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K D PRASAD
GM(Min)/(Vig)
 Definition of Explosives : Explosives is a
chemical compound or mixture, when exploded
by action of heat, impact, gives ...
 Low Explosives : The chemical reaction in
low Explosives is called deflagration which is
a rapid process of combustion w...
 High Explosives : Reaction in High Explosives
is characterised by an associated shock wave
initiated by a detonator, bas...
 Various important Explosives Characteristics
are
 Velocity of Detonation (VOD)
 Weight Strength
 Fume Characteristics...
 Velocity of Detonation : It is the speed at which
detonation wave travels through the media, it
depends upon Explosive t...
 Bulk Strength : It is the energy released per unit volume
of Explosive as compared to ANFO. Bulk strength can be
calcula...
 Sensitivity : An Explosives is required to be
insensitive to normal handling, shock and
friction, but must remain suffic...
 Density : The density is important when selecting an
Explosive for a particular use. With a high density
Explosive the e...
 The DGMS stipulates that no blast hole shall be
charges if the temperature in the borehole
exceeds 80oC when blasting in...
 Properties of NG & AN :

 Nitro Glycerine (NG) - it is a liquid, insoluble in water,
highly sensitive to stock, fricti...
 A SPECIAL EXPLOSIVES FOR CONTOUR
BLASTING

 It is known as pipe charges or Gruit charge. Consist of
a plastic pipe (PV...
 BULK EMULSION :
 Solar Explosives Ltd. has geared up for supply of
Bulk delivered system. This Emulsion technology
has ...
 To deliver the product down the borehole,
company is offering initially repumpable type
and Pumped Doped Emulsion. For t...
 The system, which we are offering now, is named as
Repumpable Bulk Doped Emulsion, Solar BE 101. For
this system the emu...
 Various important blasting accessories are as
under :
1) Safety Fuse
2) Plastic Ignitor Cord.
3) Detonators.
 Plain Det...
4) Cord Relay
5) Detonating Cord
6) Magnadet
7) Anodet
8) Ohm Meter
9) Exploder
 Safety Fuse :
 A cord of special black powder wrapped in envelope made
up of various layers of textile yarn & water pro...
 PLAIN DETONATORS :

 Used for initiating high explosives but are them selves
ignited by safety fuse consist of 6mm dia...
 These are fired electrically.

 INSTANTTANEOUS ELECTRIC DETONATORS :
 Comprises of Cu of Al. Tube of 7mm dia and a li...
 ELECTRIC DELAY DETONATORES :

 Special use in shaft sinking tunneling, drifting where
successive rounds are better fir...
 SHORT DELAY :

 Short Delay electric detonators are same as long delay in
construction and strength and above nominal ...
 Non-electric delay detonator basically consist of a length
of plastic single tube to which is fitted a powerful delay
de...
 CORD RELAY :

 These devices permit short delay to be introduced into trunk
lines of detonating cords. A cord relay co...
 DETONATING FUSE :

 It serves the same purpose as detonators and
directly initiates the high Explosives while them
nee...
 OHM METER :
 Used for testing the continuity and resistance of blasting
circuits.These are of two types.
 Powered by l...
No. of Charge Total
Holes Per Hole Charge
Per Ring (Kg) Per Ring (Kg)
Ring 5 1.40 7.00
Sumpers 8 1.12 8.96
Inner Easers 12...

