How to Use
- AutoStem Safety Cartridge is the world’s first range of non-detonating, self-stemming blasting product designed for mining and blasting applications. The technology was developed over many years, in response to a global requirement of new rock breaking technology adhering to greater safety standards, efficacy and cost effectiveness.
- As per the current practice conventional explosives (Gelatin, TNT, PETN, Power Gel etc.) are used for rock breaking and associated applications such as rock cutting, benching, trenching, tunneling, shafting, road widening, excavation for field fortification etc.
- Conventional explosives have the following shortcomings: –
- Can be initiated only with detonators – adds to the risk and safety aspect.
- Require Stemming. The boreholes charged with conventional explosives require stemming (tamping) which is time consuming and laborious.
- Velocity of Detonation. Conventional explosives must be detonated using detonators. This produces a blast wave with very high velocity of detonation which pulverizes everything around it.
- Fly Rock. Breaking of the rock using high explosives, results in the broken rock pieces (fly Rock) being thrown/ ejected to large distances.
- Safety/ Clearance Distance To avoid injury/ damage due to blast wave and flying rocks, all personnel and equipment require to be moved to safety distances as specified. (Generally, more than 500 m).
- The blast wave is associated with high noise levels which in the long run is harmful to human ears.
- Release of toxic fumes and gases.
- Leaching of chemicals into the soil
- Comparatively low Shelf Life.
- Stocking and Carriage. Conventional explosives fall under the UN classification of 1 ZZ which require special storage conditions and have restrictions on the mode of transportation and handling.
- AutoStem is a rock breaking product which uses a new patented technology for blasting rocks. It overcomes the limitations of conventional explosives.
- AutoStem cartridges are available in a wide range of dimensions and charge weight, catering to every need of the client.
- The diameter ranges from 9mm to 87mm.
- The charge weight ranges from 3 g to 1700 g.
- The cartridges of diameter 9mm and 17 mm are known as Micro Cartridges.
- The availability of AutoStem Cartridges as per diameter and charge weight is as per Table- 1. However, the charge weight and diameter can be varied to suit the customer’s requirement.
DESCRIPTION AND FUNCTIONING
- A standard AutoStem Safety Cartridge comprises of the following components: –
- Outer Casing
- Obturating Rings (yellow)
- Electric Ignitor housing (red)
- Electric Ignitor
- Electric wire
- Flash Tube
- Safety Tab (Yellow)
- Cartridge end Cap
- Ignitor end Cap
- Proprietary Mixture- main components – Nitrocellulose and Ammonium Nitrate.
- Description of AutoStem Cartridge. (Fig. 1 and 2)
- The outer casing of patented AutoStem Cartridge is a cylinder made of PVC material which is capable of ballooning and exerting pressure against the walls of the bore hole.
- The outer surface of the casing has alternate helical grooves to improve coupling between the cartridge and the bore hole.
- Obturating rings (yellow) are provided at each end of the casing to assist in self-stemming and ensuring an effective gas seal.
- The two ends of the cylinder are closed with end caps, an Ignitor End Cap and Cartridge End Cap respectively. The Ignitor end cap has a fire channel/ flash tube which extends up-to the center of the cylindrical casing.
- The Ignitor End Cap is fitted with a Safety Tab (Yellow) which is to be pushed in, to prime/ arm the Cartridge.
- Above the ignitor End Cap is an Ignitor Housing (red colour) which houses the electric ignitor/ fuse head.
- The electric cable of the ignitor emerges from the central hole in the Ignitor Housing/ holder.
- Proprietary Mixture. The casing is filled with a proprietary high energy mixture with Ammonium Nitrate & Nitrocellulose as its main ingredients/ constituents. This composition is packed in the casing as per the specified charge weight.
- Working of AutoStem Cartridge.
- When the Safety Tab is pushed inwards, the electric ignitor is placed directly over the Flash Tube. When the cartridge is fired, the flash from the ignitor in the Safety Cap travels through the flash tube up to the middle of the Cartridge and ignites the Nitrocellulose mixture.
- The mixture deflagrates (burns at a very rapid rate/ high speed) and produces large volumes of non- toxic gases.
- These gases expand and exert pressure radially on the inner walls of the casing. The casing along with the obturating rings, balloons and snugly fits against the walls of the bore hole and prevents escape of gases. As the pressures continues to build up, the weak natural fissures in the rock give way causing the rock to break.
