SME Annual Meeting Feb. 23 - 26, 2014, Salt Lake City, UT

1 Copyright 2014 by SME

Preprint 14-021

DRC1200 HARD ROCK SIZER A TWIN ROLL SIZER DESIGNED FOR MOBILITY

T. Good, Joy Global Inc., Franklin, PA J. Zimmerman, Joy Global Inc., Franklin, PA

ABSTRACT

Twin roll sizers are neither compactly designed machines nor are they configured to accommodate underground mobility; in fact, twin roll sizers leave room for improvement in many aspects of the design. The DRC1200 capitalizes on the weaknesses of these machines to make a more productive, easily maintained, and compact twin roll sizer than current market offerings. These strides were made through the inception of the Hard Rock Extraction System (HRXS), which requires a mobile sizer as part of the system. After use of a third party sizer on the HRXS, potential improvements were evident. These improvements include improved structural design to reduce overall footprint and an optimized design to reduce operating cost.

HARD ROCK EXTRACTION SYSTEM (HRXS)

Introduction to the HRXS The Hard Rock Extraction System (HRXS) is a progressive

method of reaching autonomous production in block caving mines. The HRXS consists of a loading machine coordinated with a sizer mounted on a mobile chassis, a discharge conveyor, and a means of removing the sized ore from the mine. The HRXS was conceived to reduce and possibly eliminate the heat loading and ventilation issues associated with the usage of diesel engines in conventional block caving equipment. Utilizing the HRXS concept also improves production efficiency and lowers operating costs when compared to conventional block caving practices. The need for LHDs as the main production equipment will be eliminated as well as stationary crushers unless secondary crushing is desired for ore size. The HRXS was planned to be designed, tested, and instated in three major stages. The first stage was a mine site surface test with ore from an open pit to control the environment and simulate underground production methods. The second stage was the operation of the HRXS underground via remote and evolving to remote operation of up to three systems from the surface. The third stage of the HRXS was an autonomous system requiring minimal input during the production process.

Stage one machine specification discussions began in February 2011 and by July 2011 we received the customers intent to purchase agreement. In February, the Innovation team began the conceptual and rough design of the HRXS. In July, we began ordering long lead time parts. In August, engineering started releasing packets of documentation to manufacturing who began procuring material in September. The HRXS was built and shipped by January 2012.

Inception of the DRC1200 The HRXS stage one surface trial is where the need for the

DRC1200 originated. The DRC1200 was required for the HRXS to remain feasible as well as to expand JOYs existing crushing portfolio.

After commissioning the prototype HRXS and resolving start-up issues, the trial was commenced to acquire production time and ore tonnage through the third party sizer. Throughout commissioning and testing, several issues were noticed with the third party sizer. The sizer was too large for underground mobility as expected from earlier documentation and the sizer required too much maintenance by utilizing a greaser, a large amount of external mounting for additional oil coolers, and slow replacement of wear parts. JOYs Innovation team continued to actively interact with the HRXS as the trial

proceeded. During the trial, it was noticed that the sizer bits were wearing at unacceptable rates to meet the mines operating cost/tonne requirement for the sizer to be viable. These high wear rates were attributed to the open pit ores hardness. A different grade of ore, similar to what would be experienced underground, was tried as well as a different bit material. The trial concluded that the sizer was not a viable option for the mine due to higher than feasible operating cost/tonne. These increased costs were accumulated by the bits high wear rates and were amplified by the time required to replace the bit. Replacement of the bit required it to be cut off of the rotor, the new bit and rotor to be pre-heated, welded together, and then post-heated. This would have to be done 15+ times on each rotor, which added up to over 40 hours of labor to replace bits on the third party sizer. For the HRXS to continue as a progressive step change in underground block caving mines, eliminating the LHD and large stationary crushers while producing more tonnes without any diesel emissions, a better sizer needed to be designed.

DRC1200

Figure 1. DRC1200.

Productivity The DRC1200 is powered by a 310kW AC motor coupled to a

compact gear reducer by a replaceable torque shaft and a torque limiting clutch. The gear reducer is available in two reductions 65:1 and 80:1, for 50 Hz and 60 Hz supplied power. The usage of the torque shaft and torque limiting clutch provides stiff power to the gearbox and maximizes the torque and power available to break rock and eliminates the need for a fluid coupling. This drive method provides maximum motor torque and inertial effects of the drivetrain to the rock while eliminating a major maintenance item in the fluid coupling. The DRC1200 provides sizing in three steps: primary, secondary, and tertiary. Primary and secondary sizing takes place via the bits and the rock entering between the rotors, at the 1200mm center to center distance. The tertiary sizing occurs between the rotors and breaker bar. The breaker bar is adjustable to achieve the desired size of ore in the final sizing step.

