END PIECE OF DRILL PIPE, DRILL PIPE ASSEMBLY AND METHOD

Description

RELATED APPLICATION DATA

This application is a § 371 National Stage Application of PCT International Application No. PCT/EP2023/073151 filed Aug. 23, 2023, claiming priority to EP 22192053.1 filed Aug. 25, 2022.

TECHNICAL FIELD

The invention relates to an end piece of a drill pipe for a rotary or DTH drilling rig.

The invention further relates to a drill pipe assembly and to a method of forming a drill pipe assembly to be used in a rock drilling rig.

BACKGROUND

In mines and at other work sites different type of rock drilling rigs are used for drilling drill holes in rock surfaces. In rotary drilling and DTH drilling drill pipes are connected to a rock drilling machine or unit and are rotated by a rotation device. The drill pipe is an elongated hollow tubular and thin-walled element trough which drilling fluid is pumped down the hole to a drill bit. The drill pipe transfers rotation and torque from the rotation device to the drill bit and it also transmits axial feed forces.

Typically, the drill pipe is provided with separate end pieces at its opposite ends. Joints between the end pieces and the drill pipe have shrink fits. However, the known solutions have shown some disadvantages, and especially relating to crack formation and overall durability of the joints between the components.

SUMMARY

An object of the invention is to provide a novel and improved end piece and drill pipe assembly for rotary or DTH drilling, and a method for forming a drill pipe assembly to be used in a rock drilling rig.

An idea of the disclosed solution is that a drilling tool intended for a rotary or DTH drilling rig includes one or more drill pipes. The drill pipe is provided with end pieces. The end piece is an elongated tubular piece having a first end provided with first coupling means including thread surfaces for thread mounting with other drill components. An opposite second end is provided with second coupling means for coupling the end piece to the drill pipe by means of a shrink fit. The second coupling means has a radial, outwardly facing first contact surface extending a first axial distance from the second end towards the first end.

Further, the first contact surface for providing the shrink fit has a tapered configuration. In other words, the tapering second coupling means are formed on a male configuration, which is configured to be received by a female configuration formed at an end of the drill pipe. The female part can also be considered as a socket part with the receiving feature and is provided with mating tapering surfaces.

An advantage of the disclosed solution is that the shrink fit with the tapering shapes provides improved stress distribution between the assembled components and decreases the risks for cracks in the joint. This way high load carrying capacity is possible. Further, less interference is required to transfer the forces and the lower degree of interference means less stresses for the joint.

The tapering surfaces also provide proper alignment for the end joints and drill pipe and thereby facilitate assembly of the components of the solution.

Further, due to the tapering outer surfaces the drill pipe ends may have greater wall thicknesses, which is also beneficial for the load carrying capacity and durability of the solution.

A further advantage is that the disclosed structure is relatively simple and inexpensive to manufacture. The tapering contact surfaces are relatively easy and quick to manufacture accurately by means of modern lathes.

According to an embodiment, the first contact surface forms a truncated cone, which can be inserted inside the socket part formed at the end of the drill pipe. An interference fit between the truncated cone and the socket part is formed when the contact surfaces of the truncated cone and the socket part overlap because of the insertion. In the interference fit, or shrink fit, there is a slightly oversized truncated cone (shaft part) assembled into a slightly undersized socket part (hole part). Thus, the two parts being connected are of slightly different sizes, and this discrepancy holds the parts together. Prior to assembly, the truncated cone, i.e., an inside component, is larger than the socket part, i.e., the outside component, to form the desired interference fit.

The end piece and the drill pipe wherein the end piece is mounted are intended to be connected between a rotating head and a drill bit of the rock drilling rig. The end piece is part of a drill string and is configured to transmit torque and axial forces between components of the drill string during the drilling.

The outer diameter of the first contact surface has a minimum value at the second end that increases towards the second end. In other words, the tapering of the truncated cone is arranged so that diameter of the truncated cone increases from the second end towards the first end.

According to an embodiment, an angle of the tapering first contact surface is 0.2-12°. The magnitude of the angle of the tapering contact surface is dependent on dimensions of the end piece, and especially on the diameter of the end piece.

