403W2 Winch Drive Planetary Gearbox Reducer — 2-Stage

Read the 402W2 page. Now read this one. The two products share the same housing diameter, the same two-stage planetary architecture, the same 3,500 rpm input ceiling, the same 4,000 Nm output rating, and the same FEM M5 duty classification. The difference is 5 kg and a set of friction discs.

The 403W2 adds a 270 Nm spring-applied, hydraulically released multi-disc negative brake inside the rotating housing. This brake engages the moment hydraulic pressure drops — whether by deliberate operator action, emergency shutdown, hose failure, or total system power loss. It holds the drum, the cable, and whatever is hanging on the cable in position, independently of any external component. No motor brake needed. No counterbalance valve needed. The winch drive planetary gearbox itself is the safety system.

Choose the 402W2 when:

The hydraulic circuit already provides dual-independent holding (counterbalance valves + motor brake). The system is class-certified with external braking architecture. Ratios below 15.4 are needed for fast hoisting speeds. Brake disc maintenance access inside the drum is impractical (FPSO davits, subsea winches).

Choose the 403W2 when:

The applicable standard requires a brake within the drum assembly. The winch must hold a load even if all hydraulic lines and motor connections are severed simultaneously. The system is a standalone winch unit (not part of a certified crane circuit). Personnel lifting requires the maximum number of independent holding mechanisms.

Tower Crane Auxiliary Hoists

Secondary hoist mechanisms on tower cranes that handle lighter loads (1-3 tonnes) for tool baskets, concrete skips, and personnel platforms. Tower crane standards (EN 14439, ASME B30.3) require the hoist to hold the load independently of the hydraulic supply. The 403W2 integral brake satisfies this requirement without adding a separate drum brake to the already space-constrained tower head. The slewing drive handles the crane rotation, and the wheel drive propels the trolley travel.

Offshore Pedestal Crane Hoists

Pedestal-mounted cranes on offshore platforms handling 3-5 tonne cargo transfers between supply vessels and the platform deck. These cranes operate in sea states where the load swings unpredictably, generating dynamic torque spikes at the drum. The 403W2 brake provides an independent holding point that the crane operator can engage instantaneously by dumping brake release pressure — faster than any counterbalance valve or motor brake response. In emergency situations where a supply vessel separates unexpectedly from the platform, this speed of engagement prevents the load from swinging into the platform structure.

Mining Shaft Service Winches

Service winches in mining shafts that lower tools, pumps, ventilation ducting, and supplies to underground work levels at depths of 50-200 metres. The shaft environment is wet, dusty, and remote from surface maintenance facilities. The 403W2 sealed housing and integral brake provide a self-contained hoisting unit that does not depend on external braking components exposed to the shaft atmosphere. Mine safety regulations in most jurisdictions require that any winch operating in a vertical shaft must have an internal mechanical hold — the 403W2 provides this within the gearbox.

Why does the 403W2 ratio range start at 15.4 when the brake-free 402W2 starts at 12.4?

The multi-disc brake assembly occupies axial space inside the housing that is otherwise available for the first-stage sun gear. With the brake installed, the first-stage sun gear diameter is constrained to a smaller maximum size, which limits the minimum achievable ratio per stage. The net effect across two stages is a minimum total ratio of 15.4 instead of 12.4. This is a physical geometry trade-off, not a design compromise — the brake assembly and the gear set share the same housing volume.

How is the brake release pressure supplied to a rotating housing?

Through a rotary hydraulic union (swivel joint) at the output shaft centre. The stationary hydraulic supply line connects to one side of the union; the rotating brake piston channel connects to the other side. The union contains carbon-graphite sealing rings running against hardened steel races, rated for 50+ bar at up to 25 rpm. Release pressure is typically 25-40 bar. The rotary union is the only wearing component in the brake release path — inspect it every 2,500 hours and replace when external leakage exceeds 5 drops per minute.

What is the brake engagement time during an emergency stop?

