FIELD OF THE INVENTION

THIS INVENTION relates to transport of explosives. More specifically, the invention relates to vertical transport of explosives, particularly of emulsion explosives. The invention provides a method of vertically transporting an emulsion explosive. The invention also provides an installation for vertically transporting an emulsion explosive.

BACKGROUND TO THE INVENTION

VERTICAL TRANSPORT OF EMULSION EXPLOSIVES, for example down mine shafts for underground blasting operations, remains wrought with challenges.

The applicant has sought to address these challenges with the inventions of ZA 201 1/01044 and ZA 2012/07171 , which have been successfully exploited in practice.

Nevertheless, a need for alternative approaches remains, both to address the operational, safety and logistical challenges that are discussed in the specifications of the abovementioned patents, and to protect the emulsion product during its transport.

More specifically, an emulsion that is transported vertically may, if dropped freely within a conduit over a sufficient distance, break up as a result of shearing and turbulent flow. A challenge in vertical transport of emulsion explosives is therefore to maintain laminar flow of emulsion explosive. The present invention finds application in the above respects.

SUMMARY OF THE INVENTION

IN ACCORDANCE WITH ONE ASPECT OF THE INVENTION IS PROVIDED a method of transporting emulsion explosive vertically, the method including,

feeding emulsion explosive into a vertically extending conduit, onto a support member that is located in the conduit such that emulsion explosive is supported on the support member in the conduit, the support member being vertically movable along the conduit at a predetermined, variable, controllable rate of descent; and

moving the support member vertically downward in the conduit at a predetermined, variable, controlled rate of descent, thus transporting emulsion explosive vertically in the conduit.

It will be appreciated that the rate of descent at which the support member may at any given time move vertically along the conduit, thus transporting the emulsion explosive vertically along the conduit, would therefore be a predetermined rate of descent, and that it may be varied from time to time, in a controlled manner. In this regard“control” envisages intentional intervention in determining, e.g. limiting, the rate of descent, thus avoiding freefall of the support member, and of emulsion explosive, in the conduit.

The conduit may be provided by a pipe.

Feeding of emulsion explosive into the conduit may be under gravity and/or by means of pumping. Vertical movement of the support member in the conduit, thus transporting emulsion explosive vertically along the conduit, may occur simultaneously with feeding of emulsion explosive into the conduit.

The rate of descent of the support member in the conduit may approximate a rate of feeding of emulsion explosive into the conduit, at least while emulsion explosive is being fed into the conduit. Thus, the rate of descent of the support member along the conduit may be controlled to approximate the rate at which emulsion explosive is fed into the conduit, thus avoiding free-fall of emulsion explosive in the conduit and overflow of emulsion explosive from the conduit.

Vertical movement of the support member along the conduit to transport emulsion explosive vertically along the conduit may continue after feeding of emulsion explosive into the conduit has ceased.

In one respect, vertical movement of the support member along the conduit to transport emulsion explosive vertically along the conduit may be caused, at least in part, by feeding of emulsion explosive into the conduit. Thus, feeding of emulsion explosive into the conduit may drive vertical movement of the support member along the conduit, through contact between emulsion explosive with the support member inside the conduit. In such an embodiment, the method may include, as a manner of control, offering resistance, by means of the support member, to the rate of descent of emulsion explosive in the conduit exceeding a predetermined maximum rate of descent. In another respect, vertical movement of the support member along the conduit, to transport emulsion explosive vertically along the pipe, may be caused, at least in part, by the weight of the emulsion explosive in the conduit moving under gravity. Thus, movement of emulsion explosive in the conduit under gravity may drive vertical movement of the support member along the conduit, through contact between emulsion explosive with the support member inside the conduit. In such an embodiment, the method may also include, as a manner of control, offering resistance, by means of the support member, to the rate of descent of emulsion explosive in the conduit exceeding a predetermined maximum rate of descent.