 Tunneling in rocks is currently performed mainly by blasting,
as this method only is capable of providing sufficiently...
 Cut holes : Shot holes in this group are generally longer
(approx. 15 cm) than the shot holes of other group. These
hole...
 The following type of cuts commonly use in Drifting /
Tunneling :
 (A) Cone / Pyramid / Diamond cut : Four or Six cut h...
 (C) Parallel holes cut (Burn Cut, Cylinder Cut,Coromant Cut ) :
 A cluster of parallel shot holes are drilled at perpen...
1. Making of blast hole: It should be made as accurately as
possible, particularly the line holes. This can be effected by...
2. Charging and shooting of blast holes: To reduce
the charging time it is possible to employ composite
explosive charges ...
4. Periphery holes: To control over break,
effective decoupling is required. It can be
done by,
 By using 25mm dia. Cartr...
Thumb rules for u/g coal
blasting:
A) Cut face blasting:
1. No. of holes
For each 1 square meter area =
1 hole
2. Depth of...
1.
a)No. of holes a)For normal conditions,0.7 sq.mt = 1
hole
b)Tougher conditions, 0.5 sq.mt = 1 hole
2. Maximum depth of ...
1. 'Freedom to Move : Insitu Coal needs free
passage to move out during blasting, i.e. Free
face to be created either by
1...
3. Solid Blasting :
a) To create an initial cut, holes need to be drilled in
inclined position so as to provide direction ...
 Solid Blasting :
d) Stemming less than 60% of hole length or un
proper packing may not be able to sustain
the volume / p...
(Numbers show sequence of firing rounds)
Depth of Hole - 1.5 Meters
No. of Holes - 8
Charge /
Holes - 300 g
Total yield of...
 The technique of blasting off-the solid (BOS) has been
found to be simpler, more economical and less
hazardous that the ...
 The delay detonators, required for use with this
type of explosives, must be non-incentive.
Typical rounds of shot holes...
Type of Number Depth of Explosive / hole Delay Stemming
Holes Holes Number
Cut Holes 6 1.7 m (5.6) 3 555 Z 60-65%
Other 6 ...
Degree of Classification of Gassiness Type of Permitted
Gassiness of Coal Explosives
seam
I < 0.1% of gas in the general b...
1. Explosives:
Types of Explosives
Degree of gassiness /
Type of Max
Application
Permissible charge
per
Shot hole (gms)
P1...
2. Delay Detonator :

a) While using non-incentive delay detonators in ‘BOS’ application,
the maximum delay period betwee...
1. Explosives are also used for a variety of other
applications some of which are listed below :
2.
3. Agriculture.
4. Bre...
1. While storing transporting of handling explosives, do
not smoke or have in your possession matches, naked
light or appa...
6. Do not force a detonator into a cartridge.
7. Do not try to soften hardened explosives by heating
over fire or by rolli...
1. Test the exploder before use.
2. Stop all blasting work during an electrical storm and clears the
working area of all m...
7. To ensure good insulation and avoid short circuits in wet
conditions use insulating tape.
8. The key of the exploder sh...
 There are many circumstances under which a misfire
can occur and there are official regulations covering the
treatment o...
1. Misfires with Safety Fuse Initiation :
 In safety fuse firing faulty cutting of safety fuse, loose
crimping, use of no...
3. Misfires with Detonating Fuse :
 While firing with detonating fuse incorrect
method of limiting the detonating fuse, l...
4. Misfire with Exploders :

 A large number of misfires are generally caused by the
use of faulty exploders and use of ...
 Wherever possible, it is safer to fire the
explosives using a fresh primer than to
attempt to dislodge it and recover th...
 (Cir.Tech. 11/1979)
 Use of L.O.X. in opencast Coal Mines :
 Recently, there was an incident of fire with the use of L...
 Managements are requested to furnish
DGMS with a list of the shot fires in service at
their respective
 1. Name in Full...
 A copy of the list should be sent to the
Superintendent of Police having jurisdiction
in the area, which the mine is sit...
THANK
YOU !!!
UG Explosives and Blasting
UG Explosives and Blasting
UG Explosives and Blasting
UG Explosives and Blasting
UG Explosives and Blasting
UG Explosives and Blasting
UG Explosives and Blasting
UG Explosives and Blasting
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UG Explosives and Blasting

Explosives used in underground coal mines and method of drilling and blasting adopted explained in simple way.