AutoStem offers unparalleled inbuilt safety features.
The inbuilt Safety Tab ensures that cartridge cannot be initiated unless it is pushed inwards thus preventing any accidental functioning during transport, storage and handling.
Simultaneously the Safety Tab if not pushed in will not allow the cartridge to be inserted in the hole, thereby ensuring it has to be charged for easy insertion.
AutoStem cannot function unless it is fired in a confined space of a bore hole. If initiated outside the bore hole, it poses no danger and burns just like a cracker. This is unparalleled safety in the explosive world. Other explosives explode and cause immense harm if initiated outside. One should however desist from this activity
AutoStem is United Nations Explosives Class 1.4 S explosive (Class-6 Div-1- Cat-Y as per Indian Explosives Rules 2008). This means that it falls under the small arms ammunition/ pyrotechnics/ fire crackers category. As such the product itself is very safe and there is no risk of mass explosion unlike conventional explosives.
AutoStem can be easily transported and stored with minimal restrictions applicable to UN 1.4 S class explosives. Accordingly, it can be shipped by land, air and sea. AutoStem is the only self- stemming rock breaking explosive in the world with UN classification of 1.4 S.
- In addition, the following features make AutoStem an environment friendly product which is safe for initiation: –
- There is no risk of detonation.
- Minimal vibrations, hence, No collateral damage.
- Less noise.
- No harmful gases, hence safe for humans.
- No leaching of chemicals into the soil.
METHOD OF USAGE
- AutoStem Cartridge is very safe to use. There is no potential for any operator error while priming the bore holes. It is a complete ‘drop and fire’ solution with no requirement of stemming. This product allows continuous firing throughout the day.
- There are three simple steps for the use of AutoStem Cartridges, namely, drilling the bore hole, loading & wiring up the cartridges and initiation of the cartridges. Fig 3 refers.
Step 1: Drilling Bore Hole
- Select a rock and assess the type of cartridge based on the volume and type of the rock to be broken. Appropriate charge weight selection is essential, for optimum breakage. Over charging will result in smaller fragments and higher noise level.
- Depending on the diameter of the selected cartridge, drill a hole of the required diameter which should be 1 to 4 mm more than the diameter of the cartridge, e.g. a bore hole of 38 mm for 35mm Cartridge. (Refer Table – 1).
- The depth of the bore hole should be 2/3 (66%) the height of the rock.
- In case of evenly shaped rocks a single borehole would generally be adequate as shown in Fig 4.
- In case of unevenly shaped rocks one can drill a single hole and use a larger charge. Alternatively, to get a better fragmentation, one can drill more than one hole and use smaller charges. Fig 5 refers.
- Burden is the distance between the borehole to the nearest free face of the rock. Spacing, is the distance between two boreholes. Burden, spacing and the charge weight determine the size of the fragmentation. The smaller the fragmentation required, the smaller should be the burden and spacing, whereas, the charge required would be larger.
Step 2: Loading and Wiring up the Cartridge
- Select a cartridge to be used and unwind the wire and check for continuity using continuity tester.
- Push the Safety Tab inwards to prime the Cartridge. The cartridge is now primed.
- Lower the cartridge into the hole gently, by releasing the connecting wire from the center of the cartridge slowly and ensuring the electric connections do not snap. Fig 6 refers.
- Make sure the cartridge has rested at the bottom of the hole. If required, the cartridge can be pressed down into the borehole using a wooden baton/ rod.
- Connect the two ends of the cartridge wire to the blasting wire and withdraw up to at least 50 m from the rock.
- In case of multiple cartridges, the cartridges are to be connected/ wired up in series as shown in Fig 7.
Step 3: Initiation
- Move back to the required safety clearance distance.
- Check for the continuity of the entire blasting circuit again using the continuity tester.
- Connect the two ends of the firing cable to the Shot Exploder by inserting one wire in each of the slots of the shot exploder. Fig 8 refers.
- Blow the warning whistle and ensure no one is present up-to 70 meters of the rock.
- Shout the firing sequence as – Firing now…(pause)… 3…2…1 and turn the key of the shot exploder clock wise, 90 degrees and hold for a few seconds till the AutoStem fires and the rock is broken. Upon turning the key, a current of 2.2 amperes will be passed down the wire into the cartridge, initiating the fuse head / initiator, which in turn will ignite the blasting composition generating intense gas pressure to break the rock.
