West Elk, located in Somerset, Colorado, and the not too distant Sufco mine, located in Sevier County, Utah, are both top performers in the Arch stable.
While both mines had historically achieved high output around the 6 million ton per annum mark, Arch decided to invest in replacement longwalls based upon the criteria of life cycle, maintenance history, mine reserves and geology.
Sufco ranges in seam thickness from 6ft to 20ft with a longwall cutting height of 8-12ft and a face width of about 1110ft.
West Elk is similar to Sufco, with 6-18ft for seam thickness, 8-12ft for the cutting height and 1081ft for face width.
The Arch team began developing specifications for the new longwall mining systems in 2005 and ordered the two systems from Bucyrus in 2006.
Delivery and set-up were completed at Sufco during the first quarter of 2007, while the West Elk longwall was completed in the fourth quarter of 2008.
For both faces, the primary manufacturing and assembly of the shearer and shields were done in Germany. The AFC and BSL drives plus crusher were also manufactured in Lunen, Germany, but the AFC line pans were made in the US. Sufco had the first PF6 line pan manufactured in the US.
The first longwall to roll out of Bucyrus’s manufacturing facilities was Sufco’s system which was designed to accommodate higher horsepower and more capacity to better cope with Sufco’s wider panels, which have been expanded from 930ft to 1105ft.
The Sufco and West Elk specifications were almost identical. Each mine ordered two EL3000 shearers with 78in diameter drums and 1200hp ranging arms. Total installed shearer power was 2795hp.
The mines ordered 2m wide shields (169 shields for Sufco and 163 shields for West Elk) which boast a 1273.5-ton support capacity and use PMC-R controls. Several of West Elk’s shields were on show at this year’s MINExpo before being transported to the mine for underground installation.
The stage loaders are rated at 4000t per hour at 426ft per minute, BSLs at 800hp with 42mm Power chain and the AFCs have a capacity of 5000tph, using a 72in wide panel belt.
Both longwall face conveyor systems are equipped with three 1650hp/4160-volt electric motors. Bucyrus US longwall market director Al Hefferan said this equalled the highest connected horsepower on any longwall system in the United States.
The Sufco longwall order marked the first time Bucyrus had held compatibility trials of a full mini build at its Huntington service center, rather than Houston.
“This also greatly assisted the mine in training as it was only 90 minutes from the mine. We set the AFC/shearer and 28 shields for this. This was done in December 2006 for Sufco and repeated in June 2008 for West Elk,” Hefferan said.
Prior to installing the longwalls underground Bucyrus also carried out its standard classroom trailer training.
For Arch a special feature on both new longwalls was Minesafe vibration monitoring which observes the bearing and gear vibration of all major AFC/ BSL/crusher components.
“This allows Arch to keep its focus on predictive maintenance by using technology to monitor vibration, sample oil and detect unusual heat patterns,” Arch told Coal USA.
“Arch’s new longwalls are also standardized as much as possible so the company has flexibility in the use of equipment as well as with spare parts and experience on operating and maintaining the longwalls.”
Hefferan said the technology was developed in conjunction with German company DMT.
“This is our first time in the USA to use this, although a variation of it is used at a DSK mine in Germany,” Hefferan said.
Another innovation for the West Elk shearer, according to Bucyrus shearer product manager David Hardzog, was the coal sizer design on the EL3000-113 shearer.
The coal sizer was designed to be compact but carry more horsepower to stop larger chunks of coal getting stuck in the throat of the shearer.
The biggest design challenge for Bucyrus was getting the diameter of the crusher small enough to allow the sizer to come up over the tail drive and still allow a reasonably low tail mining height (under 9ft). Hefferan said this required a specially designed 100kW motor to be installed to overcome the size problems.
With a number of US firsts for the Sufco and West Elk longwalls, Arch and Bucyrus have worked together closely over two years to get a productive outcome.
“Arch’s progressive nature helped the early adoption process. I think we are proud that while we encountered some start-up difficulties at Sufco with the AFC and shearer, we persevered with Arch Western Bituminous Coal Group through that, and in a couple of months had the system up to where it needed to be – a first-class system,” Hefferan said.
“The shearer on the second panel ran between 98 per cent and 99 per cent availability the entire second panel and is now into the third panel.
“They were also the first to use our new 42mm Power chain on the BSL and completed an entire panel, and were able to put the chain in for the following panel. We continue to monitor and tweak the performance of these chains.”
West Elk shields
Extended height: 174in (4420mm)
Canopy width: 76.8in (1950mm)
Support weight: 71.6 tons (37.7 tonnes)
Leg size diameter: 15.8in (400mm)
Total support capacity: 1232 tons (10,965kN)
Electronic controls: PMC-R