range, or the lubricant's benefits will not reach the flank. Gearless drives above ≈18 MW have no open gear and are outside this scope [E1].

13How to use & selection logic

14References

Bibliography from the CMD literature review (Daniel, June 2026). Project papers [1]–[7] and [17]; web supplement [8]–[16].

1. [1]Wankhede, A.K., Sharma, A. and Fernandis, B.G. (2021) ‘Overview of Grinding Systems and MV Drive Technologies in Mines’, International Journal of Engineering Applied Sciences and Technology (IJEAST), 6(4), pp. 171–194. ISSN 2455-2143. doi: 10.33564/IJEAST.2021.v06i04.020.
2. [2]Almond, D.G. and Valderrama, W. (2004) ‘Performance Enhancement Tools for Grinding Mills’, in Proceedings: International Platinum Conference ‘Platinum Adding Value’, The South African Institute of Mining and Metallurgy (SAIMM), Johannesburg (28–40 ft SAG/ball mills; 8–20 MW operating range).
3. [3]Rodríguez, J.R. et al. (2005) ‘Technical Evaluation and Practical Experience of High-Power Grinding Mill Drives in Mining Applications’, IEEE Transactions on Industry Applications, 41(3), pp. 866–874. doi: 10.1109/TIA.2005.847321.
4. [4]Ackle, W. ‘Central Drive or Girth Gear Drive’. Zurich: MAAG Gear AG (9,000 HP / 5 m cement mill case study). Company technical paper.
5. [5]Ustynenko, O. et al. (2023) ‘Design, Research, and Production of Gear Wheels for Mining Machines’, MATEC Web of Conferences, 387, 01003. doi: 10.1051/matecconf/202338701003 (coal combine gearbox; not tumbling mill).
6. [6]Krot, P.V. (2019) ‘Dynamical Processes in a Multi-Motor Gear Drive of Heavy Slabbing Mill’, Journal of Vibroengineering, 21(8), pp. 2064–2081. doi: 10.21595/jve.2019.20973.
7. [7]Dorkhah, A., Arab Solghar, A. and Rezaeizadeh, M. (2020) ‘Experimental Analysis of Semi-autogenous Grinding Mill Characteristics Under Different Working Conditions’, Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, 44, pp. 1103–1114. doi: 10.1007/s40997-019-00318-8.
8. [8]Druce, I., Kalra, R. et al. (2013) ‘Updates on Geared vs Gearless Drive Solutions for Grinding Mills’, SME Preprint 13-050. SME Annual Meeting, Denver, CO (12.2 m SAG and 8.5 m ball gear design table).
9. [9]Rufli, M., van de Vijfeijken, M. et al. (2011) ‘Copper Mountain: Overview on the Grinding Mills and Their Dual Pinion Mill Drives’. ABB Switzerland, Document 9AKK1074920735 (34 ft SAG and 24 ft ball face widths).
10. [10]Ahrens, M. and Gonser, J. (2007) ‘Technical and Commercial Benefits of Gearless Mill Drives for Grinding Applications’. SME Annual Meeting / OneMine (tooth width vs. alignment discussion).
11. [11]ABB (n.d.) Gearless Mill Drives [product brochure]. Available at: library.e.abb.com (22 MW / 28 ft ball; 28 MW / 40–42 ft SAG reference list).
12. [12]Greer, S.A. (1990) ‘Selection Criteria for SAG Mill Drive Systems’, IEEE Transactions on Industry Applications, 26(5), pp. 901–908 (cited in [3]; pinion power limits).
13. [13]Kivari, D.B. and Chapman, J. ‘Mill Drive Selection for Semiautogenous Grinding Mills’, Mining Engineering / 911Metallurgist (34 × 16 ft, 2 × 6,000 HP twin pinion).
14. [14]Errath, R.A. (1996) ‘15000-HP Gearless Ball Mill Drive in Cement — Why Not!’, IEEE Transactions on Industry Applications, 32(3), pp. 663–669. doi: 10.1109/28.502179.
15. [15]Kumera (n.d.) Girth Gear Technical Manual (selection torque method; face-width factor table; up to 8 MW/mesh).
16. [16]ANSI/AGMA 6114-B15 (2015) Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment. Alexandria, VA: American Gear Manufacturers Association (module 8–50; max 10.16 m/s pitch-line velocity).
17. [17]Bacigalupo, C. and Soressi, E. (2001) ‘A Synchronous Motor Drive with Great Speed Accuracy and High Dynamic Range for Rolling Mill Applications’, EPE 2001 — Graz (3–10 MW rolling-mill drives; not tumbling-mill girth gear). Project folder.