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UG Explosives and Blasting

  1. 1. K D PRASAD GM(Min)/(Vig)
  2. 2.  Definition of Explosives : Explosives is a chemical compound or mixture, when exploded by action of heat, impact, gives large volume of gases in a very short time at high temperature & pressure.   Classification : All commercial Explosives are broadly divided in two categories.   Low Explosives  High Explosives
  3. 3.  Low Explosives : The chemical reaction in low Explosives is called deflagration which is a rapid process of combustion without accompanying any shock wave but gives a heaving effect.  Example : Gun Powder  Chemical Composition :  Sodium Nitrate - 72%  Sulphur - 12%  Coal - 16%
  4. 4.  High Explosives : Reaction in High Explosives is characterised by an associated shock wave initiated by a detonator, basically contains.   Oxidisers - Such as Ammonium Nitrate Fuel Oil  Sensitizers : MethyleAmino Nitrate, Per chlorate Salt Physical Sensitizer : Entrapped Air Bubbles
  5. 5.  Various important Explosives Characteristics are  Velocity of Detonation (VOD)  Weight Strength  Fume Characteristics  Thermal Stability  Sensitivity  Density  Water Resistance
  6. 6.  Velocity of Detonation : It is the speed at which detonation wave travels through the media, it depends upon Explosive type. VOD is measured by, some electronic means or by Dautriche test. Average VOD varies form 2500 M/Sec - 5800 M/Sec.   Weight Strength : Weight strength is the energy generated by an Explosive relative to that produced by an equal weight of 94 AN 6 FO (94%) Fuel Oil.
  7. 7.  Bulk Strength : It is the energy released per unit volume of Explosive as compared to ANFO. Bulk strength can be calculated from weight strength using the equation  Relative Bulk Strength =  Relative Wt. Strength x Density  ------------------------------  Density of ANFO  Water Resistance : Explosives differ widely in resistance to water and moisture penetration. Some Explosives deteriorate rapidly under wet conditions, but others are designed to withstand water for long periods. When blasting is to be done under wet conditions, a water resistant Explosive is preferable.
  8. 8.  Sensitivity : An Explosives is required to be insensitive to normal handling, shock and friction, but must remain sufficiently sensitive to be satisfactorily detonated, and capable of propagating satisfactorily, cartridge to cartridge, even over gaps such as may occur in practice.   Fume Characteristics : Explosives, when used under stipulated ventilation conditions, should liberate a minimum of harmful gases in the products of detonation.
  9. 9.  Density : The density is important when selecting an Explosive for a particular use. With a high density Explosive the energy of the shot is concentrated a desirable feature in tunneling and mining operations in hard ground. On the other hand when the output of lump coal from a mine is important, it is advisable to use a low density Explosive, which distributes the energy along the shothole.   Thermal Stability : Explosives compositions should be such as to be stable under all normal conditions of usage.
  10. 10.  The DGMS stipulates that no blast hole shall be charges if the temperature in the borehole exceeds 80oC when blasting in hot ground. Sometimes Explosives have to be used in sub zero conditions in which some explosives become insensitive. Explosives compositions of M/s. Solar Explosives Ltd. are designed to be stable and safe, under all conditions of use. When blasting in hot ground, precautions as stipulated by the DGMS should be adhered to.
  11. 11.  Properties of NG & AN :   Nitro Glycerine (NG) - it is a liquid, insoluble in water, highly sensitive to stock, friction and heat. In all Explosives of N.G. based on nitroglycol is mixed for lowering the freezing point, used for hardest rocks and metals and for shooting oil wells.   Ammonium Nitrate (AN) :   It is a weak Explosives base. Difficult to initiate, so a sensitizer like NG or TNT is used. It is Oxygen positive, Hygroscopic, soluble in water. Tendency to form hard cakes.
  12. 12.  A SPECIAL EXPLOSIVES FOR CONTOUR BLASTING   It is known as pipe charges or Gruit charge. Consist of a plastic pipe (PVC) of dia 11mm & of length 460mm, containing Explosives within it at concentration 0.11 Kg/m & 1.24 Kg/m respectively. Rate of detonation 4000 m/Sec. These are used in presplitting, smooth blasting and when blasting close to buildings. Advantages being saving in handling & charging time, over charging is eliminated, less over break, less cracking & less vibration.
