Testing Of DF as Per IS and CCE testing methods.pptx

Testing oif Explosives

1. METHODS OF TESTING DETONATING FUSE Mr. Atul P. Dwivedi Dy. Manager (Technical & Safety) Keltech Energies Ltd. Village Garamsur , Nagpur Maharashtra, India

2. DETONATING FUSE Detonating Fuse is flexible fuse containing a uniform core-load of PETN. PETN is encased in various protective coverings, followed by an outer PVC coating. The PVC coating makes the Fuse water resistant and withstands all external abuses It has high tensile strength which make it compatible for cartridges of higher weights for open cast blasting. Detonating Fuse is a flexible cord containing a uniform core load of PETN that ensures positive initiation of cap-sensitive explosives along the entire length of the fuse. Detonating fuse is relatively insensitive to detonation by friction, shock and requires a proper initiation for detonation.

3. METHODS OF TESTING AS PER IS-6609 PART 2 &4

4. HEAT TEST OF PETN The Abel heat test is applicable to any explosive which forms oxides of nitrogen on decomposition. When the test sample is heated, oxides of nitrogen are liberated more or less rapidly according to the stability of the material. Traces of oxides of nitrogen are detected by means of brownish line produced on starch-potassium iodide test paper. The time taken to reach the standard tint gives a comparative indicator of the stability of the explosive sample under test.

5. The glass rod with platinum wire hook is inserted in the rubber stopper. A test paper is then removed from the brown glass bottle by the means of forceps, placed on the glass plate so that its edges coincide with the lines on the plate, and pierced by passing a needle through the paper and the hole in the plate. The test paper is then held by means of the forceps, and a mixture of equal volumes of water and glycerine is applied to the upper edge of the test paper by means of a glass rod or dropping bottle, in sufficient quantity to moisten the upper half of the test paper by the time the test is complete. The platinum wire hook of the glass rod is then passed through the hole in the paper. At no time the chemist shall touch the paper with fingers.

6. Put the stopper containing platinum loop and starch iodide paper on the test tube The test tube containing the sample and all the assembly is placed in the water bath. The water bath is set at 76.6°C. The sample of PETN Should be taken is 1.3 Grams. The test is carried out for at least 10 minutes . As per industrial practice the test time can be varied from 30 to 60 minutes. If no change is colour observed at the junction of two layer then the sample is passed and if their is observation of brown colour at the junction of the two layer the batch is failed, the batch should be recrystallized .

7. 35mm 16mm 76mm Glass rod with platinum hook Wet portion of Starch iodide paper Lid of water bath Test tube with platinum hook assembly 1.3 grams PETN

8. GENERAL TESTING OF DETONATING FUSE VISUAL EXAMINATION : The detonating fuse shall be visually examined for smoothness, pliability and surface blemishes. DETERMINATION OF DIAMETER: The diameter shall be measured with the help of a micrometer or callipers. The instrument shall be preferably a ratchet type or spring loaded. Take 1 m length of sample and measure the diameter at three different places and at each place in two positions right angle to each other. Record the average value giving the diameter of the detonating fuse in millimetres.

9. VELOCITY OF DETONATION By Dautrich method Cut a 1 meter length of the detonating fuse and mark on it accurately with pencil two points 25 cm and 75 cm from one end, at one end of the fuse attach detonator and stick it with the adhesive tape on to the fuse. Keep the exploder key always in possession of Short firer while connecting the detonator to the shot firing cable. In case of incomplete detonation, carefully collect all the fragments of the charge. In case of misfire wait at least for 5 min in case of shot firing electrically or for at least 30 min in case of shot firing with safety fuse before approaching the shot.

