Rotary Drilling Rig

Overview

A rotary drilling rig bores large-diameter vertical shafts for cast-in-place piles and drilled foundations, the deep concrete columns that carry bridges, towers, and heavy buildings. It works by spinning a drilling tool on the end of a telescopic bar, filling the tool with spoil, hoisting it out of the hole, and slinging the spoil clear, then repeating until the shaft reaches bearing depth. Mounted on a crawler base, the rig can move around a site and set up over each pile position under its own power.

The rig is built on a slewing Crawler Base carried by two Track Undercarriage crawler tracks. The base raises a Mast / Tower that guides the Rotary Drive Head, which spins the Telescopic Kelly Bar and its Drilling Tool.

How it works

Power from the Diesel Engine drives the pumps of the Hydraulic System, which feed every working circuit. The Rotary Drive Head uses hydraulic motors geared down through a planetary box to produce high torque at low speed; it grips the Telescopic Kelly Bar and turns it. The kelly is telescopic, nested square sections that slide to reach depth while interlocking shoulders transmit torque, so the tool can go far deeper than the mast is tall. The head also slides up and down the mast on the Crowd Cylinder crowd cylinders, pressing the tool down onto the soil.

The Drilling Tool is interchangeable: a Drilling Bucket for water-bearing or loose ground that traps spoil behind a hinged base, or an auger that screws cuttings up out of the hole. Carbide-tipped teeth cut the face. When the tool is full, the Main Winch hoists the whole kelly string out, the head spins the tool fast to fling spoil clear, and the cycle repeats.

The whole upper structure slews on a ring bearing in the Crawler Base to position the tool and dump spoil. The operator works from a tilting Operator Cab with a display showing depth, verticality, torque, and crowd, while a low-voltage Electrical System system runs the controls and lighting.