DTH Hammer Bypassing Flushing Channel for Casing Installation
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Solution Overview
Problem
Conventional percussive drilling methods for installing casings in rocky ground often result in excessive air escape, reducing ground bearing strength and posing safety risks to surrounding structures, while Reverse Circulation (RC) drilling systems compromise drilling power due to the need for a large centre opening in the percussion hammer.
Innovation Solution
The solution involves a casing installation arrangement with a boring pipe having separate flow channels for compressed air and a flushing medium, where the flushing medium flow channel bypasses the percussion piston, allowing for effective flushing without reducing drilling power by using a DTH hammer with a shell or pipes forming part of the flushing medium flow channel, and optionally incorporating splines for rotating motion and air flow management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional percussive drilling with exhaust air flushing is used, then drilling power is maintained, but excessive air escape reduces ground bearing strength and causes safety risks
Solution Approach 1:
The patent segments the flushing function from the exhaust air system by introducing a separate flushing medium flow channel that bypasses the percussion piston. This allows independent control of flushing media (water or air) delivery to the hole bottom, preventing exhaust air from escaping to the ground while maintaining drilling power through the separate compressed air channel for the percussion piston.
Solution Approach 2:
The patent introduces a flushing medium (water or air) delivered through a separate flow channel as an intermediary substance to perform the flushing function. This mediator carries released material to the surface through the casing interior, preventing harmful exhaust air from contacting the ground while the percussion piston continues its drilling function through the bypassing flow channel.
2Object-affected harmful factors
If RC drilling system with separate flushing circuit is used, then air escape to ground is prevented, but drilling power is substantially reduced due to large centre opening requirement
Solution Approach 1:
The patent merges the advantages of both conventional DTH and RC systems by combining the high-power percussion piston of a DTH hammer with a separate flushing medium delivery system characteristic of RC drilling. The flushing medium flow channel bypasses the percussion piston, allowing full drilling power to be maintained while preventing air escape to the ground through the casing interior flushing path.
Solution Approach 2:
The patent creates a universal drilling system that can operate in both conventional and RC modes. The separate flushing medium flow channel can accommodate either air or water as flushing medium, allowing the system to adapt to different ground conditions and requirements while maintaining high drilling power through the bypassing percussion piston design.
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
An arrangement and a method for installing a casing in a borehole. The arrangement (100) comprises a casing (1), a boring pipe (2) which is adapted within the casing (1), the boring pipe (2) comprising flow channels for compressed air (3) and a flushing medium (4). The flushing medium flow channel (4) is arranged to lead the flushing medium to the bottom (B) of the borehole. The arrangement (100) further comprises a percussion hammer (5) which comprises a compressed air operated percussion piston (6) adapted in a cylinder (9) of the percussion hammer, as well as hole drilling means (8) for drilling a hole for the casing (1). The flushing medium flow channel (4) is adapted to bypass the percussion piston (6) or which flushing medium flow channel (4) is adapted to pass through the percussion piston (6), and in which arrangement the drilling means (8) additionally comprise splines (28) transmitting a rotating motion and adapted to conduct the compressed air that used the percussion piston (6) through the splines (28).