Boring or penetrating the earth – Processes
Patent
1984-07-19
1986-12-02
Levy, Stuart S.
Boring or penetrating the earth
Processes
175320, E21B 700, E21B 1718
Patent
active
046258140
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The subject of the invention is a method employed in long-hole drilling in which a bit which drills a full hole is used and to which percussive energy is transferred through a steel drive rod. The rod is made up of joined extension pieces according to the depth of the hole and which are joined one to another by means of a threading system. The extension piece has an internal thread at one end and on the other end, a corresponding external thread so that the extension pieces externally form a continuous, stepless drill rod. Also in continuation of the drilling rod, there is provision in its axial direction for an internal hole or central flushing channel so that, according to the invention, intermediate pressurized fluid flushing media such as water or air can be brought into the hole to be drilled and with the aid of which the particles are conveyed out of the hole through an annular space or side flushing channel between the outer surface of the drill rod and the wall of the drilled bore. In this method the diameter of the bore to be drilled varies between 30 mm and 300 mm and the drilling machine proper is arranged so as to operate outside the hole to be drilled.
In rock drilling, a pneumatic drill, that is a drill operating on compressed air, is used. In a pneumatic drill, the greater part of the energy is used percussively although a considerable part of it is also consumed by the flushing action. In recent times, hydraulic drilling machines have, however, come onto the market and in these the energy used for percussion is fundamentally less than in pneumatic drilling machines. The development of fully hydraulic drilling machines has made it possible to economically produce high striking efficiency, so that the drilling of larger holes has become possible. Because in the hydraulic drilling machine, relatively less percussive energy is used, the significance of the energy consumed in flushing has become more important. Thus a drawback which has long been experienced in drilling has become emphasized. This drawback is the low efficiency ratio of the flushing system, occurring especially in the drilling of larger holes in excess of 75 mm diameter. When drilling large holes with the drill rods used today an exceptional quantity of flushing air is needed. Thus the situation arises in which the flushing uses even more energy than percussion. This is caused by the fact that with conventional drill rods, it is not possible to achieve sufficient flushing action to correspond with the increased drilling efficiency.
The drill rod has two functions in percussive rock drilling. First, it transfers the striking, rotation and feeding forces from the drilling head to the drilling bit. Secondly, it acts as part of a conveying system that removes the loosened rock material from the drilled hole. This transfer is carried out by a flushing system, which consists of the drill rod flushing hole or central flushing channel, through which the flushing substance is led to the bottom of the drilled hole. The drill bit connected to the lower part of the drill rod directs the flow of the flushing substance to the bottom of the drilled hole so that the hole is cleaned as efficiently as possible. The flushing substance and loosened rock material are led out of the hole through the side flushing channel, which is formed by the space between the hole which has been drilled and the drill rod.
In order that the loosened rock material may be carried away efficiently enough, the flow velocity of the flushing air or water between the hole to be drilled and the drill rod must be sufficiently high. When using air flushing, the velocity should be at least 25 m/s and with water flushing 1 m/s. If the flow rate of the intermediate flushing substance is not high enough, the drill bit has to crush the rock material several times before it is fine enough to be carried out of the hole by the flushing substance. The markedly increased efficiency of hydraulic drilling machines has led to this situation. When the flushing
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patent: 3658368 (1972-04-01), Hokanson
patent: 3730286 (1973-05-01), Weiner
patent: 3831753 (1974-08-01), Gaylord
patent: 4022285 (1977-05-01), Frank
Ala-Jokimaki Antero
Helasuo Kalevi
Hannon Thomas R.
Levy Stuart S.
Oy Airam Ab Kometa
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