Control of the rate of descent of emulsion explosive in the conduit may therefore be effected by offering resistance, by means of the support member, to movement of emulsion explosive in the conduit under force of the feeding of emulsion explosive into the conduit and/or under the weight of emulsion explosive in the conduit moving under gravity.

Preferably, the predetermined rate of descent is up to, and preferably less than, 10 meters per second (m/s), more preferably being in the range of 1 m/s to 2 m/s.

The method may include vertically moving the support member, and thus vertically transporting emulsion explosive, in the conduit, over a distance greater than 500m, preferably greater than 800m. The support member may be located liquid-tightly in the conduit, i.e. such that emulsion explosive is retained upstream of the support member.

The emulsion explosive would typically be unsensitized emulsion explosive, i.e. an explosive emulsion into which a sensitising, or gassing, agent has not yet been introduced.

The method may include discharging emulsion explosive from an outlet of the conduit. The method may include, prior or subsequent to discharge thereof from the outlet, sensitizing the emulsion explosive, e.g. by introducing a gassing agent into it.

The emulsion explosive may, in one embodiment of the invention, be so-called“up- hole” or“sticky” emulsion explosive, e.g. UG101 S as manufactured by the applicant.

IN ACCORDANCE WITH ANOTHER ASPECT OF THE INVENTION IS PROVIDED

an installation for transporting emulsion explosive vertically in accordance with the method of the invention, the installation including

a vertically extending conduit; and

a support member that is located in the conduit to support and vertically transport emulsion explosive in the conduit in use,

wherein the support member is vertically movable along the conduit at a predetermined, variable, controlled rate of descent. The installation may therefore include means for controlling vertical movement of the support member along the conduit such that it is at a predetermined, variable rate of descent.

The conduit may be provided by a pipe.

The installation may include means for feeding emulsion explosive into the conduit, upstream of the support member. Such means may be selected from a pump and/or a feed hopper, for feeding emulsion explosive into the conduit by pumping and/or under gravity, upstream of the support member.

The support member may be located liquid-tightly in the conduit, i.e. such that emulsion explosive is retained upstream of the support member in the conduit.

The support member may be provided with resistive means, operable to resist movement of the support member along the conduit beyond a predetermined maximum rate of descent, which movement is e.g. under force of emulsion explosive fed into the conduit by pumping and/or under weight of emulsion explosive contained in the conduit moving under gravity.

In a preferred embodiment of the invention, the resistive means may comprise a flexible line, e.g. a cable, that is connected to and extends upstream from the support member, and is operable to limit the rate of descent the support member along the conduit, e.g. by way of a motor. The pump and the motor may be in electronic communication with an electronic controller that may be configured to approximate the rate of descending movement of the support member, as controlled by the motor, with the rate at which emulsion explosive is fed into the conduit, as controlled by the pump, while emulsion explosive is pumped into the pipe.

The support member may be of a non-metallic material. For example, the support member may be of foam rubber. The conduit may extend vertically over a distance greater than 500m, preferably greater than 800m.

The conduit may have a diameter of about 4 inches. The installation may be located at a mining site, for example a shaft mine or open case mine.

BRIEF DESCRIPTION OF THE DRAWING

THE INVENTION WILL NOW BE DESCRIBED IN MORE DETAIL with reference to the accompanying diagrammatic drawings in which:

FIGURE 1 shows an installation according to the invention, for performing a method according to the invention, in one emulsion explosives transport condition; FIGURE 2 shows an installation according to the invention, for performing a method according to the invention, in a further emulsion explosives transport condition; and

FIGURE 3 shows an installation according to the invention, for performing a method according to the invention, in yet another emulsion explosives transport condition.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

REFERRING TO THE DRAWINGS, reference numeral 10 generally indicates an installation 12 according to the invention, installed in a mine shaft 14 sunk in a body of earth 15, for performing a method according to the invention.

