EXPLODERS & TYPES OF EXPLODERS

Exploder

Electric shotfiring is safer, quicker, and more convenient than ordinary fuse firing by flame or ignition as it provides safety to the shotfirer and his helpers. Tapping of electric power from lighting or signalling lines is not permitted by the Regulations.

The portable apparatus which provides the current necessary for firing electric detonators is called an exploder.

Magneto (or Dynamo) Exploder

The types of exploders that are currently used in India 

The magneto exploder consists essentially of a permanent steel magnet between the poles of which revolves an armature rotated through gearing by rotary handle or by a rack and pinion. The value of the voltage depends upon the speed at which the armature revolves and the flux created by the magnets. A low tension exploder gives a voltage of about 15 volts. AH.T. exploder gives about 125 volts. The mangneto exploder fires only 1 or 2 shots at a time with single shot exploder and upto 6 shots in series with a 6-shot exploder.

The exploder for U/G coal mines should be intrinsically safe. The armature is actuated by a special twist action detachable key -which should always be with the shotfirer.

Battery Condenser Exploder

The current is provided from a battery of 4 or more dry primary cells connected in series, each giving an e.m.f. of 1.5 V per cell. It is operated by a detachable key. Rotation of the handle through half a revolution first winds up a time switch against the tension of a spring and then trips the mechanism which is controlled by a centrifugal governor so that the battery is connected to the condenser during a predetermined interval of time (a small fraction of a second). The Rhino exploder in the market is an example of battery condenser exploder. It is battery operated condenser discharge type exploder capable of firing upto 3 shots at a time in Rhino 3 model (and upto 25 with Rhino-25)_; when using the exploder, the two wires of shot firing cable are connected to the terminals on the exploder. Insert key and rotate one step clockwise. The action charges a 150 microfarad electrolytic condenser and a small neon lamp glows very brightly. To fire, turn key anti-clockwise to "Off' position. This action explodes the detonator and also discharges the residual charge instantly. In Rhino-25 the firing current is 1.5 amps, input D. C. volts 6, output D.C. volts 600 and firing current duration 3-4 millisecond. The exploder uses only one P—276 Eveready battery. (Fig. 8.4)

Rhino exploders are permitted only in   degree 1 and 2 gassy mines of coalFig.  8.4 Rhino exploder . 1.Terminals.   2. Neon Lamp. 3 Key.

Condenser Dynamo Exploder

These are manufactured by Narendra & Co., The machine is suitable for operations in places where inflammable gas does not constitute a hazard. Three types are in the market.

CNT 50 to fire 50 detonators connected in series.

CNT 100 to fire 100 detonators in series.

CNT 200 to fire 200 detonators in series.

All the three are suitable where the circuit resistance is 160 ohms. The CNT-100 exploder has an output voltage of 750 V. D.C. The duration of current impulse to the line varies from 5 to 6 milli-second. It has got one visual neon indicating lamp to indicate that the exploder is ready to fire. To operate - connect the shot firing cable to the exploder terminals. Place handle on to the unlocking shaft; rewind until the moon light comes on and then fire; switch off and disconnect.