Drive equipment for marine and ship applications: gearboxes, couplings, winches and thrusters

Marine vessel operation is a distinct class of duty for drive equipment. The main gearbox of a merchant ship runs 6,000–8,000 hours per year without shutdown, the steering gear must operate in a storm at 30° heel, windlasses and cargo winches absorb impulse loads of tens of tonnes, and the cabling on deck machinery has to withstand salt spray, ultraviolet and icing. General-purpose industrial series do not fit here — what is needed are dedicated marine versions with class society certificates (CCS, RINA, DNV, ABS, RS), cast-iron housings, oversized bearing groups and a carefully matched ‘motor — coupling — gearbox — shaft line’ kinematic chain.

Industry-typical tasks

Main marine gearbox between a medium-speed diesel engine and the shaft line — 600–15,000 kW, ratio 2.5–7, reverse via fluid couplings or with a reverse gearbox
Connection of the main engine to an azimuth (Z-drive) propulsor — compensation of misalignment after thermal expansion and damping of vibrations from the main engine
Electric bow and stern thrusters of 200–2,500 kW for manoeuvring during mooring and dynamic positioning
Electrohydraulic and electromechanical steering gears — 11–200 kW, two independent circuits per SOLAS requirements
Cargo deck winches and cranes on container ships, bulk carriers and tugs — 30–500 kW, with a sea-state factor of 1.3–1.5 over nominal load
Anchor capstans and windlasses — 7.5–110 kW, peak torque on chain heave-up in heavy weather up to 2.5 of nominal
Ballast, cargo and fire pumps — explosion-proof drives for tankers and gas carriers, power up to 1,200 kW
Diesel-generator sets and shaft generators of the ship power plant — induction/synchronous machines 200–3,000 kW, IP56, marine duty

Gearboxes

Marine gearboxes split into three classes: main shaft-line gearboxes (between the main engine and the propeller), gearboxes for Z-drives and thrusters, and deck gearboxes for winches, capstans and davits. The main gearbox is the core of the propulsion train — vessel performance depends on its reliability. CGC is the sole supplier of marine gearboxes within CSSC (China State Shipbuilding Corporation), the largest shipbuilding corporation in China, and covers the needs of merchant, naval and special-purpose fleets. Beyond CGC, deck drives use general-purpose industrial gearboxes in marine-grade housings and sealing.

Main marine shaft-line gearbox — CGC marine series main gearbox — sole supplier of marine gearboxes within CSSC.

Main shaft-line marine gearboxes

Two- and three-stage parallel-shaft CGC marine series gearboxes are the brand’s flagship specialty. They couple a medium-speed diesel (450–900 rpm) to the propeller shaft (90–250 rpm) at a ratio of 2.5–7. The housing is marine cast iron; a Michell thrust bearing on the output shaft absorbs propeller axial loads up to 2,000 kN. The standard configuration includes a built-in reversing fluid coupling and a PTO for a shaft generator. CGC supplies gearboxes for merchant vessels, destroyers, frigates, icebreakers and research platforms within CSSC. Sole supplier of marine gearboxes within CSSC.

— Power 600–15,000 kW, ratio 2.5–7

— Thrust bearing for propeller axial load 200–2,000 kN

— Class CCS / RS / RINA / DNV / ABS

— Forced circulation lubrication with two independent pumps (main + emergency)

— Optional PTO to a shaft generator and a fire pump

Z-drive and azimuth thruster gearboxes

A combination of bevel and parallel stages transfers torque from a vertically mounted motor through 90° to the horizontal propeller in the submerged section of the azimuth pod. Used on tugs, cable layers and offshore wind support vessels, where manoeuvrability and bollard pull up to 100 tonnes are required. The challenge is a double 90° power flow turn through Gleason spiral bevel gears, with tooth contact pattern verified under vessel motion.

— Power 800–6,000 kW per pod

— Double 90° power flow turn

— Spiral bevel gears with contact pattern per DIN 3990

— Sea-water oil cooler via a CuNi heat exchanger

Gearboxes for deck winches and cranes

Multi-stage planetary blocks or parallel-planetary combinations with a built-in disc brake and a freewheel clutch. Used on cargo winches of bulk carriers and container ships, towing winches, davit winches for lifeboats and on offshore service vessels. Ratio 80–500; sizing is based not on the rated winch torque but on the dynamic peak under sea-state motion (factor 1.3–1.5).

— Ratio 80–500

— Built-in spring-applied brake with hydraulic release

— Freewheel clutch on the output shaft

— Marine-grade sealing (NBR rubber, marine paint on the housing)

— Corrosion protection C5-M (ISO 12944)

Thruster gearboxes

Bow and stern thrusters of tunnel and retractable type, 200–2,500 kW, are compact bevel gearboxes that transfer torque from the vertical electric motor into the tunnel housing and onto a 4–5-blade controllable-pitch propeller. Short-time duty (S2-30 min during mooring) with peak loads 1.4–1.6 of rated. Housing and shafts are marine stainless; triple sealing prevents sea water ingress into the oil sump.