10. Apparatus:- Aluminum (Al) plate- 40 x 6 x 1.25cms No. 6 Strength Detonator Exploder # In IS Standard lead plate is mentioned but test can be carried out using Lead, Aluminium, Plastic, Steel or Wood. Velocity of detonation ( V), km/s=(( dxVo /2∆L)) where d = distance between two ends of the detonating fuse, V. = Velocity of detonation of the detonating fuse in km/s, and ∆L = distance between middle point of standard detonating fuse ( scratch on the Al plate) to the point on the AL plate where the two detonation fronts travelling in opposite directions.

11. DIAGRAMATIC VIEW OF DAUTRICHE METHOD Al plate Standard DF for VOD probe Test sample Detonator 25cm 75cm

12. VELOCITY OF DETONATION By Micro timer Method Preparation of VOD probes:- Take four pieces of enameled copper wire of 0.32 to 0.56 mm diameter, each of 60cm length. Pick up two enameled wires at a time and twist together one end of each of the wires over 3 to 4 cm length. Remove the insulation of the free end of the wire. These wires twisted together should have and electrically open circuit. The twisted wires with the bare ends are called “VOD probes”. Preparation of test sample: - Take 50cm long sample and make two points 10cm apart at 30 and 40cm from one end. Insert the “start probe” at the point at 30cm mark and “stop probe” at 40cm mark.

13. Operation of the micro-timer:- The test sample as prepared above is detonated suitably and the interval of the propagation of the detonation wave between the two probes is measured on the micro-timer. Attach an electric detonator to the “start end” of the detonating fuse by means of adhesive tape and fire by a suitable exploder. The sample can be fired using safety fuse also.

14. Apparatus: Micro timer :- The micro timer is an electronic instrument which is suited for measuring very short time interval such as those involved in detonation processes. Two signals which define the beginning and end of the time interval to be measured are used as “start” and “stop” signals to operate a gate. This gate turns on the off a constant current supply to a capacitor and the voltage developed across the capacitor is measured by an electrometer-voltmeter circuit. Thus, if the capacitor starts with zero potential difference across it, the potential registered by the voltmeter circuit at the end of the time interval is directly proportional to the time interval. By suitably selecting the various circuit constants the voltmeter is made to read directly in microseconds.

15. Precautions:- Keep the timer key and exploder key always in possession of Shot firer while connecting the detonator to the shotfiring cable; In case of incomplete detonation, carefully collect all the fragments of the charge; In case of misfire, wait at least for 10 min. in case of shot firing electrically or for at least 30min in case of shotfiring with safety fuse before approaching the shot; and The timer shall be calibrated periodically.

16. TEST FOR FLEXIBILITY AND SENSITIVITY AFTER FLEXIBILITY TEST AT LOW TEMPERATURE - Take 1 m length of the sample and keep it in a chamber at a temperature of -10°C for 4 hours. Take out the fuse from the chamber after this period and quickly make 5 knots on the fuse 15 cm apart. Examine the surface of the fuse visually for any crack on the outer covering and record the number of cracks noticed in the sample. AT HIGH TEMPERATURE - Keep 1 m length of the sample in an air-oven at a temperature of 50°C for 24 hours. Take out the fuse and make 5 knots 15 cm apart quickly. Examine the surface of the fuse for any crack on the outer sheath and record the number of cracks noticed on the sample.

17. SENSITIVITY AFTER FLEXIBILITY TEST: Take the fuse after completing the visual tests lay about 5 cm of its one end over the Al plate and retain it with the help of adhesive tapes. Detonate the fuse from the other end and record if the full length of the fuse has detonated and whether the end portion has left any burning mark in the Al plate. Apparatus:- AL plate- 40 x 6 x 1.25cms No. 6 Strength Detonator Blasting Machine # In IS Standard lead plate is mentioned but test can be carried out using lead, AL, Plastic, Steel or Wood.

