Method and device for monitoring operation of a mining machine unit

1. A method for monitoring operation of a mining machine unit, particularly of a longwall mining system, having a shield unit connected to a material removing unit by an actuator for adjusting a distance between the shield unit and the material removing unit, the method comprising:

using reflectometry to determine a position change of the shield unit during an actuating operation of the actuator; and

detecting a malfunction of the mining machine unit based on the determined position change.

2. The method according to claim 1 , wherein the actuating operation is a retracting operation of the actuator.

3. The method according to claim 1 , wherein the determined position change is indicative of a displacement length of the shield unit, in particular with respect to an initial position of the shield unit.

4. The method according to claim 1 , wherein the position change is indicative of a change of the shield unit's position along a direction (X) pointing towards the material removing unit.

5. The method according to claim 1 , wherein a failure condition of the mining machine unit is detected when the determined position change does not indicate a change of the shield unit's position, and wherein a proper condition of the mining machine unit is detected when the determined position change indicates a change of the shield unit's position.

6. The method according to claim 1 , the failure condition of the mining machine unit is detected when the determined position change does not exceed a threshold, and wherein a proper condition of the mining machine unit is detected when the determined position change is equal to or exceeds the threshold.

7. The method according to claim 1 , further comprising determining a stroke change of the actuator during its actuating operation, wherein the step of detecting a malfunction of the mining machine unit is performed based on the determined stroke change.

8. The method according to claim 7 , wherein the determined stroke change is indicative of a stroke change length, in particular with respect to an initial stroke of the actuator prior to being operated in its actuating operation.

9. The method according to claim 7 , wherein the failure condition of the mining machine unit is detected when the determined stroke change and the determined position change do not correlate, and wherein the proper condition of the mining machine unit is detected when the determined stroke change and the determined position change correlate.

10. The method according to claim 7 , wherein the failure condition is detected when an absolute value of the determined stroke change is greater than a first threshold or when an absolute value of the determined position change is lower than a second threshold, and wherein

the proper condition is detected when an absolute value of the determined stroke change is equal to or greater than the first threshold and an absolute value of the determined position change is equal to or greater than the second threshold.

11. The method according to claim 10 , wherein the second threshold is determined based on the determined stroke change.

12. The method according to claim 1 , wherein the actuator is connected to at least one of the shield unit and the material removing unit by means of a shear pin which is configured to release a connection between the actuator and the at least one of the shield unit and material removing unit when a mechanical force acting on the shear pin exceeds a predetermined value.

13. The method according to claim 1 , wherein the actuator is a linear actuator, in particular a telescopic actuator comprising a cylinder secured to the shield unit and a piston secured to the material removing unit.