According to an embodiment, the angle of the tapering first contact surface is 1-6°. In practical tests, it has been found that this range is suitable especially for drilling tools with commonly implemented diameters.

According to an embodiment, the length of the first axial distance is 75-160 mm. In other words, the axial dimension of the tapered male portion at the second end of the end piece is in accordance with the mentioned range 75-160 mm.

According to an embodiment, the axial length of the tapering first contact surface is defined by a stop surface being orientated perpendicularly in relation to longitudinal axis of the end piece. In other words, the truncated cone ends to the stop surface, which is orientated perpendicularly in relation to longitudinal axis of the end piece. Accordingly, the stop surface is configured to set in the assembly against the front end of the drill pipe. The stop surface defines the axial length of the tapering first contact surface and the axial length where the contact surfaces of the truncated cone and the socket part intermesh.

According to an embodiment, the second end of the end piece is provided with a radial inner surface extending an axial distance from the second end towards the first end. The inner surface has tapered configuration. In other words, the end piece has two tapering surfaces at its second end portion. A magnitude of angle of the tapering of the inner surface is significantly greater as compared to the tapering of the outer surface.

According to an embodiment, an outer surface of the end piece is provided with at least one discard indicator with a recess having a predetermined depth. An advantage of the discard indicator is that a simple, robust, and reliable visual indicator is provided for providing information on the degree of wear of the drill pipe assembly.

An outer surface of the drill pipe assembly is subjected to wear during the use and material is loosened on the outer surface causing a decrease in depth of the discard indicator. Thus, the operation of the discard indicator is based on a phenomena wherein loosening of the material surrounding the recess leads to the decrease in depth and information on degree of wearing is provided for an operator in an intuitive manner. The discard indicator is inexpensive to manufacture.

According to an embodiment, the depth of the discard indicator is defined in relation to a wall thickness of the drill pipe.

According to an embodiment, the depth of the discard indicator is dimensioned to be half of a dimension of a wall thickness of the drill pipe.

According to an embodiment, the depth of the discard indicator is dimensioned to be 5-70 % of a dimension of a wall thickness of the drill pipe.

According to an embodiment, the depth of the discard indicator is dimensioned to be 10-60 % of a dimension of a wall thickness of the drill pipe.

According to an embodiment, the depth of the discard indicator is dimensioned to be 30-50 % of a dimension of a wall thickness of the drill pipe.

According to an embodiment, the discard indicator is located at a maximum axial distance 150 mm from the weld joint between the end piece and the drill tube. The discard indicator is intended to provide wearing data of the weld joint and to indicate when the wearing degree has reached a level where there is a risk that the weld joint is no longer capable of transmitting axial loads and torque.

According to an embodiment, the discard indicator includes at least one notch, groove, blind drilling, or any other type of recess.

According to an embodiment, there may be several discard indicators in the end piece. Alternatively, or in addition to, one or more discard indicators may be provided on the drill pipes.

According to an embodiment, there may be several discard indicators with different depths indicating wearing of the drill pipe or drilling component. The discard indicators may form a group of blind holes, grooves, or recesses with different depths. The depths of the recesses may grow by predetermined steps and they may clearly indicate wearing degree of the examined component.

According to an embodiment, the disclosed solution relates also to a drill pipe assembly for rotary or DTH drilling. The drill pipe assembly comprises a drill pipe and two end pieces mounted fixedly to opposite ends of the drill pipe. The end pieces comprise male portions with second coupling means provided with outwardly facing first contact surfaces and being inserted inside socket portions at ends of the drill pipe whereby the end pieces are connected to the ends of the dill pipe by means of shrink fits based on differences in the diameters existing between the male and socket portions. The mentioned end pieces are in accordance with the features disclosed in this document. Thereby mating radial contact surfaces between the male portions and the socket portions have tapered configuration.

According to an embodiment, the magnitude of the mentioned shrink fit is 0.1-0.8 mm. Am amount of interference (tightness of fit, or degree of tightness) is controlled by the amount of interference.