18. IMAGE OF TEST OF FLEXIBILITY

19. WATER PROOFNESS AND SENSITIVITY AFTER WATER-PROOFNESS TEST Take 1.5 mtrs of Fuse and seal its both ends. Take the fuse with sealed ends and lay it longitudinally inside the vessel with ends of the fuse vertical. Fill the vessel (Provided with Pressure guage ) with water in such a way that the sealed ends are always above the water surface. Subject the sample to a water pressure. Maintained pressure up to 4Kg/Cm 2 . Duration shall be as specified in the relevant material specification. At the end of the period, take out the fuse, wipe dry of water and pierce it with a sharp pin at various points and then twist it to see if any water oozes out through these holes.

20. If any water comes out, slitting of the fuse and examining the PETN for water absorption would not be required. In case no water oozes out, then cut a piece of the fuse 1 m long and examine the explosive core for any water absorption. SENSITIVITY AFTER WATERPROOFNESS TEST: Take the fuse after completing the visual tests lay about 5 cm of its one end over the Al plate and retain it with the help of adhesive tapes. Detonate the fuse from the other end and record if the full length of the fuse has detonated and whether the end portion has left any burning mark in the Al plate.

21. IMAGE OF WATERPROOFNESS TEST (test chamber assembly)

22. IMAGE OF WATERPROOFNESS TEST (Inside the test chamber)

23. TEST FOR TRANSMISSION OF DETONATION Take 6 sample of 4 m each. Take one sample as the main line and to this tie the other samples by clove hitch knots at 1 metre intervals and at an angle of 60° to form five branch lines as Shown in Fig. Place 1 sample of detonating fuse at an angle of 90 to one of the sub-branches. Detonate the main line using a No. 6/8 strength detonator and record the result giving the particulars of the detonating fuse and the number of branch lines detonated.

24. Detonator 60˚ Branching 90˚ 1mtr DIAGRAMATIC VIEW “TRANSMISSION OF DETONATION”

25. DETERMINATION OF MASS OF EXPLOSIVE CORE Cut a 20 cm long sample of the detonating fuse. With a sharp knife, cut lengthwise the PVC layer and peel it-off making sure that no PETN is sticking to the PVC. Hold the fuse ,over a filter paper thimble and gently tap the PETN from the yarn core into the Beaker. Place 250 ml of acetone in the flask which has been tared and set it on a water-bath and extract for about one-and-a-half hours. At the end of the period remove the flask, evaporate the acetone to dryness on a water-bath and dry the flask in an oven at 60°C for about an hour. Cool in a desiccators and weigh.

26. Conduct the blank using the same length and quality of the yarn as used in the making of the detonating fuse. Subtract the mass of the extract obtained from the yarn from the mass of the PETN extracted from the detonating fuse. Calculate the mass of PETN in one metre of the detonating fuse.

27. DETERMINATION OF MASS OF EXPLOSIVE CORE- Alternate Method Cut a 20 cm long sample of the detonating fuse, weigh it accurately (A). With a sharp knife, slit it open in such a way that only the outer covering is cut. Peel this covering off carefully and keep it aside. Take out the inner yarns, plastic covering, if any, paper/plastic tape, etc, carefully, brush these to free any PETN sticking to those and keep aside. Weigh the plastic covering, yarns, inner covering the tape, etc, together (B). From the difference in the mass (A) and (B), the PETN charge mass is calculated.

28. AIR GAP TEST Cut two pieces of detonating fuse of 0.5Meter length each. Place the two pieces in the gap of 50mm in a aluminium tube for better confinement. The tubes are sealed on both sides so that the detonating fuse does not move. Note:- Detonating fuses of 10gms and above should maintain a gap of 50mm whereas for Detonating Fuse below 10gms should maintain a gap of 25mm to 50mm. One end of the donor Detonating Fuse should be tied with electric detonator no. 6 and blasted. Both the pieces of Detonating Fuse should be detonated.

29. SIDE BRISANCE TEST Take 2 pieces of 30 cm length of the Detonating fuse to be tested. Place them apart across specified wooden spacer (5cm long, 1.5mm thick) 5mm,10mm or 15mm wide as required and tie by means of suitable material so as to ensure good contact with spacer be tightly on an assembly bench. The portions of fuse tied should be parallel. Place the assembled sampled on the firing ground. Initiate the detonating fuse donor end by a no. 6 cap observing usual precautions. Record the data where in the acceptor detonating fuse has detonated in full or not. Normally detonating cord 10gm will pass 10mm gap.

