AU2005202663B2

AU2005202663B2 - Improvements in Blasthole Plugs

Info

Publication number: AU2005202663B2
Application number: AU2005202663A
Authority: AU
Inventors: Nicholas Grant Bodley; Terence Peter Clarke; Barry Raymond Rose
Original assignee: MTI Group Pty Ltd
Current assignee: MTI Group Pty Ltd
Priority date: 2005-06-17
Filing date: 2005-06-17
Publication date: 2013-07-11
Anticipated expiration: 2025-06-17
Also published as: AU2005202663A1

Abstract

- 27 A blast-hole plug system comprising an inflatable bag for frictional engagement when in an inflated state 5 with the sides of a blast-hole; said bag provided with a valve arrangement allowing high inflation and deflation rates; said valve arrangement further providing high retention forces between said valve arrangement and an inflation medium supply line 10 attached thereto. / - --2' r/2-

Description

P/00/009 Regulation 3,10 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention Title: IMPROVEMENTS IN BLAST-HOLE PLUGS The invention is described in the following statement, including the best method of performing it known to us: Our Ref 052011 -2 IMPROVEMENTS IN BLAST-HOLE PLUGS The present invention relates to preparation of blastholes and, more particularly to the construction, preparation and placement of inflatable blast-hole plugs. 5 BACKGROUND Inflatable bags for use in blast-holes for support of stemming material and blast charges, commonly use one of two types of inflation methods. One of these utilizes a canister of pressurized 10 aerosol gas attached to or contained within the bag. The canister is set to discharge as the bag is lowered to its required location in the blast-hole. This system is attended by a number of disadvantages. Firstly, the rate of flow from the canister is 15 temperature dependent so that in a high ambient temperature situation, the bag may inflate so rapidly that it seizes in the hole before the desired location is reached. Yet in very cold conditions, inflation may be delayed unacceptably or in extreme conditions not occur at all. 20 A further disadvantage of gas canister inflation systems is that, at high temperatures the gas pressure may increase to the point of explosion. This situation has been known to occur when a canister was left in an exposed position in a vehicle standing in the sun on a hot day. 25 Yet a further disadvantage is that once inflated, the bag cannot be deflated and repositioned or retrieved for -3 re-use. If the bag has to be moved because of incorrect positioning for example, it has to be pierced for deflation. This is clearly an awkward operation if the bag is at depth in a blast-hole. 5 The second commonly used inflation system includes an external supply of air fed to the bag via an air tube when the bag has been lowered to the desired depth. Known systems typically inflate the bag through a needle valve, such as found on footballs and the like, with the air 10 supply tube ending in a needle which, during the lowering and subsequent inflation, remains inserted in the valve of the bag. Disadvantages associated with needle valve air bags include problems of leakage and deflation of the bag prior 15 to completion of the placement of stemming material and charge, so that the bag may fail to retain its position within the hole. Such valves also have a relatively slow air flow rate and a low retention force of the needle in the valve so that care must be taken to avoid dislodgement 20 of the bag- during placement. Needle valves are essentially one-way valves, relying on positive inwardly directed pressure to provide an air passage into the bag, so that once inflated they do not permit of deflation. Low retention force also prevents additional weights 25 being attached to the bag, for example if the bag needs to be located under water.

-4 It is an object of th resent invention to address or at least ameliorate sl e of the above-mentioned disadvantages. 5 BREIF DBSCRIPTION OF IENTION Accordingly, in a first broad form of the invention there is provided a blast-holo p ug system comprising an inflatable bag for frictional engageme t. when in an inflated state with the 10 sides of a blast-holo; aid bag provided with a valve arrangement allowing high inflation and deflation rates; said valve arrangement further pro iding high retention forces between said valve arrangement and a inflation medium supply line attached thereto; wherein the hi h retention forces between the valve 15 arrangement and the inf ation medium supply line are sufficient to resist detachment wh n the bag is inflated to working pressure unless a tension force 's applied to the supply line in excess of the retention forces; a d sufficient to resist detachment when the bag in a partly inf l ted state a partially and is pulled 20 upwardly in sliding enga ement with said sides of the blast hole; wherein the retention fo ce is substantially more than an attachment force require to connect the supply line to the valve. 25 Preferably, said inflati n medium supply line is attached to said valve arrangement by q s ap-on connection. Preferably, said valve a rangement comprises a mechanically actuated valve; said val e adapted for rapid inflation and 30 deflation under control f a user. Preferably, said valve h an air flow rate in a range of 1 to 10 cubic meters per hour at supply pressure of 700 kilopascals.

