ZA200610336B

ZA200610336B - A stemming device

Info

Publication number: ZA200610336B
Application number: ZA200610336A
Authority: ZA
Inventors: Mcintyre Benjamin Bartlomeus; Van Den Berg Zacharian Joseph
Original assignee: Mcintyre Benjamin Bartlomeus; Van Den Berg Zacharian Joseph
Priority date: 2005-12-14
Filing date: 2006-12-11
Publication date: 2008-05-28

Description

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I | A STEMMING DEVICE e006 / 10330 fi

Field of the Invention

This invention relates to a stemming device, and more particularly, but not exclusively, to a stemming device suitable for use in blast holes in the mining industry.

Background to the Invention

For purposes of this specification, the following terminology and associated meanings have been adopted.

The term “stemming” material or composition refers to the material used on top, in front of or around a charge or explosive, so as to contain or confine the gaseous products of a detonation in a blast hole. The term “stemming” material or composition is often used by those in the art synonymously with the term “tamping” material or composition and shall be understood, for purposes of this specification, as embracing such terminology as well.

The term “stemming device” refers to a device comprising a stemming material or composition.

The term “tamp” refers to the packing, of usually a blast hole, with stemming material or a tamping bag or stem plug or the like.

It is well known, in the field of blasting with explosives for the purpose of breaking rock, to drill blast holes into the rock. Into these blast “holes a selected explosive charge comprising detonator, primer and main explosive composition is then introduced. It is further well known to insert some form of stemming material into the blast hole after charging it with the explosive charge. Such stemming material serves to ensure that the effect of the explosion is directed to the rock, thereby to break the rock. Without such stemming material serving to contain the explosion, to some extent at least, the expanding gases : created during the explosion simply would escape through the blast

: hole drilled into the rock. In that event the explosion would be far less efficient, if not entirely inefficient for breaking the rock as intended.

For South African purposes, Regulation 9.30.3.3. of the Minerals Act 50 of 1991 states that “no person shall fire a charge of explosives, or cause or permit any other person to fire a charge of explosives, unless the explosives are contained in a shot hole, properly tamped”. Further, regulation 8.10.30 of the Minerals Act 50 of 1991 states that “ever hole charged with explosives other than with ammonium nitrate blasting agent must be tamped.” Accordingly the use of stemming devices, especially in the mining industry, are of utmost importance.

Without wishing to be bound by theory, the purpose of utilising stemming material is to effectively contain gas energy emanating from an explosion in a blast hole and to direct the resultant expanding gases into newly formed cracks in the rock into which the blast hole is provided. It is therefore desirable to prevent the stemming material from simply being blasted out the blast hole as a projectile in that the requisite gas containment is greatly reduced. :

It is therefore necessary to ensure that stemming material, when exposed to the enormous pressures of a blast, is wedged within the blast hole for an optimal period of time, in order to effectively contain the resultant gas from the explosion.

Various stemming materials and compositions and devices have been employed in mining over the years.

Most commonly, blast holes are tamped with a clay plug which is inserted into the hole and tamped down with a tamping tool, which is normally a wooden stick. While such clay plugs are adequately effective, it suffers from the disadvantage that it is very difficult to remove from the blast hole as needs to be ‘done in the event of a misfire. Where a misfire has occurred it is necessary, before working : 35 in the blast area, to remove the entire charge from the blast hole where the misfire has occurred. This is normally done by means of a water lance through which water is fed under high pressure into the :

‘ hole and by which the charge is then washed out. However, because of the sticky consistency of the clay it can take up to an hour properly to wash out a misfired charge from a blast hole tamped with clay.

An alternate to the above is the use of a stemming material in the form of a polymeric foam composition that is introduced into the blast hole.

This arrangement has the disadvantage of being relatively expensive.

A third known form of stemming material is provided in the form of a paper pulp composition.

In some applications water is used as a stemming material, i.e. where the blast hole drilled into the rock face is submerged below water, the water itself, provided it fills the blast hole, is regarded as adequate tamping for the purpose explained above.

Object of the Invention

It is an object of the invention to provide a stemming device that at least partially overcomes the disadvantages set out above.

Summary of the Invention

The applicant refers to the size of a particle by means of a mesh size.

The term mesh herein refers to the classification of a collection of particles according to a range of sizes of such particles, and is derived from the sizes of the opening in standard or test sieves used for classifying such particles.

According to the present invention, there is provided a stemming device including a stemming material comprising a first slurry component including a fine powdery composition and a second slurry component including a granular composition, the first slurry component and second slurry component being separate and each being contained in a capsule which is adapted in use to be inserted into a charged blast hole and to be ruptured when located against the charge y PE

LL conned 0H : so as to thereby plug the blast hole in the area immediately towards the open end of the blast hole and immediately adjacent the charge.

