AU2009202411A1 - Air Supply System for a Drill Rig - Google Patents

Description

-1 "Air Supply System for a Drill Rig" FIELD OF THE INVENTION The invention relates to an air supply system for a drill rig. The invention is particularly suited to an air supply system for a reverse circulation drill rig. 5 BACKGROUND TO THE INVENTION The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known or part of the common general knowledge in [0 any jurisdiction as at the priority date of the application. Reverse circulation system require a supply of air to effect drilling. Examples of current air supply systems for reverse circulation systems are shown in Figures 1 and 2. As shown in Figure 1, there is an air supply system 100. The air supply system 100 functions to provide air to a drill string 102 by way of apertures 104 provided in a centre 15 spindle 106. The centre spindle 106 is connected between a drill head 108 of the drill rig concerned (not shown) and the drill string 102. The air supply system 100 includes a hollow collar 110 which encircles the centre spindle 106. The hollow collar 110 has an aperture 112 provided therein to receive an air hose 114. When connected, the end of the air hose 114 not received within the 20 aperture 112 is connected to an external air compressor (not shown). Roller bearings 118 maintain the hollow collar 110 in a static position. The hollow collar 110 encircles the centre spindle 106 at the position of the apertures 104. This allows air supplied by the air hose 114 to be directed to the centre spindle 106 by way of an air chamber 116 and apertures 104. 25 Encircling the centre spindle 106 at positions either side of the air chamber 116 are a plurality of "O"-rings 122. The "O"-rings 122 engage the centre spindle 106 and abut the hollow collar 116. In this manner, the "O"-rings 122 prevent air from leaking from the air chamber 116 when the centre spindle 106 is rotating.

-2 Each "O"-ring 122 sits in a bearing housing (not shown) to prevent movement. Additional bearings are provided to keep the hollow collar 110 in a stationary position. The problem with this arrangement is that the whole air supply system 100 sits on the centre spindle 106 at a position below the drill head 108. By placing the air supply 5 system 100 at such a position, a number of problems arise, including: * The weight of the drill string 102 places significant strain on the centre spindle 106. This strain can eventually cause metal fatigue in the centre spindle 106; " The chance to lose air supplied by the air supply system 100 is greater due to the need for roller bearings 118 to be constantly lubricated and maintained at a 10 preset tension in order to ensure that the minimal clearances and tolerances required for high pressure reverse cycle drilling are met. " There is still a need to bolt a static valving and diversionary system 204 for the sample to the top of the dynamic drill head which further complicates the machinery on the drill rig by requiring a secondary sample swivel. .5 For these reasons, a number of drill rigs operate a second prior art air supply system 200 as shown in Figure 2 (like numerals reference like parts). This air supply system 200 operates in an identical fashion to air supply system 100, except that it is bolted between the top of the dynamic drill head shaft 202 and the static valving and diversionary system 204. 20 By placing the air supply system 200 in this position the valving and diversion systems 204 can be bolted onto the support structures for the air supply system, thereby simplifying the general mechanical arrangement of the drill rig. It also removes the weight strain on the initial drill pipe 106. In doing so, though, the weight of the valving and diversionary system 204 on the housing can result in misalignment and tolerances 25 being exceeded - resulting in failure of the air supply system 200 as a whole (a phenomenon known as "side loading"). The problem of needing to seal off the hollow collar 110 remains, except this time it is against the rotation above the drill head 202 rather than the rotation of the initial drill pipe 106 below the drill head 202.

-3 It is therefore an object of the present invention to overcome, or at least alleviate in part, one or more of the above problems mentioned above. SUMMARY OF THE INVENTION Throughout this document, unless otherwise indicated to the contrary, the terms 5 "comprising", "consisting of', and the like, are to be construed as non-exhaustive, or in other words, as meaning "including, but not limited to". In accordance with a first aspect of the present invention there is an air supply system comprising: a housing adapted to be mounted on to the drill head of a drill rig; and 10 at least one sleeve adapted to be received within the housing. where the weight of the air supply system is borne by the drill head and, during drilling operations, the housing remains stationary while the sleeve rotates. The advantage of this configuration is that the weight of the air supply system does not contribute to reducing the life span of the centre spindle or sample return tube. 15 Furthermore, this form of air supply system allows the sample return tube to flex without impacting on the efficiency of the sealing systems used. At the same time, the arrangement removes the need for roller bearing structures. Preferably, the at least one sleeve is adapted to be received within a bush and the bush is adapted to be received within the housing, a dynamic "O"-ring operating to seal the 20 area between the sleeve and bush during operation. Preferably, the air supply system has an upper sleeve and a lower sleeve, the upper sleeve adapted to be received about a sample return tube and the lower sleeve adapted to be received about a head shaft such that air supplied by the air supply system is forced down the centre of the head shaft. 25 Preferably, the upper sleeve has a plurality of static "0" rings to seal the area between the sleeve and the sample return tube. Preferably, the upper sleeve has dowelling projections thereon to receive rotational force applied to it by way of a similar projection provided on the sample return tube.

