By PMDD Motor · Reviewed
Screen torque, energy and retrofit constraints.
Illustrative defaults. Screening only.
Collect mill drawings, trunnion NDT, measured load/start logs, grid data and cooling duty. Request engineering review before selecting equipment.
No weighted score: a structural or critical-speed HOLD cannot be offset by other selections. Every discipline still requires engineering review.
Request engineering reviewREVIEW
Condition is user-reported (unknown); no capacity or alignment verification is performed. Obtain NDT, load-path and foundation checks.
REVIEW
Demand scenario: 2.2× shell torque. Motor current, duration, converter overload and grid reserve are unknown; no electrical pass is inferred.
REVIEW
77.0% of approximate Nc. Process suitability and frozen-charge protection require OEM validation.
REVIEW
IC71W is a proposed method only. Verify losses, ambient/altitude, coolant or blower duty and loss-of-cooling interlocks.
236.1 kN·m
At entered useful shell power and speed; not pinion motor torque.
519.5 kN·m
2.2× continuous; no motor/current capability is verified.
23.6 RPM
Operating at 77% Nc; ball-size correction omitted.
2.43 mm
Uniform steel shell; fixed 45°C rise. Actual displacement depends on bearing arrangement.
301.2 MWh/yr
Positive = saving; negative = increased input. Equal mechanical output assumed.
N/A
Annual benefit: USD 30,119.6. Requires positive entered cost and benefit.
Baseline / retrofit grid input: 3,835.2 / 3,534 MWh/yr. Electricity cost delta: USD 30,119.6/yr. Constant load, hours and output assumed. Cooling auxiliaries, demand charges, tax, finance and throughput effects are excluded unless entered as added annual costs. No discounted LCC is calculated.
Contact buttons open a draft. Attach drawings and measured start/energy logs yourself.
| Decision dimension | Proposed trunnion/shaft PM drive | Pinion-direct PM drive | Reducer refurbishment |
|---|---|---|---|
| Torque path | 1:1 shell coupling, if structurally feasible | Motor → retained pinion/girth gear | Existing geared path |
| Critical evidence | Added mass, bending, reaction support, alignment | Gear rating, ratio, bearing duty, load sharing | Inspection and remaining component life |
| Maintenance boundary | Removed gear duties may disappear; bearings and cooling remain | Girth gear lubrication and alignment remain | Gear oil and wear duties remain |
| Energy comparison | Obtain total grid-to-shell duty efficiency | Include retained gear and converter losses | Measure repaired baseline at equal output |
| Cost and outage | Unknown until scope, rigging and site plan exist | Unknown until interfaces and gear condition verified | Obtain comparable repair scope and warranty |
Evidence scope: ABB — Ring-geared mill drive system; ABB — Gearless mill drives; ANSI/AGMA 6014-B15 — Gear power rating for cylindrical shell and trunnion supported equipment. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
Compare gearbox replacement architectures when the retained gear path is your main decision.
Five workstreams: mechanical/civil, electrical, process protection, thermal/environmental and commercial. They run together; a failed safety requirement blocks selection.
| Workstream | Collect | Resolve before selection | Reviewer |
|---|---|---|---|
| Mechanical/civil | GA drawings, NDT, runout, bearing and foundation records | Load path, support, fatigue and dynamic response | Mill OEM and structural engineer |
| Electrical | Voltage, grid fault level, transformer data, motor/start logs | Torque-time capability, harmonics, insulation and protection | Drive supplier and power systems engineer |
| Process/protection | Charge behaviour, liner/media data, product specification | Operating range, charge detection and validated safe stop | Process and functional safety team |
| Thermal/environment | Ambient, altitude, cooling utilities, dust and washdown | Full-duty heat rejection, enclosure and interlocks | Motor/cooling supplier |
| Commercial | Energy and maintenance records, quotes, outage plan | Comparable installed scope and acceptance plan | Plant owner and procurement |
Removing a gearbox changes the load path; it does not prove lower foundation fatigue. Check static loads, transients, modal response, anchor condition and bearing arrangement. Gear-mesh excitation depends on tooth counts and shaft speed; no measured vibration spectrum is available for this proposed retrofit.
