Joy engineers said the needs and demands of the Eastern European longwall mining industries were not the same as those in the West, where the emphasis has long been on larger, more powerful machines capable of producing ever-higher tonnages.

“In Russia and Poland, a machine was needed with a proven performance record, one that offered technology specific to their requirements of increased productivity and lower operating costs within existing mine infrastructures,” the company said.

The introduction of Joy’s 1000-volt AC variable frequency drive, Optidrive, allowed Joy engineers to design into the 4LS shearer a more powerful haulage unit with JNA controls; creating the 4LS20 model, a competitively priced machine that featured Joy’s common specifications but at a slightly lower power than the Joy 7LS shearers.

“In replacing what had been the standard DC haulage on the 4LS shearer with the AC optidrive on the 4LS20, Joy allows the use of a mine’s existing 950- or 1100-volt primary voltage source, thus saving the mine operator the additional expenditure to change the incoming voltage source to 3300 volts,” the company said.

“The 4LS20 also increases total horsepower from 570hp to 937hp [425kW to 698kW], haulage pull from 98,000lb to 135,000lb [44,452kg to 61,235kg] and total weight from 68,000lb to 89,000lb [30,844kg to 40,370kg].”

At the same time, ranging arm length was increased from 76 inches to 93 inches (1930mm to 2362mm) and the cutting range from up to 9 feet 2 inches to 14 feet (2.8m to 4.3m).

“The latest advances in the 4LS series of shearers increases production, improves productivity, lowers operating and maintenance costs and requires only minimal retraining of personnel to familiarise them with the improved, yet simpler, haulage system and controls,” the company said.