A NEW INITIATION SYSTEM THAT REMOVES THE OUTSIDE OR SURFACE DETONATORS FROM THE UNDERGROUND FACE. M Davis and J Fenwick Master Blaster

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1 A NEW INITIATION SYSTEM THAT REMOVES THE OUTSIDE OR SURFACE DETONATORS FROM THE UNDERGROUND FACE Master Blaster Abstract The underground mining industry in South Africa drills in excess of 120million holes annually. A major safety concern in the blasting process is that either, a detonator, detonating cord or igniter cord is used outside the hole for timing or initiating the in-hole detonator. Each of these products poses a very real risk to the underground worker. Three years ago Master Blaster set out to develop alternative underground shock tube products and systems, aimed at removing as much risk of this risk as possible from the underground working face. Through this paper we will present unique products and systems that will reduce the risks posed by the various products currently in use, thereby eliminating 120million chances of an incident or accident happening at the underground face involving detonators or detonating cord. We contend that our pyrotechnic 3, 4 and 5 way clip systems will provide the safest underground system currently available and represents a paradigm shift in blasting safety. 1. INTRODUCTION Over the past 100 years the South African underground mining industry has relied almost exclusively on capped fuse and igniter cord (CFIC) as the initiation system of choice. Although shock tube was introduced to the industry over thirty years ago it has always been classed as a superior product when compared to CFIC and as such commanded premium prices. This price discrepancy resulted in the underground mines using shock tube only if they had specific safety concerns. With the recent arrival in South Africa of various international explosives companies the underground mining industry saw the introduction of quality imported shock tube products at much reduced prices to those on offer at the time. These developments had an immediate and dramatic impact on underground initiation systems prices and policies in South Africa. Suddenly shock tube prices fell drastically, new factories were being built and shock tube was finally being promoted by the local manufacturers as a cost effective replacement for CFIC. Calls for genuine improvements in mine safety were being made by government and the mining industry, and a widespread acceptance began to emerge within the mining industry itself, that CFIC should be replaced with safer alternatives. Shock tube is widely accepted as a safer and more efficient product and was therefore deemed the obvious replacement. Page 265

2 Notwithstanding these qualities it should be understood that current underground shock tube initiation systems still have certain safety flaws, one of the most obvious being the use of an outof-hole timing detonator and the continued use of detonating cord. Questions remain over the absence of any meaningful improvements to the safety of the current shock tube initiating systems since their introduction over thirty years ago. Three years ago Master Blaster together with Chinese counterparts, took up the challenge to research and develop significantly safer underground shock tube initiation systems. Not only did this new system have to offer a major departure from currently available CFIC and shock tube products, it had to be safer, friendlier to the environment, easier to use at an acceptable price. The result of this research culminated in the development of a pyrotechnic 1.4S non-explosives classified out-of-hole initiation system suitable for all stoping and development applications. This product developed is branded the 3, 4 or 5 way clip system depending on configuration, and is a unique pyrotechnic alternative. 2. RISK ASSOCIATED WITH CAPPED FUSE AND IGNITER CORD (CFIC) CFIC systems have served the mining industry admirably for over 100 years. It is an uncomplicated, low cost system which the underground industry knows and understands very well. Over many years the manufacturers have made numerous positive changes to the individual components of the system but there was always going to be a limit as to how safe, accurate and reliable they could make this iconic product. While the relative limits of accuracy of fuse is well-known the majority of incidents, accidents and deaths attributed to the CFIC system underground have been as a direct result of the out-ofhole igniter cord initiation system. Igniter cord can be initiated by impact which means in a tough environment like underground there is always a good chance of accidental ignition happening with disastrous consequences. Safety problems associated with CFIC systems. Igniter cord is impact sensitive. It is inaccurate causing misfires and out of sequence firing. Large quantities of noxious gasses produced. Fire hazard. Not 100% waterproof. It has now widely accepted by most progressive mining groups that the CFIC system is less efficient than shock tube systems in terms of safety, blasting efficiency and cost. Page 266