A conceptual review flow. No vibration reduction or allowable runout is inferred.
| Check | Relation and units | Worked example / limitation |
|---|---|---|
| Shell torque | T = 9550 × P(kW) / n(RPM), N·m | 450 kW / 18.2 RPM → 236.1 kN·m; no acceleration inertia included |
| Axial expansion | ΔL = α × L × ΔT | α = 12 µm/(m·°C), ΔT = 45°C: 5 m → 2.7 mm; 12 m → 6.48 mm |
| Reaction force | F = T / r, N with torque in N·m and perpendicular arm in m | 200,000 N·m / 1.5 m → 133.3 kN, before design load combinations |
| Bearing/support | OEM load and lubrication analysis | Unknown: motor mass, journal bending, start lubrication and axial freedom |
Equations follow rotational power, linear expansion and static moment balance. The tool assumes uniform steel temperature; actual movement depends on fixed/floating bearings and coupling geometry. Inspect defects and obtain site-specific structural calculations; no generic shock factor, oil pressure or journal tolerance is supplied.
Converter switching, cable layout and grounding affect machine insulation and shaft-current paths. Review the complete motor/drive system. Bearing insulation, grounding and filtering are engineering options requiring coordination; this page does not prescribe a universal threshold or bearing arrangement.
Specify voltage class, cable length and manufacturer limits before selecting grounding, bearings or output filters.
| Interface | Evidence requested | Possible response to evaluate |
|---|---|---|
| Insulation | Terminal peak voltage, rise time, cable length and duty | Compatible insulation system and output filtering |
| Shaft currents | Bearing type, current path and grounding layout | Insulated/hybrid bearings or grounding provisions |
| EMC and bonding | Cable screen termination and equipotential bonding plan | Coordinated installation and commissioning measurements |
Evidence scope: IEC TS 60034-25:2022 — AC machines used in power drive systems. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
A charge that adheres to the shell after a stoppage can create a dropped-charge hazard. ABB documents angle and dynamic-torque monitoring as part of mill protection. Detection is different from removal: a frozen-charge alarm does not authorize automatic rocking or a restart.
Concept only. No trip angle, rocking amplitude, timing or controller program is provided. Inhibiting inverter pulses alone is not a demonstrated safe stop.
Ask for the approved sensing, stopping, alarm, recovery and proof-test procedure. Include loss of supply, sensor failure, rollback and stored charge energy. An unvalidated release function is a reason to hold commissioning.
Evidence scope: ABB — Mill application features (white paper); OSHA 29 CFR 1910.147 — Control of hazardous energy. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
The tool calculates total shell torque. For a retained ratio i = n_pinion / n_shell and gear efficiency η_g, total pinion torque is approximately T_shell / (i × η_g). With two pinions an equal split is only a starting assumption; load imbalance and transients require separate ratings.
Active load sharing is a documented drive function, not an assumed precision guarantee. Verify gear loads and fault responses.
Request gear condition/rating, torque split, synchronization architecture, torsional study and degraded-operation behaviour. No universal communication latency, preload bias or load-sharing accuracy is established.
Evidence scope: ABB — Ring-geared mill drive system; ANSI/AGMA 6014-B15 — Gear power rating for cylindrical shell and trunnion supported equipment. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
AFE, multipulse and other front ends require a system study. No fixed current percentage, bus clamp or automatic stator-shorting design is selected here.
| Question | Required evidence | Decision limit |
|---|---|---|
| Starting capability | Motor torque/current map, inertia, start duration and frequency; converter limits | Assumed breakaway factor is a demand, not a capability check |
| Harmonics | PCC definition, grid strength, background distortion and applicable criteria | Drive THDi alone cannot demonstrate PCC compliance |
| Supply loss/rollback | Back-EMF, kinetic/potential energy, braking duty and failure analysis | A PM rotor can generate voltage; no universal braking circuit is safe by default |
| Maintenance isolation | Hazardous-energy procedure, stored-energy control and isolation verification | Powered holding or a control stop is not energy isolation |
Evidence scope: IEEE 519-2022 — Harmonic control in electric power systems; IEC TS 60034-25:2022 — AC machines used in power drive systems; OSHA 29 CFR 1910.147 — Control of hazardous energy. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
At low shaft speed, a shaft-driven fan may not provide the required heat rejection. Independent air or liquid cooling can address this, subject to a supplier thermal rating. For a fixed fan geometry the affinity relations approximate airflow ∝ speed and fan power ∝ speed³; airflow does not follow the cube law.