From the moment the brake release pressure drops below the spring return threshold (approximately 15 bar), the Belleville springs push the brake piston against the disc stack in approximately 150-250 milliseconds. At 25 rpm drum speed, this corresponds to less than 0.1 revolution of drum rotation during engagement. The engagement torque profile is progressive — the brake torque ramps from zero to 270 Nm over the engagement period, not instantaneously — which prevents shock loading of the cable and the suspended load. For dynamic (moving) emergency stops, the 270 Nm static rating applies after the drum has decelerated to standstill.

Can the 403W2 brake be used for controlled lowering (dynamic braking)?

The 403W2 brake is a parking brake — it is designed for static holding, not for dynamic speed control during lowering. Using it as a lowering brake (slipping it partially to control descent speed) will overheat the disc stack and dramatically reduce disc life. Controlled lowering must be handled by the hydraulic circuit: either through a counterbalance valve, a motor-integrated brake, or controlled meter-out flow through the directional control valve. The 403W2 brake should engage only after the drum has stopped or in an emergency where stopping the load is more important than disc longevity.

What brake disc life can be expected in an FEM M5 tower crane auxiliary hoist?

In a properly designed system where the brake is used only for static holding (not dynamic braking), the multi-disc stack life exceeds 20,000 hours of crane operation. The discs wear primarily during engagement (the fraction of a second when they are sliding) and not during static hold (when they are clamped and stationary relative to each other). At 100 engagements per day, the disc stack accumulates approximately 25-50 seconds of sliding contact per day — negligible wear per cycle. Replace the discs when the measured disc thickness reaches the minimum value stamped on the disc housing, typically at 15,000-25,000 hours depending on the daily engagement count.

Does the winch drive planetary gearbox need a separate overload protection device?

Yes. The 403W2 does not include a torque-limiting device. Overload protection must be provided by the hydraulic circuit — typically a pressure relief valve set to limit the system pressure at the motor ports to a value that corresponds to the maximum permissible gearbox torque. For a 403W2 at ratio 25 with a 45 cc/rev motor: maximum motor torque at 4,000 Nm drum torque = 4,000 / 25 = 160 Nm. The relief valve setting should limit the pressure to the value that produces 160 Nm at the motor. Contact Koreas evige magt for the recommended maximum motor torque at your selected ratio.

Auxiliary hoist on a luffing jib tower crane, 2.5-tonne SWL. The 403W2 at ratio 25 replaced a competitor unit that had failed the EN 14439 brake holding test after 8,000 hours — the disc stack had worn beyond the minimum thickness and the spring force had degraded. The 403W2 Belleville spring design maintains consistent clamping force over a wider disc wear range than the competitor coil spring design. After 6,000 hours on the 403W2, the brake test results are identical to the day-one readings. We are specifying the 403W2 for all new cranes in the product range.

Pedestal crane hoist on a jack-up drilling rig operating in the Arabian Gulf. The 403W2 at ratio 30 handles 3-tonne cargo transfers in sea states up to 1.5 metres significant wave height. During a recent emergency vessel disconnect, the operator dumped the brake release pressure and the 403W2 brake engaged in under 300 milliseconds — halting a 2.8-tonne load that was mid-swing between the supply vessel and the platform. The load stopped cleanly with no cable shock. This single event justified the decision to specify an internal brake over the brake-free 402W2. The external counterbalance valves would also have held, but the speed of the gearbox brake engagement gave the operator instantaneous control that the hydraulic hold could not match.

Service winch in a gold mine shaft, 150 metres deep, lowering pumps and ventilation equipment to working levels. The 403W2 at ratio 35 handles loads up to 1,200 kg at 10 m/min. The integral brake is essential — our mine safety authority will not certify any vertical shaft winch without an internal mechanical hold. Performance is reliable and the sealed housing handles the wet shaft conditions without any water ingress after 14 months. The 4-star is because the rotary union started showing external seepage at approximately 4,500 hours — earlier than the 10,000+ hour specification. Replaced under warranty in 2 days. The shaft environment (high humidity, fine quartz dust) may have accelerated the seal wear. We now inspect the union at 2,000-hour intervals instead of 2,500.