Blast Effects Measurement of See under Blast Meters

Blast-furnace Dust(Gichtstaub in Ger). It was used in some expl compns Ref: Kast-Metz(1944), 467

Blastinea A safety expl consisting of a mixt of NH4CI04,NaN03,DNT& 5% paraffin wax(Ref 1). It was claimed by Kedesdy to be 50% more powerful than dynamite. According to Barnett(Ref 3) this is a Swedish expl, but Stettbacher(Ref 4) and Thorpe (Ref 5) report a British expl called Blastine which consists of NH4CI04 60, NaN03

22, TNT 11 & paraffin 7%. Marshall (Ref 2) notes that the expl Blastine was used extensively during WWI. Kostevitch(Ref 3a) gives for a Blastine used during WWI: NH4C10463, NaN03

Refs: 1)E.Kedesdy, SS 3,97(1908) 2)Mar-shall 1(1917),387 3)Barnett( 1919), 112 3a)M.M. Kostevitch, "Burning Ground", Imp d'Art Voltaire, Paris(1927),40 4)Stettbacher(1933),3l6 5) Thorpe 4(1940),464

Blasting, A process of loosening rocks, earth, coal, ores and other materials by the use of expls is called blasting. The blasting action may be that of a- shattering, percussive or heaving nature, depending upon the type of expl used and the method of placing it within or near the material to be blasted

Limiting charge is defined as the max per-missiblechges ofan expl used in gas-endangered mines. Seleznev(Ref 4) tested the validity of this concept by firing charges of various wts (including chges exceeding considerably the wt of a limiting chge) of safety and unsafe expls. The limiting chge concept proved to be without foundation in fact, provided the chge was made to do work, that is, spend itself on blasting coal or rock. If the chge misfired or was faultily placed, then any wt of it (safety or unsafe expls is dangerous. In view of these results, Seleznev (Ref 4) suggested a revision of the safety rules

Suzuki (Ref 3) patented an app with liq C02 expl to be used instead of dynamite in coal mines. Jinda et al(Ref 6a) reported that the toxic gases C02 CO & N02 are evolved from exploded cartridges in testing galleries and in metal ore mines. Lechner in Explosivst 1959, 33-6 discusses poisoning by gases produced on blasting

Numerous handbooks, pamphlets and other refs describing the blasting process are available. See also Ammonium Nitrate Blasting Explosives, Vol l,p A341; Ammonium Nitrate Dynamite, Vol l,p A355; Ammonium Nitrate Gelatin, Vol 1, p A367; and Blasting Explosives in this vol Refs: l)Colver(1918),485ff & 560 2)Ensign-Bick-ford Co, "Efficient Blasting & Prevention of Blasting Trouble",Pamphlet(1941),22pp 3)Y.Suzuki, JapP 3,4 &5 (1950) & CA 46,8376(1952) 4)A.I. Seleznev,Ugol' 26, No 5, 29-30(1951) & CA 45, 8248(1951) 5)Blasters' Handbook(1952) 6)F. Weichelt, "Handbuch der gewerblichen Sprengtechnik",Marhold,Halle/Saale(1953) 6a)T.Jinda et al,JIndExplsSoc(Japan)14,210-12(1953) & CA 49,11281(1955) 7)B.Stoces,"Introduction to Mining",Lange, Maxwell & Springer,London NW, Vols 1 & 2(1954) 8)H.Stapf,"Bergbauchemie", Fachbuchverlag,Leipzig(1954),427pp 9)Imperial Chemlndustries Limited,"31asting Practice", Pamphlet, 2nd Ed, The Kynoch Press, Birmingham (1956) 10)0,Kühnl, "Handuch der Sprengtechnik", Verlag des Osterreichischen Gewerkschaftsbundes, Wien(1958), 155pp ll)Ministry of Power, "The Use of Explosives at Quarries", HMSO,London (1961),60pp

BLASTING CAP (also called Commercial Detonator) (Zündkapsel Zünder or Sprengkapsel in Ger; Detonateur in Fr; Detonator in Rus; Detonadore da mina in Ital and Cebo or Capsula detonante in Span).

When black powder was used exclusively for blasting, charges were exploded by igniting them with miner's fuse, or by other igniters. When NG and dynamite were invented, it was found that they could not be exploded by such means of ignition, hence a different device was needed-one which produces a deton wave. The problem was solved by Nobel in 1867(BritPat 1345) with his invention of the blasting cap. The first cap consisted of a copper cylinder closed at one end and partially filled with MF, which was exploded by the flame of a miner's fuse. The explosion of MF produced a deton wave of great intensity, which caused the expln of the dynamite chge. The charge of MF was varied to provide the initiating strength desired

The modern blasting cap may be defined as a device intended to initiate by means of a detonating wave a HE, coml or a military demolition chge. If such a device is used as a part of an expl train in a projectile or a bomb, it is called a "Detonator" (qv)

Blasting caps may be of either the non-electric or electric type:

I) Non-electric Blasting Caps may be subdivided into single component and compounder composite) caps a) Single-component Cap consists of a small metallic tube closed at one end and partially filled with an Initiating Composition(see under Blasting Caps, Charges and Compositons for).

