Introduction
In foundation construction using rotary drilling, drill pipe jamming is a common issue that can lead to significant downtime and operational challenges. This article analyzes the causes of drill pipe jamming and provides practical solutions to prevent it, ensuring smoother and more efficient drilling operations.
Causes of Drill Pipe Jamming
Most domestic rotary drilling projects utilize slurry static pressure technology. When working in sandy layers or areas with high groundwater levels, the quality of the drilling fluid must be improved by increasing its density and viscosity. However, this also raises the sand content in the slurry.
If the drill pipe’s drive joint lacks drainage holes at the upper end, sand-laden slurry entering the pipe gets trapped by the upper step of the drive joint. While the slurry slowly drains, the sand particles accumulate, eventually leading to pipe jamming.
High-Risk Scenarios for Pipe Jamming
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No Drainage Holes – Drill pipes without any drainage holes significantly increase the risk of sand-induced jamming.
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Lower-End Drainage Holes Only – If drainage holes are only present at the lower end near the tray, they are ineffective because the sand is blocked by the upper step of the drive joint.
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Drainage Holes at Both Ends – The key to effective drainage is having holes at the upper end of the drive joint, allowing sand-laden slurry to escape promptly.
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Misaligned Drainage Holes – Even if drainage holes exist, misalignment between sections of the drill pipe can drastically reduce their effectiveness.
Preventive Measures
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Check for Drainage Holes – If the drill pipe’s drive joint lacks drainage holes, operators should be extra cautious to avoid jamming. An electric drill can be used to create the necessary holes.
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Adjust Slurry Properties – When slurry density and viscosity are too high, shake the drill pipe side-to-side after lifting the drill bucket to help discharge excess slurry.
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Flush Out Sand Accumulation – If sand jamming is confirmed, use clean water to flush the drill pipe interior, removing trapped sand deposits.
Conclusion
A small drainage hole can prevent major operational failures. When purchasing drill pipes, ensure they have properly positioned drainage holes. If existing pipes lack them, consider drilling holes with an electric drill and monitor performance closely during operations.
By understanding these risks and implementing preventive measures, drilling efficiency can be significantly improved, reducing downtime and maintenance costs.