The magnitude of the shrink fit indicates how much greater is a diameter of the shaft part in relation to a diameter of the hole part before being mounted. Since mating contact surfaces of the shaft part and the hole part are tapered, the examination needs to be done at cross-sections, which have the same axial location and will match in the final shrink fit joint.

According to an embodiment, magnitude of the mentioned shrink fit is 0.2-0.6 mm. It has been found in practical tests that this range for the shrink fit is particularly suitable for drilling pipes and end pieces with commonly used diameters.

According to an embodiment, joints between the end pieces and the drill tube are provided with weld joints for providing additional fastening and ensuring the interference fit.

According to an embodiment, the disclosed solution is utilized in rotary drilling wherein no impact devices are utilized in rock breaking.

According to an embodiment, the rock drilling rig is utilized in down-the-hole drilling (DTH). In the DTH drilling a drill bit end of a rotated drilling tool is provided with an impact device, i.e., the impact device is located at a bottom of the drill hole during the drilling.

According to an embodiment, the disclosed solution relates to a method of forming a drill pipe assembly to be used in a rock drilling rig. The method comprises: mounting end pieces to opposite ends of a tubular drill pipe; providing first ends of the end pieces with first coupling means comprising thread surfaces for thread mounting; providing opposite second ends of the end pieces with truncated cones wherein radial outer surfaces of the truncated cones form first contact surfaces; forming socket parts to both ends of the drill pipe for receiving the truncated cones and being provided with second contact surfaces; heating the ends of the drill pipe at the socket parts to expand diameters of the second contact surfaces by means of the thermal expansion; pushing the truncated cones inside the thermally expanded socket parts; allowing the heated socket parts to cool and shrink whereby shrink fits are formed between the first and second contact surfaces; and securing the mountings between the drill pipe and the end pieces by welding. The method further comprises providing the mating first and second connecting surfaces with tapered shapes.

The above disclosed embodiments may be combined to form suitable solutions having those of the above features that are needed.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments are described in more detail in the accompanying drawings, in which

FIG. 1 is a schematic side view of a surface rock drilling rig intended for rotary drilling,

FIG. 2 is a schematic view of a rock drilling unit suitable for down-the-hole drilling,

FIG. 3 is a schematic side view of a drill pipe assembly,

FIG. 4 is a schematic and cross-sectional view of a detail of a joint between a first end piece and a drill pipe in the drill pipe assembly of FIG. 3;

FIG. 5 is a schematic and cross-sectional view of a detail of a joint between a second end piece and a drill pipe in the drill pipe assembly of FIG. 3;

FIG. 6 is a schematic cross-sectional side view showing a joint between an end piece and a drill pipe, and

FIG. 7 is a schematic cross-sectional side view of a connecting end portion of an end piece, and

FIG. 8 is a schematic cross-sectional side view of a connecting end portion of a drill pipe.

For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION

FIG. 1 shows a rock drilling rig 1 intended for surface drilling. The rock drilling rig 1 comprises a movable carrier 2 and at least one drilling mast 3 connected to the carrier 2. The mast 3 is provided with a drilling unit 4 provided with a rotating head 5 supported on the mast 3 and being movable in a drilling direction A and return direction B by means of a feed device 6. The rotating head 5 is connected to a drilling tool 7 by means of a sub-assembly 8. The drilling tool 7 is shown in a simplified manner for clarity reasons.

The drilling tool 7 includes one or more tubular elongated drill tube assemblies and a drill bit 9 at its distal end. The rotating head 5 rotates the drilling tool 7 in the direction R around its longitudinal axis and the drilling tool 7 is simultaneously fed towards a rock surface being drilled. This is known as the rotary drilling method.

Drilling cuttings are flushed by feeding flushing fluid from a flushing system Fs via the drilling tool 7 to a drill hole 10 being drilled so that the drilling cuttings are flushed away from the drill hole 10. The drilling unit 4 may be hydraulic whereby it may be connected to a hydraulic system Hs.

FIG. 2 discloses another solution, which differs from the one shown in FIG. 1 in that there is an impact device 11 mounted between a drill bit 9 and a drilling tool 7. The disclosed solution is intended for a down-the-hole drilling method, known also as DTH-drilling. A drilling unit 4 can be mounted movably on a feed beam 12, or in a similar manner as is shown in FIG. 1. The drilling tool 7 may include a drill pipe assembly, which is in accordance with the solution disclosed in this document.

