| Rated Torque and Power | Continuous torque, rated speed, peak torque, duty cycle, and generator operating profile. | Select a gearbox whose continuous rating exceeds the calculated operating torque and whose peak rating covers starting, switching, and transient loads. A service factor of approximately 1.25–1.50 is often used for variable-load industrial duties, subject to calculation. | Adequate torque margin reduces tooth fatigue, shaft overload, and premature bearing damage. | Rated-load calculations, transient-load analysis, duty-cycle data, and sizing calculations based on recognized gear-rating methods such as ISO 6336. |
| Gear and Bearing Reliability | Gear tooth stress, bearing load, shaft deflection, alignment tolerance, and expected operating hours. | Require documented gear and bearing calculations. For continuously operating equipment, specify a bearing rating life appropriate to the duty, commonly evaluated with ISO 281 methods and a defined reliability target. | Properly calculated gears and bearings are central to long service life and stable electrical output. | Load-rating reports, bearing-life calculations, material specifications, heat-treatment records, and dimensional inspection results. |
| Thermal Capacity | Heat generation, enclosure ventilation, ambient temperature, oil temperature, and continuous operating duration. | The gearbox should dissipate heat at the required continuous load without exceeding the lubricant, seal, bearing, or gear temperature limits. Provide oil-temperature monitoring for critical or continuously loaded installations. | Excessive temperature accelerates lubricant oxidation, seal aging, and bearing degradation. | Thermal rating calculations, heat-run test results, temperature alarm settings, and installation ventilation requirements. |
| Lubrication Requirements | Oil type, viscosity grade, oil quantity, filtration, sampling method, and oil-change interval. | Use the lubricant viscosity specified for the actual speed, load, and ambient temperature. Industrial gear oils commonly use ISO VG 150, 220, 320, or 460, but the correct grade must be confirmed by the gearbox design and lubricant supplier. | Correct lubrication prevents scuffing, micropitting, wear, corrosion, and overheating. | Lubrication chart, oil compatibility statement, filtration specification, oil-analysis procedure, and commissioning instructions. |
| Maintenance Accessibility | Access to inspection ports, oil drains, breathers, seals, couplings, sensors, and lifting points. | Prefer designs that allow oil level checks, sampling, draining, breather servicing, and coupling inspection without removing the gearbox from the installation. | Good accessibility reduces planned downtime, labor cost, and maintenance errors. | Maintenance drawings, service clearances, replacement procedures, spare-parts list, and estimated maintenance time. |
| Condition Monitoring | Vibration, temperature, oil debris, oil pressure, speed, and abnormal noise. | For critical distributed-generation equipment, provide at least temperature and vibration measurement, with oil analysis or debris monitoring where failure consequences are high. | Early detection can identify bearing wear, gear damage, misalignment, imbalance, and lubrication problems before a forced outage. | Sensor list, alarm and shutdown logic, baseline vibration data, and inspection methods aligned with ISO 20816 principles where applicable. |
| Ingress Protection | Exposure to dust, rain, water spray, washdown, and temporary water contact. | For outdoor installations, specify sealed breathers, protected shaft seals, and an enclosure or ancillary electrical component rating appropriate to the site. Under IEC 60529, IP65 indicates dust-tight protection and protection against water jets; IP66 provides protection against more powerful water jets. Neither rating indicates immersion protection. | Water and dust ingress can contaminate oil, damage seals, corrode components, and increase wear. | Ingress-protection documentation, seal design, breather specification, enclosure test evidence, and site washdown requirements. |
| Temperature Range | Minimum and maximum ambient temperature, start-up temperature, solar heating, and cold-start lubrication behavior. | Do not assume a standard temperature range. Confirm the gearbox, seals, bearings, heater, cooler, and lubricant are suitable for the complete site range, including cold starts and maximum enclosure temperature. | Temperature extremes affect oil viscosity, sealing performance, clearances, and heat dissipation. | Operating-temperature limits, cold-start test data, heater or cooler requirements, and lubricant viscosity-temperature information. |
| Corrosion Resistance | Humidity, salt spray, chemicals, industrial pollutants, coating system, fasteners, and exposed shafts. | Specify the coating and corrosion-protection system according to the site corrosivity category described in ISO 12944. Coastal, marine, chemical, and wastewater environments generally require more protection than sheltered indoor locations. | Corrosion can weaken housings, damage seals, obstruct inspection points, and shorten equipment life. | Surface-preparation standard, coating system, dry-film thickness, fastener material, and corrosion-resistance test documentation. |
| Noise and Vibration | Gear-mesh noise, structural resonance, torsional vibration, alignment, and mounting stiffness. | Require factory vibration and noise limits for the specified speed and load, and verify that the mounting structure and coupling are compatible with the gearbox torsional system. | Excessive vibration accelerates fatigue and may transfer damaging loads to the generator and prime mover. | Factory test results, torsional analysis, alignment tolerances, balancing records, and installation acceptance criteria. |
| Seals and Leakage Control | Shaft-seal material, pressure conditions, contamination risk, leakage detection, and replacement access. | Select seal materials compatible with the lubricant and site chemicals. Provide leak inspection points and avoid shaft loads or misalignment beyond the seal design limits. | Leakage causes lubricant loss and environmental contamination while allowing water and dirt to enter the housing. | Seal material data, shaft-finish requirements, leakage test results, replacement instructions, and lubricant compatibility confirmation. |
| Spare Parts and Service Support | Availability of bearings, seals, coupling elements, sensors, filters, and emergency repair capability. | Prioritize standardized, documented replacement parts and a planned spare-parts package sized according to failure consequence and access to local service resources. | A reliable gearbox still creates extended downtime if essential parts or technical procedures are unavailable. | Parts catalogue, recommended spares, repair manuals, training requirements, warranty terms, and documented response procedures. |