Voith first recognised a need in the longwall market for a reliable, actively-controlled drive system in 1996. As a result, development began on a new coupling targeted at higher powered, complex underground conveyors and one year later the TPKL Fill Controlled Coupling was completed.
Traditionally fluid couplings used an open loop control circuit design, where oil was pumped from a large oil reservoir through coolers to the coupling’s working circuit and then returned to the reservoir through drain nozzles or a scoop tube. Voith’s innovation was to use a closed loop circuit oil scheme which resulted in a significant reduction in the oil reservoir and housing dimensions whilst still enabling effective cooling.
The first mine to take on the new innovation was an Alabama longwall operation in 1998. The result was an exceptional improvement in the performance and availability of its conveyor.
Based on the TPKL’s performance on the initial installation, the mine developed a plan to eventually replace all underground drives using the couplings. Since October 2003, 14 miles of conveyor have been driven by TPKL couplings, with future projections of 18 miles of conveyor by the end of this year.
A further challenge at the Alabama mine was the step up of haulage capacity from 3.7 million tons per annum in 1997 to 7Mtpa last year. The increased capacity was amplified by the fact that all coal must last pass over three old mainline 48” belt conveyors. The conveyors had a 100% CEMA rating capacity of 2500tph, but according to North River Energy’s conveyor system coordinator Jim Patilla, the soft starting performance resulting from the TPKL’s allowed capacity to be pushed up to 3500tph ,well past the original design limits.
Prior to 1997 belt haulage availability at the mine was less than 85%. With the progressive installation of the couplings, lowest single conveyor availability for 12 months ending August 2003 was 99.2%, resulting in combined underground haulage system availability greater than 97%.
The second installation of the new TPKL technology was another tripper booster longwall panel conveyor, commissioned at a Utah mine in 1998. This installation provided the opportunity for Voith to prove its couplings could be used with a conveyor with multiple tripper boosters.
The Utah mine successfully completed five panels before moving the drives to mainline conveyors in a different section of the mine. The mine has since closed and the TPKL drives have been relocated to a sister mine.
The next mine Voith tackled was one of the United States' most productive underground mines, producing more than 11 million clean tons of coal last year from two longwall systems. The mine, located in the Pittsburgh coal seam of Western Pennsylvania, began replacing electronic drives with TPKL’s on five of their mainline conveyors in 1999. The mine made the decision in 2001 to install TPKL’s on their two panel conveyors and replace the AC-VFD drives which had previously driven both longwall panel belts. The overall result was improved performance and availability.
The next challenge for the fluid couplings was the world’s highest powered tripper drive installation at a mine in New Mexico. The new operation standardised on 750 HP x 4160 Volt conveyor drive modules for all surface and mainline underground drives using the TPKLs. The tripper installation was part of an expanding mainline conveyor application.
The conveyor was commissioned in October 2002 and is approximately 7200 feet in length, with plans to increase length as the mine develops longwall panels deeper into the coal reserves.
More than 100 TPKL couplings have been delivered to the US market since 1998 for conveyor applications.
Voith now has its sights firmly set on TPKL installations in Australia, recently installing couplings on underground conveyor drives at BHP Billiton Illawarra Dendrobium mine (562 and 650 TPKL for 375 kW and 450 kW drives respectively), through Continental Conveyor & Equipment
"The TPKL couplings give creep speed for inspections and slow start up to reduce load spikes," said BHP Billiton Illawarra special projects manager Peter Whittall. To date the conveyor installations have been successful and are performing as planned.
These were not the first installations in Australia: 562 TPKL couplings are operating at Centennial Coal’s Springvale Coal mine in New South Wales (315 kW drives) on its underground trunk (head and tripper drives) and gate conveyors. Eight units have been delivered to date, the first in 2002.
Voith have current orders for other NSW coal mines including Centennial Coal’s Mandalong mine, via Continental Conveyor & Equipment, for 450 kW drive modules (13 x 650 TPKL) and BHP Billiton’s Westcliff mine for 320 kW / 450 kW drive modules (650 TPKL). Negotiations are under way for further units at Westcliff and Appin.