Rock Drilling Rig Operation: The Key Skill Is Pressure Control
A rotary drilling rig looks massive from the outside, and once inside the cab, the large number of levers and buttons can make operation seem complicated. In practice, the workflow does involve many coordinated actions, from machine travel and positioning, to auxiliary functions, to main drilling operations. But to truly master a rotary rig and achieve high productivity, one control is more important than all others: crowd pressure management.
Here, “pressure” does not mean simply pushing the control lever downward all the time. It means applying the right force for the right duration based on formation conditions, and switching flexibly among different modes: lift pressure, suspension, spot float, long float, spot crowd, short-stroke crowd, long-stroke crowd, and crowd with pullback.
1) Improve Productivity
The rig’s primary job is drilling, and drilling both faster and better depends on pressure control. During operation, the operator must keep adjusting pressure mode according to geology, machine load, and vibration feedback.
Many operators assume pressure control is just pushing down on the lever, but that is a misconception. The essence of good operation is flexibility: in some situations, float mode alone is enough; in others, controlled pullback is necessary. Only by switching pressure strategies based on real working conditions can the rig deliver maximum output.
2) Protect Equipment Components
During drilling, bit load changes continuously as the tool cuts through different strata. By adjusting pressure mode and force in real time, operators can avoid overload, protect key components such as the Kelly bar and drilling tools, and maintain continuous penetration for faster progress.
Blindly applying constant pressure does the opposite: machine load spikes quickly, and the risk of damaging rods and tools rises sharply, shortening service life.
3) Eliminate Operational Risks
Prevent hole deviation
A deviated borehole can trigger a series of follow-up problems, including rod dragging, cage sticking, and casing complications. In certain geological conditions, pressure applied too aggressively or at the wrong level can cause the hole to drift. Precise control of pressure rhythm is therefore essential for preventing deviation.
Support unlocking operations
Unlocking a mechanical-lock Kelly bar relies on the resistance of a fixed drilling bucket. The required torque resistance is mainly built up through prior pressure action, not by directly adding pressure at the instant of unlocking. Preparing in advance by controlling pressure force and duration creates better unlocking conditions and reduces the risk of rod dragging caused by incomplete locking.
4) Avoid Damage from Rod Drop
When using friction Kelly bars or segmented mechanical-lock Kelly bars in an unlocked state, especially in hard formations or when bit slippage prevents penetration, many operators choose long-stroke continuous pressure. If bucket penetration speed is not proportional to the pressure stroke, the inner rod can be pushed upward. When pressure reaches the bottom stop or the machine reverses, the raised rod may drop suddenly, damaging the rod or crowd cylinder and causing a rod-drop impact fault.
Conclusion
Rotary drilling depends on the coordinated action of crowd pressure and torque; neither can be neglected. Torque load can only be generated after the bit is pressed into the formation, which is why pressure control is the most critical action in main drilling operations.
Only by accurately controlling pressure magnitude, timing application properly, and adjusting methods to formation and job conditions can operators achieve the best overall performance—high efficiency, strong equipment protection, and safe operation.
