Araos. 2002. Influence of Different Parameters in the VoD of Gasses Bulk Explosives

Influence of Different Parameters in the VOD of Gassed Bulk Exrdosives.

Miguel Araos’.Chemist.

Enaex SA - R&D laboratory,Calama, Chile.

The aim of this study was to understand clearly how VOD of emulsion-based gassedexplosives is influenced by parameters such as nitrate salt composition in the oxidizingphase, product density, blend composition, gassing rate, type of sensitization, etc. Alsosome VOD testing was performed on watergel-based gassed explosives in order tocompare the results with those obtained for emulsions. VOD measurements wereconducted in the surface blasting facility at the Research and Development laboratory ofENAEX SA (Calama, Chile).

Despite the fact that the influences of some parameters on VOD of emulsion-basedgassed explosives are easily predicted, there was found to be an unexpected correlation.Although it is commonly believed that the VOD of gassed explosives depends on thedensity, this study found that the VOD depends on the both size and the amount of gasbubbles incorporated into the product as well as type of sensitisation, regardless of whetherthe explosive was straight emulsion or a blend. Density is just a consequence of theincorporation of voids into the explosive.

Future work in this area may examine variation of other parameters, in order toobtain a greater knowledge of detonation properties and therefore to design more efficientexplosives.

‘Current ly Development Chemist at Mt. Thodey Technical Centre, Dyne Nobel Austral ia (email:[email protected])

1 of 14Copyright © 2002 International Society of Explosives Engineers

2002G Volume 2 - Influence of Different Parameters in the VOD of Gassed Bulk Explosives - P 293

1.0 Introduction. It has been more than 3 decades since bulk commercial explosives were developed

and introduced into mine operations1. During their first phase, they were sensitized either by adding high explosives, because of war surplus, or adding fine metal powder as well as organic agents. Currently, bulk commercial explosives are sensitized and have their density controlled through the voids in the product. In most cases small bubbles of air or other gas are required in bulk explosives so that the product will properly detonate.

The bubbles introduced can noticeably enhance sensitiveness according to the hot

spot theory2,3 on the detonation of explosives. Gas bubbles are adiabatically compressed by the mechanical energy transmitted by detonation wave, promoting a transformation of that mechanical energy into thermal energy in the collapsed gas bubbles. This compression forms hot spots in the explosive, and because of the relatively higher temperature generated in that hot spot in a very short time, it is assumed that the explosive reaction is generated at the hot spot sites followed by reaction in the surrounding material.

Several methods have been described and are currently used to create voids in

explosives, eg. mechanical aeration4,5,6, solids containing entrapped gas7 and chemical gassing. The latter method can be performed using organic salts (azo-compounds8,9), inorganic salts (nitrites10,11, carbonates12) or liquids (hydrogen peroxide / KI13 or hydrogen peroxide / MnO2

14 system). Nonetheless, the usage of N2 from nitrite decomposition to sensitize bulk commercial explosives, which dates back 30 � 35 years in water based composition explosives, represents the most reliable, low cost, simple method to control in field and environmentally attractive alternative to solid density control addition or any other type of sensitization.

Although many investigations have been carried out for sensitized explosives, those

primarily refer to determination of shock and bubble energy in commercial bulk explosives15,16 or desensitization because of pressure in packaged explosives17,18. Other evaluations have been done in bulk products but by using a lead block compression test19. However none of the above mentioned studies have evaluated VOD in gassed commercial bulk explosives in medium diameter when other parameters are varied. Thus, the primary goal of this work was to determine the influence of the parameter listed below in the VOD of gassed bulk explosives.

• Influence of oxidizing phase composition. • Influence of gassing rate. • Influence of different density modifiers. • Influence of product temperature. • Influence of blend composition.

2.0 Experimental work

Tests were carried out under unconfined conditions, i.e. 6-inch in diameter (15,2 cm)

and 1-m long cardboard pipe unless otherwise specified. The primers consisted of a 450 g APDTM booster, fuse cap and safety fuse. Detonation rates of explosive were measured with a point-to-point-based system. Distance from booster to first target is around 5 � 6



diameters to allow a steady VOD in the product. Weight of charges varied from 15 to 23 kg. Figure 1 shows the set up of the VOD measurement system.