The shaft 14 has a depth greater than 500m, typically greater than 800m. The installation 12 comprises a vertical conduit in the form of a 4 inch diameter pipe 16 that extends down the shaft 14, to a depth greater than 500m, typically greater than 800m.

The installation 12 also comprises a pump 18 that is configured to pump emulsion explosive 20, specifically unsensitised sticky emulsion explosive, into the pipe 16, to be transported down the pipe 16, for discharge from an open end 28 of the pipe 16 at a location along the shaft 14, e.g. a gallery, at which the emulsion explosive 20 would be used. The installation 12 further comprises a liquid-tight support member 22 that is moveably located inside the pipe 16, such that it can liquid-lightly move along the pipe 16. In this sense, liquid-tight means that liquid (emulsion explosive) cannot pass from an upstream side of the support member 22 to a downstream side thereof, or vice versa.

The installation 12 also comprises an electric motor 24 that is connected to the support member 22 by means of a cable 26 that extends into the pipe 16. The pump 18 and the electric motor 24 are in electronic communication with a controller, as illustrated by broken line 25.

The electric motor 24 is operable selectively to extend and retract the cable 26 with respect to the pipe 16, thereby selectively to allow movement of the support member 22 downward along the pipe 16 and to move it upward along the pipe 16.

In Figure 1 , a volume of emulsion explosive 20 has been charged into the pipe 16 by the pump 18. This would have caused movement of the support member 22 to its location illustrated in Figure 1 , under force of pumping of emulsion explosive into the pipe 16 and under weight of the emulsion explosive 20 moving under gravity, limited by the rate at which the electric motor 24 allowed extension of the cable 26 into the pipe 16.

In Figure 2, the volume of emulsion explosive 20 in the pipe 16 has increased due to continued charging thereof into the pipe 16 by the pump 18. This caused movement of the support member 22 to its location illustrated in Figure 2, under force of pumping of emulsion explosive into the pipe 16 and under weight of the emulsion explosive 20 moving under gravity, limited by the rate at which the electric motor 24 allowed extension of the cable 26 into the pipe 16. Thus, emulsion explosive 20 has been transported vertically downward along the pipe 16

In Figure 3, the volume of emulsion explosive 20 in the pipe 16 is the same as in Figure 2, but it has been transported further vertically downward along the pipe 16 due to movement of the support member 22 under weight of the emulsion explosive 20 moving under gravity, limited by the rate at which the electric motor 24 allowed extension of the cable 26 into the pipe 16.

Still referring to Figure 3, it will be seen that the support member 22 has been allowed to exit the outlet 28 of the pipe 16, thereby allowing emulsion explosive to be discharged from the pipe 16 for use. Such discharge would typically be into a container for the emulsion explosive.

The rate at which the electric motor 24 allows extension of the cable 26 into the pipe may be at most 10m/s, typically less than 10m/s, e.g. 1 -2m/s.

Typically, in use, the rate at which the electric motor 24 allows extension of the cable 26 into the pipe 16 would approximate that required to sustain the rate at which emulsion explosive is being fed into the pipe 16, at least while it is fed into the pipe 16.

After feeding of emulsion explosive has ceased, the rate may remain the same, or may be slowed or increased subject to operating conditions. DISCUSSION

Employment of the support member 22 and control of its movement, or more specifically limitation of its rate of descent, along the pipe 16 under the weight of the emulsion explosive 20 by means of the motor 18 allows for transport of the emulsion explosive 20 along the pipe 20 to be effected in a controlled manner, that limits the rate at which the emulsion explosive 20 moves down the pipe 16.

Over the distances, or rather the depths, that the emulsion explosive 20 is transported in accordance with the invention, i.e. greater than 500m and more specifically greater than 800m, the method and installation of the invention prevent break-up of the emulsion explosive due to shear between the emulsion explosive and the pipe walls by limiting the rate at which the emulsion explosive moves down the pipe 16, by means of the support member 22.