What should you do if a kelly bar breaks?

Preventive measures for broken kelly bar


Kelly bar is a perishable part. Check the kelly bar once before each start-up, remove the kelly bar periodically and inspect it thoroughly, especially the parts where the two parts are in contact for a long time. Regularly check the wearable parts of the kelly bar and complete the welding and polishing. Maintenance of the kelly bar can reduce failure and the probability of broken.


According to the type of rock, strength, and pile diameter, control the engine speed, power head speed, pressurization method, and single bucket feed depth to control the load, relieve the shock and Bean rotation to protect the kelly bar.

Matching of drilling tools

Matching the type and diameter of drilling tools according to the type, strength and pile diameter of the soil. Drill tooth type and model selection.

Elevation and positioning

According to the rock and soil, the guide teeth should be selected and the height of the central guide teeth should be lengthened to enhance the positioning ability in the rock and soil where the hole is easily deviated. In addition, as the pile diameter increases, the required anti-deflection resistance increases. Therefore, adding composite guide teeth can increase the guiding range and improve the positioning ability. In addition, the use of a straight barrel and the increase in barrel height can improve the binding force of the drill body in the hole. This helps to prevent or reduce the deviation of the hole. A positioning ring is added to the drill bit to force guidance and prevent deviated holes.

Split drilling process

For large holes with high geological strength, a split drilling process can be adopted to disperse the torque, reduce the shaft pressure and protect the kelly bar.

Key maintenance parts

Two parts of long-term contact wear or impact, weak points or other reasons resulting in the part under abnormal stress, resulting in the part of wear, deformation, metal fatigue, cracks, etc.

Crack repair

Most broken kelly bar have cracks first. Because of the lack of timely inspection and repair, the cracks spread and eventually led to broken pipes. Therefore, the cracks of pipe should be repaired in time to eliminate or reduce the occurrence of broken accidents.

Solutions for broken kelly bar

Tube joint

Disconnect all the pipe bodies. Remove the pipe from the main machine and place it on the ground pulley frame for leveling. Cut off the pipe body at the broken section, and weld and polish parallel alignment pairs of pipe bodies of the same material, diameter and wall thickness of the required length. Finally weld the key strip.

Welding specifications

The butt joint will be sanded with a grinding wheel with a 30-degree break, as narrow as possible, to sand the mouth. Then preheat 200 ℃, shall not exceed 250 ℃. Steel pipe diameter greater than 245 mm with J506, J507, or equivalent performance wire welding; diameter 245 mm below the drill pipe with 80 kg of low-hydrogen, low-sulfur resistance to cold cracking, heat cracking welding material. Welding according to the recommended specifications for the use of welding consumables, but welding should try to use a small weld multi-layer welding. After welding to polish the whole. Do not weld leakage. After welding attention to insulation. Weld leakage of the weld tumor should find ways to remove.

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