-5 Preferably, said valve has an air flow rate in a range of 3 to 1.0 cubic meters per hour at a supply pressure of 700 kilopascals. 5 Preferably, said valve has an air flow rate in a range of 5 to 10 cubic meters per hour at a supply pressure of 700 kilopascals. Preferably, said valve has an air flow rate in a range 10 of 8 to 10 cubic meters per hour at a supply pressure of 700 kilopascals. Preferably, said valve has an air flow rate greater than 10 cubic meters per hour at a supply pressure of 700 15 kilopascals. Preferably, said valve is located in a tubular protrusion; said tubular protrusion adapted for said snap on connection to said inflation medium supply line such 20 that the retention force of said connection is sufficient to maintain said connection at said flow rate and at said supply pressure. Preferably, said retention force is sufficient to 25 allow a partially inflated bag to be pulled upwardly in sliding engagement with said sides of a blast hole. Preferably, said retention force is at least about twice as much that the attachment force. 30 Preferably, said retention force is in the range of 10 to 20 Newtons. Preferably, said retention force is in the range of 12 35 to 20 Newtons.

Preferably, said retention force is in the range of 14 to 20 Newtons. Preferably, said retention force is in the range of 16 to 20 Newtons. 5 Preferably, said retention force is in the range of 18 to 20 Newtons. Preferably, said retention force is greater than 20 Newtons. Preferably, said mechanically actuated valve is a 10 spring-loaded valve. Preferably, said spring-loaded valve is a Schrader type valve. Preferably, pressure of inflation is monitored electronically by an inflation medium supply system in 15 communication with said inflation medium supply line. Preferably, said inflation medium supply system is adapted to automatically inflate said bag to a predetermined pressure. Preferably, said inflation medium supply system is 20 adapted to automatically inflate said bag with a predetermined volume of said inflation medium. Preferably, said inflation medium is a gas.

Preferably, said inflation medium is a liquid. Preferably, said bag is deflated from said inflated state by application of vacuum pressure to said inflation medium supply line. 5 Preferably, said bag is inflated by injection of a predetermined volume of said liquid. Preferably, said liquid acts as a stemming material so as to provide additional resistance to blast when installed as a blast hole plug. 10 Preferably, said bag may be disengaged from said sides of said blast-hole for repositioning or removal after deflation. Preferably, said inflation control system is adapted to partially inflate said bag for sliding engagement with 15 sides of said blast-hole so as to allow detection of voids in said sides of said blast-hole. Preferably, said bag is weighted so as to reduce buoyancy of said bag; said buoyancy reduction sufficient for submersion of said bag under water prior to inflation. 20 Preferably, said inflation medium supply line is weighted.

-8 In a second broad form of the invention there is provided a method for stemming a blast-hole with an inflatable bag provided with a mechanically actuated valve arrangement allowing high inflation and deflation rates; 5 said method including the steps of: (a) attaching an inflation medium supply line connector fitting as a snap-fit to a tubular protrusion of said inflatable bag, said attaching requiring an attachment force required to connect the supply line to the 10 tubular protrusion; (b) lowering said bag by means of said supply line to a predetermined depth in said blast-bole, (c) inflating said bag by supplying said inflation medium from an inflation medium supply and 15 control system, (d) detaching said connector fitting and said inflation medium supply line from said tubular protrusion by applying a tension force to said supply line in excess of said connector fitting 20 retention force; wherein the retention force is substantially more than the attachment force. Preferably, said valve arrangement has a flow rate in excess of 8 cubic metpes per hour at a supply pressure of 25 700 kilopascals. Preferably, said conneptor fitting retention force is in excess of 12 Newtons.