  13. 13.  BULK EMULSION :  Solar Explosives Ltd. has geared up for supply of Bulk delivered system. This Emulsion technology has been developed indigenously and engineered a plant, which can manufacture refined & reliable product. Emulsion technology comes in the following categories :   Repumpable Emulsion  Site Mix Emulsion with Support Plant  Augered Heavy ANFO  Pumped Doped Emulsion
  14. 14.  To deliver the product down the borehole, company is offering initially repumpable type and Pumped Doped Emulsion. For this company has designed special pump, truck capable of pumping Bulk Emulsion after mixing with density control agent on site.
  15. 15.  The system, which we are offering now, is named as Repumpable Bulk Doped Emulsion, Solar BE 101. For this system the emulsion of oxidiser and fuels is prepared at location, where this facilities are available. The emulsion can be stored in ambient conditions and is non-explosive. This non-explosive emulsion matrix after doping with Prilled Ammonium Nitrate is mixed with gassing agents are charged into bore hole by pump truck. The mixture becomes sensitive only after the same is delivered in to the blast hole and the gassing reaction completed in above 15 minutes.
  16. 16.  Various important blasting accessories are as under : 1) Safety Fuse 2) Plastic Ignitor Cord. 3) Detonators.  Plain Detonators  Electric Detonators  Instantaneous Electric Detonators  Long delay Detonators  Short Delay Detonators  Non Electric Detonators
  17. 17. 4) Cord Relay 5) Detonating Cord 6) Magnadet 7) Anodet 8) Ohm Meter 9) Exploder
  18. 18.  Safety Fuse :  A cord of special black powder wrapped in envelope made up of various layers of textile yarn & water proofing material. Used for directly igniting low Explosive of initiating high Explosive through plain detonator. Burning rate 100-130 sec/m.   Plastic Ignitor Cord :  Used for ignition of several fuses in quick succession in any desire sequence. It is 1.8-2.5 mm dia fuse, which gives intense flame at uniform rate. Rates 3.3 S/M of 33 S/M. slower one contains a core of a cu wire coated with plastic incendiary composition and an iron wire added for strength, with plastic covering.
  19. 19.  PLAIN DETONATORS :   Used for initiating high explosives but are them selves ignited by safety fuse consist of 6mm dia Al. Tube partly filled with detonating charges. Modern detonators have a base charge of PETN (Penta Erithetetrol Tetra Nitrate) with a priming charge of A.S.A. (Lead Azide, Lead Styphnate and Al. Powder) strength depends upon amount of base charge.   No.6 & No.8, No.6=0.22gm. of PETN & 35mm long. No.8=0.45gm. PETN & 48 mm long both contains 0.2 gm ASA.
  20. 20.  These are fired electrically.   INSTANTTANEOUS ELECTRIC DETONATORS :  Comprises of Cu of Al. Tube of 7mm dia and a little longer than the plain detonator so as to accommodate the fuse head and the neopren plug. Copper Detonators are for gassy coal mine where highly incendiary Al. is prohibited. Explosive charges are ignited by an electric fuse head of Nickel-Chromium-Iron alloy bridge wire soldered to the ends brass foils separated by an insulating piece of card board.  Fuse Head Composition : Potassium Chlorate, Nitro Cellulose, Charcoal (See Sketch)
  21. 21.  ELECTRIC DELAY DETONATORES :   Special use in shaft sinking tunneling, drifting where successive rounds are better fired in a certain sequence with adequate time interval in between rounds so that each round breaks into clear free face. In delay detonators a time lag is deliberately introduced between the firing of the fuse head and the explosion of the detonator.   LONG DELAY DETONATORS :   These are also known as half second delay detonators having nominal delay interval of around 300 to 500 ms for each. These are widely used for tunneling work and generally from 1 to 10 Nos. are available.
  22. 22.  SHORT DELAY :   Short Delay electric detonators are same as long delay in construction and strength and above nominal delay interval of 25 ms. for each delay.   Delay composition of long delay detonator comprise of antimony and KMNO while it is Red Lead & Silicon for short delay.   NON ELECTRIC DETONATORS :   Earlier mentioned plain detonator also fall under this but due to its restricted use it is explained under separate heading.
  23. 23.  Non-electric delay detonator basically consist of a length of plastic single tube to which is fitted a powerful delay detonators.  The single tube is made of a special plastic material. The outer dia being 3 mm and inner dia 1.0 mm. Its inner surface is lightly coated with a mixture of reactive powders which provide the energy transmitting medium with in the tubing on initiation by a detonator cord or by a detonator a shock wave propagates along inside the tube at a velocity of about 2000 M/sec. without bursting the tubing and therefore having no effect on any Explosives through which is passes.  The resulting flame front ignites the top of the delay element with in the detonator tube.