It is envisaged that the first slurry component will provide the requisite seal around a charge placed in a blast hole by filling the voids about the charge and part of the blast hole between the open end thereof at the face and the charge in the hole. Accordingly the first slurry component may have a semi-flowable consistency.

It is further envisaged that the second slurry component assists in maintaining the stemming material within the blast hole by arching and locking into the walls of the blast hole as a result of being subject to detonation pressure and having the first slurry component forced there-through.

The fine powdery composition may be made up of any suitable combination of ingredients that are capable, upon being mixed with a liquid, to form a slurry of the consistency having the characteristics discussed above. In this regard it has been found to be useful to employ a powdery composition of which the ingredients are predominantly composed of oxides of metals such as alumina or calcium oxide and silica.

The fine powdery composition according to the present invention is preferably composed of fly ash. It will be appreciated that other ingredients such as clay may also be used, provided that the same characteristics are obtained.

The liquid may be water that is mixed in the required proportions with the fine powdery composition to give the mixture a semi-flowable consistency. Alternatively the liquid may be oil or any other suitable wetting agent. Preferably the liquid is a mixture of the water and oil.

The oil may be chosen from the group consisting of mineral oils, synthetic oils, organic oils and a combination thereof. Preferably the oil is sunflower cooking oil.

The second component may comprise crushed stones.

The granular composition may comprise particles, preferably stones, having a particle size corresponding to a mesh size of from 2.00mm

S and 6.30mm. Further, the particles must be angular in nature as it is believed by the inventors that spherical particles do not provide the requisite compaction or arching. In one form of the invention, the granular composition may comprise crushed stones or angular gravel.

The granular composition is preferably mixed with a liquid. The liquid may preferably be water.

In a preferred form of the invention, the ratio of the first slurry component to the second slurry component is 0.33": 0.66".

The capsule is preferably a flexible tubular capsule which is closed off at both ends thereof. The capsule may be of any suitable polymeric material. The capsule may be translucent or transparent but is preferably of an opaque and brightly colored polymeric material thereby allowing the packed capsule to serve a secondary function in use, namely as a marker for misfired blast holes which are required to be cleaned out.

The capsule may be filled with the first slurry component and second slurry component by means of any convenient filling arrangement.

The ends of the capsule may be closed off by any convenient closing means and may, for example, be heat-sealed or closed by means of a wire tie or any other suitable closure device.

It is intended, in use, that the capsule be placed in the blast hole such that the first slurry component is next to the charge in the blast hole.

The length of the capsule is expressed by the formula (1): f=aX@ .....

: wherein { is the length of the capsule; a is a multiplying factor which is 5 to 15, preferably 8 to 13, and more preferably 10; and ¢ is the diameter of a blast hole. :

According to a second aspect of the invention, there is provided a method of tamping a blast hole, the method being characterised in that a first slurry component including a fine powdery composition and having a consistency allowing it to be worked into close contact with an explosive charge in a blast hole is provided and a second slurry component including a granular composition is provided subsequent to the introduction of the first slurry component and on top thereof so as to plug a charged blast hole.

According to a third aspect of the invention, there is provided a method of tamping a blast hole, the method including the step of introducing a stemming device as hereinbefore described into the blast hole.

Preferable the stemming device is ruptured such that the first component forms a seal around an explosive charge in the blast hole.

According to a fourth aspect of the invention, there is provided the use of a stemming device including a stemming material comprising a first slurry component including a fine powdery composition and a second slurry component including a granular composition, the first slurry component and second slurry component being separate and each being contained in a capsule which is adapted in use to be inserted into a charged blast hole and to be ruptured when located against the charge so as to thereby plug the blast hole.

Brief Description of the Invention

An embodiment of the invention is described below, by way of example only, and with reference to the accompanying drawing wherein:

Figure 1 is an illustration of the stemming devite according to the invention. s

Detailed Description of the Invention :

Referring to Figure 1, there is illustrated a stemming device 10, including stemming material 12 provided in a flexible elongate capsule 14, which is cut open in order to illustrate the stemming material 12.

The stemming material 12 comprises a first slurry component 12a made up of a slurry from a fine powdery composition which for purposes of this example was prepared by mixing about 40 Kg of fly ash obtained from the power station located at Vereeniging with about 15 litres of ordinary tap water and 20 milliliters of sunflower cooking oil. It is of course not necessary to use new cooking oil and it has been found to be acceptable to utilize oil which has been used previously for frying purposes and that is no longer fit for use in food preparation for human consumption. Accordingly the use of such oil provides an alternative to simply disposing of it. It will be appreciated that other fine powdery compositions aside from fly ash may be used to the same effect.

