QUADREX

A mill drive system with up to 32 MW in horizontal mill comminution

Gear / Pinion Mill Drive

The Quadrex Mill Drive is the next step in the evolution of mill drive architecture, allowing the system to be created with components that are currently available in the market. We’re effectively delivering up to twice the power of a traditional twin pinion drive. Moving from a twin pinion to a quad pinion arrangement is a natural development to a sturdy, creative mechanical solution that allows our customers to move forward with large gear driven equipment to meet their comminution goals.

Extensive research was undertaken for the  Quadrex Mill Drive system to determine all the parameters influencing the complete kinematic chain. Throughout the life of the system, these were assessed for both the drive and the mill itself, ensuring that no single parameter was overlooked. Many of the parameters addressed in the overall design that may have a combined direct influence on power sharing are depicted in the diagram below.

The Quadrex Mill Drive was created in partnership with CMD and Ferry Capitain Engineering as a large mill drive solution for the mining industry. Internal torque splitting capability of the Quadrex Mill Drive transmits motor input power to the pinion shaft and evenly divides among two mill pinions. Since the early 1960s, this form of torque splitting gear box technology has been in use. To apply high-powered transmission to huge grinding mills in the mining industry, we reconfigured the drive design.

Test Bench

To test the Quadrex Mill Drive torque dividing system under the most severe operating conditions, a full-scale instrumented test bench was designed and built.

The test bench, driven by a VFD motor, is composed of two torque splitting sub-assemblies operating in closed loop. Both sides are tested simultaneously. The torque is generated, maintained or adjusted as wanted, to produce the required power of 14 MW.

Besides validating our concept at power level never attained before, our test bench also helped validating calculation models which were used for developing our solution.

The Quadrex® Mill Drive is nearly identical to a typical dual pinon drive.

Foundation – Standard foundation loading is calculated as derived from mill power, critical speeds, and total mill load. Unlike gearless drive installations, there is no need to perform costly static or dynamic modal analyses.

Lubrication – Lubrication for the Quadrex® Mill Drive is provided by standard lubrication systems which can be located in a lube room away from the mill operating floor. This type of unit is common in the industry and is easily maintainable. Lubrication for the open gearing is provided by a closed loop oil circulating system, separate from the Quadrex® internal gear lube unit.  This type of lubrication allow continuous application, oil recycling and filtering for a wide range of lubricants.

Mill Gearing – The open gearing design is unchanged from that of a dual pinion drive.  Gearing components are rated to AGMA or ISO standards. The division of power between four pinions reduces the overall load per pinion which allows ring gear sizing to remain below currently achievable limits. This also keeps the gear material hardness levels at present-day levels.

Mill Motor Configuration – Motor arrangement for the Quadrex® is simple and conventional, similar to the largest dual pinion drive mills in operation.  Variable speed motors can be used with power up to 16 MW per drive, extending to 32 MW for dual drives. LSS motors with VSD are coupled to the Quadrex® input shaft via a torque limiting coupling.  Large brakes and brake foundation piers are not required as seen for GMD installations. Frozen charge upon start-up can also be detected.

Quadrex® Installation – The installation procedure of the Quadrex® is the same as a standard alignment process used for dual pinon drive mills. A base plate bolted to the foundation and grouted in place is allowing adjustments needed for alignment. Gear to pinion alignment is achieved by shimming and is measured the same way as a standard dual pinion alignment. Unlike a gearless drive, the mechanical portion of the installation can be completed by trained site personnel under supervision.

Quadrex® Maintenance – Quadrex® gear unit can be maintained by trained site personnel. Most components of the Quadrex® are built as removable cartridges. Maintenance procedures for any of these components can be performed on site using recommended spares. This design reduces downtime and increases equipment availability.

 

40′ SAG Mill of 28 MW with QUADREX Drive Solution