Cooling designation and ingress protection are separate. No flow, noise, IP or full-torque capability is inferred from a selection.
| Option | Utility / duty evidence | Risks and mitigation |
|---|---|---|
| Liquid arrangement, e.g. IC71W | Loss map, inlet temperature, flow, water quality and pressure drop | Leaks, corrosion or utility loss; specify monitoring and safe loss-of-cooling response |
| Independent blower, e.g. IC416 | Air path, ambient, altitude, filter pressure drop and blower supply | Dust, clogging and auxiliary failure; review filtration and monitoring |
| Shaft-driven fan | Measured thermal capability at required low-speed torque | Do not assume high-speed catalogue rating applies; derate or choose another arrangement |
Evidence scope: IEC 60034-6:1991 — Methods of cooling (IC Code); IEC TS 60034-25:2022 — AC machines used in power drive systems. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
From particle force balance, ω²R = g gives Nc ≈ 42.3 / √D in RPM. A finite media diameter changes the radius to (D − d)/2. The simplified tool omits d, so its critical-speed hold is approximate; operation below it is not proof of a suitable or safe process speed.
The 65–82% review band is an editorial screening assumption. Do not set speed from this band or from Bond Work Index alone.
Validate product size, throughput and specific energy at comparable feed hardness, filling, media and liner condition. Variable speed can support tuning; induction-motor drives may also offer it. No automatic power saving or throughput gain is credited by this tool.
Evidence scope: Metso — Correct liner selection, optimal mill efficiency; ABB — Ring-geared mill drive system. Public sources checked 2026-11-01; site acceptance values remain to be confirmed.
These are hypothetical calculations using the same tool model. No customer deployment, measured vibration improvement or commercial return is claimed.
450 kW shell output, 18.2 RPM, 7,500 h/yr, 88% baseline and 95.5% retrofit efficiency.
Continuous torque: 236.1 kN·m. Energy delta: 301.2 MWh/yr, worth USD 30,120 at USD 0.10/kWh.
Next: validate both efficiencies; payback is N/A until a project cost is entered.
Same 450 kW and 7,500 h/yr, with 92% baseline and 90% retrofit efficiency.
Input rises by 81.5 MWh/yr. With zero maintenance credit, annual benefit is negative and payback is N/A.
Next: compare repair and inspect the assumed efficiency boundary.
Use default energy inputs but report severe trunnion/foundation damage, or set 8 m diameter and 20 RPM.
Severe damage creates HOLD. The speed example is about 133.7% of approximate Nc and also creates HOLD.
Next: resolve defects and the OEM operating envelope before selection, regardless of energy delta.
| Risk | Decision consequence | Minimum next step / alternative |
|---|---|---|
| Structural damage or unknown capacity | Hold selection where severe defects are reported | Obtain NDT and structural review; consider repair before conversion |
| Poor or unverified energy benefit | No energy-led investment case is established | Measure equal-output input; compare reducer refurbishment |
| Cooling, grid or rigging mismatch | Project scope and cost remain unresolved | Survey utilities and lifting access; compare retained-gear options |
| Low duty or short remaining asset life | Simple payback alone may mislead | Use expected operating life and full cost scope in a separate investment review |
For equal useful shell power P and annual hours h: E_grid = P × h / η / 1000 in MWh. Energy saving is E_base − E_retrofit; a negative value is an increase. Annual benefit = energy delta × 1000 × tariff + entered maintenance saving − entered added annual costs. Simple payback = entered installed cost / positive annual benefit.