— Power 200–2,500 kW, duty S2

— Triple oil-sump seal with leakage monitoring

— Housing and shafts in stainless steel 1.4571 / 316L

— Electric clutch for idle (free-wheeling) mode

Steering gear gearboxes

Self-locking worm or strain-wave gears on electromechanical steering gears for small-tonnage vessels, or two-stage parallel-shaft units paired with axial-piston pumps on electrohydraulic steering gears of tankers and container ships. SOLAS requires two redundant independent circuits; each must rotate the rudder fully from one side to the other within 28 seconds at maximum service speed.

— Ratio 50–200 (worm) / 80–250 (planetary)

— Two redundant independent circuits (SOLAS)

— Rudder swing time from 35° to 30° on the opposite side ≤ 28 s

— Self-locking, or a fail-safe brake on power loss

Marine-duty electric motors

Marine electric motors must withstand continuous salt spray, 95–100 % humidity, vibration from the main engine and vessel motion with rolls up to 22.5° transverse and 7.5° pitch. Large vessels use low-voltage 0.4 kV machines for deck machinery and high-voltage 6.6 / 10 kV machines for main propulsion drives and ship electrical plants. WOLONG produces dedicated IM (Industrial Marine) and IS (marine duty with salt protection) series — class H insulation, anti-corrosion coatings, IP56/IP66, CCS/RS/ABS certificates.

Bow thruster — Tunnel-type bow thruster: vertical electric motor + bevel gearbox + controllable-pitch propeller.

Thruster motors

Squirrel-cage induction motors of 200–2,500 kW at 0.4 / 0.69 / 6.6 kV. Mounted vertically above the tunnel and operated in short mooring cycles. The Wolong YE-M / YHTM marine series uses forced water jacket cooling and bearing vibration sensors. Frequently paired with a frequency converter for dynamic positioning (DP-2 / DP-3).

— Power 200–2,500 kW, duty S2-30 min

— IP56, class H insulation, class B temperature rise

— Vertical mounting IM3611 / V1

— VFD-compatible (NEMA MG1 Part 31)

— CCS, RS, RINA or DNV certificate

Cargo winch and windlass motors

Marine-duty induction motors of the Wolong YBK series (explosion-proof for tankers) and YEJ (with an electromagnetic brake). Power 7.5–500 kW, short-time duty S3-40 % or S4 with frequent loaded starts. Windlasses and capstans need a high breakaway torque (1.8–2.2 of nominal) — chain heave-up starts from standstill in a storm.

— Breakaway torque ≥ 1.8 of nominal

— Duty S3-40 % or S4 (60 cycles/hour)

— IP56, class F or H insulation

— Built-in electromagnetic brake (YEJ series)

— C5-M corrosion protection, labelled terminal boxes

Main propulsion electric motors

On all-electric vessels (ferries, icebreakers, cruise ships, offshore service vessels) the main propulsor is a synchronous or induction motor of 2–10 MW, fed from the ship power plant through a frequency converter. The Wolong WD3000 marine and YHTM series cover this range: water cooling, insulated bearing on the coupling side, shaft-current protection, Pt100 RTDs on the windings and bearings.

— Power 2–10 MW, voltage 6.6 / 10 kV

— Insulated bearing, shaft-current protection

— Forced water cooling IC81W or IC86W

— Pt100 on windings and bearings, vibration monitoring

— Marine certificate CCS/RS/DNV/ABS

Ballast, cargo and fire pump motors

On tankers, gas carriers and product carriers — explosion-proof Ex d IIB T4 or Ex de IIC T4. Wolong YB3 / YBX3 marine motors 11–1,200 kW with ATEX marking and CCS certificate for handling oil and oil products. Fire pumps form a separate emergency circuit with a dedicated diesel generator; IMO requires guaranteed start within 30 seconds of the command.

— Explosion protection Ex d IIB T4 / Ex de IIC T4

— Power 11–1,200 kW

— IP56, marine certificate CCS / RS

— Guaranteed fire pump start ≤ 30 s (IMO)

— Class H insulation for tropical duty

Brakes and stoppers

On deck machinery brakes serve a dual role: dynamic braking of a winch or capstan during load haul-in, and static holding while the vessel is at anchor or carrying a load on the hook during a storm transit. The design must operate under salt spray, icing, at heel up to 22.5° and temperatures from −40 °C (Arctic routes) to +55 °C (tropics). HUAWU supplies marine versions of brakes and electrohydraulic thrusters with enlarged sealing clearances and stainless hardware.

Capstan and windlass on a ship deck — Windlass with chain wildcat and a stopper brake: peak torque during chain heave-up in a storm up to 2.5 of nominal.

Cargo winch and windlass brakes

HUAWU YPZ2 / YWZ5 electrohydraulic disc and shoe brakes in marine duty, with C5-M anti-corrosion coating and stainless fasteners. A cargo winch carries an operational brake for controlled lowering and a spring-applied emergency brake for holding on power loss. Braking torque is sized with a 1.75 reserve over the maximum hoisting torque accounting for sea-state motion.