-4 Preferably, the at least one sleeve has a grease channel for providing grease to each dynamic "O"-ring. More preferably, the grease channel includes a grease gallery for storage and delayed delivery of grease to the dynamic "O"-ring. 5 BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a first prior art air supply system for a drill rig. Figure 2 is a cross-sectional view of a second prior art supply system for a drill ring. .0 Figure 3 is a cross-sectional view of an air supply system for a drill rig according to one embodiment of the present invention. PREFERRED EMBODIMENTS OF THE INVENTION Specific embodiments of the present invention are now described in detail. The terminology used herein is for the purpose of describing particular embodiments only, 5 and is not intended to limit the scope of the present invention. In accordance with a first embodiment of the invention there is an air supply system 10 for a drill rig 1. The air supply system 10 is shown in cross-section in Figure 3. The air supply system 10 includes a cylindrical housing 12. The housing 12 has an aperture 14, 16 in opposing sides 18, 20. Extending from the circumference of side 20 20 is a mounting flange 22. The mounting flange 22 is adapted to facilitate mounting of the housing 12 to a drill head 24. An inlet aperture 26 is provided in the wall of the housing 12. The inlet aperture 26 is sized and shaped so as to allow an air connection hose 28 to connect thereto and thus direct air through the housing 12. An end of the air connection hose 28 that does not 25 connect to the inlet aperture 26 is connected to an external air compressor (not shown). Aperture 14 is sized so as to allow a first bush 30 to be received therein. First bush 30 takes the form of a short hollow cylinder. Grooves are provided in the interior profile of the first bush 30 to facilitate placement of dynamic "O"-rings 32. Dynamic "O"-rings 32 -5 securely fit into these grooves. When the whole air supply system 10 is assembled, dynamic "O"-rings 32 make contact with an upper sleeve 34. Upper sleeve 34 comprises a cylindrical base 36 and a flange 38. It is only the cylindrical base 36 portion of the upper sleeve 34 that makes contact with the dynamic 5 "O"-rings 32. Upper sleeve 34 also has an aperture 40 extending through it. Aperture 40 is cylindrical and sized to the diameter of a sample return tube 42 to be used by the drill rig 1. The upper sleeve 34 contains a plurality of static "O"-rings 35, spaced throughout the aperture 40. When the upper sleeve 34 is received within first bush 30, the static "0" L0 rings 35 make contact with the sample return tube 42 Situated within the housing 12 is a bottom sleeve 46. The bottom sleeve 46 is a hollow cylinder. The diameter of the internal profile of the bottom sleeve 46 is equal to that of a head shaft 48. In this manner, when the air supply system 10 is assembled, the bottom sleeve 46 encapsulates the upper end of the head shaft 48, while the sample 5 return tube 42 extends therethrough towards the upper sleeve 34. The bottom sleeve 46 is designed to fit within a second bush 50. The second bush 50 also takes the form of a short hollow cylinder. The bottom sleeve 46 is designed to bolt directly to the head shaft 48. The bottom sleeve 46 also contains a plurality of static "O"-rings 51, spaced throughout 20 its internal aperture 53. When the bottom sleeve 46 is received within second bush 50, the static "O"-rings 51 make contact with the head shaft 48. Like the first bush 30, grooves are provided in the interior profile of the second bush 50 to facilitate placement of dynamic "O"-rings 52. Dynamic "O"-rings 52 securely fit into the grooves to make contact with the bottom sleeve 46 when fitted within the second 25 bush 50. In this manner, the diameter of the bottom sleeve 46 should be sized so as to provide correct sizing to the dynamic "O"-rings 52. This embodiment will now be described in the context of its intended use. Static "O"-rings 51 are placed in the grooves of the bottom sleeve 46. Once so placed, the bottom sleeve 46 is placed over the top of the head shaft 48 and sample return tube 30 42. Once placed, the bottom sleeve 46 is securely affixed to the head shaft 48 by a -6 plurality of bolts. Spring washers (not shown) assist in preventing damage to the head shaft 48 and the bottom sleeve 46. This placement causes the static "O"-rings 51 to make contact with the head shaft 48 and thereby seal off the gap between the bottom sleeve 46 and the head shaft 48. 5 With the bottom sleeve 46 securely connected to the head shaft 48, attention shifts to the housing 12 and second bush 50. Dynamic "O"-rings 52 are placed in the grooves of the second bush 50. The second bush 50 is then frozen to allow for placement within the housing 12. Once appropriately placed, as the second bush 50 returns to normal temperature, an interference fit [0 between the second bush 50 and the housing 12 is formed. The combined housing 12 and second bush 50 is then placed over the top of the sample return tube 42 to a position where it encloses the bottom sleeve 46. The housing 12 is then bolted to the drill head 24. In this manner, rotation of the bottom sleeve 46 relative to the second bush 50 activates 15 the dynamic "O"-rings 52. The dynamic "O"-rings 52 then act to seal the gap between the bottom sleeve 46 and the second bush 50 while allowing some tolerance for the rotation of the head shaft 48. Dynamic "O"-rings 32 are then placed in the grooves of the first bush 30. The first bush 30 is then frozen to allow for placement within the housing 12. This involves placing the 20 first bush 30 over the sample return tube 42. Once appropriately placed, as the first bush 30 returns to normal temperature, an interference fit between the first bush 30 and the housing 12 is formed. Static "O"-rings 35 are placed in the grooves of the upper sleeve 34. Once so placed, the upper sleeve 34 is placed over the sample return tube 42 on to the housing 12. 25 This placement causes the static "O"-rings 35 to make contact with the sample return tube 42 and thereby seal off the gap between the sample return tube 42 and the upper sleeve 34. As described above, rotation of the upper sleeve 34 relative to the first bush 30 activates the dynamic "O"-rings 32. The dynamic "O"-rings 32 then act to seal the gap -7 between the upper sleeve 34 and the first bush 30, while allowing some tolerance for the rotation of the sample return tube 42 and upper sleeve 34. Once so inserted, the space between the first bush assembly 30 and the second bush assembly 50 define an air chamber 54. The inlet aperture 26 sits to one side of the air 5 chamber 54. The air connection hose 28 is then inserted into the inlet aperture 26 through to the air chamber 54. Due to the stationary operation of the housing 12, there is no additional rotational stress placed on the air connection hose 28. Pressurised air supplied by way of the air connection hose 28 is then forced into the air 10 chamber 54. The pressurised air is prevented from escaping the air chamber 54 by way of the static "O"-rings 35, 51 and dynamic "O"-rings 32, 52.. This leaves the space between the sample return tube 42 and the internal wall of the head shaft 48 as the only free space that the pressurised air can travel along. In accordance with a second embodiment of the system, where like numerals reference [5 like parts, there is an air supply system. This air supply system operates substantially as described in the first embodiment of the invention, but with the following additions. The upper sleeve 34 has three dowel projections (not shown) in its interior profile. Each dowel projection is arranged lengthwise about the interior profile. The purpose of the dowel projections is to engage with a similar projection provided on the sample return !0 tube 42. Thus, the rotation of the sample return tube 42 imparts rotation to the upper sleeve 34 making the joint between the upper sleeve 34 and the sample return tube 42 a static joint. Dynamic "O"-rings 32 then create a dynamic sealing surface about the upper sleeve 34 and the first bush 30. An additional modification in this embodiment sees grease channels 56 inserted for 25 each dynamic "0" ring 32, 52. Each grease channel 56 extends through its respective bush and the housing 12. At the end of each grease channel 56 is a grease gallery (not shown). Each grease gallery provides storage for reserve supplies of grease. Each grease gallery is downwardly stepped towards its respective dynamic "O"-ring 32, 52. In this manner, as the grease heats and turns to a liquid form, it slowly travels 30 under influence of gravity down each step to the dynamic "O"-ring 32, 52. The resulting effect is that the air supply system is semi-self lubricating.