Size One area of major improvement for the DRC1200 was overall

size, as this is required by the HRXS and will adapt well to other market segments with space constraints. The DRC1200 was designed

SME Annual Meeting Feb. 23 - 26, 2014, Salt Lake City, UT

2 Copyright 2014 by SME

to be the smallest possible package with a 1200mm center to center rotor distance. This size allows the DRC1200 to easily be mobilized underground and complete 90 turns in 4.5m x 4.5m entries without issue. The overall dimensions of the sizer are 4273mm long, 3060mm wide, and 1600mm tall. That is 40% shorter and 10% narrower than the competitions machine that was used on the HRXS trial. These dramatic size reductions were achieved by utilizing a unique component configuration with the majority of the length reduction coming from the gear reducer. The reducer package was designed to utilize the width of the machine and minimize the length of the reducer and motor as a combination. With JOYs gear reducer only 25% of the motor protrudes beyond the reducer.

Maintenance An important aspect of the DRC1200s design was maintainability.

Simplified design and quickly replaceable components will reduce labor and increase uptime which will contribute to meeting our low operating cost goals. Leveraging JOYs cutting and bit knowledge, a replaceable bit was designed. The use of a replaceable bit will decrease the time required to change all of the bits to a few hours. Replacing the bits will not require any cutting or welding. Bits can be easily replaced until a rotor needs a rebuild, at which point the set of rotors can be removed and exchanged with a new or rebuilt set without adjusting a single bearing. The rotors are plugged into the input hubs which transmit motor torque to the rotor then the front of the sizing chamber is installed along with side fingers and the breaker bar. At this point, the sizer is back into production. The rotor is modularly configured for flexibility to allow bit indexing to be varied upon manufacture as well as simplify rebuilds. This also allows customer input for different ore materials and configuration preferences.

Figure 2. Star Wheel Section of Rotor.

Along with the easily replaced rotor bits, the breaker bar that is required for tertiary sizing of the ore is designed with replaceable breaker bits retained by a protected bolt. The breaker bar is easily accessed from underneath the sizer with bit replacement possible without removing the breaker bar.

The sizing chamber is lined with a wear resistant overlay material to resist highly abrasive hard ores. This overlay is fastened to the structural sidewalls by way of protected bolts, making replacement

very easy and increasing total life of the main DRC1200 structure. Other overlay wear plates are welded to the rotor assembly for added wear resistance and increased life.

To reduce other routine maintenance items commonly found on competitive sizers, everything requiring lubrication will be oil lubricated. This will eliminate a cumbersome greaser and external grease lines that can be damaged. The sizer motor and oil will be cooled by water that is sent to sprays that suppress dust generated by the sizing process.

Software The DRC1200 has two modes, a production mode and a

maintenance mode. In production mode, the machine can be operated locally, or via teleremote. This can be advantageous when utilizing batch haulage; the sizer can be started by the haulage operator while en route. The DRC1200 also utilizes the JOY Optidrive AC Variable Frequency Drive System; the usage of the VFD in production mode allows the sizer to have soft start functionality. This soft start feature minimizes current inrush when the 310kW motor is started reducing infrastructure requirements and adapting better to generator sets if utilized. If a jam occurs while in production mode, a sequence will automatically initiate to clear the jam reducing operator inputs and downtime. Maintenance mode is provided to allow bit replacement and controlled diagnostics. While in maintenance mode the VFD will allow slow, controlled rotor rotation to get components into more ergonomic or accessible positions.

The DRC1200s onboard electronic controls provide machine component protection, fault detection, system interlocking, and diagnostic capabilities. The supplied component controls are:

Motor thermal overload protection Motor jam protection Machine cooling detection Rotor jam detection Torque shaft breakage detection Oil and bearing temperature measurement Low oil level detection Cooling water flow measurement

These sensing capabilities provide machine state, protection and fault status, and troubleshooting information locally at the machine and additionally this information can be provided outby or on the surface. The advanced and proven controls for the sizer dramatically decrease troubleshooting time and can provide early failure detection of components for a scheduled maintenance replacement, both of which increase machine uptime and reduce cost.

Interlocking of upstream and downstream equipment, such as a feed conveyor and a discharge conveyor, into a system is an easily adapted option to the DRC1200 software. The interlocking of JOYs sizer into surrounding equipment will allow automated start-up and shutdown sequences optimizing material flow and energy usage during the production process.

Going Forward The design of the DRC1200 is nearing completion and the

Innovation team is looking for a mine site to trial the sizer. After the trial, the DRC1200 will be ready for production and the HRXS will once again be a viable future for block caving as well as other applications.

AbstractHard Rock Extraction System (HRXS)Introduction to the HRXSInception of the DRC1200

DRC1200ProductivitySizeMaintenanceSoftwareGoing Forward