25 years down the line and FLSmidth MAAG® Gear has revamped a classic and created a state-of-the-art gearbox: the PPU gearbox for roller presses and other applications.
Roller presses in cement plants are used for the primary reduction of the grinding stock. For this application, FLSmidth MAAG Gear offers a special series of gearboxes for roller presses.
The gearboxes are always used in pairs for the drive of the two grinding rollers. They can be used in both directions of rotation. The gearboxes for roller presses have been designed as two-stage planetary reducers with spur pre-stages. This ensures optimal design of the planetary stages with good load distribution and adaptation to the required gearbox ratio.
The new version
Experience gained over the last 25 years was analysed in order to fully redesign the PPU gearbox. The following objectives were met:
• Weight reduction of 25%
• 15% smaller outer diameter
• Diversity of parts reduced by 20%
The main focus of the redesign was in the toothing and the bearing system of the individual components. The choice of an optimum bearing system and good sizing has resulted in a high level of reliability.
With a bearing lifetime in excess of 100.000 hours, the PPU is like a marathon runner who leaves the competition way behind.
Compared with other gearboxes in the same application class, the new PPU uses just five different types of antifriction bearings instead of up to eight, which simplifies the management of spare parts.
PPU in assembly
Operating costs are reduced thanks to efficiency and optimised maintenance intervals. Lubrication oil consumption has been optimised. The ideal oil level reduces churning losses and improves efficiency.
The dimensions and configuration of the gearbox were aligned to the application and other components in the drive train, such as shrink disk, overload coupling and cardan shaft.
Top gearing quality
The tooth geometry was designed following the well-proven MAAG® standard and recalculated according to the latest ISO and AGMA standards MAAG. This guarantees optimum load distribution across the teeth and therefore maximum power transmission.
The toothed components are manufactured in-house to the strictest quality standards and are made from case-hardened and heat-treated steel. In-house heat treatment gives complete control over the hardening processes and material properties. After assembly, each gearbox is tested on the internal test bed.
Installation of PPU
The first gearbox of the latest PPU generation was installed in India.
Machine FLSmidth Roller Press (HRP R-3.00)
Drive power 2 x 1600kW
Gearbox type 2 x PPU-44
Gearbox weight 6.300kg
The other parts of the drive train, such as the torque arm, overload coupling, driving shafts, shrink disks and oil supply systems, were also supplied by FLSmidth MAAG Gear. The customer benefitted from FLSmidth's ability to deliver a full range of products from one source.
A local team of technicians installed the gearbox under the supervision of a MAAG service engineer. The crew was well-trained and the individual drive train components were assembled quickly.
Alongside classic roller press applications, the PPU is flexible enough for other uses:
• Central drive for small ball mills
• Furnace drives
• Industrial drives (sugar)
Through the use of a wide range of options and components, the modular gearbox design allows the adaption of the drive train precisely to the customer's needs. The drive train for a ball mill application is being supplied as a complete system by FLSmidth MAAG Gear for a customer in the Far East:
• PPU gearbox unit with limited end float
• Gearbox foot for transferring load into the foundation
• Oil supply system
• Low speed ZCF gear coupling with intermediate flange for ball mill
• Water injection unit via the coupling
• Torsionally flexible high speed coupling
• Auxiliary drive for maintenance work
• Main drive motor