Rig Selection Guide
Rig Selection Matters
Rig sizing is more than matching a brochure capacity. A rig must handle the planned load, ground resistance, tool weight, depth, and working clearance. A small error can cause delays, unsafe lifts, poor drilling speed, or costly standby time.
Capacity Planning
The first check is hoist demand. This value combines tool weight, casing load, and extra site load. Dynamic effects are added because loads rise during extraction, vibration, rotation, and sudden sticking. A safety factor then raises the design load for selection.
Torque and Crowd
Torque demand depends on bore diameter, ground condition, and cutting method. Larger diameters need much more torque. Harder ground also increases demand. Crowd force is checked because penetration may slow when the rig cannot apply enough downward force. These two checks help compare rigs that have similar hook load ratings.
Depth and Clearance
Depth capacity is critical for piles, anchors, wells, and geotechnical drilling. The chosen rig should reach the target depth with reserve. Mast clearance is also important. Tool length, working clearance, and headroom must fit safely under the mast. A rig can have enough power but still fail because the working envelope is too tight.
Using the Results
This calculator reports utilization percentages for hoist, torque, depth, crowd, and power. Lower utilization means more reserve. Very high utilization can be risky on variable ground. Review the limiting item first. It shows the capacity that controls selection.
Practical Review
Use manufacturer data, site records, and method statements together. Check access width, platform bearing, transport limits, fuel use, and crew skill. Also confirm local safety rules and lifting procedures. The final choice should suit both calculations and site conditions.
Better Decisions
Good rig sizing improves productivity and safety. It reduces mobilization mistakes and makes tender comparisons clearer. Exported reports help engineers, estimators, and supervisors share the same assumptions. Keep inputs updated when soil logs, pile sizes, or construction methods change.
Risk Control
Document every assumption. Record the data source for capacity values. Note whether capacities are rated, nominal, or derated for slope and weather. Include contingency for worn tooling, unstable platforms, and mixed strata. This record protects the team when site conditions change and supports faster review before mobilization starts on site.