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For drilling and blasting operations industrial explosives are very rarely used in its original form (granular or emulsion). Almost always explosive package operation, that is forming singular cartridges in shell with certain material solidness inside, takes precedence of its usage. This operation is necessary to ensure free transportation of explosives to the work place, storage, stable detonation and continuity of explosive characteristics, minimizing human contact with toxic components of explosives.
Package method depends on the physical state of material. At present in the world the bulk (granulated) explosive are most used. This is due to their not-too-high price, which is often a critical characteristic. For the cartridge formation of this explosive a several methods are used. A material is incurred for pressure to achieve necessary solidness and strength (compaction), and then is wrapped in paper shell. This is particularly dangerous process, which is always carried out without human presence. Compaction requires a cumbersome equipment, permanent monitoring of work tool and it is long enough. Another method of compacting granular explosive materials is usage of screw extruder (e.g. Korostylev machines). It is also particularly dangerous process, besides the additional danger is the formation of dust that settles on the parts of mechanisms, and permanent possibility of pinching the product but this method requires less time than compaction, and easier to automate. For the large cartridge formation (with a diameter over 90 mm) compacting explosive with the vibration is used. But this method gives a lower solidness of cartridges than others, and requires a ready shell of paper or other material.
For molding of plastic explosives extrusion method is used, that is pressing the material through forming bushing necessary form under compression which is created by screw-propeller. The process is particularity dangerous, there is always a possibility of pinching or overconsolidation of product. The method has a relatively high productivity.
In the most of devices for emulsion explosive package the necessary pressure is created by screw-propellers. In view of emulsion explosive insensitivity to mechanical and thermal actions, we can conclude that just emulsion explosive package is the most secure of all these methods and than it is well automated.
Emulsion explosives are fundamentally new mixtures that have high working ability, comparatively maximum safety and environmental safety, opportunity to adjust their detonation characteristics, composition permanence and waterproof.
These qualities have nominated them to the forefront and encourage wide use, especially in irrigated soils.
In Ukraine's mining industry emulsion explosives consumption is increased every year. They are made mostly in bulk form at the place of blasting operations. The use of package emulsion explosive has a place in the quarries remote from the places of emulsion compositions manufacture, and with a small amount of blasting. Package emulsion explosives are used in the combined borehole charges ZARS, they are intended for blasting as the main charge in the manual loading of dry and irrigated wells of any flooding degree in strong, medium, weak rocks and coals, including those prone to ignite in an explosive fragmentation and sulfide ores. They also can be used as intermediate detonators, for detonation reactivation column charge of low-sensitive explosive. Package emulsion explosives can retain their physical and chemical characteristics and explosive properties of a wide temperature range (for emulsolit of +50 to -50 0C).
Since emulsion explosives are the most promising direction in the development of industrial explosives, particular attention is given to features in the work with this type of explosives. Work concern is testing different kinds of shells and evaluation their usability to explosive package, particularly emulsion.
With the increase emulsion explosive usage arised a problem with their package, since all the curent range of industrial explosive package equipment was unsuitable. The investigations of different shells for usage in contact with the explosives would enhancing the capacity of emulsive explosive, which are safer to usage and relatively environmentally safe, and minimize human contact with explosives.
Certain types of shells are used to prevent ignition of methane-air mixture. Inert protective shells are made from powdered or pressed flame arrestors (salts) or aqueous ammonium nitrate solution. The thickness of the protective shall around the explosive cartridge is 4-5 mm. The guard effect of protective shells is mainly reduce to this acting: in detonation of explosive the shall surrounding them absorb 25-30% of the explosion heat and the temperature of gaseous explosion products is diminish. In the process of explosive detonation protective shell disintegrates in extra fine inert dust or in waterlogged fog (if protective shall is liquid), which blends with gaseous explosion products and saturates neighboring mine air with inert material. An additional point is that protective shall limits dispersion of detonation products and burning explosive particles, which contributes more stable detonation expansion in blast.
All these cumulatively acting factors significantly reduce the ignition risk of methane-air and dust-air mixtures. Explosive in a protective shell is advisable to apply in a particularly dangerous of methane faces and, above all, in dummy gates and air gates, which are carried out in fractured rocks. Explosive in a protective shell hasn’t consolidate because consolidate explosive complicates making the primed cartridge. Also, consolidate explosive loose sensitivity to detonation and can burns up.