  24. 24.  CORD RELAY :   These devices permit short delay to be introduced into trunk lines of detonating cords. A cord relay consists of two delay detonators mounted inside a resilient plastic shell. They are bi-directional in operation, Cord Relays are available in the 15 Ms, 17 Ms, 25 Ms, 50 Ms, 75 Ms, 100 Ms, delay time. The shorter delay intervals are generally required for small (65- 90mm) dia blast holes drilled on close spacing whereas the longer intervals are suited to larger blast holes drilled on wider spacing.   Cord Relays are designed for use with detonating cords, which have core loads of 10 gm/M. No special connecting tool is needed.
  25. 25.  DETONATING FUSE :   It serves the same purpose as detonators and directly initiates the high Explosives while them needing a detonator for initiation. Useful in simultaneous multiple shot firing minimising the use of several detonators. Advantageous in blasting long hole. It comprises of PETN (Penta Erithetetrol Tetranitrate) train enclosed in a tape wrapped in textile yarn and whole thing covered by plastic. Finished dia 5 mm for the D.F., which contain 10 gm PETN meter (See Sketch).
  26. 26.  OHM METER :  Used for testing the continuity and resistance of blasting circuits.These are of two types.  Powered by low voltage hand operated generator.  1.5v dry battery type.   EXPLODER :  Used for firing shots electrically, these are of two types:  i) Generator type :- Magneto of dynamo (for large capacity) operated by a quick twist of strong down ward push of handle.  ii) Condenser discharge type :- Can be battery of dynamo powered.
  27. 27. No. of Charge Total Holes Per Hole Charge Per Ring (Kg) Per Ring (Kg) Ring 5 1.40 7.00 Sumpers 8 1.12 8.96 Inner Easers 12 0.98 11.76 0.98Quter Easers 16 15.68 Trimmers 41 1.05 43.40
  28. 28.   Tunneling in rocks is currently performed mainly by blasting, as this method only is capable of providing sufficiently high effectiveness and economics in the construction of tunnel in tough rocks.   Tunneling by tunnel borers is considered to be less effective especially as regards the construction of tunnels of large cross sectional areas.   Drifting /Tunnel Driving Methods in Rocks :  The shot holes in a stone drift or tunnel are arranged in a particular form or pattern. The drifting pattern, holes are generally divided into three groups, e.g. Cut holes, Easer and Trimmers.
  29. 29.  Cut holes : Shot holes in this group are generally longer (approx. 15 cm) than the shot holes of other group. These holes are fired first to created free face for the shots of easers. Since these holes first make the opening in the face, they are prime responsible for the depth of pull.   Easers : The shot holes of this group are placed in the drift around the cut holes in two or more rings depending on the cross - sectional area. These holes ease the burden between the succeeding shot holes to enlarge the excavation area of the drift.   Trimmers : The shot holes of this group are place around the easer which are fired at the last to make the final shape of the drift.
  30. 30.  The following type of cuts commonly use in Drifting / Tunneling :  (A) Cone / Pyramid / Diamond cut : Four or Six cut holes are driven at the middle of the face which converge at the end to form either a Cone or a Pyramid or diamond shape. Maximum concentration of charge is at the apex of these cut holes, which are fired first to create a free face for the rest of the shot, which are fired next with the help of delays.   (B) Wedge Cut : Horizontal cut holes are driven in inclined at an angle less than 45 degree to the face towards the centre. Like Cone / Pyramid cut maximum concentration of charge at the apex of these cut holes, which are fired first to create a free face for the rest of the shot, which are fired next with the help of delays.
  31. 31.  (C) Parallel holes cut (Burn Cut, Cylinder Cut,Coromant Cut ) :  A cluster of parallel shot holes are drilled at perpendicular to the face to blast out a cavity in the centre of the heading. Some of the holes are heavily charge with explosives while others are kept empty to provided free face for reflection of shock waves. There is specific geometrical relationship between the diameter of empty hole and spacing between the centres of empty hole and charged holes in a given rock, which gives the essential condition of free breakage.   (D) Drag Cut / Draw Cut : These type of cut is most suitable for the laminated rocks for "controlled blasting " in drivage of smaller cross-sectional area to brake the rock along the cleavage planes.