Most of the VOD testing was carried out on both straight emulsion and emulsion /

ANFO blends - 70 / 30. Formulae of base emulsions are shown in table 1. Notation 100/0, 86/14 and 70/30 refers to the AN/SN composition in the oxidizing phase. ANFO with a density of 0,74 g/ml was utilized. Explosives were gassed to different densities by using NaNO2-based technology. The density range studied was between 0.85 � 1.39 g/ml. Densities lower than 0.85 g/ml were not evaluated because the column of explosive tends to collapse. Gassing time was in a range of 15 - 20 minutes and temperature of the product was 20º (± 3ºC) unless otherwise specified. Each density point on the graphs is the average of three detonations.

3.0 Results. 3.1 Influence of oxidiser phase composition in the VOD.

Most emulsion blasting agents use NH4NO3 (AN) as the sole or principal salt. In certain locations, as in Chile, SN is more abundant and therefore less expensive to use. At the same time, SN is used to lower the crystallization point of AN-based oxidizing phases, which means that stability of emulsion explosives is improved. However, it is generally considered that SN is a less effective oxidizer than AN and as such would tend to desensitize the composition.

This study concentrated on the effect that SN has on the VOD of gassed emulsion

explosives. Table 1 shows the different compositions of oxidizing phases used in this trial. Oxygen balance of fuel phase was considered to be �3.30 (instead of using the common value referred by literature �3,48) because of the diesel � emulsifier ratio. Results for VOD on straight emulsion are shown in figure 2. Products with densities higher than 1.30 g/ml have to be considered poorly gassed (with nearly no voids present).

All samples, regardless of composition, exhibit a peak in the zone 1.10 � 1.20 g/ml. Emulsion with just AN in the oxidizer phase reached the highest VOD in the explored range. It was observed that the higher the amount of SN in the oxidizing solution, the lower the VOD in the investigated range and that dissimilarity of both curves is kept in the entire range studied. 3.2 Influence of gassing rate in the VOD.

Due to mine constraints, field operations may require a fast gassing rate, namely in less than 10 minutes, in order to get the required density. In this stage of the study it was intended to explore any eventual difference in VOD that might occur when explosives are gassed at different rate. Rapidly gassed explosives were ready to detonate at the required density in less than 5 minutes and slow gassing tests took more than 25 minutes to reach the expected density. Emulsion utilized was Enaex 100/0 (see table 1).

As seen in figure 3, emulsion that was gassed more rapidly exhibits a slightly higher

VOD at lower density values when compared against low gassing rate emulsion. Both products exhibit a VOD peak at the same density.



3.3 Influence of different density modifiers.

S. Nie20 studied detonation properties of emulsion explosives when using different sensitiser. However that investigation concentrated on the influence of pressure in desensitization of small diameter explosives and in a narrow range of density. T. Okamoto21 also studied the influence of different types of sensitization and the influence of their particle size on the VOD of watergels, but no range of densities are specified in those results.

Thus, in order to relate the changes in VOD due to the use of different type of

sensitization in a larger diameter, a study was carried out where 3 sensitizers were incorporated in straight emulsion and VOD was measured at different densities. These sensitizers were chemical gassing, solid sensitization (GMB K-1 from 3M) and polystyrene beads (PE beads with an average size of 2 mm). Emulsion utilized was Enaex � 86/14.

