Expertise
Precautions for the Use of Drill Rods
2026-04-24
1. During construction, avoid connecting large-diameter drill rods with small-diameter drill rods (i.e. mixed use of different diameter drill rods), so as to prevent the small-diameter drill rods from fracture or deformation due to insufficient structural strength.
2. When clamping drill rods with a vise, do not clamp the box thread part of the female connector to avoid deformation of the box thread.
3. When connecting drill rods, make-up preload torque pressure shall be controlled within 15 MPa, to prevent breakout difficulty caused by excessive pressure.
Do not heat the connector with open flame, otherwise the mechanical properties of the connector (especially the female connector) will be reduced and the service life will be affected.
Insufficient preload will cause oscillation of the threaded connection, resulting in mutual abrasion of threads, sharpened thread crests and ridge formation on thread flanks, further leading to thread damage or galling.
Without proper preload, the shoulder of the box thread cannot be fully compressed, which may cause fatigue fracture at the thread root of the pin connector; under the action of high-pressure fluid flow, the female connector may be punctured and eroded, easily resulting in longitudinal cracking of the female connector.
4. Before connecting drill rods for trenchless horizontal directional drills, thoroughly clean the pin threads and box threads, then apply dedicated thread compound. Waste oil or inferior pressure oil shall not be used as a substitute, to prevent premature wear and damage of pin and box threads.
5. Clean the water channel hole before drill rod connection, prevent foreign matter from blocking the channel and causing pressure hold-up of the mud system.
6. Forbid forced make-up of threads. During thread alignment, the pin thread shall not impact the shoulder and thread of the box thread, and ensure accurate alignment of male and female connectors. Keep good concentricity between the breakout device and power head main shaft of the drill rig.
7. Inspect the wear condition of all parts of drill rods regularly, and identify the cause in time if abnormal wear occurs:
(1) Check whether the drill rod is scratched by sharp hard substances in the hole;
(2) Check whether the scratch is caused by the guiding device of the drill rig.
If the scratch depth on the rod body of trenchless drill rods reaches about 1mm and presents a spiral shape for more than one circle, the drill rod shall be used with caution, to avoid drill rod fracture during construction and subsequent major losses.
8. If thread damage (mis-threading, disordered threads, severe abrasion, etc.) is found on drill collar subs, replace the damaged drill rod in a timely manner to protect intact threads.
9. Avoid impact damage to pin threads during hoisting and handling of drill rods.
10. Do not mix drill rods of different thread types; do not mix drill rods from different manufacturers. (Due to differences in technical parameters, processing methods, cutting tools and mechanical equipment among manufacturers, there are inevitable deviations in machining tolerance and standoff distance of drill rods.)
Drill rods with huge differences in service life and wear degree shall not be mixed, so as to eliminate construction risks.
11. If local minor thread damage (about 1-2 threads with a thread length of 10mm) is found on drill rods, repair the damage before reuse.
12. Do not clamp any part of the drill rod body with a vise, to prevent rod body bruising by slips and avoid reduction of drill rod service life.
13. Use qualified zinc-based thread grease; ordinary butter is not suitable for thread lubrication.
Insufficient thread grease will cause shoulder damage and height deviation of connectors, easily resulting in loose threaded connection and thread failure.
No thread grease or unqualified thread grease will cause adhesion on thread surfaces and lead to thread galling.
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