3 3. RISK ASSOCIATED WITH CURRENT UNDERGROUND SHOCK TUBE INITIATION SYSTEMS. Current shock tube systems in use underground are far safer, more efficient and environmentally more acceptable than CFIC, which however, is still seen to be more user friendly. This is probably because CFIC has been used exclusively for the past 100 years or so. While current shock tube systems are safer they do require more training and are not completely risk free. In addition to being awkward to use, due to some complicated and diverse connectingup methods there are a number of safety, health and environmental issues surrounding the use of current shock tube systems. The following are of genuine concern; 3.1 Safety During charging up and when connected there are always live out-of- hole detonators on the face or lying on the footwall. Detonating cord continues to be used underground for initiation in development ends and for secondary blasting. Most mines accept that there is a need to remove this product from underground, but there have never been viable alternatives available. MISFIRES: Not only can misfires lead to direct harm to underground personnel through unplanned detonations they can lead to unsafe hanging wall conditions and roof support being blown out during the blasting operations, all of which are major safety concerns. Plastic shrapnel from the out-of-hole detonator clips can cause trunk line cut offs and misfires (see environmental issues). During and after priming all the out-of-hole detonators from both the top and bottom holes normally lay on the floor before connecting-up because the length of the shock tube units are too long. There is the constant risk that these out-of-hole detonators will be accidentally detonated by the underground workers in the stope. Figure 1: Out-of-hole detonators lying on the floor during charging. Shock tube lengths are generally too long. Page 267

4 3.2 User friendliness The current method of tying up is relatively more difficult for the underground charging operators. Incorrect timing leads to misfires. Misfires lead to accidents. 3.3 Environmental issues Each out-of-hole shock tube detonator used underground in South Africa is housed in a plastic clip of some sort. This clip is not fully consumed during the blast. The underground mining industry uses approximately 80million out-of-hole plastic clips in narrow reef stoping. Each clip weighs around 10 grams which means the industry is using 800 TONNES of plastic clips underground per year. At least 4 grams of this plastic clip is blasted away by the out-of-hole detonator during the initiation process and ends up on the floor of the stopes. 320 TONNES of plastic per year ends up in mine plants throughout the country. When the out-of-hole detonator is initiated it causes the plastic out-of-hole clip to fragment (figure 2) resulting in shrapnel which can and does cut the other shock tube lines in the stopes causing misfires. The underground mining industry uses around 240million meters of shock tube per year. A saving of 200mm of shock tube per stoping hole, which is possible with the 3, 4 and 5 way clip system, would result in a reduction of approximately 24million meters or around 136 tonnes of plastic tube. Figure 2: Damage to out-of-hole C clips after detonation. Each clip started off at 12.5 grams and after detonation weighs an average of 8.5grams. The gasses produced by the detonation of Master Blaster s C clip (out-of-hole) are in the region of 0.9 litres per clip. Assuming this is the case for all the clips used in the industry, it would follow that approximately 72million litres of various gasses are produced from the out-of-hole detonation process. The 4 way clip produces around 1.6 litres of gas per clip or 2 holes, meaning a saving of 0.1 litres per hole or 12million litres per year. Page 268

5 4. THE 3, 4 and 5 WAY CLIPS: 4.1 Technical Features The plastic bodies contain no explosives. Figure 3: The 3, 4 and 5 way clip bodies. The out-of hole Maxfire delay igniter is a 1.4S incendiary device. The Maxfire does not detonate when it initiates, it discharges sufficient signal into the clip chamber which is sufficient to initiate up to four lengths of shock tube inserted into and crimped to the clip. Figure 4: The 5 way clip Maxfire delay igniter incendiary units before and after firing. The Maxfire igniter does no damage the 3, 4 or 5 way clips during detonation. The Maxfire igniter cannot be ignited by impact. Page 269