Figure 4 shows that depending on the sensitization utilized the VOD peak is reached at different densities. Furthermore, for PE beads, the curve is nearly flat and the peak is not as distinct. Also the VOD is low for the PE beads product. No significant difference was seen for maximum VOD values with chemical gassing Vs solid sensitization. 3.4 Influence of product temperature. Enaex operation sites are located at 4000 meters above sea level, which means that during winter time temperature can drop to values close to �10 / �20ºC and explosives have to detonate under such conditions. In contrast, emulsion can arrive at temperatures above 35ºC when those sites are not far away from manufacturing plants. Thus, the above mentioned facts instigated this study, in order to clearly assess the impact of temperature on the VOD of gassed explosives. Emulsion evaluated was Enaex 86/14. For the 35ºC test, emulsion was transported to the Enaex blasting site immediately after manufacturing. During transport, the emulsion temperature dropped from 70ºC to 35 � 40ºC. In the case of the low temperature test, emulsion was stored overnight in a freezer at a temperature of �15º. The following day, charges were transported, fixed and detonated. The temperature increased to 0ºC approximately. Product at normal temperature (20ºC) was also detonated in order to compare results.

Figure 5 shows the correlation between emulsion temperature and VOD. No significant differences were evident. 3.6 Influence of blend composition. Most mine operations use emulsion blends / ANFO due to the presence of wet holes in the pattern or for powder factor. This aspect of the study focused on assessing the correlation between blend composition and VOD. Emulsion types 100/0 and 86/14 were used. The percentage of ANFO incorporated into the emulsion was 20 and 40%. Initial density of these products (ungassed) did not vary significantly in the range of blends studied (around 1.33 and 1.35 g/ml for AN- and AN/SN-emulsion based blends) . Results are depicted in figures 6a and 6b. It was observed that emulsion 100/0 shows a decreased VOD when incorporating ANFO and, in contrast emulsion 86/14 shows an increased VOD. The VOD peak remained in the range 1.10 � 1.20 g/ml for both tests.



3.7 VOD in Watergel products.

Enaex is a licensee for Dynolite22, which is a watergel-based product that can be used at densities of 0.5 g/ml or lower. The initial density of this product (as a blend) is in the range of 1.20 � 1.23 g/ml. Initially, this study was intended to investigate VOD at density values lower than 0.85 g/ml (limit of gassed emulsion product). Figure 7 shows VOD values for a watergel / ANFO blend � 70 / 30 and 30 / 70.

It was observed that product still detonates at densities of 0.3 g/ml and again a peak in curve VOD-density was evident, regardless if the product was 70 / 30 or 30/70. However that peak occurs at lower values of density when compared with previous tests. Furthermore, a disparity is perceived amid both curves, because blend 30/70 showed a higher VOD in the entire range.

4.0 Discussion The results from the studies show that there is a definite trend for a peak to be

observed in the zone 1.10 � 1.20 g/ml, when density is plotted Vs VOD. These results correlate with work by Conrad5, which showed a similar trend in a system watergel / mechanical aeration. Influence of oxidiser phase composition in the VOD.

Curve density VOD for both AN and AN/SN-based emulsions exhibit a peak at the same density range. However, the presence of SN in emulsions resulted in a lower VOD despite the fact that SN-based emulsion can theoretically release more energy per mass unit. It is suggested that energy provided by SN might be diverted toward bubble energy instead of shock energy, as Al does23, thus changing the shock-to-bubble energy ratio16. However, it might also be implied that the activation energy (initiation threshold) for SN is by far greater than that for AN (Lead Azide, PETN, HMX have a lower activation energy threshold). This would mean that as long as the detonation threshold of SN in not surpassed, SN just absorbs energy, namely energy is wasted in heating SN rather than improving the reaction at the detonation front. Therefore, the low VOD observed in SN-based emulsions would be an issue of activation energy rather than energy content. Clearly, no matter what the reason is, most of the energy was primarily provided by AN detonation, and on the other hand, SN lowers product VOD.

Influence of gassing rate in the VOD.

With respect to both maximum VOD and VOD peak, no significant differences were observed between products gassed either fast or slow in the range 1.10 � 1.33 g/ml. The small difference observed between both curves can be attributed to the margin of error of the measurement equipment. Nonetheless, at lower density values a clear split of curves is seen. This fact can be attributed to the size of bubbles generated by a fast gassing rate, which promotes coalescence and a larger size of them at densities at or below 1.00 g/ml. The larger size assists gas bubbles to achieve a higher temperature during collapse (see below for further explanation) rendering products more sensitive.