  32. 32. 1. Making of blast hole: It should be made as accurately as possible, particularly the line holes. This can be effected by template, or marking use of spray paint as convenient. A very efficient procedure of pointing holes on the working face with a light projector with an optical attachment consisting of metallic casing, lenses and a frame that receives a metallic plate carrying the location of the blast holes. Each hole is represented on the plate as an orifice 1mm in dia. The projector is placed at a distance from the working face equal to 1.5-3 times the height of the working. Source of the light is a lamp of 1000W. The apparatus is located using two marks. Spotted on the face is an advance light spot projected through the plate on the face correspond to the holes to be drilled.
  33. 33. 2. Charging and shooting of blast holes: To reduce the charging time it is possible to employ composite explosive charges consisting of several cartridges placed whether in paper shell or PVC pipes. The use of composite charge, which is 5-10 times the carting length, shortens the charging time by 50-60%. 3. Parallel wiring is generally used for firing shots from an electric power mains and series for a blasting machine. In case of NONEL use of D-cord and electrical instantaneous detonators is fired with exploder.
  34. 34. 4. Periphery holes: To control over break, effective decoupling is required. It can be done by,  By using 25mm dia. Cartridge in 38mm dia. Hole.  By using comparative weaker explosive  By keeping air gap between two explosives cartridges by using hollow bamboo spacer of 150mm long.
  35. 35. Thumb rules for u/g coal blasting: A) Cut face blasting: 1. No. of holes For each 1 square meter area = 1 hole 2. Depth of hole 15cm less than cut length 3. Charge per hole 40% of hole length 4. Stemming 60% of hole length 5. Explosive P1 type (Solarcoal-1) for degree 1 mines P3 type (Solarcoal-3) for degree 2/3 mines
  36. 36. 1. a)No. of holes a)For normal conditions,0.7 sq.mt = 1 hole b)Tougher conditions, 0.5 sq.mt = 1 hole 2. Maximum depth of cut holes 0.7 x height of gallery 3. Depth of other holes = 0.8 x cut hole length 4. Charge per hole = 40% of hole length 5. Stemming = 60% of hole length 6. Explosive = P-5 type 7. Max. Possible pull = 0.8 x cut hole length . No. of holes a)For normal conditions,0.7 sq.mt = 1 hole
  37. 37. 1. 'Freedom to Move : Insitu Coal needs free passage to move out during blasting, i.e. Free face to be created either by 1. CCM - Cut face blasting 2. Creating wedge opening by drilling and blasting a few additional holes preferably at centre of face. 2. Cut Face Blasting : Holes need to be shorter by 15 cm from cut depth because explosives energy released during blasting hits in a crater shape and the point of concentrated energy is 15 cm beyond the end of cartridges, where free face should be available for breakage of coal.
  38. 38. 3. Solid Blasting : a) To create an initial cut, holes need to be drilled in inclined position so as to provide direction and force for coal to move outwardly, to create free face for other holes. (Lever action theory) b) Wider the opening (i.e. Free face) easier it would be for other holes to perform better. It is advisable to give zero delay for 6 cut holes in the centre. c) Considering Beam theory, hole length beyond 70% of seam height would not bring expected result. Rather long sockets will be left and explosive energy will be wasted and P.F. will be reduced.
  39. 39.  Solid Blasting : d) Stemming less than 60% of hole length or un proper packing may not be able to sustain the volume / pressure of gases generated during blasting and explosive energy will be wasted in form of a blown out shot. e) Cut holes should be charged more as compared to other holes. f) Initiation sequence should be maintained so as that cut holes give way first, nearest hole next and farthest holes last.
  40. 40. (Numbers show sequence of firing rounds) Depth of Hole - 1.5 Meters No. of Holes - 8 Charge / Holes - 300 g Total yield of Coal - 14 tones Yield per kg - 6.00 tones
  41. 41.  The technique of blasting off-the solid (BOS) has been found to be simpler, more economical and less hazardous that the conventional method of breaking coal with machine cutting and blasting. Mechanised methods using BOS with scraper loaders and side loaders have already proved successful. Several long wall mining faces employing BOS are also tired out. The hazards associated with blasting off the solid in gassy coalmines, are such that the usual permitted explosives of the category P1 and P3 are not considered safe. Solarcoal-5 belongs to P5 category and has been designed to meet the exacting safety requirements in blasting coal off-the solid.
