ZL75 Winch Drive Planetary Gearbox

ZL75 at 175,000 Nm Peak

Handles transient events — grab crane impacts, snatch loads, emergency stops — that reach 175,000 Nm for sub-10-second durations. The gear teeth absorb these peaks through their bending strength margin above the 70,000 Nm continuous fatigue limit. Between peaks, the gears recover and cool. This is electric winch duty: high peaks separated by periods at or below continuous load.

414W3 at 140,000 Nm Continuous

Sustains 140,000 Nm for hours or days without rest — the defining characteristic of mining production winders and AHTS anchor handling where the load never drops below 80% of rated for entire shifts. The ZL75 cannot sustain 140,000 Nm continuously — its continuous limit is 70,000 Nm. The mega-class exists for applications where the sustained load exceeds what any ZL model can deliver at continuous rating.

All-Electric Offshore Platform Cranes (40-60 t)

The ZL75 at ratio 80-120, 2-3 stage, with 350-600 kW electric motors replaces the entire 410W3-413W3 hydraulic tier for new-build offshore cranes. The 175,000 Nm peak handles the dynamic load amplification from vessel motion (DAF 1.3-2.0) without derating the continuous capacity. The slewing drive e wheel drive complete the all-electric crane package from the same supplier.

Electric Construction and Shipyard Cranes

Heavy tower cranes, luffing-jib cranes, and shipyard gantry cranes in the 45-60 tonne class. The ZL75 at ratio 100-180 provides the hoist torque for steel erection, hull section positioning, and heavy modular construction where the crane operates near residential areas or inside buildings under construction. Helical gear noise (60-66 dB(A) at 1 m) keeps the crane within urban construction noise limits that hydraulic cranes at this capacity cannot meet.

Electric Mining Main Production Hoists

The ZL75 at ratio 200-600, 3-4 stage, with 300-600 kW AC motors provides the production winding torque for mines at 300-600 metre depths with 15-25 tonne skip loads. At these shaft depths, the combined skip and rope weight falls within the ZL75 continuous capacity, and the 175,000 Nm peak absorbs the skip-loading impact at the bottom of the shaft. Regen braking during skip descent returns 20-35% of the potential energy to the mine electrical grid.

Why does the ZL75 peak-to-continuous ratio jump back to 2.5:1 after the ZL55 dropped to 2.04:1?

The ZL75 uses a new, larger housing class with a larger gear module that provides proportionally more material headroom above the continuous fatigue limit than the ZL55 gears. The ZL55 was designed to maximise the continuous torque from its housing size — pushing the gears closer to their fatigue limit and leaving less peak margin. The ZL75 housing is sized with a focus on the peak-to-continuous balance rather than pure continuous maximisation, resulting in gear teeth that carry 70,000 Nm at 80% of their fatigue limit instead of 95% — leaving 2.5x headroom for transients.

Can the ZL75 replace the 414W3 mega-class for mining production winding?

Only if the sustained drum torque remains below 70,000 Nm. The 414W3 at 140,000 Nm continuous serves mines where the combined skip, ore, and rope weight produces sustained drum torques of 80,000-140,000 Nm during every hoist cycle. The ZL75 cannot match this sustained capacity. However, for mines at moderate depths (300-600 metres) where the drum torque stays below 70,000 Nm during the loaded hoist, the ZL75 is the better choice — it provides the same torque with electric-drive advantages (regen, VFD control, no hydraulic oil) at a fraction of the 414W3 weight and cost.

How does one ZL75 cover both a 40 t and a 60 t crane?

A 40 t crane at rated load uses approximately 40,000-50,000 Nm of drum torque (depending on drum diameter and reeving). The ZL75 at 70,000 Nm continuous provides 40-75% utilisation at rated load — with 20,000-30,000 Nm of margin. A 60 t crane at rated load uses approximately 60,000-70,000 Nm — approaching the continuous limit. The 175,000 Nm peak handles the transient overloads on the 60 t crane that the continuous rating alone cannot cover. Both cranes use the same gearbox at different operating points — the 40 t crane with more margin and longer component life, the 60 t crane closer to the rated envelope with shorter overhaul intervals.