However, it must be mentioned that, although there is no difference in the range 1,0

g/ml and greater amid low and fast gassing rates, the disadvantage of the latter method in



the field is the risk that the product will gas either in truck pipes or parts of the truck that are open to air. Consequently a fast gassing rate must be prevented in order to avoid a detonation whilst pumping explosives through pipes. Experience in this R&D department has shown that a straight emulsion chemically gassed is cap sensitive in the range 1.10 � 1.20 g/ml.

Influence of different density modifiers on VOD.

In all tests performed, a VOD peak was observed in the plot density vs VOD. The position of the peak was found to fluctuate according to the type of sensitization (refer to figure 4). When chemical gassing is utilized in combination with emulsion, the peak is situated between 1.10 � 1.20 g/ml. If emulsion is used with solid sensitization such as GMB K-1, the peak moves to higher values of density, i.e., 1.25 � 1.31 g/ml. The latter agrees with previous work performed on solid sensitized emulsion-based packaged explosives24,25. Furthermore, if the initial density of the explosive is lower than 1.25 g/ml (as in Dynolite blend products), the VOD peak will move to lower values of density, as observed in figure 7. From these observations, it can be inferred that the VOD value and VOD peak observed depends on the following parameters:

• Surface exposed to �hot spots� • Tº (ºC) reached for �hot spot� during detonation wave compression. • Initial density of explosive. • Dilution of explosive imparted by voids • Material that sensitizer is made from. • Characteristics of hot spot during compression. Surface exposed to �hot spots�. This parameter is closely related to size of voids and obviously to solid sensitization (GMB), as the smaller the void size the higher the surface of explosive exposed to the hot spot. This was already mentioned by Y. Hirosaki et al26. Table 2 shows a comparison between GMB and chemical gassing with regard to the surface of explosive exposed to the hot spot. It is clearly observed in table 2 that the amount of GMB voids present in a determined amount of explosive is by far greater (almost 3 orders of magnitude) than the amount of any other sensitizer at higher densities (1.25 g/ml and up). To be more exact, just a small percentage of GMB in volume is necessary for the VOD to reach the peak.

When the detonation wave compresses voids, the amount of them present facilitates

the process of detonation due to the total surface exposed to hot spots. That means that detonation depends largely on the specific surface voids. For chemical gassing and PE beads sensitisation, the exposed area is by far less. In the case of PE beads, not many hot spots can be included in the explosive, because of the PE beads size (> 2mm), thus lowering the surface of contact for that phenomenon to occur.

Tº reached for �hot spot� during detonation wave compression. This parameter can be applied to any type of sensitization, but it influences chemical gassing more significantly than either GMB or PE beads-based sensitization. According to the ideal gas law, the temperature of an ideal gas is given by the equation PV=nRT. Thus, bigger initial sizes of gas bubbles will reach a higher temperature during compression, and as a result, VOD and detonation properties will be influenced. In that respect, Leiper and Cooper27 state that hot



spot temperature can be as high as 2460k at 8.75% of voidage and rising to 2700K at 30.5% voidage.

For chemical gassing, where average size of gas bubbles is in the range of 300 � 1000 µm (0,03 � 0.1 cm, when density is in the range 1.00 � 1.25 g/ml), a VOD peak is achieved at values of density between 1.10 � 1.20 g/ml. If compared the gas bubble-to-GMB ratio, gas bubbles are 5 � 10x larger in diameter (and 81 � 1000 times in volume), which promotes a higher Tº inside them during adiabatic compression. That high temperature would facilitate the propagation of the detonation front in the explosive. Conversely, GMB do not have the alternative of reaching a temperature higher than chemically gassed bubbles do. This means that for GMB sensitization the surface of explosive exposed to hot spots is more important than temperature.