Ease of Use –
The AutoStem Cartridges (especially lower calibres – 9 mm and 17 mm) are very convenient for use by anyone with minimal training. They can be used by drilling holes with a hand-held drilling machine and portable generator. Because of this convenience and portability, AutoStem can easily be utilized by any trained blaster for preparing trenches, clearing sites in hard rock areas or in the most difficult locations. As far as higher calibers are concerned, these also can be used by the blasters using available facilities for drilling boreholes. Charging the boreholes and initiation is not very technical, it can be done by any technical supervisor with minimal training. This capability will enable the user to plan primary and secondary blasting’s in the most optimum manner.
HANDLING OF MISFIRES
- No misfires have been reported in this product so far. However, in remote occurrence of a misfire, drill as prescribed below should be followed.
- Wait for about two minutes, disconnect the blasting cables from the shot exploder and check for continuity. In case there is no continuity, carefully approach the rock and check whether the connections between the blasting cable and the connecting wires from the cartridge are intact. In case the wires are disconnected, the connection between the blasting cables and the cartridge should be re-established and the firing drill be followed as laid down.
- In case all connections are intact and if the bore hole permits, prime and drop another cartridge on top of the misfired cartridge and follow the firing drill as laid down.
- In case there is an obstruction in the misfired bore hole, then, drill another hole about six inches from the misfired borehole (ensuring correct alignment to avoid drilling into the misfired cartridge under all circumstances) and drop another cartridge and follow the firing drill as laid down.
- In the case of AutoStem there is no risk of any sort, in handling misfires, because of the following reasons.
- Combustion of the blasting mixture will take place only with a flash from the ignitor. Once the current passed by the initiator/ shot exploder has not activated the ignitor, it will not get activated by any other disturbance or movement. A current of 2.2 amperes generated again only can activate the initiator.
- There is no detonation in the case of AutoStem and hence there is no risk of partial detonation leading to instability of the explosive and rendering it susceptible to detonation on disturbance/ movement.
APPLICATIONS OF AUTOSTEM
- AutoStem Cartridge can be used for any type of rock breaking, be it civil or military blasting applications, just as we use conventional explosives.
- It produces very low vibrations and less fly rock, hence, can easily be used in the cities/ towns and villages i.e. close to habitation or any structure without causing any collateral damage.
- Different applications for which AutoStem can be used are: –
- Primary and Secondary rock breaking
- Rock benching i.e. cutting a portion of the rock.
- Box cutting.
- Overhang cutting – cutting of a rock jutting on to a road or into a tunnel at a height.
- Trenching and shafting – cutting a trench or making a vertical shaft.
- Tunneling and mining
- Underwater blasting up to 30 m.
- Road and rail track widening, clearing of rocky sites etc.
- Execution of each of the applications mentioned above requires boreholes to be drilled as per specified drilling patterns. Drilling patterns for some applications are depicted in Fig 9 and 10.
ADVANTAGES OF AUTOSTEM
- AutoStem offers a high performance, non-detonating, self- stemming alternative to conventional explosives for rock breaking. It is a more economical/ cost effective alternative with the added advantages of high versatility & ease of usage, reduced manpower requirement & efforts, environment protection compliance and a host of other advantages.
- The following advantages with respect to AutoStem need to be taken into consideration as several of them indirectly contribute towards additional cost effectiveness.
- The availability of AutoStem in a wide range of diameters and charge weights facilitates selection of cartridge most suited for the work at hand depending on the rock to be broken and the desired degree of fragmentation i.e., precision blasting to some extent.
- Reduced fly rock permits lesser safety distances which offers two distinct advantages.
- As per prevalent norms for conventional explosives, manpower and equipment must withdraw to a safe distance of more than 500 m prior to the blasting. For AutoStem, the requirement of withdrawal distances is 50 m and maximum up to 100 m. This is considerable cost credit, as the withdrawal distance is only 30% of conventional explosives.
- Lesser withdrawal distance permit faster/ more number of blasting, thereby improving pace of work resulting in reduction of time required for completion of the project and thereby the cost.
- Reduced Fly Rock also permit availability of maximum quantity of blasted rock material for development work such as construction of road, embankments, fortifications etc. or any construction work requiring the usage of broken rocks. This aspect gives two distinct cost benefits over conventional explosives namely significant enhancement of blasted material for construction and significant reduction in the requirement of blasted rock material to be disposed off.