What thermal power does the ZL75 provide at 2-stage for mainstream crane duty?

At 2-stage (ratios approximately 15-50): Pt is approximately 65 kW without external cooling. With an external cooler: approximately 98-130 kW. Most 40-60 t crane hoists with 350-600 kW motors at 30-50% duty cycle produce average thermal loads of 50-80 kW. The 2-stage ZL75 without cooler handles light-duty crane work (30% duty, 50 kW average). With a cooler, it handles heavy-duty (50% duty, 80 kW average). For offshore platform cranes running 24/7 at high utilisation, always specify the external cooler.

What noise level does the ZL75 produce compared to a 40 t hydraulic crane hoist?

The ZL75 gearbox alone at full load: approximately 60-66 dB(A) at 1 metre. The equivalent hydraulic system (motor + pump + HPU + cooling fan + gearbox): approximately 78-86 dB(A) at 1 metre. The difference: 12-20 dB(A) — which is perceived as 2-4 times quieter to the human ear. On an all-electric crane with no diesel engine, the ZL75 hoist noise is typically the loudest component on the machine. On a hydraulic crane, the gearbox noise is masked by the engine, pump, and cooling fan — so the switch to electric makes the gearbox noise more noticeable even though it is objectively quieter.

Does the ZL75 work with regenerative braking during every lowering cycle?

Yes. The ZL75 helical gear train transmits regenerative torque from the drum (driven by the descending load) back through the gears to the motor, which acts as a generator. The VFD converts the generated AC to DC and feeds it back to the DC bus — where it can supply other crane motors (slew, travel), charge a supercapacitor or battery, or export to the grid through a regen-capable supply unit. The energy recovery is proportional to the load weight and the lowering distance: for a 40 t load lowered 30 metres, approximately 120 kWh of potential energy is available, of which 85-110 kWh (70-90%) is recoverable after gearbox and motor losses. Contact Coreia Ever-Power for regen energy calculations at your specific crane duty cycle.

50 t all-electric offshore construction vessel crane, ZL75 at ratio 90, 2-stage, 500 kW PMSM. This is the crane that convinced our board to standardise on all-electric for the next generation of offshore cranes. The 175,000 Nm peak absorbed the classification test drop — 55 t at 1.25x dynamic factor — without the VFD recording any overcurrent fault. Noise in the operator cabin during full-load hoisting: 48 dB(A). The vessel electrical system recovered 24% of the crane energy consumption through regen over the first 6 months. The ZL75 is now our standard main hoist drive for the 40-60 t electric crane family — 8 units ordered across 3 vessel contracts.

The ZL75 replaced three separate gearbox part numbers across our 40 t, 50 t, and 60 t crane range — all now use the ZL75 at different ratios. Spare parts inventory: reduced from 3 kits to 1. Field service training: one programme instead of three. The 40 t crane operates at approximately 55% of the ZL75 continuous capacity with a projected overhaul interval of 30,000+ hours. The 60 t crane operates at approximately 95% continuous with a projected interval of 20,000 hours. Both are acceptable business cases. The single-gearbox strategy saves our factory approximately EUR 120,000 per year in parts logistics and training costs across the three crane models.

Main production winder at a 480-metre copper mine, ZL75 at ratio 300, 4-stage, 450 kW AC motor with VFD. The skip carries 20 tonnes of ore; rope weight at full depth is 2,400 kg. Sustained drum torque during loaded hoist: 55,000 Nm — 79% of the ZL75 continuous rating. Regen recovery during empty skip descent: 28% of the hoist energy, measured at 18.5 kWh per cycle. The mine electrical bill has dropped by 14% since the ZL75 replaced the previous hydraulic winder. The 4-star reflects a commissioning expectation: the mine safety inspector expected an integrated in-drum brake (as per the 4xxW tradition). The ZL75 does not have one. We satisfied the inspector with a motor electromagnetic brake plus an external drum calliper — both independently rated for full load hold. The approval process took 6 weeks longer than it would have with an in-drum brake. For mines transitioning from 4xxW to ZL, briefing the mine inspector on the ZL braking philosophy before the gearbox arrives would prevent this delay.