Initial density of explosive. It was noticed that, when chemical gassing is used, the VOD peak is achieved at a density 0.15 � 0.20 units lower than the initial density (or �natural density�) of the explosive. Thus, an AN-based emulsion, whose initial density is 1.33 g/ml at 20ºC, exhibits a VOD peak at 1.10 � 1.20 ml. For Dynolite-based products whose initial density is around 1.20 g/ml (for blend 70/30) and 1,05 g/ml for blend 30/70, the VOD peak occurs at a density around 0.85 � 1.00 g/ml (see figure 7). Also, it can be estimated that for a CN-based emulsion, whose density might be around 1.45 g/ml, its VOD peak will be achieved in the range of 1.25 � 1.30 g/ml. In contrast, if solid sensitization is used, the VOD peak can locate to densities 0.05 � 0.15 units lower than the initial density (see figure 4).

Dilution effect promoted by voids. This effect was already mentioned by Alynova et al25, and it is applicable to all types of sensitization. Once the VOD peak is achieved, a dilution effect starts influencing VOD, as the explosive is separated by larger gaps when density lowers. This fact causes difficulties with the propagation of the detonation waves. This effect is more severe in GMB sensitized product as a small percentage by weight means a higher dilution in the explosive. Material of sensitizer. As noted in figure 4, the VOD peak moves along the curve density � VOD as a result of sensitization utilized. For instance, addition of PE beads into the explosive was not found to influence VOD in the range of densities studied, as the curve remains nearly flat. It is supposed that it happens because the material which PE beads are made from does not allow a fast heat transfer from the hot spots to the surface of explosive after compression by the detonation wave. Alternatively, compression that PE beads may undergo is also poor owing to mechanical properties of this type of sensitization. As a result, both facts would promote the undistinguishable peak noticed in figure 4. Low heat conductivity of material also affects GMB-based sensitization, as the material they are made from does not conduct heat quickly, despite GMB being broken (because of shock compression) heat generated inside the void is in direct contact with emulsion. In contrast, chemically generated bubbles are not affected by any of the factors mentioned above.

Characteristics of hot spot during compression. It is acknowledged that knowing the exact average size of voids at which detonation occurs in the explosive will help to understand this phenomenon much better. It is believed that the detonation would occur when a specific size of voids is reached under compression. This means that GMB, with an average size in the range of 50 - 150 µm, can be compressed to 1 µm or slightly less (GMB walls have to be considered incompressible) when detonation occurs. This situation also



applies to PE beads, whose material is not as compressible as GMB or gas bubbles. In the case of chemically generated gas bubbles, whose average size is bigger (300 � 1000 µm) the minimum possible size during compression is by far less than the size reached for GMB, as there is no inferior limit (no walls surround gas bubbles).

It can also be suggested that detonation might occur at a predetermined size (detonation would occur when voids reach a size of 5 µm) regardless of the material that the sensitizer is made from. However, no facts can be provided so far to support this theory. Influence of temperature in VOD of product. Previous studies have been conducted on this parameter28. These tests were made in small diameter explosives and a low temperature, and it was shown that only an extremely low temperature would effect explosive detonation (-35ºC).

In our tests, no significant decreasing VOD was observed in straight emulsion when

detonation occurred in the range of temperature 0º / 35 ºC. This can be attributed to the emulsion temperature during detonation (>1000ºC), which is high if compared with 0 or 35ºC. In addition, it can be considered that at 0ºC and lower, droplets in emulsion are still in a �melt� state rather than frozen. If the latter happens, VOD may be eventually influenced due to the heat of fusion involved. VOD in Dynolite products. As explained previously, the shift in the VOD peak, noted in figure 7, resulted from the initial density of the Dynolite blends. The difference between curves was because Dynolite/ANFO � 30/70 contains more AN than blend 70/30, which is reflected in VOD values. 5.0 Conclusions

In order to improve the blasting performance of gassed bulk explosives, it is necessary to understand clearly their detonation characteristics. VOD in bulk explosives can be altered extensively by varying the type of sensitization, composition of nitrate salts in the oxidizing phase, density, etc. At the same time, VOD exhibits a peak in curve density vs VOD, which is in the range of 1.10 � 1.20 g/ml for emulsion products chemically gassed. That VOD peak depends on the amount of voids, distribution size and total area of voids, type of voids, material that voids are made from, etc. Factors that do not alter VOD of straight emulsion are PE beads-based sensitization and Tº of product in the range of 0 � 35ºC.

