Explosive initiative devices

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Mine developement 3rd sem project.

Mine developement 3rd sem project.

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  • 1. Explosive Initiative devices By Ankur kishlay and Rahul Raj Rana
  • 2. EXPLOSIVES • Brief Introduction to Explosives • What is an explosive? • An explosive can be solid, liquid or a mixture of substances. When a suitable stimulus, (e.g. electric, flame, spark, percussion) is applied to the explosive substance, it is capable of developing a sudden high pressure by the rapid formation or liberation of stable gases at high temperatures.
  • 3. Initiation Systems Some form of initiation systems are: i. safety fuse and plain detonators ii. detonating cord iii. electric and electronic detonators iv. nonel or shock tube detonators  safety fuse and plain detonators (capped fuse): A plain detonator consists of an aluminium tube 42 mm long and 6.4 mm in diameter which contains an explosive charge pressed in the bottom of the tube. Safety fuse burns at a rate of 120 seconds per metre.  Detonating Cord Safety fuse burns but detonating cord detonates. It detonates at a rate of 7000 m/s. A detonating cord is carrier of detonating wave which is used to detonate the primer. There are many uses of detonating cord including production blasting to fire main shots, presplitting, smooth blasting, seismic exploration, cutting tree limbs and old pier piles.
  • 4.  Electric detonators It looks the same as the plain detonators but the only difference is the two leg wires attached to the detonators. Most of the detonators has the resistance of 1 to 2 ohms and the current needed to detonate the detonators is 1.5 amperes. There are two types of electric detonators which are the instantaneous type and the delay type. The instantaneous will detonate at zero second upon initiation. The delay detonators are manufactured in the same way as the instantaneous but the only difference is the presence of a delay element. . Electric delay detonators series are: 1)Half second series: the range of delays available is 1 to 12 giving a total of 12 detonators in series, where a half second interval between each delay. 2) Millisecond series : basically 25 ms delay time interval. 3)Carrick short delay series : these detonators complemented the permitted explosives and are specially designed for use in coal mines Structure of a typical electric detonator
  • 5.  Nonel system or shock tube system The invention of a shock tube or signal tube is basically a modern version of safety fuse, where a flame can travel through the center of the tube. The tube is made of plastic with 3mm OD and 2mm ID. An explosive powder called HMX covered the inside surface of the tube. The powder detonates at a velocity of about 2000 m/s and this sends a detonating wave to the detonator. The plastic tube is not destroyed after detonation of the explosive powder. The tube can only be initiated by a detonator or by a nonel exploder. Its usage is more appropriate in areas where electric detonators are not advisable to be used.
  • 6. Relay connectors Relay connectors are blasting delay elements primarily for use in surface mining and quarrying operations. There are two main types: 1)Detonating relay connectors(DRC) 2)Nonen trunkline delays(TLD)  A DRC consists of two delay detonators, of from 5 millisecond (ms) to 60 ms duration. The complete unit is in the shape of a sealed plastic dog bone. The DRC is inserted at an appropriate position in the detonating cord line  A TLD unit consists of a plastic “bunch block” connector which houses a Nonel delay detonator attached to a length of signal tube. The delay periods vary, depending on the particular manufacturer’s product. The relay type of each TLD, which functions unidirectionally, ensures true hole-by-hole initiation with correct sequencing. Bunch block connector
  • 7. Exploders Exploders or blasting machines are used in the electrical initiation system. These are available depending on the number of electric detonators in the circuit. The common range is for 1, 12, 25 30 and 100 detonators. Some exploders are compound-wound generator types, whereas others are battery operated capacitor-discharge types. A type of dynamo-condenser exploder can fire 100 detonators in series. This is a hand-driven generator together with a condenser is incorporated in this exploder. A neon lamps indicates when the condenser is charged with a least 1200 volts AC, and a button switch applies the voltage from the condenser to the output terminals. Exploder
  • 8. THANK YOU Submitted to Dr. Rajesh Rai