-8 Another modification made for this second embodiment relates to the air connection hose 28. A diversion line (not shown) extends from the air connection hose 28 to connect with an aperture in an adaptor 58. The diversion line thereby supplies air to the adaptor. 5 The adaptor sits over the top of the invention. The air fed through the adaptor operates to clear the seals of any dirt and thus relieves the need for gland packing. In accordance with a third embodiment of the invention, where like numerals reference like parts, there is an air supply system. The air supply system is identical to that described in either of the prior two embodiments, but includes a diversionary adaptor 10 58. The diversionary adaptor comprises a bush 60 and a sleeve 62. A static "O"-ring (not shown) is provided in the bush 60. While it should be appreciated by the person skilled in the art that the above embodiments have been described in the context of reverse circulation drill rigs, the invention can be adapted to supply air to conventional drill rigs. For example, the .5 sample return tube 42 can be removed and, with the top of the invention sealed in some manner, air can be forced down the internals of the drill pipes as described above. It should be appreciated by the person skilled in the art that the above invention is not limited to the embodiment described. In particular, the following modifications and improvements may be made without departing from the scope of the present invention: 20 e So as to minimise the space envelope of the air supply system 10, the housing 12 should be sized so that the open portion of side 20 allows for a close fit to the second bush 50. * The first bush 30 and second bush 50 can be made of any material that, either individually or in combination, provides good strength and heat 25 dissipation. In particular, the applicant has found that bronze is the best material for manufacture due to the friction caused between the bush and the steel components of the housings and its low cost. Nylon is another material that can be used, but is prone to heat build up. If cost is not a consideration, aluminium is a good manufacture material for all parts due to its high 30 resistance to friction and its light weight.

