The coal plow systems which Ostroj a.s. has been manufacturing for more than 50 years are used for coal mining in seams with dip angles of up to 40°, coal strength of up to 40 MPa and seam thickness of 0.6 m to 1.8 m and these plow systems can be as efficient as a shearer face in the right conditions.
The coal plow system operates using a specially designed chain conveyor with a plow chain placed either on the pillar side or the goaf side of the AFC.
The plow unit itself has a modular design and consists of a main body and intermediate pieces. The plow is equipped with cutting picks/blades to extract the coal in slices across the face..
While the basic principles of the plow system have not changed over the years, there have been steady improvements and increases in the drive power, the size of the plow chain, and the speed of the plow. We have gone through several stages of design, with various types of plows used alongside each other for many years.
At present, two types of plow machines are used – one with a plow guide and chain on the face side (known as a Gleithobal plow) and the other with a plow guide and chain on the goaf side (known as a Sliding plow).
The Sliding Plow has its base fastened to a steel plate which moves underneath the conveyor; this steel plate is designed with a hinge connection, enabling it to smooth out the unevenness of the floor.
The haulage chain is enclosed and runs along the goaf side of the conveyor. This type of plow is suitable for mining in seams with lower coal strength and a with a more solid floor. It works well in lower thickness seams because access to the chains at the goaf side is easier.
In Gleithobal plows, the plow unit is pulled by a chain on the face side of the AFC. There is no steel plate under the Gleithobal plow. Compared with the Sliding Plow, the greater efficiency of the Gleithobal plow system allows coal to be cut utilizing higher power. Gleithobal plows are therefore more suitable for mining coal of higher strengths and for thicker seams.
For strong coal it is necessary to plow the entire thickness of the seam, whereas for coal with lower strength and good cleat, it is sufficient to cut the bottom part of the seam and allow the top part to fall onto the AFC.
Depending on the thickness of the seam and the conditions in the mine, the coal plow systems may be operated:
- with powered roof supports
- with individual hydraulic supports (only for the Gleithobal Plow).