FIG. 3 discloses a drill pipe assembly 13 having a drill pipe 14 and two end pieces 15, 16 mounted fixedly to opposite ends of the drill pipe 14. FIG. 3 discloses the drill tube 14 in a shortened view for clarity reasons. On the upper end, i.e., on the drilling unit end, of the drill pipe 14 there is a first end piece 15 and on the lower end i.e., on the drill bit end, of the drill pipe 14 there is a second end piece 16. The end pieces 15, 16 are mounted to the ends of the drill tube 14 by arranging their joint ends one inside another and utilizing a shrink fit between their substantially radial contact surfaces. The mounting is typically ensured by weld joints 17.

The end pieces 14, 15 may be provided with one or more discard indicators 18, which may be blind drillings, for example. FIG. 3 further shows boxes 19 and 20 at the joint areas and detailed structures of the joints are shown in FIGS. 4 and 5.

FIGS. 4 and 5 disclose that the end pieces 15, 16 have male portions 21 provided with outwardly facing first contact surfaces 22 and being inserted inside socket portions 23 at ends of the drill pipe 14. The socket portions 23 are provided with mating contact surfaces 24. As can be seen, the substantially radial mating contact surfaces between the male portions 21 and the socket portions 22 have tapered configurations. The end pieces 15, 16 are connected to the ends of the dill pipe 14 by means of shrink fits based on differences in the diameters existing between the male portions 21 and the socket portions 23.

FIGS. 4 and 5 further discloses that the ends facing towards the drill pipe 14 are provided with radial inner surfaces 25 extending an axial distance from the second end towards the first end and having tapered configurations. Accordingly, the end pieces 15, 16 have two tapering surfaces at their end portions. A magnitude of an angle of the tapering of the inner surfaces 25 is significantly greater as compared to the tapering of the outer surfaces.

The end pieces 15, 16 are elongated tubular pieces and have outer surfaces 26 and inner surfaces 27.

FIG. 3 further discloses that the end pieces 15, 16 have first ends 28 provided with first coupling means 29 including thread surfaces 29 for thread mounting with other drill components. Opposite second ends are provided with the tapering second coupling means for the shrink fit with the drill pipe ends.

FIG. 6 discloses a joint between a second end portion 30 of an end piece 15,16 and a drill pipe 16. A male portion 21 with an angled contact surface 22 is mounted inside a socket portion 23 of the drill pipe 14 provided with a mating angled contact surface 24. The magnitude of angle K of the tapering contact surfaces 22, 24 may be 0.2-12°.

FIG. 7 discloses an end of an end piece 15, 16 provided with a male portion 21. The male portion 21 forms an axially protruding truncated cone at the end of the end piece 15, 16. There is a substantially radial outwardly facing contact surface 22 extending a first axial distance L from the distal end towards the opposite end. A length of the axial distance L may be 75-160 mm. The axial length L of the tapering first contact surface 22 may be defined by a stop surface 31 being orientated perpendicularly in relation to the longitudinal axis of the end piece 15, 16. There may also be a shaped surface 32 for forming together with a correspondingly shaped end surface of a drill pipe a groove for a weld joint.

FIG. 8 discloses an end of a drill pipe 14 provided with a socket portion 23 for receiving a male portion of an end piece. Length L2 of the socket portion 23 is at least equal or greater compared to the length of the male portion and the socket portion 23 includes a tapered contact surface 24. A distal end of the drill pipe 14 may have a shaped surface 33 forming part of a welding groove.

The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.

A drilling tool component for a rotary or DTH drilling wherein an outer surface of the component is provided with at least one discard indicator having a recess having an initial depth and wherein decrease of the initial depth is configured to indicate wear of the component is also provided.

The drilling tool component may be a drill pipe, an end piece of a drill pipe, or any other component connectable between a rotating unit and a drill bit. Thus, the disclosed drilling tool component may or may not include tapered contact surfaces.