A hydraulic system, mining machine and method of controlling a hydraulic actuator. The hydraulic system (HS) is provided with a control valve (23) for controlling movement direction and speed of a hydraulic actuator (HA) connected to the system. Generated force of the hydraulic actuator is controlled independently relative to the control valve by means of counterbalance valves (Cb1, Cb2) and servo valves (Sv1, Sv2) controlling their opening pressure. The counterbalance valves and the servo valves operate as a meter-out control assembly which controls flow of hydraulic fluid discharged from working pressure spaces (16a, 16b) of the hydraulic actuator. The disclosed system may be implemented to control a mining boom (3) of a mining machine (1).

A method of transitioning from rotary to slide drilling while maintaining a bit of a bottom hole assembly (“BHA”) on a wellbore bottom includes (a) recording a first toolface value of the BHA that is coupled to a drill string; (b) identifying a correlation between the first toolface value and a first quill position of a quill coupled to the drill string; (c) identifying a breakover torque for the drill string; (d) performing rotary drilling; (e) recording a second toolface value while the bit remains on the wellbore bottom; (f) receiving, while the bit remains on the wellbore bottom, a target toolface value; (g) calculating, while the bit remains on the wellbore bottom, an unwind amount to unwind the drill string; and (h) unwinding the drill string by the unwind amount to bring the second toolface value closer to the target toolface value while the bit remains on the bottom.

A method of transitioning from rotary to slide drilling while maintaining a bit of a bottom hole assembly (“BHA”) on a wellbore bottom includes (a) recording a first toolface value of the BHA that is coupled to a drill string; (b) identifying a correlation between the first toolface value and a first quill position of a quill coupled to the drill string; (c) identifying a breakover torque for the drill string; (d) performing rotary drilling; (e) recording a second toolface value while the bit remains on the wellbore bottom; (f) receiving, while the bit remains on the wellbore bottom, a target toolface value; (g) calculating, while the bit remains on the wellbore bottom, an unwind amount to unwind the drill string; and (h) unwinding the drill string by the unwind amount to bring the second toolface value closer to the target toolface value while the bit remains on the bottom.

The invention relates to a rotary drive arrangement for a drill rod having an outer pipe and an inner rod running at least in sections inside the outer pipe, in particular for double-head and/or overburden drilling, with a first gearbox for driving the inner rod in a rotating manner and a second gearbox for driving the outer pipe in a rotating manner, wherein the first gearbox and the second gearbox are independent of each other. According to the invention provision is made in that the first gearbox and the second gearbox are supported in a common gearbox housing and are surrounded by the same.

The invention relates to a rotary drive arrangement for a drill rod having an outer pipe and an inner rod running at least in sections inside the outer pipe, in particular for double-head and/or overburden drilling, with a first gearbox for driving the inner rod in a rotating manner and a second gearbox for driving the outer pipe in a rotating manner, wherein the first gearbox and the second gearbox are independent of each other. According to the invention provision is made in that the first gearbox and the second gearbox are supported in a common gearbox housing and are surrounded by the same.

Embodiments of the invention relate to bearing apparatuses in which one bearing surface of the bearing apparatus includes diamond, while another bearing surface includes a non-diamond superhard material (e.g., silicon carbide). For example, a bearing apparatus may include a bearing stator assembly and a bearing rotor assembly. The bearing stator assembly and bearing rotor assembly each include a support ring and one or more superhard bearing elements generally opposed to one another. The bearing surface(s) of the rotor or stator may include diamond, while the bearing surface(s) of the other of the rotor or stator do not include diamond. Another bearing apparatus may include both thrust- and radial bearing components. The generally opposed thrust-bearing elements may include diamond, while the generally opposed radial bearing elements may not include diamond, but include a non-diamond superhard material, such as silicon carbide.

An embodiment of a method of detecting and correcting for spiraling in a downhole carrier includes: deploying the carrier in a borehole in an earth formation as part of a subterranean operation; acquiring time based data from at least one sensor disposed at the carrier; acquiring time and depth data, the time and depth data correlating time values with depths of the carrier; generating a depth based profile based on the time based data and the time and depth data; generating a frequency profile by transforming the depth based profile into the frequency domain; detecting a spiraling event based on an amplitude of the frequency profile; and taking corrective action based on detecting the spiraling event.

An embodiment of a method of detecting and correcting for spiraling in a downhole carrier includes: deploying the carrier in a borehole in an earth formation as part of a subterranean operation; acquiring time based data from at least one sensor disposed at the carrier; acquiring time and depth data, the time and depth data correlating time values with depths of the carrier; generating a depth based profile based on the time based data and the time and depth data; generating a frequency profile by transforming the depth based profile into the frequency domain; detecting a spiraling event based on an amplitude of the frequency profile; and taking corrective action based on detecting the spiraling event.

A hydraulic system, mining machine and method of controlling a hydraulic actuator. The hydraulic system (HS) is provided with a control valve (23) for controlling movement direction and speed of a hydraulic actuator (HA) connected to the system. Generated force of the hydraulic actuator is controlled independently relative to the control valve by means of counterbalance valves (Cb1, Cb2) and servo valves (Sv1, Sv2) controlling their opening pressure. The counterbalance valves and the servo valves operate as a meter-out control assembly which controls flow of hydraulic fluid discharged from working pressure spaces (16a, 16b) of the hydraulic actuator. The disclosed system may be implemented to control a mining boom (3) of a mining machine (1).

A mining system with an inertial guidance system configured to enable precise excavation of geological material without a need to advance a survey line over a long distance and/or nonlinear excavation path, thereby maximizing productivity of the mind by minimizing a width of un-mined material necessary for support between adjacent excavation paths and minimizing equipment downtime.