In West Virginia type conditions, where longwall coal seam height generally averages four to five feet, operators typically cut six feet to attain operating height, which requires cutting of rock. Being able to lower the chain height with a different chain, means the required operating height can be lowered.
“The often-heard claim is, if you can lower the operating seam height on the typical West Virginia longwall by one inch, you can save several hundred thousand dollars per panel,” said Terence Scrutton, global AFC applications manager.
Other than achieving these initial goals, Joy is finding the innovative chain offers several benefits such as greater power for higher seam operators with larger equipment. The increased power made possible with Joy’s BROADBAND low profile chain also means longer faces can be installed, reducing panels and development work.
“As a general example, with the increased power derived from replacing a 42mm conventional chain by a 50mm BROADBAND low profile chain, the length of the panel could be increased from 300m to 400m. The savings in development work is significant, as is the increased coal production associated with less face moves,” Scutton said.
Using the same lower AFC line pans Joy said the BROADBAND low profile chain could replace smaller traditional round or flat link chain. A 26mm flat link chain could be replaced with a 34mm BROADBAND low profile chain, 34mm flat link with 42mm BROADBAND low profile chain, 42mm flat link with 50mm BROADBAND low profile chain and 48mm flat link with 58mm BROADBAND low profile chain.
Manufactured exclusively by Parsons Chain, the flat, forged chain links provide larger interlink, which reduces wear while increasing the strength of the chain, thus helping to maintain chain stiffness.
“A 42mm flat link chain will operate with up to 2x855kW installed power while the 50mm BROADBAND low profile chain replacement permits 3x1000kW installed power,” Scrutton said.
BROADBAND also offers a 100% improvement in the link contact area, reducing wear. To identify just how much better the wear factor is the BROADBAND chain underwent factory trials against a conventional flat link chain at a Joy facility in the UK.
Engineers expected to realize an increased wear factor of two in tests but achieved a factor well is excess of that.
“Of course, we have to anticipate that the operational condition may be different when the chain is tested underground but, having exceeded our design objectives during testing, we have great expectations,” Scrutton said.
A field trial of 42mm BROADBAND low profile chain is underway on a BSL at Xstrata Coal’s Ulan mine in New South Wales where Joy recently won an order for a complete face of 2.05m roof supports and AFC.
“The BSL application will enable us to quickly confirm the increased wear life that prototype testing demonstrated,” Joy said.
Joy is controlling the release of the new chain until the completion of the trial. The company reports a great deal of market interest in the chain, particularly from operators in thinner seams. Additional interest is also expected from operators with high tonnage panels and from those who want to increase the capacity (tonnes/hour rating) of existing AFCs, or go to longer faces.
At MINExpo in September, Joy exhibited a 2.05m line pan fitted with a length of 50mm BROADBAND low profile chain. This chain size will be installed on Ulan's 400m long, 3x1000kW face in 2005.
Retrofitting an existing longwall pan line with stronger chain to allow a greater face width requires the new chain, new sprockets with wider teeth, and new flight bars. Scrutton said the incremental cost of this upgrade at the time of overhaul would be minor compared to the benefits of running a longer face.