Drives for the cement industry: gearboxes, motors, brakes and couplings
Cement production runs in continuous S1 duty around the clock, with abrasive clinker and raw-meal dust, heavy starts of mills and crushers under load, and long conveyor galleries with significant elevation changes. The main power consumers — rotary kilns, vertical roller mills (VRM) and ball mills — require purpose-built gearboxes and high-voltage motors paired carefully with the matching gearbox and fluid coupling. Any unplanned kiln stoppage costs hundreds of thousands of dollars per day, so only proven, specialized product lines are used here.
Industry-typical tasks
- Main drive for rotary kilns 4–6 m in diameter and 50–100 m long — two-stage gearboxes with a girth gear, dual-drive arrangement 200–1,000 kW
- Drive for raw and cement vertical roller mills (VRM) — large low-speed planetary gearboxes 4–10 MW with an oil pump station
- Drive for cement and slag ball mills (horizontal) — central or girth-gear pinion drive with a fluid coupling, power rating 1,500–8,000 kW
- Drives for limestone roller crushers and clinker hammer crushers — heavy starts under choked feed and jam protection
- Long belt conveyors for limestone, marl, coal and clinker — heavy starts, fluid couplings, backstops on inclined sections
- Bucket elevators for raw meal and clinker — mandatory backstop, brakes on the head shaft
- ID and FD fans for the kiln and clinker cooler — HV motors 800–3,500 kW with VFD speed control
- Separators, dedusting systems, packing lines and clinker silo cranes — general-purpose gear motors and brakes
Gearboxes
Cement is CGC's flagship reference industry: more than 10,000 cement gearbox sets supplied worldwide, with roughly 60 % market share for cement gearboxes in China. These are not general-purpose lines but purpose-built designs for three key drives: the rotary kiln, the vertical roller mill and the ball mill. Each runs 24/7 in S1 duty, so selection criteria include a service factor of at least 1.8–2.0, forced circulating lubrication with an oil cooler, vibration and bearing temperature monitoring, and the ability to operate as a dual drive feeding a single girth gear.
Main drive for rotary kilns
Two- or three-stage helical gearboxes drive the girth gear that wraps around the kiln shell. For large-capacity kilns the typical arrangement is two identical gearboxes operating in dual-drive on a single girth gear to share torque. The ratio is selected to deliver a kiln output speed of 1–4 rpm. CGC supplies complete packages — gearbox + girth gear + supporting rollers — featuring a patented dual power split via a torsion shaft.
- — Ratio 200–500
- — Output torque 200–800 kN·m at the shell, drive power 200–1,000 kW
- — Dual-drive arrangement with torque balancing between the two gearboxes
- — Oil pump station with filtration and cooling
- — Vibration and bearing temperature monitoring per ISO 10816-3
Vertical roller mill (VRM) gearboxes
The heart of modern grinding lines — low-speed planetary gearboxes with a thrust bearing that absorbs the vertical load from the grinding rollers and table. Power rating 4–10 MW, output speed 20–35 rpm. These are the most critical units in a cement plant: an unplanned VRM gearbox repair takes 4–8 weeks. CGC produces the MLX series and similar designs for raw and cement VRMs.
- — Power rating 4–10 MW
- — Ratio 35–60
- — Thrust bearing for a vertical load of 5–25 MN
- — High-pressure jacking oil system (table lift-off before startup)
- — Dual circulating lubrication with a backup pump and heat exchanger
Gearboxes for cement and slag ball mills
Two arrangements are used on horizontal ball mills: a girth-gear pinion drive (open gear pinion plus a helical gearbox) or a central drive (a planetary or helical-planetary gearbox coaxial with the drum). The central drive saves space and keeps better alignment; the girth-gear pinion drive is easier to service. Power rating 1,500–8,000 kW, ratio 30–60. CGC's standard package combines the gearbox with a Jiaohua fluid coupling and a Wolong HV motor.
