Kelly bar is a telescopic drill pipe for rotary drilling rigs. It connects the rotary drive head and drilling bucket, transmitting torque and crowd force for pile foundation hole-forming. It can extend and retract step by step to achieve deep drilling.
Two Main Types
- Interlocking Kelly Bar Equipped with locking blocks on inner and outer tubes. Once locked, it transfers heavy torque and pressure. Suitable for hard soil, weathered rock and rock layers. Disadvantage: locking and unlocking operations are required during drilling.
- Friction Kelly Bar Torque is transferred by friction between nested bars. Ideal for soft soil and shallow holes with high continuous drilling efficiency. Not applicable for heavy-load rock drilling.
Structure & Material
Composed of 2 to 5 layers of nested steel tubes with internal and external keys. Common materials: 42CrMo, 27SiMn. Compatible with Bauer, Soilmec, Sany, IMT rotary rigs. Common OD series: 355, 368, 394, 419, 470 mm.
