Rotary head inspection must cover both the cold state and the warm-up process
On a used rotary drilling rig, the rotary drive is the core system that converts hydraulic power into torque. A video of the rotary head running without load does not show whether the gearbox bearings are worn, whether the brake can hold the load, or whether the drive keys are tight.
Inspect the rotary drive in its cold state and through a controlled warm-up, combining the pre-run visual record with post-run behavior to assess the risk of this high-cost component.
Create an identity information sheet for each specific stock item
Before discussing price, record the exact rotary drive configuration. Check the gearbox nameplate, motor number, brake type, drive-key arrangement and lubrication points. Comparing these with the original manual helps identify configuration differences; replacement history also requires records and professional inspection.
Match any repair or rebuild claims to the record for the exact stock ID. If the seller says the rotary head has been rebuilt, ask for the invoice or the scope of work. New paint, clean oil and a shiny housing are only cosmetic.
Cold-State Visual Inspection and Leak Baseline
Before operation, qualified personnel should, according to the applicable manual and under safe conditions, record oil traces, pooled fluid, residue around hoses and seals on the rotary drive, inspect oil in the dipstick or sight glass, and note its color, smell and visible signs of an oil change. A leak that occurs only under pressure differs from a static drip.
Qualified personnel should inspect the drive keys and their contact with the Kelly bar, loose bolts, housing welds and inspection cover condition according to the applicable manual and under safe conditions. Wear of the drive keys can produce impact loads; this baseline can be compared with the condition after testing.
Inspect warm-up and operation according to the manual
Clear the work area and confirm safe access routes. Qualified personnel should arrange warm-up and operational checks according to the specific machine’s manual, under safe conditions and within the equipment’s permitted operating conditions, observe abnormal noise and vibration, and record the test conditions.
Qualified personnel should check the holding function according to the specific machine’s manual and permitted operating conditions. Reverse operation may be checked if the equipment supports it and the manual and safety conditions allow. Observe the pressure gauge where safely visible and permitted, and record engagement, brake holding, delayed response, abnormal noise or slipping. Record any functions that could not be checked.
Torque: Published figures are not on-site proof
Manufacturer torque figures describe the configured product, not a measurement of the used machine. An unloaded video cannot establish torque. A drive may run normally without load while still having worn gears or bearings; some problems may become more apparent under load. Do not let factory specifications conceal abnormal behavior.
When equipment and site safety conditions permit, have qualified personnel arrange a controlled-load test according to the applicable equipment manual to obtain more evidence. If it cannot be performed, document what remains unverified and account for uncertainty in the price.
Post-Test Evidence: Temperature, Noise, New Leaks
Qualified personnel should record the rotary drive temperature after testing, ambient temperature and any available normal operating range, and check for new leaks according to the applicable manual and under safe conditions. Abnormal heating or new leaks warrant further assessment alongside other records; temperature alone does not establish the cause.
Qualified personnel should record and assess abnormal sounds during operation and after shutdown according to the applicable manual and under safe conditions. If an oil sample can be taken under the applicable procedure, it may be sent for contamination analysis; any metal particles found should be evaluated by a professional in context.
Check refurbishment records
For the seller’s refurbishment claims, request a dated invoice corresponding to the exact stock ID, together with the scope of work, original parts list, work specifications and test results. Note any records that are unavailable.
Freshly changed gearbox oil does not mean the component is in good condition, and it may also mask bearing wear or gear scoring. Without written documentation and a test plan, refurbishment remains an unverified claim.
Decision rule: when to walk away or dig deeper
If you cannot arrange a load test, accept the level of evidence you have achieved. The rule is simple: obvious play, metal contamination, abnormal noise during warm-up, or a brake that cannot hold should trigger expert review. Do not negotiate based on guesswork.
Request the cost of a professional inspection and consider it alongside possible repair costs. If the seller refuses any testing or verification, treat this as a risk signal. Buyer inputs include geological conditions, tooling and casing requirements, repair records and the acceptable level of inspection.
Request inspection information for a specific machine from GLOBMACH
Look through GLOBMACH's multi-brand used rotary drilling rig pages and related videos, and first shortlist machines with a stock ID and rotary-head records available for review. When requesting a quote, ask for the exact model and serial number of that machine's rotary head, the gearbox invoice, an oil sample, and a controlled warm-up test video. Require an inspection record that corresponds to that stock ID, not a brochure; if the reply has no video or documents and only verbal statements, lower your bid.
