Factors which influence proper operation of hydraulic system of the powered roof support 
Potempa J., Wojtacha M.

S u m m a r y
Basing on own studies, it was found that the hydraulic system is a main reason of roof support failures. Problems with life of hydraulic components have arisen together with an installation of cylinders of a diameter greater than 300 mm and pumps of volume flow Qv greater than 150 l/min. Now it is common to use the legs of very high load-bearing capacity, what means high diameters of cylinders. Rate of pressure grow increased in over-piston and under-piston areas of legs, especially during their lowering. The problem is important especially when a heavy piston rod is not moving yet and overflow valve is far from the receiver. Apart from that, line of hydraulic medium supply have been extended. Thus, it is suggested to make essential changes in a hydraulic system of powered roof support control. Mines and pump producers should be convinced to this idea. Some important problems, which have an impact on a proper operation of roof support and life of its components were presented.