From the results obtained, it can be suggested that for soft rock, a combination of

SN/low-density gassed emulsion or SN/PE beads may be adequate. In the case of hard rock, solid sensitization might be the appropriate choice, as a high VOD can be achieved while still maintaining a high density in the product (if compared with chemical gassing).

This study can also assist in improving gassing performed by trucks, as it has to be

considered that the tests conducted were only in a column of explosive of 1 mt. in length. A field situation will differ due to both diameter and length of borehole are bigger, which causes an increase of density in chemically gassed explosives at the bottom of borehole owing to hydrodynamic pressure, which evidently changes the VOD. Therefore, trucks should be designed to deliver trace chemicals at different ratios whilst loading a borehole to



maintain a consistent density along the column of explosive. If improvements are made in trucks, chemical gassing will provide more alternatives and compete more robustly with solid sensitisation regarding to VOD.

Most of the VOD�s measured were in straight emulsion and blend 70/30. Future work

will involve measuring VOD in a wide range of blends (50/50), using different types of salts in the oxidizing phase and using different average size solid sensitization, confinement, a more extensive range of density to find out at what density emulsion will no longer detonate, etc.

Finally, it is thought that there are still many physical aspects yet to be fully

understood regarding the detonation properties of explosives using different sensitization. Once those physical aspects are understood, a mining engineer will have an extra tool to be applied in blasting science

Acknowledgements. The author expresses his appreciation to Dickson Lopez and Oscar Navarro (R&D

technicians) for their cooperation and assistance in completing the tests and collecting data. Also the help of Fernando Olivares, Herman Pizarro and Heriberto Gonzales is also acknowledged.

The permission of Enaex management to publish this work through the Technical

Manager, C. Orlandi, is acknowledged with thanks.

References 1 Hopler, R.B. �History of the development and use of bulk loaded explosives, from

black powder to emulsions�, Proceedings of the 19th Conference on Explosives and Blasting Technique, San Diego, California, January 31 � February 4, 1993. ISEE. pp. 177 � 197.

2 Engineering design Handbook, Principle of Explosive Behavior. US Army Material Command, AMC Pamphlet 706-180, p 10.15 � 10.18; 11.13 � 11.23.

3 M. Cook, The Science of Industrial Explosives, IRECO Chemicals, Graphic Service & Supply, Inc. Salt Lake city, UTAH.1974. pp 294 � 299.

4 M. Cook; �Thickened aqueous explosive composition containing entrapped gas�; US Patent 3382117 (1968).

5 K.L. Conrad; �Method of controlling density in gas-sensitized aqueous explosives�; US Patent 3642547 (1972).

6 Fremaux at al; �Inert paste of the nitrate-fuel type, explosive product obtained therefrom by the incorporation of air and processes of manufacture thereof�; US Patent 4564404 (1986).

7 J.H. Owen; �Emulsion-type explosive composition and method for the preparation thereof�; US Patent 4287010 (1981).

8 Bhattacharyya et al; �Water-in-oil emulsion explosive and a method for the preparation of the same�; US Patent 4409044 (1983).

9 Vatipalli et al: �Method of manufacture of emulsion explosives�; US Patent 6027588 (2000).



10 A.A. Albert; �Gelled aqueous slurry explosive composition containing an inorganic nitrite�; US Patent 3390031 (1968)

11 D.W. Prest; �Chemical foaming of emulsion explosive composition�; US Patent 4875951 (1989).

12 J.D. Ferguson and R.B. Hopler; �Aerated explosive composition�; US Patent 3288658 (1966).

13 K.S. Mortensen and L. Udy; �Column of blasting agent of controlled density�; US Patent 3617401 (1971).

14 C.M. Lownds; �Emulsified gassing agent containing hydrogen peroxide and methods for their use�; US Patent 5397399 (1995).

15 G.R. Eck, O. Machacek; �Underwater energy measurements for aluminized and non-aluminized emulsion and watergel type commercial explosives�. Proceedings of the 6th Annual Symposium on Explosives and Blasting Research, Orlando, Florida, February 8 � 9, 1990. ISEE. pp 43 � 65.

