This type of installation is known as "drill and leave." The swivel prevents rotation of the product pipe.įor some telecommunications or power cable projects, the drill pipe itself becomes the conduit and is left in the ground upon reaching the exit point. Drilling fluid is pumped downhole to provide lubrication, and the product pipe is pulled in while rotating the drill pipe and reamer. When the bore hole is at least 25% larger than the pipe to be installed, the end of the drill pipe is connected to a reamer attached to a swivel connected to the product pipe. Drill pipe is added behind the reamer or hole opener so that there is always drill pipe in the bore hole. The reamer is pulled back while rotating the drill pipe to enlarge the bore hole, with as many consecutive passes as required. Upon reaching the exit point, the bit is detached and the end of the drill pipe is attached to a reamer or hole opener (for rock), if the bore hole must be enlarged. ![]() Some systems use a dual pipe exclusively. In cases where the ground is unstable, a washover pipe, or casing, can be pushed down the bore hole to prevent the collapse of the hole walls. Steerage is accomplished by aligning the angle of the mud motor to the desired direction. In rock, a mud motor, which converts the hydraulic pressure of the drilling fluid into mechanical rotation, is used to rotate the bit and the drill pipe is not continuously rotated. The directed jet of the drilling fluid and forward thrust cuts a new path. To steer, rotation is stopped, the angle of the bit is aligned to the desired direction, and forward thrust is applied. In softer soils, an angled bit is used and the pipe string is rotated, if necessary, to bore straight. Drilling fluid is classified as non-toxic and can be disposed of accordingly. As fluid is pumped down the hole, the cuttings are carried back out to the surface, where they are either allowed to settle out in a pit or removed mechanically in a cleaning system. In softer soils, the high-pressure jet of fluid cuts through the soil, with the cuttings suspended in the fluid. Drilling fluid is generally a mixture of bentonite clay and water, with additives used to improve performance. Most directional boring machines use drilling fluid (mud), with a few machines designed to use air or air and foam. As each joint of drill pipe is pushed into the ground, a new one is added behind. Any procedure deemed unsafe will be reported to the supervisor and drilling operations will cease until a safe method is approved.*Complete Safety Plan upon request.The process begins when a directional bore machine pushes a bore head connected to hollow pipe into the ground at an angle.
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