- 9 Preferably, inflation pressure in said bag is electronically monitored. Preferably, volume of said inflation medium is electronically monitored. 5 Preferably, inflation of said bag is limited to a predetermined pressure of said inflation medium. Preferably, inflation of said bag is limited to a predetermined volume of said inflation medium. In a third broad form of the invention there is 10 provided a method for avoiding locating a blast-hole plug adjacent a void in a blast-hole; said method including the steps of: (a) releasably connecting an inflatable bag to an an inflation medium supply and control system 15 via an inflation medium supply line, (b) lowering said inflatable bag to a first preferred predetermined depth, (c) partially inflating said inflatable bag sufficient to provide sliding engagement with 20 sides of said blast-hole, - 10 (d) pulling said partially inflated bag upwardly by means of said supply line thereby inducing vibrations in said supply line, (e) deflating said inflatable bag by means of 5 application of vacuum pressure to said supply line if said vibrations are indicative of said void, (f) repositioning and reinflating said inflatable bag at an alternative preferred level in said 10 blast-hole. Preferably, inflation and deflation of said gas-tight bag is through a mechanically actuated valve. Preferably, said supply line is connected to said bag by a snap-on connector fitting of said supply line engaging 15 an "0" ring provided in an annular groove of a tubular protrusion housing said mechanically actuated valve. Preferably, retention force between said snap-on connector and said tubular protrusion is in excess of 12 Newtons. 20 In a further broad form of the invention there is provided a method of inflating a bag of a blast-hole plug under water in a blast-hole; said method including the steps of: - 11 (g) providing said bag with a valve adapted to accept inflating medium ar a flow rate greater than 8 cubic metres per hour at a pressure of 700 kilopascals, 5 (h) applying weights to said bag to decrease buoyancy of said bag to a level of buoyancy at which said bag remains under water during inflation of said bag. 10 In yet a further broad form of the invention there is provided a mechanically actuated valve for an inflatable bag of a blast-hole plug; said valve having an air flow rate in excess of 8 cubic metres per hour at a supply pressure of 700 kilopascals. 15 In still a further broad form of the invention there is provided a valve for an inflatable bag of a blast-hole plug; said valve adapted to allow deflation of said bag by application of vacuum pressure to an inflation medium 20 supply line attached to said bag. In further broad form of the invention there is provided an inflatable bag for a blast-hole plug; said bag provided with a valve cap ble of receiving therethrough a 25 liquid inflation medium, Wherein said valve provides high retention forces between the valve and an inflation medium supply line sufficient to resist detachment when the bag is inflated to working pressure unless a tension force is applied to the supply line in excess of the retention forces; and sufficient to resist detachment 30 when the bag in a partially inflated state and is pulled upwardly in sliding engagement with said sides of the blast hole; wherein the retention force is substantially more than an attachment force required to connect the supply line to the valve.

- 12 BRIEF DESCRIPTION OF DRAWINGS Embodiments of the present invention will now be described with reference to the accompanying drawings wherein: $ Figure 1 is a diagrammatic representation of a blast hole with the arrangement of a preferred embodiment of a blast-hole plug system in use, Figure 2 is a partially sectioned view of the bag and Fig. 1 showing the spring-loaded valve and connection end 10 of an inflation medium supply line. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to the schematic representation of the present invention in Fig. 1, a system 10 for a blast-hole plug comprises an inflatable, substantially gas-tight bag 15 12 located in a blast-hole 14, an inflating medium supply system 16 and an inflating medium supply line 18. With reference to Fig. 2, substantially gas-tight bag 12 comprises at least an inner bag of a flexible plastic material provided at one end with a tubular protrusion 20 20 adapted to accept a spring loaded valve 22. Preferably, valve 22 is of the Schrader type such as commonly used on the inflatable tyres of road and other transport vehicles. The outer surface 24 of tubular protrusion 20 is provided with an annular groove 26 adapted to accept an "0" 25 ring 28 therein such that at least an outer portion of "0" ring 28 projects beyond the surface 24 of protrusion 20.