Live web references, accessed June 2026

• [1]Druce et al. (2013) — geared vs gearless preprint (PDF)
• [2]ABB — dual-pinion mill drives paper, Document 9AKK1074920735
• [3]ABB — gearless mill drives brochure (PDF)
• [4]OneMine — Ahrens & Gonser (2007), GMD benefits
• [5]IEEE Xplore — Errath (1996), 15000-HP gearless cement mill
• [6]911Metallurgist — SAG mill drive selection (Kivari & Chapman)
• [7]911Metallurgist — variable-speed SAG mill drives (Greer context)
• [8]AGMA — ANSI/AGMA 6114-B15 standard
• [9]Fuller Technologies — girth gear product specs (max Ø11,200 mm, F = 1,250 mm)
• [10]ISO 6336-1:2019 — spur and helical gear load capacity
• [11]US Patent — multi-pinion grinding mill drive (up to 36 MW mechanical)

Lubrication evidence references [E1]–[E8]

Sources for the selector, cost-in-use and evidence content in sections 02 and 07–10. Documents not published here are held in the CMD project record.

• [E1]Daniel, M.J., Daniel, K. and Davies, L. (2026) ‘Energy and wear savings on grinding mill girth gears and reducing gearboxes through advanced open gear and gear oil lubrication’. Technical conference paper, CMD Consulting Pty Ltd, Brisbane, and Whitmore Manufacturing LLC, Rockwall, Texas. Download the PDF.
• [E2]Metso:Outotec (2021) Open Gear Lubrication of Grinding Mills. Document 3-21-003, 05 March 2021 (Table 1 minimum requirements; Table 2 qualified open gear lubricants; AGMA 6014-B15 application guidance).
• [E3]Whitmore Manufacturing LLC. Envirolube® XE Extreme — product sales sheet (FZG A/2.8/50 results; 66% friction and wear reduction claim). Pending under the datasheet-verification protocol.
• [E4]SKF Lubrication Systems Germany GmbH, Walldorf (2021) Statement of suitability — Whitmore Envirolube XE Extreme Medium/Heavy in centralised and Lincoln SD spray systems, 28 April 2021 (pumpability minima per pump model). Named and dated; pending verification.
• [E5]CMD Consulting Pty Ltd (2026) Mill Lubrication Energy Trial — reanalysis of a 2015 milling-circuit lubrication trial at a South African gold mine, and the statistical case for a definitive ON/OFF trial, 15 July 2026. Independent assessment by L. Lamont, Pr.Eng (North West University), February 2016.
• [E6]Whitmore Manufacturing LLC (2025) Use of Envirolube® XE and XE Extreme on New Gears — surface smoothing without a separate run-in compound, October 2025.
• [E7]Impala Platinum — signed open-gear conversion reference letter, 10 June 2014. Lubrication Engineers / C. Ford, Lubrication, energy consumption and reliability (5–15% power-reduction reference) and The Cost of Incorrect Lubrication. STLE/TLT (December 2022) ore-processing-plant specialty OGL field test.
• [E8]ANSI/AGMA 6014-B15, Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment — open gear lubricant application rates (Table D.3). Napier-Munn, T.J., Statistical Methods for Mineral Engineers (JKMRC) — switchback trial design and power calculation.