AU2014201775A1 - An Inflatable Borehole Plug - Google Patents

Abstract

An inflatable borehole plug assembly comprising an inflatable bag and inflation means to inflate the inflatable bag, wherein at least a portion of a surface of the assembly includes a non combustible or fire retardant material.

Description

AN INFLATABLE BOREHOLE PLUG TECHNICAL FIELD [0001] The present invention relates to an inflatable borehole plug. In particular, the present invention relates to an inflatable borehole plug at least partially fabricated from a non combustible and/or fire retardant material. BACKGROUND ART [0002] Bore holes are drilled so that explosive charges may be placed in the borehole at a particular position. Sometimes, the borehole is entirely filled with explosive, but other times an explosive charge must be placed somewhere along the borehole length. For this type of use, a plug is lowered down the borehole to the desired area to form a support platform for the explosive. In a typical arrangement, an explosive charge (or base charge) is located at the bottom of a borehole, while a mid-level explosive charge is supported by the plug. [0003] Inflatable borehole plug assemblies are well known. The assemblies comprise an inflatable bag which can be inflated to form the borehole plug. Inside the bag is a pressurised can which contains the inflating substance. The can is provided with a valve which can be opened to expel the inflating substance into the bag to inflate the bag. The pressurised can has a one-way valve which can be locked into the open position to expel the inflating substance (typically hydrocarbons). The plug assembly is attached to a measured length of rope and is lowered down the hole to be supported by the rope until the plug inflates to be jammed against the wall of the borehole. [0004] There are some environments in which standard borehole plugs are not suitable. For instance, borehole plugs used in coal mining require the use of non-flammable and/or non combustible components (including the inflating substance). In addition, borehole plugs used in coal mining must effectively seal a borehole in order to prevent toxic and/or flammable gases (such as methane) from entering workspaces. [0005] Some attempts have been made to overcome these problems. For instance, some efforts have been made to make use of a borehole plug that uses a chemical reaction between reactants (such as acid and sodium bicarbonate) to produce an inflating substance (carbon dioxide) to inflate a gas bag. However, these inflatable bags have a serious drawback in that the low pressure generated in the bag by the inflating substance is generally insufficient to seal a borehole against the flow of gas. Thus, it is common that multiple plugs must be used to provide an effective seal against the flow of methane. This not only increases the time taken to install the plug, but increases the cost of forming a seal due to the use of multiple plugs. [0006] In light of the foregoing, there would be an advantage if it were possible to provide an inflatable borehole plug that could be used to rapidly create a non-flammable and/or non combustible seal against the flow of flammable and/or toxic gases such as methane. [0007] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. SUMMARY OF INVENTION [0008] It is an object of the present invention to provide an inflatable borehole plug that overcomes at least one of the advantages of the prior art, or that provides a useful or commercial choice. [0009] In one aspect, the present invention resides broadly in an inflatable borehole plug assembly comprising an inflatable bag and inflation means to inflate the inflatable bag, wherein at least a portion of a surface of the assembly includes a non-combustible or fire retardant material. [0010] The inflatable bag may be fabricated from any suitable material. For instance, the inflatable bag may comprise multi-layer plastic bags which are gas tight. These bags may be formed from suitable material such as plastics, such as, but not limited to, polyethylene (including high density polyethylene (HDPE) and low density polyethylene (LDPE)), polyvinyl chloride (PVC), polypropylene, polystyrene, polycarbonate, polyurethane, silicone, polyester or the like, or any suitable combination thereof [0011] The size and volume of the bag can also vary depending on the borehole size and the weight of explosives to be supported by the plug and the like. Typically, however, the borehole will be substantially circular. Thus, it is envisaged that, once inflated, the bag will be substantially circular in cross-section. The diameter of the bag when inflated will be largely determined by the diameter of the borehole in which the bag is to be located. However, in general it is envisaged that the diameter of the bag (when inflated) may be between about 20mm and about 300mm. More preferably, the diameter of the bag (when inflated) may be between about 50mm and about 200mm. Still more preferably, the diameter of the bag (when inflated) may be between about 100mm and about 150mm.