  42. 42.  The delay detonators, required for use with this type of explosives, must be non-incentive. Typical rounds of shot holes wedge cut and fan cut patterns, and a schematic diagram indicating blasting pattern and initiation sequence in long wall faces are shown on the following pages. For effective blasting off-the solid, full face firing in a heading is necessary both form safety as well as productivity point of view indigenously available Schaffer type 350 and Rhino 25 shot exploders are designed to meet this requirement of BOS.
  43. 43. Type of Number Depth of Explosive / hole Delay Stemming Holes Holes Number Cut Holes 6 1.7 m (5.6) 3 555 Z 60-65% Other 6 1.6 m (5') 3 555 I 60% Holes 3 1.6 m (5') 3 555 II 60% Total Explosives per Expected Pull Expected Coal Powder Factor Detonato r Round (Insitu) T/Kg. Factor 8.32 Kg. 1.27 m (4') 19.74 M.T. 2.37 1.31
  44. 44. Degree of Classification of Gassiness Type of Permitted Gassiness of Coal Explosives seam I < 0.1% of gas in the general body of air and P1 / P3 / P5 rate of emission of such gas is less than 1 cu. m/t of coal production II > 0.1% of gas in the general body of air and P3 / P5 rate of emission of such gas is greater than but less than 10 cu. m/t of coal production III Rate of emission of the gas is greater than 10 P3 / P5 cu. m/t pf coal production
  45. 45. 1. Explosives: Types of Explosives Degree of gassiness / Type of Max Application Permissible charge per Shot hole (gms) P1 Degree 1 mines, 800 P3 Cut face 1000Degree I, II & III mines, P5 Cut face 1000Degree I-‘BOS’, P5 Degree II &III-‘BOS’ 565
  46. 46. 2. Delay Detonator :  a) While using non-incentive delay detonators in ‘BOS’ application, the maximum delay period between the first and last shot in a degree I and II Gassy coal seams will not exceed 150 ms.  b) While using non-incentive delay detonators in ‘BOS’ application the maximum delay period between the 1st & last shot in Degree III gassy coal seams will not exceed 100 ms.  c) The delay period between 2 consecutive shots with different delay numbers will not exceed 60 ms. 3. Distance between 2 adjacent shots with different delay numbers will not come closer than 0.6 m at the explosives charges ends.
  47. 47. 1. Explosives are also used for a variety of other applications some of which are listed below : 2. 3. Agriculture. 4. Breaking blast furnace hearths / salamander blasting. 5. Cutting dimensional stones. 6. Demolitions. 7. Metal breaking. 8. Metal forming. 9. Salvaging scraps and wrecks. 10. Seismic prospecting. 11. Presplitting, smooth wall blasting etc. 12. Underwater blasting. 13. Roads & railway Construction.
  48. 48. 1. While storing transporting of handling explosives, do not smoke or have in your possession matches, naked light or apparatus of any kind capable of producing flame or spark. 2. Do not keep explosives and detonators in the same container or magazine. Explosives and detonators must be transported separately to the blasting site. 3. Do not use tools made of iron or steel for opening cases or for making holes in primer cartridges. Use implements of hard wood, brass or other non-sparking material. 4. Do not break an explosives cartridge. 5. Check the condition of shot holes with a scraper/stemming rod before inserting cartridges.
  49. 49. 6. Do not force a detonator into a cartridge. 7. Do not try to soften hardened explosives by heating over fire or by rolling cartridges on the ground. 8. Do not fire a blast until you have made sure that all surplus explosives have been removed, and all persons, vehicles and equipment are at a safe distance. 9. Post guards with red flags around the site to prevent persons approaching the danger area inadvertently while the shots are being fired. 10. Keep primed cartridges separately and away from other explosives until they are loaded into the holes.
  50. 50. 1. Test the exploder before use. 2. Stop all blasting work during an electrical storm and clears the working area of all men. 3. While straightening the lead wires, do not hold the electric detonator by the tube. Grip the wires about 10cm from the detonator with one hand and smooth them out with the other. This will avoid any pull on the fuse head. 4. While charging and stemming, take care to avoid damaging the insulation of the lead wires of the electric detonator, which may cause misfires. 5. Twin-core cables have top conductors and care should be taken to make sure that the stands of one conductor are mot in contract with those of the other. It is good practice to have the exposed ends of the conductors staggered in relation to each other. 6. While making connections, the bare ends of the conductors should be twisted together tightly for a length of about 3 cm. The conductors should be thoroughly cleaned since greasy of dirty wires give a poor connection and may cause misfires.