30. This test is a measure of the ability of the detonating fuse/cord to initiate the another cord when it is kept at a distance apart by its side. This distance/gap that is normally kept where is from 5mm to 15mm depending upon the core loads of the detonating fuse. Apparatus:- Wooden spacer:- Size: 5cm long, 1.5mm thick, width 5mm, 10mm or 15mm as required.

31. DETERMINATION OF BREAKING LOAD OF LIVE DETONATING FUSE The ends of a small length of detonating fuse are secured to two separate holders ( as shown in Fig. ) provided with hooks. To one of the holders is attached the required weight. The whole assembly consisting of knurled holders, fuse and weights is lifted off the ground by a suitable arrangement in such a way that the holder with the weight is vertically below the other holder with the fuse stretched tightly between them and under tension on account of the weight attached to the bottom holder. The load at which the fuse breaks within 20 seconds of suspension is taken as the breaking load.

32. PRECAUTIONS: Take all the usual precautions for testing explosives. It is advisable to keep the apparatus inside a building and observations made from outside. However, if the observations are also made inside, the operator should be protected during the test by interposing a 6 mm thick mild steel shield between the operator and the machine.

33. Top Holder Bottom Holder 175±1.25cm DF sample DETONATING FUSE BREAKING LOAD TEST ASSEMBLY Weight to be added

34. DETONATING FUSE BREAKING LOAD Alternate Method This is the safest method to calculate the breaking load of the detonating fuse. In this method live detonating fuse is not used instead the materials used for making fuse is used: Method: Calculate the breaking load of Yarns & BOPP strip used in the manufacturing of Semi fuse. Multiple the breaking load of each components by the no of each components used and them together. This will give you approximately the same breaking load as will be given by Live detonating fuse.

35. Calculation: For Example if we are using 16 Yarns and One BOPP strip and for one yarn the breaking load is 4 kgs and for BOPP strip it is 2 kgs then the breaking load of the Fuse will be: Yarn = 16nos *4 kgs= 64kgs BOPP = 1nos * 2kgs = 2kgs Total = 66 Kgs Breaking Load of Fuse will be approx: 66 Kgs .

36. SAFETY PRECAUSTION WHILE HANDLING LIVE DETONATING FUSE Use Non Sparking tools for cutting the Fuse. The Detonators should be properly short while inserting in the fuse. The Cutting of Fuse Should be done on the tray so as to avoid spillage of PETN. After the cutting of the fuse, the ends of the fuse should be properly sealed using tape. The Fuse and Detonators should not be carried in same box. The testing should be done under the supervision of competent personals. Only trained personnel's should be allowed to handle the Explosives.

37. TESTING OF CLASS II EXPLOSIVES

38. Determination of Moisture Content : ( Azeotropic Distillation) The basic principle of this method is using solvent to dissolve soluble components in emulsion explosives, which forms mixture with ammonium nitrate aqueous solution. 2. When heated , these mixture azotrope in the flask of measuring apparatus, and through such processes as distillation, condensation, separation water content can be read out in moisture receiver. Moisture content (%): ( Vo*100)/Go Vo- Measured moisture volume after separation. Go- Weight of Emulsion explosive taken.

39. Determination of Density: As the Class II slurry & Emulsion explosives does not dissolve in water. The density can be measured by taken a known weight of emulsion and by putting it in the specified volume of water, then by noting the volume change before and after immersion of emulsion density can be determined. Density (gm/cc): W/(V2-V1) W- Weight of emulsion taken. V1- Initial volume of water. V2- Volume after immersion of emulsion.

