Longwall shearer drums are far more site-specific than are those on continuous miners and are required to have a bigger range of functions. The company’s Drum Center of Excellence in Franklin, Pennsylvania has been making important changes to the company’s shearer drum designs.
The result of a recent study were changes in both design and manufacturing processes that enabled Joy to produce superior drums at the same cost of a few years ago; and more flexible drums that are more conducive to rebuild than ever before.
Longwall drums perform more tasks than simply cutting, and are also designed to scroll the coal onto the conveyor. Additionally, all shearer drums must incorporate water sprays for dust and spark suppression, something not required of all continuous miner drums. And those two elements, scrolling and water sprays, change with each longwall.
Longwall drums are also more sensitive to seam height than are those in continuous mining and drum width is critical as the mine operator may be using a hybrid longwall mining system comprised of components from a variety of manufacturers. The drum must be designed to clear the components while at the same time be designed to cut proportionately to the advance of the panline/conveyor.
“A third consideration,” said lean manufacturing specialist Chris Wright, “is cutting speed; variations in revolutions per minute (RPM) could lead to changes in the scroll design and the angle of the bits. These factors combine to make every longwall shearer drum unique, both in its original design and in its rebuild.”
While Joy has been a dominant manufacturer of longwall and continuous mining machines and their respective cutting drums, because of the perennial driving forces of the market place—supply and demand and costs—over time the rebuilding of the drums had become highly competitive, attracting a number of both large and small companies.
Initially, smaller companies in particular had the advantage of shorter turn-around times as they literally would drop everything to bring a drum rebuild into their shops. And, with considerably lower overheads, there was a definite difference in pricing. Today, delivery time no longer is an issue and pricing has become more competitive.
“At the same time,” said Mike O’Neill, Joy Mining Machinery’s senior engineer, “Joy has retained a major advantage in that the same technical expertise and demanding quality control that went into the manufacture of our drums is applied to the rebuilding of the drums; it’s the very same skilled professionals and the very same facilities, the largest number of such facilities in the industry.”
O’Neill said Joy drum designers had an inherent advantage over the outside shops when it came to knowledge of the mining machines to which the drums are fitted. These machines are controlled by microprocessors that utilize inputted parameters to determine the level of performance a given machine can produce. Outside shops cannot determine what is possible to expect from a given machine in terms of horsepower and torque. Nor can they determine how these outputs are adjusted via the parameter settings, he said.
The electronic systems that control the shearers all are configured to log performance data. Joy maintains a library of this data and uses it to determine norms for its machines and in troubleshooting.
The same engineers and technicians who design cutting drums are involved in analysing those returning to the shop to be rebuilt. Among other properties, they study the wear patterns on the bits and bit holders to determine what design changes could be made to improve the performance and extend the operating life of future cutting drums.
“Better machines today leading to better designs for tomorrow,” O’Neill said.