  51. 51. 7. To ensure good insulation and avoid short circuits in wet conditions use insulating tape. 8. The key of the exploder should always be in the possession of the shot fire. 9. All connections should be made by the shot fire himself; this work should be not entrusted to any other person. 10. Before returning to the blast site, remove the exploder key, disconnect the cable form the exploder and short circuit the cable by twisting together the bare ends of the two conductors. 11. Keep the exploder in a dry place. 12. Do not leave bare conductors on wet ground. 13. Take precautions against stray currents while blasting near electrically operated machines or high voltage power lines.
  52. 52.  There are many circumstances under which a misfire can occur and there are official regulations covering the treatment of misfires. These should be strictly adhered to and nothing in this chapter should be construed as altering or amending such regulations. All misfires should be treated with greatest care and all operations dealing with them should be entrusted only to experienced conscientious and careful men.   No person should be allowed to approach a misfire until either it has exploded or a sage period has elapsed. This period should be at least 30 minutes with safety use initiation and at least 5 minutes with electric shot firing.
  53. 53. 1. Misfires with Safety Fuse Initiation :  In safety fuse firing faulty cutting of safety fuse, loose crimping, use of non-waterproof fuse in watery conditions can lead to misfires.  2. Misfires with Electric Shot Firing :  In electric shot firing faulty connections, detonators left- off unconnected, lead wires becoming bare during stemming internally shot-circuited cable / damage in the insulation, inadequate firing current due to failure of the exploder toreach the rated output or the number of detonators being greater that that can be fired by the exploder, current leakage and other factors can cause misfires.
  54. 54. 3. Misfires with Detonating Fuse :  While firing with detonating fuse incorrect method of limiting the detonating fuse, loop cross-over, approach of a different branch of detonating fuse, improper joints and branch-line failure, use of detonators with too long a delay interval, wrong sequencing of shots and improper handling / use if delay detonator-relays could lead to cut-offs of detonating fuse.
  55. 55. 4. Misfire with Exploders :   A large number of misfires are generally caused by the use of faulty exploders and use of wrong type of exploder for a given purpose; Maintenance of exploders is very essential to obtain the output. Following are the causes of misfires with exploders :  a) Inadequate exploder capacity b) Faulty exploder-defective generator/conductor c) Poor contact in rotating crank type exploders d) Exhausted cells e) Faulty indicator
  56. 56.  Wherever possible, it is safer to fire the explosives using a fresh primer than to attempt to dislodge it and recover the cartridges from the debris. However, before deciding on the repriming of the explosives, consideration should be given to the possibility of excessive cracks in rocks, which may occur because of the relief of the burden of the misfired hole, by adjacent shots.
  57. 57.  (Cir.Tech. 11/1979)  Use of L.O.X. in opencast Coal Mines :  Recently, there was an incident of fire with the use of L.O.X. under the following circumstances.   Blasting was done with L.O.X. in the overburden of the opencast workings if a coalmine. Old developed coal pillars were being quarried. One of the shot holes in the overburden punctured into the underground working and as such it could not be stemmed properly before blasting. L.O.X. cartridges in the inadequately stemmed hole were thus blasted without sufficient confinement. In all probability, a part of the charge which had not blasted, communication down below and configurated to set the coal debris lying belowground in the gallery on fire.   In order to avert such situations, you are advised that L.O.X. shall not be used for blasting in overburden within 15 m of ug workings in the coal seam immediately below or in the vicinity.
  58. 58.  Managements are requested to furnish DGMS with a list of the shot fires in service at their respective  1. Name in Full :  2. Father's Name :  3. ResidentialAddress :  4. Home Address :  5. Number and kind of certificate he holds for firing shots :
  59. 59.  A copy of the list should be sent to the Superintendent of Police having jurisdiction in the area, which the mine is situated.   Managements are also advised to enforce strict check or kind of personal search by the attendance clerks at the mine entrance at the time the unspent balance is brought to the surface by shot fires.
  60. 60. THANK YOU !!!

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