40. Stability: Thermal Cycle Method: In this method emulsion explosives are subjected to low temperature for some know time and then suddenly subjected to higher temperature for known time. This cycle is continuously done till the emulsion get damaged. The number of cycle is noted up to which the emulsion holds its properties. Its is generally observed that it emulsion withstand the 10 thermal cycles, it will be stable for more than 6 months. Solution Method: In this method the emulsion explosives are dissolved in water. If there are any un emulsified ammonium nitrate present in the emulsion system it will get dissolve in water and by calculating the AN content in water its stability can be determined.

41. Water Resistance test Take 5 cartridges of the sample explosives. Make three 6mm dia holes (having a depth slightly less than the radius of the cartridges) on the cartridges surface in the form of spiral, each hole 25mm apart in such a way that the 1 st hole is at least 50mm from one end of the cartridges and also the first hole and the third hole are in line with each other. Make a detonator hole at one end of the cartridges of such depth that there is at least a clearance of 25mm between the end of this hole and the first hole on the cartridge surface. Plug the end hole with a dummy detonator. Take metal trough of 20cm height and fill it with water. Keep the cartridges horizontally under 15cm depth of water. Examine the cartridge after every half and hour .

42. Velocity of Detonation by Dautriche Method: Take at least a 200 mm long cartridge. In case the length of the cartridge is small, take two cartridges, cut one of the ends of both, keep the cartridges with the cut ends in contact and roll the cartridges in S-fold manila paper so as to make a single cartridge. Make a hole at one end of the cartridge using a brass or aluminium pricker for inserting the detonator. equal depth into the cartridge at a Make two radially driven holes of known -distance apart in such a way that the-first hole is at least 1.5 times the diameter of the cartridge away from the detonator end of the cartridge.

43. Calculation: Velocity of detonation ( V), m/s = dxV /2∆L Where, d = distance between two ends of the detonating fuse, V = Velocity of detonation of the detonating fuse in km/s, and ∆L = distance between middle point of standard detonating fuse ( scratch on the plate) to the point on the plate where the two detonation fronts travelling in opposite directions meet. Remove the cartridges when they start becoming soggy. Remove the dummy detonator from the end hole, replace it with a No.6 detonator and fire the charge following the recommended shot firing procedure.

44. Precautions: The following precautions shall be observed : Retain the exploder on firing panel key in possession while connecting the bare leads of the detonator with the firing cables. Also keep the bare leads of the detonator short-circuited prior to making connection with the firing cable. Collect the fragments of un-detonated explosives after firing of the charge. In case of misfires, wait for at least 10 mins . Before approaching the charge if it is fired electrically. In case of misfires, while firing with safety fuse, wait for at least for half an hour before approaching the charge.

45. Velocity of Detonation Using Micro timer The micro timer is an electronic instrument, which is suited for measuring very short time intervals, such as those involved in detonation processes. Two signals, which define the beginning and end of the time interval to be measured, are used as ‘start’ and ‘stop’ signals to operate a gate. This gate turns on and off a constant current supply to a capacitor and the voltage developed across and capacitor is measured by an electrometer voltmeter circuit. Thus if the capacitor starts with zero potential difference across it, the potential registered by the voltmeter circuit at the end of the time interval is directly proportional to the time interval. By suitably selecting the various circuit constants the voltmeter is made to read directly in microseconds .

46. Take four pieces of enameled copper wire of 0.32 to 0.56mm diameter, each of 60cm length. Pick up two enameled wires at a time and twist together on end over 3 to 4 cm. Remove the insulations of the free ends of the wires. The twisted wires with the bare ends are known as ‘VOD probes’. Take at least a 200mm long cartridge. In case of small cartridges, take two cartridges, cut one end of each, keep the cartridges in contact with bare ends facing each other and roll in a 3-fold manila paper to make a single cartridge. Take a brass or aluminium pricker and make a hole at one end of the cartridge for inserting detonator. Make two radially driven holes of 2mm diameter through the cartridge at a known distance apart in such a way that the first hole is at least 1.5 times the diameter away from the end of the detonator in the cartridge.