16 A.R. Cameron, A.C. Torrance; �The underwater evaluation of the performance of bulk commercial explosives�. Proceedings of the 6th Annual Symposium on Explosives and Blasting Research, Orlando, Florida, February 8 � 9, 1990. ISEE. pp 27 - 41.

17 Mohanty, R. Deshaies; �Pressure effects on density of small diameter explosives�. Proceedings of the 5th Annual Symposium on Explosives and Blasting Research, New Orleans, Louisiana, USA. February 8 � 9, 1989. ISEE, pp 93 � 107.

18 S. Nie.; �Dead-pressing phenomenon in emulsion explosives�; Proceedings of the 9th Annual Symposium on Explosives and Blasting Research, Las Vegas, Nevada, January 31 � February 4, 1993. ISEE. pp 1 � 10.

19 R.R. Rollins, R.W. Givens, G.S. Williams. �Emulsion comparison test�. Proceedings of the 6th Annual Symposium on Explosives and Blasting Research, Orlando, Florida, February 8 � 9, 1990. ISEE. pp 1 � 14.

20 S. Nie, �Pressure desensitization of a gassed explosive in comparison with microballoons sensitized emulsion explosive�. Proceedings of the 13th Annual Symposium on Explosives and Blasting Research, Las Vegas, Nevada, USA, February 2 � 5, 1997. ISEE. pp 161 � 172.

21 T. Okamoto, S. Sato, T. Sunagawa. �High performance watergel explosives�. Proceedings of the International Symposium on Pyrotechnic and Explosives. China Academic publishers, Beijing, China. October 12 � 15, 1987. pp 313 � 317.

22 D. Cranney; �Low density watergel explosive composition�; US Patent 5490887 (1996).

23 K. Kurokawa, K. Hashimoto, M. Kawamura, Y. Kato, �Correlation between vibration and performances of explosives�, Proceedings of the 7th Annual Symposium on Explosives and Blasting Research, Las Vegas, Nevada, USA, February 6 - 7, 1991. ISEE, Cleveland, Ohio, pp. 219 - 228.

24 Y.V. Alynova, V.E. Amikov, D.N. Kondikrov. �Determination of VOD in emulsion explosives�. 20th International Pyrotechnic Seminar, Colorado Springs, Colorado, USA, July 25-29, 1994. pp 11 � 30.

25 W. Xuguang; �Emulsion explosives�; Metallurgical Industry Press, Beijing, China. 1994, pp 230 � 234.

26 Y. Hirosaki, S. Tanaka, Y. Kato, S. Itoh; �Detonation behavior of emulsion explosives�. Proceedings of the 26th Annual Symposium on Explosives and Blasting Technique, Anaheim, California, February 13 � 16, 2000. ISEE, Cleveland, Ohio, pp. 243 - 252.



27 G.A. Leiper and J. Cooper. �Effect of voidage and void size on the detonation of aerated liquids�. 11th International Detonation Symposium, Snowmass, Colorado, USA. August 31 � September 4, 1998. pp 378 � 383.

28 G.O. Reddy, F.P. Beitel. �Effect of low temperature on the detonation velocity and sensitivity of water-in-oil emulsion explosives�. Unknown source.

Appendix.

Figure 1. VOD measurement system.

Table 1. Composition of emulsions.

Name of product 100/0 88/14 70/30 Composition oxidiser phase NH4NO3 (%) 75.2 64.8 52.6 NaNO3 (%) --- 10.4 22.6 H2O (%) 16.5 16.5 16.5 Catalyst (%) 0.30 0.3 0.30 Fuel phase Diesel 6.5 6.5 6.5 Emulsifier 1.5 1.5 1.5 Parameters. Ratio AN / SN 100 / 0 86 / 14 70 / 30 Density (g/ml) at 20ºC 1.33 1.39 1.41 Ratio Oxidiser / Fuel 92 / 8 92 / 8 92 / 8 Energy (KJ/Kg) 3087.7 3196.7 3248.7 OB -11.7 -7.7 -5.7

100 cm

15,2 cm

Cardboard tubePrimer

Targets

Cables

To instrument

Explosive



Figure 2. Influence of SN content in VOD of straight emulsion.