6 Once inserted into the clip the Maxfire connection can with withstand over 10kg s of force. Figure 5: Once inserted the Maxfire delay igniter is secure and cannot be removed by hand. The Maxfire delay igniter is a sealed unit ensuring 100% water resistance. There is an internal O-ring in the receiving port of all three clips to prevent moisture ingress once the Maxfire delay has been inserted. There is an external cap on the receiving port as extra protection against moisture while the clip is exposed on the face prior to connecting up. Figure 6: The end cap on the 4 way clip Page 270

7 5. FACTORY ASSEMBLY PROCESS OF THE 4 WAY CLIP ms in-hole delay detonators 2 x 4000 millisecond in-hole 8d detonators are crimped to two predetermined lengths of shock tube. The length of the in-hole shock tube unit is usually determined by the length of hole added to the hole spacing with a little bit of extra to compensate for wayward drilling. The in-hole shock tube units then connected to two of the outgoing ports on the 4 way clip. Figure 7: 2 X 8D 4000ms in-hole delay detonators connected to 4 way clip millisecond Maxfire delay igniter A 200millisecond 1.4S Maxfire delay igniter is crimped to a predetermined length of shock tube. The length of the Maxfire delay igniter shock tube is usually determined by the burden between the holes plus a little extra for wayward drilling. The 200ms Maxfire delay igniter is then connected to the third outgoing port on the 4 way clip. Figure 8: A 200ms Maxfire delay igniter (1.4S non explosives) connected to a 4 way clip resulting in a complete unit ready for packaging. Page 271

8 6. INSERTING AND CONNECTING THE 4 WAY CLIPS UNDERGROUND Place the 4000ms in-hole detonators in the holes. Remove the moisture protection cap from the 4 way clip receiving port. Insert Maxfire delay igniter from previous row of holes into the receiving port of the clip until securely fastened. Once inserted correctly the Maxfire delay igniter cannot be easily removed. Figure 9: Placing the Maxfiredelay igniter into the receiving port. Figure 10: Connecting up is neat and simple with minimal wastage of shock tube and the 4 way clip cannot lie on the ground. 7. UNDERGROUND APPLICATIONS FOR THE 3,4 and 5 WAY CLIP All development blasting. Secondary blasting. Ring blasting. Narrow reef 2 hole square or staggered drilling patterns. Narrow reef 3 hole squre or staggered drilling patterns. All cut and fill stopes. Underground benching. Pillar removal. 4000ms Maxfire delay igniters can replace the in-hole detonator making the entire initiation system non explosives. This can be used in conjunction with a non-explosive type product (Nonex) creating a completely non explosives blasting system, perfect for pillar removal or where the hanging wall conditions are particularly bad. The complete non explosives system can be used for sliping in sensitive underground areas. Page 272

9 8. APPLICATION EXAMPLES 8.1 NARROW REEF STOPING Way Clip used in a 2 Hole Drilling Pattern. 200/4000ms (Staggered) Figure 11: 2 hole staggered drilling pattern. (Holes Primed) Figure 12: 2 hole staggered drilling pattern (Holes Connected) Way Clip used in a 2 Hole Drilling Pattern. 200/4000ms (Square) Figure 13: 2 hole squre drilling pattern (Holes Primed) Figure 14: 2 hole square drilling pattern (Holes Connected) Page 273

10 Way Clip used in a 3 Hole Drilling Pattern. 200/4000ms (Staggered) Figure 15: 3 hole staggered drilling pattern (Holes Primed) Figure 16: 3 hole staggered drilling pattern (Holes Connected) Page 274

11 8.2 DEVELOPMENT The Spinnekop Starter The Spinnekop Starter is a non detonating igniter starter system designed to initiate a 5 or 9 hole burn cut in development ends where the 3 way clip is being used. The Spinnekop Starter initiates the 4 corner holes of a 5 or 9 hole burn cut and ensures individual hole initiation. Figure 17: The Spinnekop Starter:-100ms,200ms...100ms,200ms Maxfire delay igniters The Cut Figure 18: Timing the cut Page 275