-Y [0012] It is envisaged that the length of the bag (when inflated) may depend on a number of factors, including the length of the borehole, the purpose of the borehole, the length of time the borehole plug must remain in place and so on. However, it is envisaged that the length of the bag may be between about 200mm and about 1000mm. More preferably, the length of the bag may be between about 400mm and about 800mm. Still more preferably, the length of the bag may be between about 500mm and about 700mm. [0013] As previously stated, at least a portion of a surface (and preferably an outer surface) of the assembly includes a non-combustible, non-hazardous or fire retardant material. Typically, the outer surface of the assembly will be the outer surface of the inflatable bag. [0014] In some embodiments of the invention, at least a portion of the outer surface of the assembly may be coated with a non-combustible, non-hazardous or fire retardant material. For instance, a non-combustible, non-hazardous or fire retardant material may be sprayed, painted, powder coated or otherwise applied to a surface of the assembly. [0015] Alternatively, a non-combustible, non-hazardous or fire retardant material may be impregnated (using any suitable technique) into the material of the surface of the assembly. Any suitable non-combustible, non-hazardous or fire retardant material may be used, such as, but not limited to, fire-fighting foams or liquids (such as, but not limited to potassium acetate, carbonate, or citrate, fluoroproteins, fluoro tensides and the like, or any suitable combination thereof), dry chemical powders (such as, but not limited to, monoammonium phosphate, sodium bicarbonate, potassium bicarbonate, potassium chloride and the like, or any suitable combination thereof), organobromides, organobromines or the like, or a combination thereof. [0016] In an alternative embodiment, the gas bag may be at least partially fabricated from a non-combustible, non-hazardous or fire retardant fabric. Any suitable fabric may be used, such as, but not limited to, certain non-combustible polyesters. [0017] In some embodiments of the invention, the outer surface of the assembly may comprise the outer surface of the gas bag. In an alternative embodiment of the invention, the gas bag may be at least partially housed within a cover (such as a sleeve, jacket, housing or the like). In these embodiments of the invention, at least a portion of the outer surface of the gas bag may include a non-combustible, non-hazardous or fire retardant material, although this not need be the case, and it is envisaged that the gas bag may have no specific non-combustible or fire retardant properties. For instance, the cover may be fabricated from plastic material (such as, but not limited to, polyethylene (including high density polyethylene (HDPE) and low density _r polyethylene (LDPE)), polyvinyl chloride (PVC), polypropylene, polystyrene, polycarbonate, polyurethane, silicone, polyester or the like, or any suitable combination thereof) that is coated with a non-combustible, non-hazardous or fire retardant material. [0018] In embodiments of the invention in which the gas bag is at least partially housed within a cover, the cover may be at least partially fabricated from a non-combustible, non hazardous or fire retardant fabric. Any suitable fabric may be used, such as, but not limited to, certain non-combustible polyesters. [0019] In alternative embodiments, at least a portion of the cover includes a non combustible or fire retardant material. In these embodiments of the invention, at least a portion of the cover (and particularly, the outer surface of the cover) may be coated with a non combustible or fire retardant material. For instance, a non-combustible or fire retardant material may be sprayed, painted, powder coated or otherwise applied to the cover. Alternatively, a non combustible or fire retardant material may be impregnated (using any suitable technique) into the material of the cover. Any suitable non-combustible or fire retardant material may be used, such as, but not limited to, fire-fighting foams or liquids (such as, but not limited to potassium acetate, carbonate, or citrate, fluoroproteins, fluoro tensides and the like, or any suitable combination thereof), dry chemical powders (such as, but not limited to, monoammonium phosphate, sodium bicarbonate, potassium bicarbonate, potassium chloride and the like, or any suitable combination thereof), organobromides, organobromines or the like, or a combination thereof [0020] In a preferred embodiment of the invention, at least a portion of a surface of the assembly further includes an antistatic material. Typically, the outer surface of the assembly will be the outer surface of the inflatable bag. In some embodiments of the invention, at least a portion of the outer surface of the assembly may be coated with antistatic material. For instance, an antistatic material may be sprayed, painted, powder coated or otherwise applied to a surface of the assembly. Alternatively, an antistatic material may be impregnated (using any suitable technique) into the material of the surface of the assembly. Any suitable antistatic material may be used, such as, but not limited to, aliphatic amines (especially long-chained aliphatic amines, and optionally ethoxylated aliphatic amines) and/or amides, quaternary ammonium salts (e.g., behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycol esters, polyols, or compounds such as indium tin oxide, or a combination thereof [0021] In an alternative embodiment, the gas bag may be at least partially fabricated from an antistatic fabric. Any suitable fabric may be used. For instance, the gas bag may be provided with one or more electrically conductive threads (such as metallic threads, including threads of silver, copper, gold, aluminium, zinc, nickel, brass, bronze, iron or platinum or the like, or any suitable combination thereof) on the surface of the gas bag, or formed with the gas bag. In order to function as an antistatic device, the gas bag may also be connected to earth using any suitable technique. Thus, in this embodiment of the invention, the gas bag may function in a similar manner to a Faraday cage. [0022] In some embodiments of the invention, the outer surface of the assembly may comprise the outer surface of the gas bag. In an alternative embodiment of the invention, the gas bag may be at least partially housed within a cover (such as a sleeve, jacket, housing or the like). In these embodiments of the invention, at least a portion of the outer surface of the gas bag may include an antistatic material, although this not need be the case, and it is envisaged that the gas bag may have no specific antistatic properties. [0023] In embodiments of the invention in which the gas bag is at least partially housed within a cover, the cover may be at least partially fabricated from an antistatic fabric. Any suitable fabric may be used, such as, but not limited to, wool, silk or synthetic antistatic fabrics. [0024] It is envisaged that, in a preferred embodiment of the invention, the assembly may comply with one or more applicable national Standards. In particular, it is envisaged that the assembly may comply with applicable national FRAS (Fire Retardant Anti Static) Standards. [0025] The inflation means may be of any suitable form. However, in a preferred embodiment of the invention, the inflation means comprises one or more pressurised containers. Any suitable type of pressurised container may be used, such as, but not limited to, a pressurised can. Preferably, the pressurised container will contain an inflating substance, such that actuation of the pressurised container will result in the inflating substance being dispensed from the pressurised container. In a particularly preferred embodiment of the invention, the pressurised container comprises an aerosol can. [0026] The inflating substance may be dispensed from the pressurised container in any suitable manner. Preferably, however, the inflating substance is dispensed through one or more valves, once the one or more valves have been actuated. [0027] The one or more valves may typically be such that once opened, the valve stays open which means that the contents of the container will be totally released without interruption until the pressure in the container and the pressure in the bag equalises.

