RENK PBLZ Drive epicyclic gears central ball mill drives

RENK PBLZ Drive epicyclic gears central ball mill drives

Well proven epicyclic gear technology

RENK epicyclic gears are used e.g. in central ball mill drives since 1974 when RENK has supplied the first epicyclic gear for a 2,5 MW ball mill featuring 2 planetary stages each with three planets. The epicyclic gear technology has been the step to take as the powers of the mill systems increased steadily. With new materials, manufacturing technologies, improved lube oils and last but not least condition monitoring technologies, the RENK central drives were improved to their third generation on the market named PBLZ type.

The Drive System Design 

The complete package of equipment
# Label
1 Auxilliary Gear for positioning an balancing of mill body with: Motor, Hydrodynamic Clutch-Retarder, Back stop Brake System,   Reducer, semi automatic Claw Clutch Ratio: > 8000.
2 Main Motor: 3000 - 10000 kW; 750 - 1500 rpm
3 Main Gear / Coupling: 14 - 18 rpm
4 Cement Mill
5 Oil System, optional with SCS Controller

Mill Stop

The mill swings to stop after a motor stop. This requires backward rotation.

RENK Auxilliary Drive System

# Label
1 Claw Clutch: Engaged until overruning takes place; manual disangagement only after balancing.
2 Auxilliary gear: Reducer.
3 Drum Brake: Opening electically only with interlock to oil pressure.
4 Hydraulic Clutch Clutch works as a dynamic brake for balancing the mill in controlled manner.
5 Auxilliary Motor Equiped with back stop – can not turn reversly

Safety and Dependability Are on Top of the List

RENK will provide all components of the drive system! The condition of all elements is continuously monitored by sensors and switches.

A logic diagram provided to configure a Programmable Logic Controller (PLC) or a readily programmed Sub Control System (reporting to the main PLC) is available. The RENK programmed and tested SCS shortens the commissioning time and reduces the risk of site work mistakes.

In any case the operation is save and interlocked against faulty operation.

The Oil System features a hot standby pump, a double switch filter system with remote clogging indicator and a temperature control valve to provide constant operation conditions also at changing cooling media. The oil quantity born in the tank is rated generously to allow an extended running time without oil change. The oil is continuously fine filtered to minimise the impact on the gear elements by abrasives which cannot be prevented to penetrate the oil circuit in the cement plant environment.

In addition to all those elements an emergency oil tank is provided to make sure the shaft system can coast down safely in case of frequent black outs or a delay in stopping the main motor in case of a major failure of the system. Two minutes of operation are possible without power source.

The backstop on the auxiliary drive motor turns the hydraulic clutch into a retarder for controlled ballancing – brake is opened electrically and is interlocked with oil pressure for gear.

The Oil System Features

# Label
1 Local Instruments: optional SCC
2 Water Cooler: optional air
3 Stand by Pump: no stop for pump failure
4 Main Line Filter: 40 um cleaneable, stainless steel
5 Pypass Filter: 10 μm non cleaneable, fleace
6 Tank: approx 5 times pump cap
7 Heating: 21 kW

  • 3-stage design for compactness and safety.
  • Moderate bearing loads to provide safety margin.
  • Hydrodynamic sleeve bearings are selected for ultimate lifetimes.

The lifetime of sleeve bearings is mainly subject to propper lubrication! In case white metal bearings are wiped out repair is possible.

PBLZ Ball mill drives feature all over hydrodynamic sleeve bearings. The bearings of the two planetary stages feature brass surfaces to be most resistant against any adverse operation condition. The brass bearing metal provides a higher strength than usual white metal spindles.

Gears are case hardened (except annulus) and precision machined. The casing is cast from cold climate enabled globular cast iron. Fine filtration minimizes wear of gears and bearings.

Before we supply our gears we carefully assemble them by skilled hands and test the complete system on our test bed.

Our Gear Lifetime Makes Your Money

Condition Monitoring and Service Completes the Package

Long life time is the result of good equipment and proper maintenance. The RENK Service group is not only present for installation and troubleshooting but can assist on a regular basis in the frame of a maintenance contract.

Such assistance includes the judgement of the outputs from the condition monitoring system which is supplied with the equipment. With such results preventive maintenance can be planned well aimed.

PBLZ rating table
(Gear size)
Maximum Torque
Typical mill speed
Maximum power
Length L
Ø of Casing
Center Distance (CD)
Weight of gear unit
160 1,750 16.5 3,000 2,750 2,120 560 32
180 2,400 16.0 4,000 3,050 2,320 592 43
200 3,200 14.8 5,000 3,300 2,620 710 56
225 4,500 14.8 7,000 3,560 2,970 830 76
250 6,500 14.5 10,000 4,030 3,330 1,000 102


RENK PBLZ Customer features and benefits

# PBLZ features Customer benefit
1 Planetary design (low speed stages) High torque Parallel shaft gears and to deflect under torque affecting the load pattern and are ultimately heavy
2 3-stage design with compact dimensions Compact parts means to save parts cost. Ratio can go up to
100 with no problem – i.e. 4-pole standard motors can be used
3 Best quality materials and QA made in Germany Cleanliness for increased lifetime of the components especially in
abrasive atmospheres; hot LP pump for uncompromising availability;
oil viscosity optimization for oil pump power saving.
4 Hot stand by pump, bypass cleaning,
temperature control valve
ISO4406 20/17/14 cleanliness increases lifetime; hot LP pump for
uncompromised availability; oil viscosity optimization
5 High margin and no restricted lifetime elements All sleeve bearing design;
AGMA Sf > 2.5; ISO6336 Ka > 1.6 & Sf > 1.6 & Sint > 2.0;
6 Temperature, Vibration and Mill Axial Position Condition monitoring for preventive maintenance and proactive maintenance
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Documents to download

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