| Item | Default model value | Known / unknown and next action |
|---|---|---|
| Baseline / retrofit input | 3,835.2 / 3,534 MWh/yr | Calculated from illustrative efficiencies; measure at matching duty |
| Annual electricity cost delta | USD 30,120/yr | Calculated at USD 0.10/kWh; no demand-charge effects |
| Maintenance / added cost | USD 0 / USD 0 per year | No credit assumed; unknown auxiliary costs must be entered |
| Installed cost and payback | Unknown / N/A | Get comparable installed quote including civil work, rigging and outage |
| Discounted life-cycle cost | Not calculated | Add discount rate, replacements, residual value, taxes and risk separately |
The model uses constant shell power for all entered hours, not a load-duration curve. Do not count maintenance savings for retained gears. Zero hours suppresses operating benefits; zero tariff removes only energy-cost benefit. Unknown project cost remains unknown. No universal payback window is supported.
It estimates shell torque, critical-speed fraction, thermal growth and equal-output energy scenarios. It identifies review needs and holds. It cannot approve a trunnion, foundation, converter, cooling system or installation.
Enter useful mechanical power at the shell. Motor nameplate rating and measured grid input are different boundaries. If shell power is unknown, request a load and efficiency review rather than treating the nameplate as measured output.
Nc ≈ 42.3 / √D is a screening approximation in RPM with D in metres inside liners. A ball-centre correction uses D − d, where d is media diameter. Liner and media geometry and the OEM process envelope must be checked before setting speed.
No. The factor is an assumed shell demand. The current needed depends on the motor torque/current map, control, saturation, gear ratio, acceleration and duration. Obtain both motor and converter torque-time/current limits.
A reported severe trunnion or foundation defect must be resolved independently. Energy benefits or a preferred cooling selection cannot offset it. Request structural and mill OEM review before equipment selection.
No. Added rotor mass, bending, reaction torque, alignment, bearing lubrication and fatigue require drawings, inspection and calculations. User-reported condition is not an NDT result or capacity verification.
Not directly. For a retained gear ratio i = n_pinion / n_shell, a first estimate is T_pinion = T_shell / (i × gear efficiency). Confirm transient duty and dual-pinion load sharing separately.
No. A large ring-motor GMD and a proposed shaft/flange-mounted PM arrangement have different electromagnetic and structural interfaces. Evidence for a ring motor does not establish availability of a shaft-mounted retrofit.
No. Evaluate the applicable voltage and current distortion criteria at the PCC using the site system data and agreed measurement method. A drive-terminal THDi figure is insufficient to demonstrate plant compliance.
There is no universal component recipe established by this page. Review motor/converter interactions, grounding, cable layout, filters and bearing arrangements with the manufacturers using IEC TS 60034-25 and the applicable motor voltage class.
No. Charge detection, controlled stopping and any removal function require a validated OEM procedure and site risk assessment. No trip angle, reversal torque, pulse-blocking time or automatic restart instruction is provided.
No. Use the applicable hazardous-energy procedure, isolate energy sources, control stored charge energy and verify isolation before work. A competent engineer must specify physical restraint and its verification; a powered holding function is not an isolator.
No. The code describes a method. Confirm full-duty losses, ambient, altitude, water or air requirements and failure interlocks. Thermal rating and enclosure ingress protection require separate evidence.
The tool accepts the scenario and shows a negative energy delta, meaning higher grid input for equal shell output. Compare refurbishment and validate assumptions before using a payback estimate.
Payback requires a positive entered installed cost and positive annual benefit. Unknown or zero cost, zero hours, zero benefit or a net loss returns N/A. No maintenance saving or capital cost is invented to fill missing data.
Send mill and interface drawings, condition reports, shell-power basis, measured speed/start logs, existing gear ratio, grid data, cooling conditions, duty and commercial scope. Ask suppliers to identify unverified assumptions and acceptance evidence.
Use the tool’s copy or email action to share assumptions. Add mill GA/interface drawings, inspection records, measured speed/start/load logs, existing gear ratio, grid data, duty and cooling conditions. If values are missing, request a data-gap review first.
Ask the supplier to confirm the proposed architecture, load path, torque-time capability, cooling duty, protection scope, comparable installed cost and acceptance tests in writing. Manufacturing availability, certification, lead time and performance remain unconfirmed until supported by project evidence.
Email the retrofit review requestReturn to the screening tool