[0028] The pressurised container may be fabricated from any suitable material, such as plastic, steel, tin plate or aluminium. It is envisaged that the use of aluminium cans may allow the container to be rated to a higher pressure than cans fabricated from other materials. In a preferred embodiment of the invention, the container has a pressure rating of greater than 12 bar. In a more preferred embodiment of the invention, the container has a pressure rating of between about 12 bar and 25 bar. In a most preferred embodiment of the invention, the container has a pressure rating of about 20 bar. However, in some situations (such as when the inflatable borehole plug is used in underground mines, and more particularly underground coal mines) safety regulations and/or concerns may dictate the use of pressurised containers fabricated from other materials. In these situations, pressurised containers made from plastic, steel or tin plate may be preferred. [0029] The inflating substance can vary to suit. The inflating substance is typically in the form of a volatile liquid which will expand and volatise once in the inflatable bag. Alternatively, the pressurised container may contain compressed gas. [0030] Preferably, the inflating substance is substantially non-flammable, non-hazardous and/or substantially non-toxic during normal use. Any suitable substance may be used, although in a preferred embodiment of the invention, the inflating substance may include 1,1,1,2 tetrafluoroethane (also known as R-134a). [0031] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention. [0032] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge. EXAMPLE [0033] In one non-limiting example of the invention, an inflatable borehole plug assembly was provided comprising an inflatable bag fabricated from high density polyethylene (HDPE). Inside the inflatable bag was provided a pressurised steel aerosol container containing 1,1,1,2 tetrafluoroethane. [0034] Prior to use, the inflatable bag was placed inside a cover fabricated from high density polyethylene (HDPE) coated with sodium bicarbonate to impart fire-resistant properties to the cover. The cover also comprises a plurality of copper threads on the surface thereof that provide antistatic properties to the cover. [0035] The assembled gas bag was partially inserted into a borehole having a diameter of about 500mm and the aerosol container was actuated so that the contents of the aerosol container were continuously dispensed into the inflatable bag until the aerosol container was empty, thereby inflating the gas bag. During the inflation of the gas bag, the borehole plug assembly was fully inserted into the borehole to a desired depth and held in position until the inflation of the inflatable bag was complete. When the inflation of the gas bag was complete, the assembly was approximately 500mm in diameter, meaning that the borehole plug assembly abutted the inner surface of the borehole. In this way, the borehole plug is held in place within the borehole in use. BRIEF DESCRIPTION OF DRAWINGS [0036] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: [0037] Figure 1 illustrates an inflatable borehole plug according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS [0038] In Figure 1 there is illustrated an inflatable borehole plug 10 according to an embodiment of the present invention. The inflatable borehole plug 10 is shown inserted into a borehole 12 and inflated. [0039] The inflatable borehole plug 10 comprises an inflatable bag 12 that has been coated or impregnated with a fire resistant material (potassium chloride). The inflatable borehole plug 10 also includes inflating means in the form of a pressurised can 13 located within the inflatable bag 12. The pressurised can 13 is fabricated from steel and contains a non-flammable inflating substance (in the form of 1,1,1,2-tetrafluoroethane) that, once actuated, is dispensed continuously through a valve 14 until all of the inflating substance has been dispensed into the inflatable bag 12. [0040] As the inflating substance is dispensed into the inflatable bag 12, the inflatable bag 12 expands until it abuts the inner surface of the borehole 11 and is retained in place so as to form a plug within the borehole 11. [0041] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers. [0042] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations. [0043] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims (16)