- AutoStem throws up very less dust which clears up in 15 to 20 seconds. This coupled with absence of toxic fumes/ gases permit immediate access after blasting. This enables more no of successive firings per day enhancing the output and speeding up the pace of project, resulting in reduction of time and cost.
- Versatile Utility. AutoStem can be used for all types of rock breaking applications in urban & rural areas.
- Can be used close to sensitive/ built-up areas/ bridges/ overhangs close to populated areas with no danger of collateral damage.
- No need for expensive alternatives like Plasma Gel or controlled blasting measures.
- Collateral damage from conventional explosives may result in cracks in the mountain rock strata thus making the area prone to eventual landslides which would require to be addressed either by way of change of route and/ or placement of buttress beams, safety nets/ grills etc. at an additional expenditure. AutoStem, thus, saves time, resources and cost.
- No/ minimal hindrance to traffic even when used for widening of roads.
- Lesser drilling effort as the number of bore holes required is much less.
- No tamping/ stemming required, hence, considerable saving of manpower, time and effort, which saves cost.
- No detonating wave, makes it safe for use.
- Noise level is much less, which does not pose any threat to human ears. The noise can further be dampened by filling the hole above the cartridge with sand/ mud.
- Additional Safety Tab prevents accidental initiation.
- UN Classification of 1.4 S (Indian class-6, division-1) enables ease of carriage, transportation and storage.
- Misfires are very remote and in the event of a misfire it does not pose any danger/ risk. There are no restrictions on approaching the site for resolving the issue, unlike conventional explosives, where the serious issues of accessibility and by-passing the site, exist, leading to loss of resources/ time.
- AutoStem is Environment friendly – reduced noise levels, no detonating wave, no vibrations, no collateral damage, no toxic fumes, no leaching of chemicals and an oxygen balanced reaction. The environmental angle is an important plus point in view of the Supreme Court ruling and guidelines on the issue.
- Shelf life of 18 months (+18 months).
- Can be used in extreme cold climate of high-altitude areas.
- AutoStem permits speedier rock breaking and hence speedier completion of a project which is the order of the day.
- Equipment Requirement. AutoStem does not require any major shift in/ capital investment for equipment.
- Any agency using conventional explosives would be already using Jack hammers with compressors and ROC machines/ Jumbo boomer as per availability. The only change required is of shifting from drill rods with fixed drill bits to drill rods with detachable drill bits.
- Today drill rods of variable lengths and drill bits of diverse sizes are available, which permit the usage of varied sizes of drill bits with a single drilling rod giving better flexibility of application. Moreover, as compared to the drilling rods with fixed drill bits which have only two cutting edges, the detachable drill bits have five cutting edges which facilitate better and faster drilling and are more durable.
- Small Team Operations. AutoStem can be used even by small teams to carry out independent tasks without the availability of major equipment like a compressor or jack hammer. The team can carry out rock breaking tasks if equipped with a portable generator and a hand-held electric drilling machines capable of drilling bore holes of requisite diameter.
- The number of AutoStem cartridges per box depends on the size of the cartridge. The AutoStem cartridges are first packed in poly-woven bags. Two such bags are then packed in one corrugated cardboard box.
- The dimensions of all boxes are 315mm x 508mm x 320mm and the weight of each box is 21 kg.
- Consignee details, description of contents, expiry date, place of manufacture, contact numbers and all regulatory markings are available on each box.
- The type and number of cartridges per box is per Table – 1.
STORAGE AND TRANSPORTATION
- The United Nations Classification System of explosives and ammunition classifies AutoStem Cartridge under the class of ‘S’ and UN Hazard Division 1.4, hence, it falls under the safest UN Classification 1.4 S. This implies that AutoStem can be stored in any type of store house/ magazine and along with any type of explosive. It can be transported by road/ sea/ air, in cargo/ passenger transport.
- The AutoStem cartridges for storage purposes can be stacked one on top of the other up to a maximum of five boxes only.
FAQS - AUTOSTEM
Q.1. How is AutoStem different from conventional explosives?