13 As shown in Fig. 3, one end of inflating medium supply line 18 is provided with a connector fitting 30 adapted for snap-on connection to tubular protrusion 20. The snap-on connection is provided by an annular recess and shoulder 31 5 in fitting 30 which engages with an annular protruding ridge 25 on protrusion 20. "0" ring 28 provides an air tight seal between outer surface 24 and the inner surface 33 of fitting 30. Connector fitting 30 is further provided with central 10 push rod 32 arranged so that when connector fitting 30 has been snap-fitted onto tubular protrusion 20, the spring loaded valve 22 is held in the open position. When connector fitting 30 is pulled free of the tubular protrusion 20, the central push rod 32 releases the valve 15 22 which then automatically reverts to its default closed condition under urging of its spring 23. An advantage of spring loaded valve 22 in the form of a Schrader valve, is that it allows rapid inflation and deflation of the bag 12. With this arrangement, the bag of 20 the present invention may be inflated with air at a flow rate in excess of 8 3 m per hour at a pressure of 700Kpa. The interference of "0" ring 28 with the internal structure of connector fitting 30 is such that the retention force, that is that force required- to separate 25 connector fitting 30 from the tubular protrusion 20, is considerably greater than the force required to effect the - 14 snap-on connection. Preferably, the force to separate is greater than 12 Newtons, while the force to connect is in the order of half of that value. This arrangement allows the bag 12 to be easily 5 connected to the inflation medium supply line 18 yet with adequate retaining force to allow an operator to manipulate the bag 12 in a blast-hole, both when lowering to a desired level or for relocating the bag to a higher level than that to which the bag was first lowered. 10 Furthermore, the strength of the connection is such as to allow for the dragging of the bag along a section of a blast-hole while the bag is in a partially inflated state and in frictional contact with the sides of the blast-hole, as will be explained more fully below. Moreover the 15 retention force is sufficient to allow weighting of the bag to lower its buoyancy to a point where it will submerge to a position under water if required. The feature of rapid inflation is of particular importance if the bag is to be located under water in the blast-hole, since the buoyancy 20 of the bag will begin to increase with inflation. Referring again to Fig. 1, the inflation medium supply system 16 comprises in a first preferred embodiment, an air compressor 15 and a control system 17. In this embodiment, the control system 17 is able to supply a given 25 capacity bag with air at a predetermined flow of air and at a predetermined pressure. During inflation, the increasing -15 pressure in the bag 12 as it comes into contact with the sides of the blast-hole 14 is continuously monitored by an electronic sensor 19, which sends a signal to cut supply when that pressure has reached the predetermined set point. 5 The predetermined set point in this arrangement need not be one which engages the bag with the side walls to that extent necessary to support a stemming load or a charge, but may be that of a lesser degree of inflation which allows movement of the bag in contact with the blast 10 hole sides. The tension in the inflation medium supply line may be monitored as the bag is dragged upwardly to ensure that the disconnection force is not exceeded, and the inflation pressure modified if required. By this means an operator is able to "explore" the sides of the blast-hole 15 for voids. In at least one preferred embodiment of the invention, the compressor and control system are augmented by a vacuum pump adapted to exhaust air from the bag, thereby reducing its bulk to allow its relocation or complete withdrawal 20 from the blast-hole, if required. In a further preferred embodiment of the invention, the inflation medium supply control system 16 is set to deliver a given volume of the medium via the supply line 18. This voluine may be predetermined based on the 25 parameters of bag size, blast-hole diameter and nature of the hole's geological structure.

- 16 In yet a further preferred embodiment, the supply line is provided with a manual control valve and pressure gauge (not shown) which may be used by an operator at the blast hole mouth 13. By this means the operator may "feel" for 5 vibrations from a partially inflated bag as indications of voids. The system of the present invention is further adapted to allow the bag to be inflated by media other than air. Thus the bag may be filled by a modified delivery system 10 with water or some viscous liquid to form a plug for stemming or for use in conjunction with other stemming material, thus offering greater resistance to blast when the plug is installed in a blast hole. In this case the delivery system injects the liquid under some pressure via 15 the inflation medium delivery tube to the bag. Again the delivery may be controlled according to a preset reference pressure or by volume. In use, a blast-hole bag sized according to the blast hole diameter and the expected stemming and charge load is 20 attached to the connector fitting of the inflation medium supply line. At this point the bag is rolled into a relatively small diameter cylinder lightly constrained in that condition by frangible ties. The bag is then lowered to the design depth as 25 indicated by suitable interval markings on the supply line. When the depth is reached the inflation medium supply is - 17 activated to inflate the bag and lock it into position. If the location does not provide proper sealing due to the presence of a void for example, the bag may be deflated with the aid of the vacuum system and the bag relocated to 5 a better position. Once the bag is properly located its engagement with the sides of the blast-hole is such that an upward force applied to the supply line will disengage the connector fitting from the tubular protrusion. The spring-loaded 10 valve then immediately snaps shut to retain the inflation medium securely in the bag. The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing 15 from the scope and spirit of the present invention.

Claims

1. A blast-hole plug system comprising an inflatable bag for frictional engagement when in an inflated state with the sides of a 5 blast-hole; said bag provided with a valve arrangement allowing high inflation and deflation rates; said valve arrangement further providing high retention forces between said valve arrangement and an inflation medium supply line attached thereto; wherein the high retention forces between the valve arrangement and the inflation 10 medium supply line are sufficient to resist detachment when the bag is inflated to working pressure unless a tension force is applied to the supply line in excess of the retention forces; and sufficient to resist detachment when the bag in a partially inflated state and is pulled upwardly in sliding engagement with said sides of the blast 15 hole; wherein the retention force is substantially more than an attachment force required to connect the supply line to the valve.