The stemming material 12 also includes a second slurry component 12b that comprises a granular aggregate of crushed stones. The crushed stones are angular in nature and are roughly between 2mm to 6mm. Water was added to achieve the appropriate slurry consistency.

It will be apparent from the accompanying drawing that the first slurry component and second slurry component are provided separately. It is believed by the inventors that should the first slurry component and second slurry component be mixed to form a single composite, that the stemming device would not provide a suitable tamping.

The capsule 14 in the accompanying drawing is an illustration of a supply roll 16 of elongated polymeric tube that is shown to be closed

: off at a pre-selected distance from the free end by means of a wire tie 18. The polymeric material may be brightly coloured so that the capsule 14 may also serve as a marker for the identification of those blast holes that are required to be cleared of debris, stemming material and charge after a misfire. The length of the capsule is determine according to the diameter of the blast hole per formula (I) set out herein.

It will be appreciated that the capsule 14 may be filled in any convenient manner.

In use the stemming device is placed within a blast hole and ruptured so that the stemming material may escape and fill the blast hole with the first slurry component forming a seal around a charge placed in the blast hole. Importantly, the stemming device is placed such that the charge is followed by the first slurry composition.

Upon detonation of the charge, the resultant expanding gases force the first slurry component through the second slurry component causing it to arch and therefor maintain the stemming material within the blast hole for the requisite time.

It will be appreciated that many variations of the invention may be devised without departing from the spirit and scope of the invention as claimed herein.

For example, the capsule may be closed off by heat-sealing either or both ends thereof. In an alternate embodiment, a first end of the capsule, nearest the first slurry component, may be heat sealed, preferably at a 45° slant, while the second end, nearest to the granular composition, may also be heat sealed. -

Claims

: dis Claims en SE —

1. A stemming device suitable for a blast hole, the stemming device including a stemming material comprising a first slurry component including a fine powdery composition and a second slurry component including a granular composition, the first slurry component and the second slurry component being separate and each being contained in a capsule which is adapted in use to be inserted into a charged blast hole and to be ruptured when located against a charge so as to thereby plug the blast hole in the area immediately towards the open end of the blast hole and immediately adjacent the charge.

2. The stemming device of claim 1, wherein the first slurry component has a semi-flowable consistency.

3. The stemming device of claim 1, wherein the first component is selected from the oxides of metals.

4. The stemming device of claim 1, wherein the first component is selected from the group consisting of alumina, calcium oxide and silica.

5. The stemming device of claim 1, wherein the first component may be selected from the group consisting of fly ash and clay.

6. The stemming device of claim 1, wherein the first component is mixed with a wetting agent.

7. The stemming device of claim 6, wherein the wetting agent is selected from the group consisting of water, synthetic oils, organic oils or a combination of one or more of water, synthetic oils and organic oils.

' 8. The stemming device of claim 1, wherein the second component comprises crushed stones having a particle size corresponding to a mesh size of from 2.00mm to 6.30mm.

9. The stemming device of claim 1, wherein the second component is mixed with a wetting agent.

10. The stemming device of claim 1, wherein the ratio of the first component to the second component is 0.33 to 0.66.

11. The stemming device of claim 1, wherein the capsule is made from a polymeric material.

12. The stemming device of claim 11, wherein the polymeric material is brightly coloured.

13. The stemming device of claim 1, wherein length of the capsule is expressed by formula (1) l=ax¢ ............. (I) wherein / is the length of the capsule; a is a multiplying factor which may be from 5to 15; and ¢ is the diameter of the blast hole

14. A method of tamping a blast hole, the method being characterised in that a first slurry component including a fine powdery composition and having a consistency allowing it to be worked into close contact with an explosive charge in the blast hole is provided and a second slurry component including a granular composition is : provided subsequent to the introduction of the first slurry component and on top thereof so as to plug the blast hole.

15. A method of tamping a blast hole, wherein a stemming device of claim 1 is inserted into the blast hole.

: 290.0% [10338 )

16. The method of claim 15, wherein the stemming device is ruptured such that the first component forms a seal around an explosive charge in the blast hole. S

17.Use of stemming device in a blast hole, the stemming device including a stemming material comprising a first slurry component including a fine powdery composition and a second slurry component including a granular composition, the first slurry component and the second slurry component being separate and each being contained in a capsule which is adapted in use to be inserted into a charged blast hole and to be ruptured when located against a charge so as to thereby plug the blast hole in the area immediately towards the open end of the blast hole and immediately adjacent the charge.

18. A stemming device substantially as herein described and exemplified and/or described with reference to the accompanying drawings.

19. A method of tamping a blast hole, substantially as herein described and exemplified and/or described with reference to the accompanying drawings.

20. Use of a stemming device, substantially as herein described and exemplified and/or described with reference to the accompanying drawings. Dated this W™ day of Cn BER SRDS, Patent | Agent for the Applicant