A.1. AutoStem is currently, the only available non-detonating and self-stemming cartridge for rock breaking which adheres to greater safety standards, efficiency and cost effectiveness. It functions by deflagration, as against, detonation in the case of conventional explosives. Therefore, detonation/ blast wave and associated ill effects of conventional explosives (collateral damage, fly rocks, high levels of sound & vibrations, dust & debris) do not occur. The output is high and there are savings in indirect costs due to reduced withdrawal distances, no over breaks & fines, reduced no of boreholes and no requirement of tamping/stemming. Further, immediate access to sight permits continuous blasting. AutoStem is a green, environment friendly explosive causing no damage to earth strata, reduced sound levels, nontoxic fumes and no leaching of chemicals into the soil.
Q.2. Is the usage of AutoStem time consuming?
A.2. No. On the contrary, it is time saving and facilitates earlier completion of the projects. AutoStem uses three simple steps of drilling, loading and firing the cartridge, with no requirement of the time-consuming process of stemming. In addition, the requirement of lesser number of bore holes as compared to conventional explosives, reduced withdrawal distances, immediate access after firing and the feasibility of continuous operations reduces the overall time required for the completion of the project.
Q.3. Is there a requirement of any specialized training for the usage of AutoStem ?
A.3. An operator can be trained to use AutoStem in a maximum of two days. No specialized training is required.
Q.4. Do we need any specialized equipment for using AutoStem?
A.4. AutoStem can be utilized using equipment which is normally used for drilling and blasting, no additional/special equipment is required.
(a) Drilling Equipment. Equipment such as hand-held drilling machine, jack hammers with compressor, ROC etc. for drilling holes with diameter from 10 mm to 95 mm and up to the required depth would be required.
(b) Exploder/ Dynamo. Equipment capable of generating 2.2 Ampere of current would be required. The resistance per cartridge is 0.52 to 0.56 Ohms (approx.).
Q.5. What is the safety distance required to be maintained for AutoStem ?
A.5. The safety distance required is 50 meters. However, to cater for cases of overcharging (using AutoStem more than the appropriate quantity), ensure a safe distance of 75 to 100 meters.
Q.6. What precautions are to be observed during transportation and storage of AutoStem ?
A.6. AutoStem falls under the UN Hazard classification of 1.4S. As such there are no restrictions for storage and transportation. It can be stored with any other type of explosive. It can be transported by land, sea or air by cargo or passenger transport.
Q.7. Can the cartridges be used by Infantry/ other arms?
A.7. The AutoStem Cartridges are very convenient for use by anyone with minimal training. They can be used by drilling holes with a hand-held drilling machine and portable generator. Because of this convenience and portability, AutoStem can easily be utilised by any certified blaster for trenching, shafting etc. hard rock areas or any task requiring rock breaking, provided facilities for drilling boreholes are available. Charging the boreholes and initiation is not very technical, it can be done with minimal training. This capability will enable the user to plan/ make the trenches etc. at the exact optimum location.
Q.8. What are the effects of overcharging/ under charging?
A.8. Effects of Over/ under Charging- As a rule, a 40-60 g cartridge is adequate for breaking one cu. m rock with approximately 40 – 50 cm burden. However, if the burden exceeds the given yardstick or lesser charge weight is used, it may lead to malfunction in terms of the cartridge ejecting itself out of the borehole on initiation or the rock may not break, or it may break into two/ three large pieces. Similarly, if the burden is less or the charge weight used is more, it may lead to an over kill and result in smaller fragmentation of the rock and fly rock up to 75 -100 m.
Q.9. How is the type and quantity of cartridges arrived at for a specific task, arrived at?
A.9. The type and quantity of cartridges required will depend upon the type and size of rock and type of fragmentation desired. The smaller the fragmentation, the larger will be the charge weight required and smaller the inter cartridge spacings. As a broad guideline the charge weight of AutoStem required to be used is as follows-
A. For free standing evenly shaped rock – 40 – 60 gm per cum
B. For uneven rock/embedded rock – 100 gm per cum.
Five Golden Rules
Rule 1. AutoStem Safety Cartridge is classified under UN Explosives Class 1.4 S, as such should be handled as an Explosive.
Rule 2. The bore hole must be at least 2/3rd the depth of the rock being addressed.
Rule 3. Push the Safety Tab inwards to “Armed position” before lowering the cartridge into the bore hole. Check the continuity of the complete circuit before connecting to the Shot Controller.
Rule 4. Though the stipulated safety distance is 50 m, it is always a safe practice to stay approx. 100 m away.
Rule 5. In case the bore hole is considerably larger than the recommended diameter, pour some sand into the hole after the cartridge has been lowered to ensure effective obturation.