- — Power rating 1,500–8,000 kW
- — Service factor ≥ 1.8 for ball mills
- — Compatibility with a fluid coupling on the input shaft
- — Pressurized forced circulating lubrication
- — Drum position and bearing pedestal vibration monitoring
Drives for limestone and clinker crushers
Limestone roller crushers and clinker hammer crushers operate under shock loads from oversized rock and large clinker lumps. Bevel-helical gearboxes (K-series) or special heavy-duty designs with an increased service factor are used. A Jiaohua YOX/COX fluid coupling is mandatory upstream of the gearbox to provide a soft start under choked feed and protect the motor from overload during a jam.
- — Service factor ≥ 2.0 (shock loads)
- — Reinforced output shaft bearings
- — Compatibility with a fluid coupling on the input
- — Seals protected against clinker dust and abrasive particles
Conveyor drives and bucket elevators
Long belt conveyors for limestone, coal and clinker run tens to hundreds of metres with elevation changes. Bevel-helical (BONENG K-series) and parallel-shaft helical (F-series) gear motors are used. A Tianiu backstop is mandatory on inclined conveyors and bucket elevators — without it the belt or elevator chain will run back under the weight of the material after a stop, destroying the gearbox and the take-up device. This is a critical, non-negotiable requirement in the cement industry.
- — BONENG K- or F-series, service factor at least 1.5
- — Mandatory Tianiu backstop on inclined conveyors and elevators
- — Optional brake or electromagnetic brake on the high-speed shaft
- — Gearbox protection against belt jam (shear pin or slip-detection sensor)
High-power electric motors
Main drives for VRMs and ball mills, plus ID fans of the kiln and clinker cooler, are the domain of high-voltage motors rated from 800 kW to 10 MW at 6, 10 or 11 kV. Wolong is the primary HV motor supplier for the cement industry (HV, YHTM and WD3000 series). The second tier is general-purpose asynchronous motors from Huali and Wolong (YE3, YBX3) for separators, dedusting, feeders, screws, packing lines and auxiliary mechanisms.
Motors for VRMs and ball mills
Power rating 1,500–10,000 kW, voltage 6 or 10 kV, speed 990–1,490 rpm. Heavy starts under load require a starting torque of at least 1.8 of rated torque and a mandatory fluid coupling between motor and gearbox. The Wolong HV/YHTM line with forced water cooling IC81W suits VRM drives; for ball mills the YHTM with air cooling IC411 or IC611 is more common.
- — Power rating 1,500–10,000 kW, voltage 6/10 kV
- — Starting torque ≥ 1.8 of rated
- — Compatibility with a Jiaohua fluid coupling (flange and spigot ring)
- — Insulated bearing on the non-drive end
- — Pt100 thermal sensors on windings and bearings
Motors for ID and FD fans
ID fans of the kiln, clinker cooler and raw mill are HV motors of 800–3,500 kW running in S1 duty around the clock. Flow control is increasingly handled by an HV variable frequency drive (rather than inlet vanes) — this saves up to 30 % electricity and significantly improves the kiln process. The motor operates with elevated vibration from the fan side and abrasive dust, so a reinforced foundation and vibration monitoring are required.
- — Power rating 800–3,500 kW at 6 kV
- — Insulation class F with class B thermal margin
- — Vibration monitoring per ISO 10816-3 (zone B)
- — Soft-starter or HV inverter starting capability
- — IP55 with additional protection against clinker dust
Motors for separators and roller presses
Dynamic cement separators, high-pressure grinding rolls (HPGR) and roller-crusher drives operate in continuous duty with variable load and demanding energy-efficiency requirements. IE3/IE4 asynchronous motors (Wolong YE3/YE4) are used, or HV machines at ratings above 1 MW. Inverter starts with torque control are possible to adapt separator speed to the current grinding regime.
- — IE3 efficiency class minimum, IE4 for replacements
- — Inverter-duty compatibility (insulation class H, NEMA MG1 Part 31)
- — PTC/Pt100 thermal protection in the windings
- — IP55 protection with additional cement-dust sealing
Motors for auxiliary drives
A cement plant has hundreds of auxiliary drives — apron and screw feeders, elevators, dedusting, packing machines, scraper conveyors, slurry pumps. This is the domain of general-purpose Huali (Y2/YE3/YE4) and Wolong YE3 asynchronous motors in standard execution with a tropicalized version for dusty areas. They are often supplied as part of BONENG K/F/R-series gear motors.