12 The Southern African Institute of Mining and Metallurgy A Development End using a Spinnekop Starter. EVERY hole is primed with a 3 way clip consisting of a 4000ms in-hole delay and a non explosive 200ms out-of-hole Maxfire delay igniter. Figure 19: Different timing showing individual firing of each hole. Every unit is exactly the same, 200ms out-of-hole Maxfire delay igniter and 4000ms in-hole detonator. Page 276

13 9. CLIP DESIGN DISCUSSION It can be seen from the various pictures and illustrations in this paper that the 5 way clip is a different design to the 3 and 4 way clip. While the clips may seem quite different the principles behind the invention remain exactly the same. Both styles ensure there are no detonators lying on the floor during charging, there are no live detonators on the face and both clips remain completely intact after ignition giving off less gas than those currently in use. The clips were made differently to allow the customer to chose the connecting up method that would best suit their particular needs. Master Blaster will be able to offer either configuration for the 3, 4 and 5 way clips. The 4 and 5 way clip design Figure 22: The 5 and 4 Way Maxfire delay igniters Figure 23: The 5 and 4 way clip bodies Figure 24: The Maxfire igniter is screwed into the 5 way clip (only 1.5 turns to full lock). The Maxfire igniter is pushed into the 4 way clip until secure. Page 277

14 10. CONCLUSION By eliminating the use of detonators outside the hole, and removing detonating cord from underground, the 3, 4 and 5 way clips reduce the risk of an unplanned out-of-hole incident or accident involving these detonators and detonating cord in over 120 million underground holes blasted in South African underground mines per year. There is no doubt that this shock tube system represents the safest out-of-hole initiation system currently available for underground blasting. Whilst local shock tube manufacturing capacity is being dramatically increased it appears that this expansion is designed to produce the same 30 year old shock tube products without any significant improvements in safety. The South African underground mining industry is under constant pressure to improve their health and safety standards and to do the best they can for environment. Safety is about reducing risk and the continued use of CFIC or what is fast becoming outdated shock tube technology, does not do anything to support efforts to mine safer. 11. FUTURE WORK Whilst the 3, 4 and 5 way systems have gone a long way toward reducing certain risks associated with out-of-hole initiation systems, the ultimate objective has always been to create the safest underground blasting systems possible. In pursuit of these objectives, products soon to be released for underground commercial use also include; The LoopDet (LD) This system is already being rolled out as an interim replacement for the 200/4000 shock tube stoping system and to replace the LP shock tube systems used in development. Whilst the LoopDet system is not as safe as the 3, 4 & 5 way clip systems it does remove 50% to 66% of the detonators from the underground face. The system also does away with the need for detonating cord in development ends. The Safedet What if a detonator only became a detonator just before priming? What if the hazardous part of that detonator could be tracked from manufacture to final use? The Spinnekop Starter This unique non-detonating delay igniter starter system is designed to start the blast in a development end without using a detonator. It also ensures individual hole timing with minimal chance of any out of sequence shots. Narrow reef hanging wall protection system - This system is essentially a 5 way clip using a different delay to ensure the hanging wall holes fire after the centre and footwall holes thereby offering much needed protection to the hanging wall. The colour of the shock tube for the hanging wall unit will differ from the centre and footwall holes so as to provide a user friendly system. Page 278

15 Shock tube secondary blasting system Consists of a continuous shock tube line with individual detonators spaced at specific intervals thereby removing the need for detonating cord during secondary blasting. The Widget This system provides a single operation loading method for cartridge explosives. The tamping plug is incorporated in the unit and once the cartridge has been primed it provides additional protection for the detonator. The widget will ensure all the serious health and environmental issues caused by using anfo underground are eradicated. 12. ACKNOWLEDGEMENTS The authors wish to acknowledge the invaluable work put into this project by the Research and Development Team at the Xi an Qinghua Explosives Factory. We would also like to thank Sean O Connor, Francois Uys, Gary Strong and Cobus Mouton for their continued patience, support and vision and express our gratitude for the valuable participation of the Northern Explosives team. The Author Mark Rodney Davis, Managing Director, Master Blaster 27 years in the explosives industry. Page 279

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