Coal Age

JUN 2019

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30 www.coalage.com June 2019 shovels and excavators continued for its 12,000-hour life before rebuild, which aligns with dipper service life. The new snubber design — a sealed, oil-immersed clutch pack — eliminates a daily maintenance touch- point and delivers much longer life than the standard snubber. Addition- ally, the wet disk snubber can be re- built three times before replacement is needed, and rebuilds are simpler and faster than standard snubber rebuilds. The snubber plays a critical role in truck loading as it provides controlled resistance to the motion of the dipper door. During opening, the damping torque slows door velocity to prevent collisions with the truck body. During closing, the damping torque prevents the door from slamming against the dipper body and dipper structure. The wet disk snubber results in reduced maintenance time and costs, improved reliability, enhanced safe- ty, and lower total cost of ownership. In field validation at a Wyoming coal mine, wet disk snubbers also reduced frequency of repairs to the dipper door and latch keeper. The wet disk snubber is retrofitta- ble and available for both latched and LatchFree Cat Dippers installed on Cat 7495, 7495 HF and 7495 HD Elec- tric Rope Shovels. The snubber up- grade can be retrofited in about two days and is typically completed when the dipper is being rebuilt. AC Drive Technology ABB is providing Komatsu with the ACS880 Multidrive lineup including a common base frame and cabinet roof with back-to-back installation. Comprising one IGBT Supply Unit and modified with a non-standard DC charging circuit and up to eight motor-inverter drives, the shovel controlled by the ACS880 Multidrive operates at low voltage AC. Using in- dividual motor inverters for all drives increases production uptime. ABB AC drives for open-pit shov- els are compact, robust units that are modified to withstand shock and vi- brations — essential technology for shovel reliability and productivity. The ACS880 multidrive, with direct torque control (DTC), delivers fast dynamic performance at low motor speeds and prevents premature aging of power components. The cabinet system has been modified to withstand shock and vibrations — technology that is essen- INJECTING STABILITY, STRENGTH AND CONTROL COMPANY PROFILE-PAID ADVERTISEMENT Roof falls at the face, voids and cavities, troublesome groundwater and other sim- ilar problematic situations often result in major production delays. Strata Worldwide excels in problem solving and has the spe- cialty products, equipment and mining ex- pertise to overcome these difficulties and deliver results. Strata Advanced Foam Solution (AFS™) Through a partnership with Grace Con- struction Products (GCP), Strata Worldwide offers an innovative injectable resin for rock consolidation, void fill and water control in underground applications. Strata AFS™ is a rapid-curing hydrophobic polyurethane foam that expands up to 30 times its orig- inal volume. When injected into the cracks and joints of rock and strata layers for consoli- dation, AFS penetrates deep into the voids where it cures and generates compres- sive strength. The result is a solid, fortified structure that significantly reduces the risk of roof and rib fall. Cured AFS is also impermeable and pre- vents the flow of water, making it ideal for controlling, stopping and/or diverting water. Sample Applications: – Consolidating coal for the development of longwalls and/or longwall extraction. – Consolidating and repairing under- ground structures for ground-to-roof stabilization. – Directing the passage of water and pre venting leaks in unwanted areas. – Consolidating strata for the construc- tion of roadways and slopes. – Grouting pipes to prevent weathering and erosion. VOID FILL Strata AFS can be used for filling large voids and cavities, particularly those at the work- ing face. Pumped into the cavity above long- wall shields, AFS expands to fill the area and consolidate loose fragments. The resulting structure serves as a solid roof against which the shields can advance. In a recent application where a longwall mine was forced to halt production due to a 10-25 foot cave above 60 of their shields, as well as a 10ft rock fall in front of the shields, Strata was contracted to find a timely resolu- tion. Strata crews constructed a 'false-roof', tip-to-face, and pumped the highly expan- sive AFS into the void above the shields and false roof. "The AFS rapidly expanded to fill the space and prevented further roof fall," stated Josh Behling, General Manager of Strata Mine Services. "It took us four shifts of pumping before the mine could resume productivity, and at about 12 hours after that, they had advanced 20 feet." To date, AFS has been used in numer- ous projects across the United States, and has successfully solved a variety of different problems. Strata's qualified mining profes- sionals are available for consultation and mine evaluation nation-wide. For more information please visit our web- site at www.strataworldwide.com or contact us at info@strataworldwide.com. A new, wet disk snubber (the yellow device on the back of the dipper above) has a longer life.

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