Figure 3. Influence of gassing rate upon VOD in straight emulsion.

Figure 4. Influence of different sensitization in the VOD of straight emulsion.

2000

3000

4000

5000

6000

0.80 0.90 1.00 1.10 1.20 1.30 1.40Density (g/ml)

VOD (ms)

100/086/1470/30

2000

3000

4000

5000

6000

0.80 0.90 1.00 1.10 1.20 1.30Density (g/ml)

VOD (ms)

Fastslow

2000

3000

4000

5000

0.8 0.9 1 1.1 1.2 1.3 1.4Density (g/ml)

VOD (ms)

Chem gassingGMB K-1PE Beads



Figure 5. Correlation between emulsion temperature and VOD.

Figure 6a. Influence of ANFO in the VOD of different blends (emulsion Enaex 100/0).

Figure 6b. Influence of ANFO in the VOD of different blends (emulsion Enaex 86/14).

2000

3000

4000

5000

6000

0.80 0.90 1.00 1.10 1.20 1.30 1.40Density (g/ml)

VOD (ms)

0° C20°C35°C

2000

3000

4000

5000

6000

0.8 0.9 1 1.1 1.2 1.3 1.4Density (g/ml)

VOD (m/s)

0% ANFO (straight emulsion)20% ANFO40% ANFO

2000

3000

4000

5000

6000

0.80 0.90 1.00 1.10 1.20 1.30 1.40Density (g/ml)

VOD (m/s) 40% ANFO20% ANFO 0% ANFO (straight emulsion)



Figure 7. VOD in Dynolite blends.

Table 2. Comparison between different sensitization methods. Chemical

gassing GMB K-1 PE Beads

Initial density (g/ml) 1.33 Final density (g/ml) 1.25 Volume increment (cm3) 0.064 0.064 0.064 Diameter of sensitization (µm) 500 100 1500 Diameter of sensitiser (cm) 0.05 0.01 0.15 Volume of sensitiser (cm3) 6.5x10-5 5.2x10-7 1.8x10-3 Surface of sensitiser (cm2) 7.9x10-3 3.1x10-4 7.1x10-2 Surface total of sensitiser (cm2) 7.7 38.4 2.6 Number of voids per cm3 9.8x102 1.2x105 3.6x101

Final density (g/ml) 1.10 Volume increment (cm3) 0.209 0.209 0.209 Diameter of sensitiser (µm) 800 100 1500 Diameter of sensitiser (cm) 0.08 0.01 0.15 Volume of sensitiser (cm3) 2.7x10-4 5.2x10-7 1.8x10-3 Surface of sensitiser (cm2) 2.0x10-2 3.1x10-4 7.1x10-2 Surface total of sensitiser (cm2) 15.7 125.5 8.4 Number of voids per cm3 7.8x102 4.0x105 1.2x102

Final density (g/ml) 1.00 Volume increment (cm3) 0.330 0.330 0.330 Diameter of sensitiser (µm) 1000 100 1500 Diameter of sensitiser (cm) 0.10 0.01 0.15 Volume of sensitiser (cm3) 5.2x10-4 5.2x10-7 1.8x10-3 Surface of sensitiser (cm2) 3.1x10-2 3.1x10-4 7.1x10-2 Surface total of sensitiser (cm2) 19.8 198.0 13.2 Number of voids per cm3 6.3x102 6.3x105 1.9x102

Note: Volume increment refers to the percentage of volume increase when

density is lowered from 1,33 g/ml to either 1,25 or 1,10 g/ml

2000

3000

4000

5000

0.2 0.4 0.6 0.8 1.0 1.2

Density (g/ml)

VOD (m/s)

Dynolite 30 / 70

Dynolite 70 / 30



Documents

Araos. 2002. Influence of Different Parameters in the VoD of Gasses Bulk Explosives