47. Precautions: The following precautions shall be observed : Keep the timer key and exploder key(in case of firing by exploder) always in possession while connecting the detonator to the shot-firing cable. In case of incomplete detonation, carefully collect all the fragments of the charge. In case of misfire wait at least for 5 mins . In case of shot firing electrically or for at least 30 mins in case of shot-firing with safety fuse before approaching the shot. The timer shall be calibrated once in 6 months. Insert the twisted ends of the probes one each into the diametrically driven holes. Split open the twisted ends and fix them in position by cello tape.

48. Impact Sensitivity Test ( Fall Hammer Test) The resistance of an explosive to initiation or decomposition by impact gives an indication of its safety in handling, transportation and use. The test consists of dropping a known mass from a known height on to a known quantity of explosive kept in between the surfaces of two stainless steel Hoffmann rollers of 6 mm diameter which are kept in position by the steel collar. The maximum height at which no detonation or decomposition takes place in 10 consecutive tests and the minimum height at which at least one detonation or decomposition takes place in 10 consecutive tests is determined.

49. Precautions:- The following precautions should be observed: Use shatter proof protective goggles while carrying out the test. Do not try to push out the jammed Hoffmann roller containing explosives in between them. In case of no detonation or decomposition from a particular height adjust either the mass or height of fall of the hammer to ensure that the explosives detonates or decomposes. The surface of the Hoffmann rollers shall be smooth and flat. Do not use dented rollers for the test.

50. Procedure: Weigh accurately 20 mg of the explosive in an aluminum boat. Transfer this explosive uniformly on the top surface of the lower Hoffmann roller kept inside the collar. Keep the upper roller on top of the explosive. Raise the release mechanism of the apparatus to a definite height. Take a hammer of suitable mass ( 1/2Kg, 1Kg, 2Kg, 5Kg, 7.5Kg or 10Kg) and fix it to the release mechanism. Drop the hammer ( by operating the release mechanism) on to the top surface of the upper Hoffmann roller. Determine the maximum height at which in 10 consecutive tests no detonation or decomposition takes place and the minimum height at which at least one decomposition takes place in 10 consecutive tests.

51. Air Gap Sensitivity Test Take at least 200 mm long cartridge and cut it into two equal lengths to form donor and, receptor. 2. If the explosive runs freely, cover the cut ends by small pieces of paper and ret& the papers in position by rubber bands. 3. Prick a hole at the uncut end of one of the test samples using a brass/ aluminium pricker for inserting the detonator prior to firing of the shot. 4. With the cut ends facing each other, place the cartridges in line at a known distance apart, roll the cartridges in three-fold paper of the type used in wrapping explosives .

52. Precautions: The following precautions shall be observed : Keep the timer key and exploder key(in case of firing by exploder) always in possession while connecting the detonator to the shot-firing cable. In case of incomplete detonation, carefully collect all the fragments of the charge. In case of misfire wait at least for 5 mins . In case of shot firing electrically or for at least 30 mins in case of shot-firing with safety fuse before approaching the shot. The timer shall be calibrated once in 6 months.

53. Test for continuity of detonation Make a one metre long column of cartridges of the smallest diameter and of the smallest mass in that diameter to be manufactured. Keep them in loose contact without any confinement in a three-fold manila paper or any other paper used for wrapping the explosive under test on a steel bar or rail. 3. Initiate the end cartridge by a detonator of the type recommended. 4. Observe whether all the cartridges have detonated or not.

54. Precautions: The following precautions shall be observed : Keep the timer key and exploder key(in case of firing by exploder) always in possession while connecting the detonator to the shot-firing cable. In case of incomplete detonation, carefully collect all the fragments of the charge. In case of misfire wait at least for 5 mins . In case of shot firing electrically or for at least 30 mins in case of shot-firing with safety fuse before approaching the shot. The timer shall be calibrated once in 6 months.

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