- — Power rating 1.5–315 kW, voltage 380/400 V
- — IE3 efficiency class
- — IP55, tropicalized execution
- — Optional encoder for variable-speed drives
- — Compatibility with BONENG gear motors
Industrial brakes
Brake systems on a cement plant are installed where a stop under load risks equipment damage: bucket elevators and inclined conveyors (back-run prevention in addition to the backstop), ball mill drives (for maintenance and emergency stops), clinker silo cranes and grab cranes for raw material unloading. Electrohydraulic shoe and disc brakes are used, with fast actuation on power loss.
Brakes for raw-meal and clinker bucket elevators
Bucket elevators lift raw meal and clinker tens of metres. A TKK/TKT shoe brake with a Huawu Ed electrohydraulic thruster is installed on the elevator head shaft — it holds the loaded elevator at standstill and prevents the buckets from running back. A Tianiu backstop performs the same function automatically; the brake is a backup and a maintenance tool. The dual scheme (backstop plus brake) is mandatory for hot-clinker elevators.
- — Braking torque with a 1.75–2.0 margin over the fully-loaded torque
- — Huawu Ed-50 to Ed-301 electrohydraulic thruster
- — Heat-resistant brake shoes for hot clinker (up to +200 °C)
- — Manual release for maintenance
- — Lining wear monitoring via a limit switch
Brakes for inclined conveyors
Long inclined conveyors for limestone and coal pose a major hazard if the belt runs back under load. The drive pulley carries a TKK shoe brake or a Huawu YPZ2 disc brake with an electrohydraulic thruster; for inclinations above 6° a Tianiu backstop on the head shaft is mandatory. The brake actuates within 0.1–0.2 s on power loss and holds the conveyor until the backstop completes the mechanical stop.
- — Braking torque with a 1.5–1.8 margin over the rated drive torque
- — Actuation time on power loss ≤ 0.2 s
- — Ed-80 to Ed-201 electrohydraulic thruster
- — Coordinated operation with a Tianiu backstop on inclined conveyors
Brakes for ball mills and grinding drives
A Huawu YPZ2/YWZ5 disc brake is fitted on the high-speed shaft of the ball mill gearbox for emergency stops and for indexing the drum during grinding-media charging or discharging. The brake must hold the inertia of the loaded drum, so the torque is sized with a 2.0 margin over the rated drive torque. It is combined with the mill auxiliary drive (inching drive) for safe maintenance.
- — Braking torque with a 2.0 margin over rated
- — Hydraulic or electrohydraulic actuation
- — Control from the mill PLC
- — Compatibility with the auxiliary (inching) drive
Brakes for clinker silo cranes and raw-material unloading
Grab cranes unloading limestone from barges and rail cars and overhead cranes serving clinker silos operate in dusty environments with significant temperature swings. A dual-brake scheme is used: a Huawu YPZ2 service brake plus a spring-applied fail-safe emergency brake on the hoist drum. Gantry cranes at open clinker yards are fitted with Jingu CWZ wind-anchor rail brakes.
- — Dual brake set (service plus emergency) on grab cranes
- — Emergency brake actuation time ≤ 0.2 s
- — IP55 protection against cement dust
- — Jingu CWZ wind-anchor rail brakes on gantry cranes at open yards
Couplings
Four classes of couplings are used in cement drives: fluid couplings for heavy starts of mills and crushers (motor overload protection), drum gear couplings between the gearbox and the kiln girth gear (transmitting large torques while accommodating misalignment), elastic pin-and-bush couplings on conveyors and feeders (damping), and backstops on bucket elevators and inclined conveyors — a critical element that prevents back-running under the weight of the material.
Fluid couplings for mills and crushers
Oil-filled Jiaohua YOX/COX fluid couplings provide a soft start for ball mills, limestone crushers and roller presses under load. Rated slip of 2–3 % protects the motor from overload during a jam. The YOXIIZ series uses a fusible safety plug that releases oil outward on overload and automatically trips the drive. VRM drives use special variable-fill fluid couplings to optimize the starting regime.