— Braking torque reserve 1.75–2.0 over hoisting nominal

— Activation time on power loss ≤ 0.2 s

— C5-M anti-corrosion coating, stainless fasteners

— Temperature range −40…+55 °C (Arctic or tropical version)

— Redundant operational and emergency brakes

Stoppers for capstans and windlasses

A band or shoe stopper brake on the chain wildcat is sized to hold the vessel at anchor in storm winds. Class society rules require it to withstand a pull equal to 45 % of the chain breaking load. It is engaged manually through a handwheel or automatically on loss of hydraulic pressure (spring-applied type).

— Holds 45 % of chain breaking load (RS / CCS rules)

— Manual handwheel backs up the automatic drive

— Marine-grade friction lining (asbestos-free)

— Anti-icing protection for Arctic routes

Disc brakes for Z-drives and thrusters

A spring-applied fail-safe brake on the thruster motor shaft prevents the propeller from free-wheeling under the incoming flow when the vessel is under way with the thruster idle. This matters most on tunnel thrusters, where idle propeller rotation creates parasitic drag and vibration. The brake engages within 0.2–0.5 s after the motor stop command.

— Spring-applied, hydraulic release

— Activation time 0.2–0.5 s

— Marine duty, IP66 brake coil

— Position monitoring via a limit switch

Deck crane and davit brakes

Container, bulker and supply-vessel cranes carry a dual-brake system, similar to teeming cranes in metallurgy: a main electrohydraulic brake on the high-speed shaft and an emergency disc brake on the drum. Lifeboat davits add a centrifugal lowering speed governor as required by SOLAS.

— Main + emergency brake (SOLAS / IMO MSC)

— Centrifugal governor for lifeboat davits

— Emergency brake activation time ≤ 0.3 s

— Marine certification by a class society

Shaft-line and deck drive couplings

The coupling between the main engine and the gearbox, between the gearbox and the shaft line, and between the shaft line and the Z-drive — these are four critical points of marine propulsion. Each coupling does three jobs at once: transmits torque, compensates for misalignment after thermal expansion and hull motion, and damps torsional vibrations from the diesel. On auxiliary drives (winches, pumps, generators) flexible pin and gear couplings similar to industrial types are used.

Cargo deck winch on a container ship — Cargo winch with a dual-brake system: an operational electrohydraulic brake and a spring-applied emergency brake.

Flexible main engine couplings

LONGXUAN rubber-metal or laminated-disc couplings with high torsional damping (dynamic stiffness 0.3–2.5 MN·m/rad) are fitted between the diesel flywheel and the gearbox input shaft. Their job is to shift the ‘crankshaft — propeller’ resonance out of the operating speed band and to cut torsional torque peaks down to levels acceptable for the gear teeth.

— Dynamic stiffness 0.3–2.5 MN·m/rad

— Torsional vibration damping

— Transmitted torque 5–500 kN·m

— Marine elastomer (resistance to oil and salt spray)

— Elastomer service life of at least 30,000 h

Gear couplings on the shaft line

YONGJING GIICL drum-type double-engagement gear couplings link the main gearbox output shaft to the intermediate and thrust shafts of the shaft line. They transmit 100–800 kN·m while compensating for radial, axial and angular shaft misalignment caused by hull thermal deformation and wave bending. The crowned tooth profile allows up to 1.5° angular offset.

— Torque 100–800 kN·m

— Angular offset up to 1.5°, radial offset 0.5–2 mm

— G6.3 balancing for peripheral speeds > 15 m/s

— Grease lubrication, 6-month service interval

— Marine duty for housing and fasteners

Cardan shafts and spindle couplings

YONGJING SWP / SWC cardan shafts are used in Z-drives, in arrangements with vertically offset engine and gearbox, and on catamarans with offset shaft lines. Each universal joint accepts up to 10° of misalignment; axial movement is taken up by a splined telescopic section.

— Torque 50–500 kN·m

— Joint misalignment up to 10°

— Splined telescopic section for axial compensation

— Forged steel crosses with rolling-element bearings

— Balanced before installation

Fluid couplings for cargo winches and compressors

JIAOHUA YOX / COX fluid couplings provide soft starting for cargo winches under full load (heavy starts during load haul-in or anchor heave-up in a storm) and protect the motor from overload on rotor jam. On marine compressor sets (refrigeration, ballast, starting-air) the fluid coupling cuts inrush surges on the ship grid during start-up.

— Nominal slip 2–4 %

— Fusible plug rated 145–160 °C

— Marine-grade seals and external fasteners

— Thermal capacity for 4–6 starts per hour

Flexible pin couplings for auxiliary drives

LONGXUAN LX / Yongjing LMC pin-and-bush couplings with rubber bushings are fitted on ballast, cargo and fire pumps, on shaft generator shafts and on compressor sets. They damp impact loads on start-up, compensate for small misalignment of 0.2–1.0 mm and need no lubrication.

— Torque 0.5–125 kN·m

— Radial offset compensation 0.2–1.0 mm

— Lubrication-free

— Marine-grade elastomer