Protective shells are divided into inert and active. Inert shells don’t contain explosive, active shells along with inert base contain small amounts of nitrate esters. Active shells are represented as a flimsy, but very susceptive to detonation explosive. Therefore in a process of explosion in active shell fuller mist-spraying arise, leading to maximal effect its guard action.
Vacuum syringe COMPO-OPTY 2000-01.
Producer country: Belarus.
This device is designed for filling different shells with adjunct vacuum.
Visual environment of device is on the figure 1.
Main characteristics:
| Parameter | Value |
|---|---|
| Productivity with full speed of displacer screw, shell diameter not less than 80 mm, cartridge length not less than 300 mm, not less than, kg/hr. | 1600 |
| Theoretical productivity (with free discharge of filling material), not less than, kg/hr. | 7500 |
| Hopper capacity, m3 | 0,25 |
| Installed power, kW, not more than | 8,35 |
| length | 1195 |
| width | 1215 |
| height | 1920 |
| Required space, m2 | 1,46 |
| Syringe weight, kg | 580 |
| Ultimate vacuum in system, not less than, MPa | 0,02 |
| Adjusting range of unit dose, g | 100 – 9999 |
| Adjusting range of time gap, s | 0,3 – 9,9 |
| Nominal voltage of a system, V | 400 |
| Supply frequency, hertz | 50 |
| Number of electric motors, pcs. | 2 |
| Main drive motor: type | 5À132Ì6 ÑÓ2 |
| version | IM1081 |
| power, kW | 7,5 |
| rate speed, rpm | 960 |
| Vacuum pump motor: type | SKh 80-2A2 |
| power, kW | 0,75 |
| rate speed, rpm | 2800 |
| Dosing devise motor: type | ÀÈÐ 80Â6 Ó3 |
| version | IM3081 |
| power, kW | 1,1 |
| rate speed, rpm | 920 |
| Average full operation time, yrs | 10 |
| Price, $ | 52 000 |
For realization testing vacuum syringe for aptitude to package explosive effort was conducted with a none-explosive blend. Physical-mechanical properties of this blend is similar of properties of emulsion explosive II class “Gramix”. The substance is represented itself an type “water in oil” emulsion. In this emulsion drops of attenuated oxidizing agent are surrounded by water-shutoff fuel film, the glass microspheres are added as a sensitizer. Simulative blend consist of oxidant solution, which was thickened with Alamo-CMC with adding chemical chalk as a solid phase. Components proportion gives the viscosity, specific gravity and abrasive properties which are conform to “Gramix”. Ten kg of blend was prepared for the test.
For package emulsion explosives usage vacuum is not necessary because gaseous impurities of air contribute of detonation in substance.
The test blend was loaded in receiving hopper of COMPO-OPTY 2000-01, polymeric sleeve diameter of 36 mm was dressed on the syringe head. When system was programmed to produce cartridges 300 g weight variation of mass was 5 g, when system was programmed on cartridges 200 g weight variation was 3 g. When device was programming to manufacture defined length cartridges, the size of cartridges was adhered to millimeter. While testing the minimal cartridge mass was 2 g, the maximal mass was 600 g. The shell filling was realized in a period of 0.2 sec regardless of defined cartridge weight.
Also, experiments by filling the shells with water were conducted to test hermiticity of embedment cartridges ends. During over 1.5 month cartridges filled with water were stored and the flowage of the product was absent, shell stayed airproof.
For reasons of safety of filling shells with emulsion explosives process some modifications were implanted in vacuum syringe: the equipment was made in the intrinsically safe design, screws distance were increased to 0.25 mm, the screws were manufactured simultaneously on numerically controlled machine tool, making their wearing process is equalized, so under all conditions surface contact will absent.
Vacuum syringe COMPO-OPTY 2000-01 successfully passed the test for aptitude to package emulsion explosive. Currently this equipment is installed at Donetsk state plant of chemical goods.
In the following I make plans to analyse different shells and find a optimal option.
Currently, work is under construction, completion is planning for December 2010. Full text of the work can be obtained from the scientific
adviser or the author.