FIELD OF THE INVENTION

The present invention relates to a bladder tank system for delivering emulsion explosives.

BACKGROUND OF THE INVENTION

Emulsion explosives, for example blends of ammonium nitrate with oil, are often delivered to blast holes in underground mines by "pumpless" pressure pot systems. The emulsion explosive is stored in situ in the underground mine in a pressure pot, and is expelled through delivery hoses into the blast holes by injecting compressed mine air into the pressure pot directly onto the head of the emulsion explosive inside the pressure pot. An advantage of pressure pot systems is that they avoid the need to use expensive, heavy-duty pumps to pump the emulsion explosive into the blast holes.

However, a major disadvantage of pressure pot systems is that they expose the emulsion explosive to dirt, moisture, rust and other air contaminants that are typically present in compressed mine air. The resulting contamination degrades the safety and performance of the emulsion explosive. Another disadvantage of pressure pot systems is that they have a low expulsion pressure and thus require high-pressure water injectors in their delivery hoses to form a lubricating annulus of water around the emulsion explosive between the interior diameter of the delivery hoses.

What is needed is a "pumpless" delivery solution for emulsion explosives which addresses the above difficulties. SUMMARY OF THE INVENTION

According to the present invention, there is provided a bladder tank system having a pressure tank enclosing a flexible bladder for isolatedly containing an emulsion explosive, wherein the bladder has an inlet/outlet communicating with a first opening in the tank for charging the bladder with the emulsion explosive and for discharging the emulsion explosive from the bladder, and wherein the tank has a pressurant inlet for charging the tank exteriorly of the bladder with a pressurant to collapse the bladder and thereby expel the emulsion explosive therefrom.

The bladder can have an overflow for overflowing the emulsion explosive from the bladder during charging thereof to prevent or minimise air bubbles from forming inside the bladder, wherein the overflow is spaced apart from the inlet/outlet and communicates with a second opening in the tank spaced apart from the first opening.

A perforated guard can be positioned across the inlet/outlet for preventing the bladder from collapsing outside the tank.

The system can further include one or more delivery hoses communicating with the inlet/outlet for respectively delivering the emulsion explosive to one or more blast holes.

The one or more delivery hoses can respectively have a selected interior diameter so that the emulsion explosive is respectively flowable therethrough without lubrication. The selected interior diameter can be between 19 and 32 mm.

The emulsion explosive can have a selected viscosity so as to be respectively flowable through the one or more delivery hoses without lubrication. The selected viscosity can be between 20000 and 35000 centipoise (cP).

The system can further include an external frame for surrounding and supporting the tank. The present invention also provides a method of storing and delivering an emulsion explosive using a bladder tank system as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a schematic piping and instrumentation diagram of an embodiment of a bladder tank system of the invention; and Figure 2 is a perspective view of a shaft-loading embodiment of the bladder tank system.

DETAILED DESCRIPTION

Figure 1 illustrates an embodiment of a bladder tank system 10 of the invention. The system 10 includes a pressure tank 12 enclosing a flexible bladder 14 for isolatedly containing an emulsion explosive, for example a blend of ammonium nitrate with oil. The tank 12 is made of, for example, stainless steel. The bladder 14 is made of, for example, nitrile rubber.

The bladder 14 has an inlet/outlet 16 communicating with a first opening in the tank 12 for charging the bladder 14 with the emulsion explosive and for discharging the emulsion explosive from the bladder 14. The inlet/outlet 16 is formed, for example, by sealing a neck of the bladder 14 to a flanged lower opening in the tank 12. A perforated guard 18 is positioned across the inlet/outlet 16 for preventing the bladder 14 from collapsing outside the tank 12.

The bladder 14 is charged with the emulsion explosive through the inlet/outlet 16 via charge line 20 and valved port 22. The emulsion explosive is pumped to the valved port 22 from a gravity tank (not shown) by a diaphragm pump (not shown). The bladder 14 has an overflow 24 for overflowing the emulsion explosive from the bladder 14 during charging thereof to prevent or minimise air bubbles from forming inside the bladder 14. The overflow 24 is spaced apart from the inlet/outlet 16 and communicates with a second opening in the tank 12 spaced apart from the first opening. The overflow 24 is formed, for example, by sealing a neck of the bladder 14 to a flanged upper opening in the tank 12. Although not shown, a perforated guard is optionally positioned across the overflow 24 for preventing the bladder 14 from collapsing outside the tank 12. Emulsion explosive overflowing through the overflow 24 is returned to the gravity tank (not shown) via overflow line 26 and valved port 28.

The tank 12 has a pressurant inlet 30 for charging the tank 12 exteriorly of the bladder 14 with a pressurant to collapse the bladder 14 and thereby expel the emulsion explosive therefrom through the inlet/outlet 16. The tank 12 also has a pressurant outlet 32 for purging residual pressurant from the tank 12. The pressurant is, for example, compressed mine air provided by, for example, an air compressor or a compressed air system of an underground mine (not shown). The compressed mine air is selectively provided to the pressurant inlet 30 via air line 34 which includes inlet valve 36, filter 38, pressure gauge 40, pressure regulator/gauge 42, charge/purge valve 44, and relief valve 46.

The charging of the tank 12 with compressed mine air provides the motive energy to collapse the bladder 14 and thereby positively expel the emulsion explosive therefrom. The fluidic isolation of the driving compressed mine air inside the tank 12 from the emulsion explosive inside the bladder 14 prevents contaminants in the compressed mine air, for example dirt, moisture, rust and other air contaminants, from contacting and contaminating the emulsion explosive and degrading its safety and performance.

Expelled emulsion explosive is provided from the inlet/outlet 16 to a delivery hose 48 via delivery line 50 which includes valves 52, 54. Valve 52 selectively isolates delivery hose 48 from the inlet/outlet 16 for maintenance. Valve 54 is remotely actuatable pneumatically or electronically, for example, via a wireless receiver and transmitter 56, 58 to deliver the emulsion explosive into a blast hole (not shown). For clarity only a single delivery hose and line is illustrated, but multiple, for example three to five, delivery hoses and lines are optionally provided for respectively delivering the emulsion explosive to multiple blast holes.

The delivery hose 48 has a selected interior diameter, for example between 19 and 32 mm, so that the emulsion explosive is flowable therethrough without water lubrication. The emulsion explosive has a selected viscosity, for example between 20000 and 35000 centipoise (cP), so that it is flowable through the delivery hose 48 without water lubrication.

Emulsion explosive is purged from the delivery hose 48, for example at the end of shifts, by blowdown air which is selectively provided to the delivery hose 48 via valve 60 and blowdown line 62 which branches off air line 34.

Figure 2 illustrates an embodiment of the bladder tank system 10 configured for shaft- loading in underground mining operations. The system 10 includes an external frame 64 for surrounding and supporting the tank 12. The system 10 may also be alternatively configured for other applications, for example, underground lateral development and surface mining operations.

It will be appreciated that embodiments of the invention provide a "pumpless" delivery solution for emulsion explosive which advantageously prevents compressed air contamination and avoids the need for water lubrication.

The embodiments have been described by way of example only and modifications are possible within the scope of the claims which follow.