WO2007033387A1

WO2007033387A1 - Shock tube centering device

Info

Publication number: WO2007033387A1
Application number: PCT/ZA2005/000156
Authority: WO
Inventors: Marianna Suzanne Van Rensburg
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-27
Filing date: 2005-10-14
Publication date: 2007-03-22
Anticipated expiration: 2007-11-27

Abstract

This inventions main object is to increase the velocity of detonation of the main explosives charge and to help contain the detonation pressure in the blast hole for longer period. It also protects the energy lines feeding the detonator when going through the center of the device, ensuring that these feeding lines are not damaged next to the sidewalls when passing by this device.

Description

Shock Tube Centering Device

Introduction and background to the invention:

This invention relates to explosives in drilled blast holes. In mining operations, especially opencast operations, a production block is identified to be drilled and blasted. The mine try to fragment the rock or ore into the most economical size which will optimize the loading, hauling, crushing, screening, purification and add value to the selling price.

The production block has a definite bench height. The blast holes are drilled in a blasting pattern. The hole diameter chosen depends on the drilling machine available or fragmentation required and bench height.

The holes are drilled in rows and the distance between the holes is referred to the spacing and the distance between the rows are referred to as the burden. When the previous face has been loaded out a free face is created before the first row of blast holes. The blast holes are normally drilled deeper than the required floor level to create an even floor on which the loading equipment and hauling equipment will move and on which the drilling machines will stand to drill the deeper mining bench.

The blast holes are loaded with a chosen type of explosives. Beforehand a booster charge of about 40Og of TNT/Pentolite with a detonator in it is placed at the bottom of the drilled hole. The main explosives charge is pumped or augured into the blast hole. The top portion of the blast hole is left uncharged and will be filled with an economical stemming material.

IKg of explosives generates about 1000 liters of gas in milliseconds during the detonation process. The detonation process has a definite velocity of detonation starting at the booster charge and moving upward away from the booster charge. This velocity of detonation (VOD) is between 3000 and 5000 m/s. The detonation pressure created in the blast hole is a function of the VOD. The higher the VOD the higher the detonation pressure. In return it will ensure a smaller fragmentation size of the rock to be blasted.

The stemming length and type of stemming material will contain the high detonation pressure more effectively to enable the gas energy of the explosives to work more effectively onto the rock to be blasted.

The booster charge must be placed in the center of the explosives column to ensure better initiation of the main charge. Some booster manufacturers manufacture a type of directional charge which must be placed symmetrical and facing the main explosives charge right in the middle or center of the drilled hole.

The detonator which is placed in the booster charge hangs from a plastic shock tube line or electrical wire which will supply energy to spark and detonate the detonator at the required time.

This invention has a hole through the center of the material placed in the blast hole below the stemming material. The booster charge will hang from this inventions center hole and therefore the booster will be able to carry over a more directional Shockwave onto the main explosives charge ensuring a higher velocity of detonation, creating more explosives energy.

The material of this invention is taper shaped towards the top and forms a natural plug in the stemming area because stemming material will wedge between this invention and the sidewalls of the blast hole during the detonation process. This wedging action protects the stemming being ejected from the blast hole and will contain the high detonation pressure longer in the blast hole ensuring that more explosives energy is transferred into the rock to be fragmented.

This invention is supplied with a cover bag sitting around it with the open side facing the top of the blast hole. This cover bag will catch all stemming material ensuring that the top of the main explosives charge will not be penetrated by stemming material which will dilute the explosives in this area and will cause a lower VOD in the diluted area.

This invention will create an air gap between the invention and the top of the main explosives charge. This invention can be placed at any required depth in the blast hole. It can hang from a suitable rope on a stick or pipe bridging the top of the blast hole.

Object of this invention.

This inventions main object is to increase the velocity of detonation of the main explosives charge and to help contain the detonation pressure in the blast hole for a longer period. It also protects the energy lines feeding the detonator when going through the center of the device, ensuring that these feeding lines are not damaged next to the sidewalls when passing by this device.

Summary of this invention.

This invention can be made out of any suitable type of material for example a strong and light concrete. It has a tapered shape towards the top ensuring that any stemming material will help to wedge against this invention and the sidewalls when it is pushed upwards during the detonation process of the main charge. This invention is slightly smaller than the drilled hole. It has a definite center hole just big enough for the detonator feeding lines to pass through. This invention can be placed at various depths in the blast hole with any suitable method. It can hang from a rope which is fixed to this device and is tied at the top to a stick or pipe bridging the hole. It has a cover bag which will catch stemming material ensuring that this material does not pass this invention to penetrate and dilute the main explosives charge below. This cover bag can be made out of any type of suitable material. The dimensions of this invention is not fixed but will be altered to ensure the required rock fragmentation order size required.

Brief description of the drawings.

This invention will now be described further by way of a non-limiting example with reference to the accompanying drawings wherein: Figure 1: is a side view of this invention and the cover bag and suspension line and bridging stick

Figure 2; is a three dimensional view of this invention. Figure 3: is a side view of this invention placed in a blast hole filled with explosives and stemmed above this invention.

Description of a preferred embodiment of this invention.

Referring to figure 3 the invention can be placed at an optimized height in the blast hole for a required fragmentation order size. It can be placed on top of the main explosives charge or above the main explosives charge creating a natural air gap between this device and the main explosives charge. It can be used with or without a cover bag. It has a definite taper shape and can be cast in a holding container such as a plastic bottle with a taper shape. It will form a resistance plug when the stemming material wedges against the plug and the sidewalls during the detonation process as this invention is pushed upwards into the stemming material.

It has a definite hole through the center of this invention which will protect the energy lines feeding the detonator when passing through. The booster charge will be aligned through this center hole to hang in the center of the main explosives charge.

Claims

1. This invention will centre shock tubes and electrical or any energy lines feeding the detonator as the pass through the center hole. The booster charge will hang from the centre of this device and will be pulled upwards to hang in the middle of the main explosives charge. This will ensure a higher velocity of detonation and creating a higher detonation pressure in the blast hole optimizing the explosives energy output.

2. The center hole protects all energy feeding lines passing through this invention feeding the detonator. This is unique to this invention.

3. The taper shape will ensure that it will create a definite wedge plug when stemming material is wedged between this invention and the side walls of the blast hole.

4. This invention will help protect the stemming from ejection due to the abovementioned wedging effect and the type of material used to create the required resistance plug. The tamping effect can be controlled by altering the dimensions and type of material used.

5. This invention will reduce air blast and will make blasting more environmental friendly.

6. This invention will help to control the required fragmentation order size of the mining operation.

7. This invention will help to control fly rock.

8. This invention will help improve loading rates of shovels, reduce wear on haul trucks, reduce crushing costs and will help to reduce the total mining cost.

9. This invention will help control air pollution due to less dust to be created during the blast.

lO.This invention helps to prevent stemming material entering and diluting the top of the main explosives charge.

11. This invention can save on the amount of explosives used.

12.This invention will ensure improved floor conditions in mining operations which will lower the total cost of mining.

13.This invention will increase the amount of diamonds released when diamond ore is blasted.

14. This invention will decrease the amount of oversize rocks in the stemming area due to creating a shorter stemming column height and ensuring that more explosives energy is entering the stemming area.