- — Rated slip 2–4 %
- — Fusible plug set point 145–160 °C
- — Oil fill 70–85 % of internal volume
- — Thermal capacity for 4–6 starts per hour
- — Motor compatibility on flange and spigot ring
Drum gear couplings for kiln and mill drives
Yongjing GIICL and Longxuan WGZ double-engagement drum gear couplings transmit torque between the gearbox and the girth-gear pinion of the kiln or mill. Thermal expansion of the 4–6 m diameter kiln shell produces significant axial and radial misalignment, so a crowned (barrel-shaped) tooth profile permits operation at angular misalignments up to 1.5°. Grease lubrication via a fitting, service interval 6 months.
- — Torque 100 kN·m – 1.5 MN·m
- — Angular misalignment capacity up to 1.5°
- — Crowned (barrel-shaped) tooth profile for misaligned operation
- — Grease lubrication, 6-month service interval
Elastic pin-and-bush couplings for conveyors and auxiliary drives
Jiaohua YOXp/YOXz and Yongjing LX (LMC) are pin couplings with elastomeric bushings. They damp shock loads and accommodate minor post-installation misalignment. On conveyor drives they are typically combined with a Longxuan brake drum (an integrated coupling-with-brake-drum), saving space and simplifying service. They are also used on feeders, screws, pumps and dedusting fans.
- — Torque 5–125 kN·m
- — Radial misalignment capacity 0.2–1.0 mm
- — Integration option with a Longxuan brake drum
- — Elastomer service life of at least 30,000 hours
Backstops for elevators and inclined conveyors
This is the most safety-critical class of couplings on a cement plant. The Tianiu backstop (NJ, NF, NYD series) is a freewheel one-way clutch that allows rotation in the working direction and locks the reverse. Without it a bucket elevator runs back under the weight of the loaded buckets after the motor stops, destroying the gearbox, the take-up device and the casing. The same applies to inclined conveyors with an inclination above 6°. The backstop is mounted on the gearbox high-speed shaft (external) or built into the gearbox (internal).
- — Tianiu NJ/NF/NYD series sized to the calculated drive torque
- — Torque margin of 2.0 over the rated motor torque
- — External (high-speed shaft) or internal (gearbox-integrated) execution
- — Compatibility with an electrohydraulic brake (dual protection)
- — Scheduled service every 6 months — inspection of oil and rollers
Applications gallery
Our solutions for this industry
SDS portfolio brands that cover typical applications in this industry.
- CGCPurpose-built cement gearboxes — kiln drives, VRMs (MLX), ball mills. More than 10,000 sets supplied worldwide and 60 % market share for cement gearboxes in China
- WOLONGHV motors for mills and ID fans (HV, YHTM, WD3000) up to 10 MW; general-purpose YE3/YBX3 for separators, dedusting and auxiliary drives
- HUALIGeneral-purpose Y2/YE3/YE4 asynchronous motors for feeders, screws, packing machines and dedusting — hundreds of auxiliary drives per plant
- BONENGIndustrial K, F and HB gear motors for limestone/clinker conveyors, bucket elevators and feeders; integration with the Tianiu backstop
- JIAOHUAYOX/COX/YOXIIZ fluid couplings for heavy starts of ball mills, crushers and roller presses; motor overload protection
- TIANIUNJ/NF/NYD backstops for bucket elevators and inclined conveyors — a critical element of back-run protection
- HUAWUElectrohydraulic YPZ2/YWZ5 disc brakes and TKK/TKT shoe brakes with Ed thrusters for elevators, inclined conveyors, ball mills and clinker silo cranes
- YONGJINGGIICL drum gear couplings for kiln and mill drives; elastic pin-and-bush LX/LMC couplings for conveyors and auxiliary drives
- LONGXUANWGZ drum gear couplings, LX elastic pin-and-bush couplings and brake drums for conveyor drives and auxiliary mechanisms in a cement plant
- JINGUDisc and shoe brakes; CWZ wind-anchor rail brakes for gantry cranes at open clinker and raw-material yards
- DEODFL/DFLA oil coolers and plate heat exchangers for VRM and ball mill gearboxes — high thermal losses demand effective heat rejection
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