-9 0 The tolerances of the various "O"-rings 32, 35, 51, 52 is dependent on the level of air pressure to be provided by the air supply system 10. It is believed that a person skilled in the art can determine the required minimum tolerances once the level of air pressure has been decided upon. 5 0 The upper sleeve 34 and first bush 30 assembly could be replaced with a simple assembly allowing dynamic "O"-rings 32, 52 make contact directly with the sample return tube 42 and head shaft 48. This is not recommended, however, as to do so would make it difficult to control the tolerances inherent in the system. 10 * An adaptor plate may be needed to facilitate mounting of the air supply system 10 to the drill head 24 on drill rigs 1. 9 A Telltile hole may be provided in the mounting flange 22. The Telltile hole allows pressure to be relieved when the dynamic "O"-rings 32, 52 fail. In this manner, the Telltile hole also acts as a diagnostic system for determining [5 when the dynamic "O"-rings 32, 52 have failed. * The grooves created for the dynamic "O"-rings 32, 52 may be enlarged to allow for at least one back-up washer to also be inserted therein. The addition of the back-up washer increases the sealing effect between the respective bush 30, 50 and the respective sleeve 34, 46. 20 Furthermore, the features described in the above embodiments and the additional features mentioned above may be combined to form yet additional embodiments that fall within the scope of the present invention.

Claims (8)

1. An air supply system comprising: a housing adapted to be mounted on to the drill head of a drill rig; and at least one sleeve adapted to be received within the housing. 5 where the weight of the air supply system is borne by the drill head and, during drilling operations, the housing remains stationary while the sleeve rotates.

2. An air supply system according to claim 1, where the at least one sleeve is adapted to be received within a bush and the bush is adapted to be received within the housing, the area between the sleeve and bush being sealed during operation. [0

3. An air supply system according to claim 2, where the area between the sleeve and bush is sealed during operation by a dynamic "O"-ring.

4. An air supply system according to any preceding claim, where the at least one sleeve has an upper sleeve and a lower sleeve, the upper sleeve adapted to be received about a sample return tube and the lower sleeve adapted to be received .5 about a head shaft such that air supplied by the air supply system is forced down the centre of the head shaft.

5. An air supply system according to claim 4, where the upper sleeve has a plurality of static "O"-rings to seal the area between the sleeve and the sample return tube.

6. An air supply system according to claim 4 or claim 5, where the upper sleeve has 20 dowelling projections thereon to receive rotational force applied to it by way of a similar or mating projection provided on the sample return tube.

7. An air supply system according to any one of claims 1 to 3, as dependent on claim 3, where the bush has a grease channel for providing grease to each dynamic "0" ring. 25

8. An air supply system according to claim 7, where the grease channel includes a grease gallery for storage and delayed delivery of grease to the dynamic "O"-ring.