Published in the December 2007 American Longwall Magazine
Continuously ranked as one of the nation's top producers, the Enlow Fork complex in the southwestern Pennsylvania town of West Finley accounts for 17% of the company's total annual output. That's a lot of pressure to put on one operation, but Enlow superintendent Chuck Shaynak said the staff of nearly 550 takes it all in their stride.
The mine is working in the F14 and F15 panels on the west side of the mains as well as E16 on the east side. Average panel sizes are 12,200 feet by 1100ft with a seam height of 60 inches and cutting height of 84in, and mining is progressing in a northeast direction.
Longwall mining at the mine is in its 16th year, with the first panel started in July 1991. Today the triple threat runs Joy 7LS-2A shearers with 63in diameter drums powered with 4160 volts of installed power.
The advancement made at Enlow Fork's faces is impressive, especially given that totals can be multiplied for the faces active during a period. Mine management estimates that retreat totals about 80-90ft per longwall daily, or about 1500-2000ft each month, with about 45,000 clean tons a day.
Once cut, the coal is carried away by a Longwall Associates 1m face conveyor with a 42mm Thiele chain that speeds along at 334ft per minute. Louis Allis provides the power behind the progress, with a triple 800hp drive, and the beam stage loader (BSL) and crusher have also been provided by Longwall Associates.
The depth of cover overall at Enlow averages 500-900ft, but the longwalls' strata control plan would make one think it was much more. Each face is secured with 192 two-leg shields manufactured by DBT, each with a 750-ton yield, PMC and PM4 controls with a working range of 45-100in.
Shaynak confirmed the observation. "We have learned to deal with the challenges that we have been dealt," he said of the complex, which mines from the Pittsburgh No. 8 seam.
"Our current roof support plan has adequately eliminated our roof control issues," he said, adding that gas is also a minimal issue underground.
"Some in-seam horizontal de-gas drilling is done ahead of the gate road development," he said of the latter. "The mine fans take care of the gas."
There are seven miles of mainline belts that tackle the output, and more than 15 miles combined subsurface. There's nothing supersonic about the infrastructure's handling speed, though.
Shaynak noted that much like other regional operations, it utilizes 72in belt lines that vary in capacity. For example, its panel belts are designed for 3500 tons per hour while the slope belt can carry about 5500tph. The wild ace in this equation is the use of a 5000t bunker: the belts inby the bunker have been designed for up to 10,000tph, and outby for 5500tph.
Several suppliers are at work at Enlow to make the output infrastructure flow smoothly. Panel belt drives have been provided by ACS, while main drives have come from several manufacturers including DBT, Long Airdox, Continental, Harrison Conveyor and Shumar.
At first glimpse, Enlow Fork appears to be constantly planning or executing a longwall panel move. Not so, Shaynak said, adding that such events are kept simple and efficient.
An average longwall move takes crews about 10 days.
"Additional bolts are installed in the tailgate and headgate recovery areas," he noted, and the final longwall face also is secured by bolting.
Not only are strata and gas non-issues at Enlow Fork, so is geology for the most part. Even so, Enlow Fork has encountered both sandstone intrusions and soft floor conditions. Shaynak called current seam conditions primarily flat with some 1-1.5% gently sloping grades.
Although there is an enormous amount of extraction underground at any time, including the two longwalls that operate in adjacent panels, an expected complex ventilation system is actually much like other inner workings of Enlow Fork - simplified, efficient and well-prepared.
Vane axial fans are installed in the mains on centers of about one mile, and the back end of the longwall panels also have bleeder fans installed about one mile apart with all fans moving bad air out.
Enlow Fork uses three main fans, six bleeder fans, three intake shafts and the slope to ventilate the underground workings. Officials also confirmed all ventilation plans take the location and intensity of production at any given time into account and have solutions to keep atmospheres within normal levels; for example, it is not unusual for faces see up to 100,000 cubic feet per mile of fresh air.
The idea of a triple longwall operation may seem head-spinning; but add to that not one, but six, active continuous miner sections mining coal daily at Enlow. Shaynak outlined that three entry headgates and 10 entry mains are driven for development, and use full-face continuous miner units equipped with integral bolters.
Making it all work are Voest Alpine ABM 14 continuous miners in the headgates and Joy 12CM and 14CM CMs at the mains, officials outlined. Output is carried on with 54in headgate belts and 72in main belts.
As work is completed, three 8ft Jennmar or Excel bolts are put in place with steel straps on 4.5ft centers, and wire mesh is installed on the roof of the mains' track and belt entries; rib mesh is included in those areas as well as headgate sections.
Once at the surface, the output from Enlow's hard-working shearers and CMs go to the Bailey Central Preparation plant, a 6300-ton per hour plant it shares with its neighboring sister mine, Bailey. A full wash, wet separation method (heavy media bath, heavy media cyclone, hydro-spiral and froth flotation) is used for cleaning and prep because, as the company noted, this method maximizes recovery and quality. All coal is delivered to the complex's 20-plus customers via rail transport.
Shaynak and the mine's officials are quick to...click here to read on.