2. The system of claim 1 wherein said inflation medium supply line is attached to said valve arrangement by a snap-on connection. -19

3. The system of anyone of claims 1 or 2 wherein said valve is located in a tubular protrusion: said tubular protrusion adapted for said snap-on connection to said inflation medium supply line such 5 that the retention force of said connection is sufficient to maintain said connection at said flow rate and at said supply pressure. -20

4. The system of anyone of claims 1 to 3 wherein said retention force is in the range of 10 to 20 Newtons.

5 S. The system of anyone of claims 1 to 3 wherein said retention force is in the range of 12 to 20 Newtons.

6- The system of anyone of claims 1 to 3 wherein said retention force is in the range of 14 to 20 Newtons. 10

7. The system of anyone of claims I to 3 wherein said retention force is in the range of 16 to 20 Newtons.

8. The system of anyone of claims 1 to 3 wherein said retention force 15 is in the range of 18 to 20 Newtons.

9. The system of anyone of claims 1 to 3 wherein said retention force is greater than 20 Newtons. 20

10. The system of anyone of claims 1 to 9 wherein pressure of inflation is monitored electronically by an inflation medium supply system in communication with said inflation medium supply line. - 21

11. The system of claim 10 wherein said inflation medium supply system is adapted to automatically inflate said bag to a predetermined pressure. 5

12. The system of claim 10 or 11 wherein said inflation medium supply system is adapted to automatically inflate said bag with a predetermined volume of said inflation medium. 10

13. The system of anyone of claims I to 12 wherein said inflation medium is a liquid.

14. The system of anyone of claims 1 to 13 wherein said bag is deflated from said state by application of vacuum pressure to said 15 inflation medium supply line.

15. The system of claim 13 wherein said liquid acts as a stemming material so as to provide additional resistance to blast when installed as a blast hole plug. 20 -22

16. The system of anyone of claims 1 to 15 wherein said bag is weighted so as to reduce buoyancy of said bag; said buoyancy reduction sufficient for submersion of said bag under water prior to inflation. 5

17. The system of anyone of claims 1 to 16 wherein said inflation medium supply line comprises a weight so as to weigh more than its inherent weight. 10

18. A method for stemming a blast-hole with an inflatable bag provided with a mechanically actuated valve arrangement allowing high inflation and deflation rates; said method including the steps of: (a) attaching an inflation medium supply line connector fitting as a snap-fit to a tubular protrusion of said inflatable bag, said 15 attaching requiring an attachment force required to connect the supply line to the tubular protrusion; (b) lowering said bag by means of said supply line to a predetermined depth in said blast-hole, (c) inflating said bag by supplying said inflation medium from an 20 inflation medium supply and control system, (d) detaching said connector fitting and said inflation medium supply line from said tubular protrusion by applying a tension force to said supply line in excess of said connector fitting retention force, wherein the retention force is sufficient to resist detachment when 25 the bag is inflated to working pressure unless a tension force is applied to the supply line in excess of the retention forces; and sufficient to resist detachment when the bag in a partially inflated state and is pulled upwardly in sliding engagement with said sides of -23 the blast hole; wherein the retention force is substantially more than the attachment force.

19. The method of claim 18 wherein said connector fitting retention 5 force is in excess of 12 Newtons.

20. The method of any one of claims 19 or 20 wherein inflation pressure in said bag is electronically monitored. 10

21. The method of any one of claims 19 to 20 wherein volume of said inflation medium is electronically monitored. 15 -24

22. An inflatable bag for a blast-hole plug; said bag provided with a valve capable of receiving therethrough a liquid inflation medium, wherein said valve provides high retention forces between the valve and an inflation medium supply line sufficient to resist detachment 5 when the bag is inflated to working pressure unless a tension force is applied to the supply line in excess of the retention forces; and sufficient to resist detachment when the bag in a partially inflated state and is pulled upwardly in sliding engagement with said sides of the blast hole; wherein the retention force is substantially more 10 than an attachment force required to connect the supply line to the valve.

23. A blast hole plug system as herein described and with reference to the accompanying drawin s. 15

24. A system according to any of claims 1 to 17, or a method according to any of claims 18 to 21, or a bag according to claim 22, wherein said valve has an air flow rate in a range of 1 to 10 cubic meters per hour at a supply pressure of 700 kilopascals. 20

25. A system according to any of claims 1 to 17, or a method according to any of claims 18 to 21, or a bag according to claim 22, wherein the retention force is at least about twice as much as the attachment force.