The MultiDrive®, which has proven successful in industrial operation since 2008, was developed by Gebr. Pfeiffer in cooperation with Siemens/Flender especially for the MVR mill.
In cement industry, while considering large and extra-large capacity solutions, the most important point for grinding raw material, cement and granulated blast-furnace slag is: Maximum throughput and utmost technical availability!
This is ensured by the Pfeiffer MVR vertical mill with its revolutionary MultiDrive®. With a drive power of up to 18,000 kW, throughput rates of more than 1,400 t/h can be reached on a single mill. An additional important feature of this system is the double active redundancy ensuring highest availability and productivity without downtime.
Active redundancy of drive system The MultiDrive®, which has proven successful in industrial operation since 2008, was developed by Gebr. Pfeiffer in cooperation with Siemens/Flender especially for the MVR mill. What makes this multiple drive unique all over the world is the fact that there may be up to six independent drive units, which are actively redundant both electrically and mechanically. Another feature to be found only with this type of drive: delicate gearbox components are not located under the grinding table, thus ensuring an unparalleled technical availability of the drive system. In case a drive unit fails, which is rather improbable, the unit concerned can be taken out of the system, with the others still operating, so that the mill will continue producing, sometimes even without a reduction of throughput. One more benefit among several: with adapted combination of Pfeiffer MVR mill and MultiDrive®, higher production rates can be achieved for which normally two vertical mills operating in parallel may be required.
MultiDrive® concept for elimination of weak spots
When designing the MultiDrive®, the engineers aimed at avoiding the weak spots of conventional single planetary gearboxes that cause long downtimes and work-intensive repair. Basically, the vertical mill gearbox serves to transmit the motor torque to the grinding table. Moreover, it directs the grinding forces into the mill foundation. Unlike on conventional gearboxes, these two functions are completely separate on the MultiDrive® what makes it so unique and trend-setting. Therefore, delicate gearbox components are not to be found under the grinding table where they would be exposed to the highest grinding forces. The benefit: considerably reduced wear and highest availability as the vertical forces occurring under the grinding table are directed completely into the foundation, passing through sliding bearings which have proven in industrial operation.
Damages on planetary gearboxes
Drive arranged under the grinding bowl: The grinding forces are directed through the gearbox into the foundation, thus straining the gearbox geometry. No weak spots with the MultiDrive®: Decentralised arrangement of drive: the grinding forces are directed through the rugged table thrust bearing into the foundation without straining the gearbox geometry.
With active redundancy someone can forget about downtime! The intelligent design of the MultiDrive® perfectly fits the MVR mill because with both elements together, active redundancy is ensured for the mill drive and grinding rollers. Up to six independent drive units, each comprising an electric motor and gear, engage with a girth gear flanged to the neck of the grinding table transmitting their torques to the latter. For maintenance purposes or in the unlikely event that a failure should occur, one or several drive units can be disengaged, without causing a stop of production. This is a protection against total failure!
Working principle: Three to six identical drive units comprising motor, coupling, and gear driving the girth gear of the table, thrust bearing, reaching total power rating up to as much as 18,000 kW.