1. An inflatable borehole plug assembly comprising an inflatable bag and inflation means to inflate the inflatable bag, wherein at least a portion of a surface of the assembly includes a non combustible or fire retardant material.

2. An assembly according to claim 1 wherein the surface of the assembly comprises an outer surface of the inflatable bag.

3. An assembly according to claim 1 wherein the surface of the assembly comprises a cover in which the inflatable bag is at least partially housed.

4. An assembly according to any one of the preceding claims wherein the inflatable bag is formed from high density polyethylene.

5. An assembly according to any one of the preceding claims wherein the inflation means comprises a pressurized container containing an inflating substance.

6. An assembly according to claim 5 wherein the pressurized container comprises an aerosol can.

7. An assembly according to claim 5 or claim 6 wherein the pressurized container is fabricated from steel.

8. An assembly according to claim 5 or claim 6 wherein the pressurized container is fabricated from plastic.

9. An assembly according to any one of claims 5 to 8 wherein the inflating substance is substantially non-flammable, non-hazardous and non-toxic.

10. An assembly according to any one of claims 5 to 9 wherein the inflating substance is 1,1,1,2-tetrafluoroethane.

11. An assembly according to any one of the preceding claims wherein the at least a portion of the surface of the assembly is coated with the non-combustible or fire retardant material.

12. An assembly according to claim 11 wherein the non-combustible or fire retardant material comprises fire-fighting foams, liquids, dry chemical powders, organobromides or a combination thereof IVU

13. An assembly according to any one of the preceding claims wherein at least a portion of the surface of the assembly further includes an antistatic material.

14. An assembly according to claim 13 wherein the at least a portion of the surface of the assembly is coated with the antistatic material.

15. An assembly according to claim 14 wherein the antistatic material comprises aliphatic amines and/or amides, quaternary ammonium salts, esters of phosphoric acid, polyethylene glycol esters, polyols, indium tin oxide, or a combination thereof.

16. An assembly according to claim 13 wherein the antistatic material includes one or more electrically conductive threads.