A piece of safety fuse(Bickford fuse) with a freshly-cut end, pricked with a pin, is inserted into the open end of the cap and pressed firmly against the charge. With the aid of a special device, the open end of the cap is crimped tightly(as near the top as possible) around the fuse, taking care not to squeeze the cap near the explosive chge because of the danger of inducing an explosion. The cap is then inserted in a cartridge or block of HE and the fuse is ignited by the flame of a match or squib. The flame of the fuse ignites the initiating mixt causing it to explode. The deton wave thus created causes the expln of the main chge(dynamite cartridge etc)

These blasting caps are usually made in eight strengths, No 1 the weakest and No 8 the strongest The present practice in the US is to manuf only No 6 and No 8 caps. The single-component No 6 contains a mixt of 0.8g MF with 0.2g KC103; the No 8 cap contains 1.6g MF + 0.4g KC103 or their equivalents b)Compound Cap. Some HE's such as TNT, PA, RDX compositions, Pentolite etc, cannot be initiated with certainty by either a No 6 or No 8 cap and it is necessary to combine them with a booster or to use a cap with two components(layers), one of which is an initiating (primary) charge(such as MF) and the other is a base(main or secondary) charge (such as pressed PETN). In these caps the base charge acts as a small booster

A typical example of such caps is one which consists of a small metallic capsuIe(Cu, A1 or gilding metal) 1ub to l7/8 long and 1/4" in diam, press -loaded at the base with tetryl, PA, PKTN, RDX, HNMnt or loose TNT to form a main chge(ca 0.4g for No6 cap and 0.55-0.9g for No 8 cap). Above this is placed a layer of priming expl, such as MF w/wo KCI03 & Sb2S3(ca 0.4g for No 6 cap and ca 0.5g for No 8 cap),or LA/LSt(ca 0.2g for No 6 cap or 0.25-0.3g for No 8 cap). One of the modern No 8 caps contains 0.55g PETN & 0.25g LA. There are also larger caps, such as US Army Special Cap described below and No 16 cap mentioned in USP 2860041(1958). The latter cap consists of a large cap contg a base chge of PETN into which is slipped a regular No 6 cap thus forming a single unit equivalent to 1.5g PETN(base chge) & 0.25g LA(priming chge)(Ref31)

MF is used now only in some foreign countries, but very seldom in the US(Ref 32)

In order to improve the performance of the cap, the initiating chge is sometimes covered with a reinforcing cap. This is a small perforated cap made to fit snugly against the inner wall of the main cap. Reinforcing caps are used only with MF chges and are not required with LA chges. With these caps the safety fuse is inserted and crimped as described for a single charge cap. In these caps the deton wave created by an initiating expl is reinforced and speeded up by the deton of the base chge expl, such as tetryl, which possesses a much higher deton vel than MF, LA or any other initiating expl. This reinforced detonating impulse will explode most expls of low sensitivity(See Fig)

At the present time, the DuPont Co manufactures two standard No 6 blasting caps, one with an A1 shell 1 3/8" long and the other with a Cu shell 1 1/2" long. Each has about 3/4 open space above the chge for inserting the fuse

Two No 8 caps are also manufd, one with A1 shell 1 5/8" long and one with Cu shell 17/8 long, but they are not used extensively in coml blasting because No 6 caps are strong enough to detonate most expl. They are used, however, for military purposes

In order to intensify the deton effect of a blasting cap, the closed end of the capsule("business end") is indented towards the inside thus utilizing the Munroe(Shaped Charge) Effect. Some investigators question the value of this improvement The compound caps described above are also called "two-part detonators" because they contain two layers: priming and base

A stronger cap, now called US Army Special Blasting Cap, designed by the US Corps of Engineers also belongs to the compound type. It is described here and also in Ref 30 Western Big Inch Blasting Caps, manufd by Olin Industries Inc, East Alton, 111, are made of A1 and contain RDX as a base chge. They are 11/8 long and 15/64 in diam and are about as powerful as the 15/8 long conventional cap. Because of their smaller size, there are some advantages in storing and handling them

It is also possible to prep three-component caps, similar to detonators of the same type(see under Detonators)

It is of interest to note that compound caps and detonators were developed in the US, by the DuPont Co, as early as 1912, but it was not until 1916 that a real advance was made when tetryl was first used for the base charge

Principal uses of non-electric blasting caps are in quarry and agriculture work and in ore mining II) Electric Blasting Caps(also called Exploders, Electric Initiators or Detonators, or Fusees)

Since non-electric caps are fired by a safety fuse, the time of firing is governed by the length of fuse and its burning rate; consequently it is not practicable to use these caps for firing several shots simultaneously, as is required in most blasting operations. For this kind of work, elec blasting caps are of great advantage

Electric Blasting caps may be divided into "high tension" and "low tension" types Historical. The original elec cap was invented in 1745 by Dr Watson of England and were improved by Benjamin Franklin in 1749. In Franklin's cap, the gap between the two wires was encased in a charge of compressed BkPdr which acted as igniter for the main chge of BkPdr. This device could not detonate the chge but only ignited it and therefore could not be used for dynamite or other HE. Franklin did not exploit his invention and it was forgotten until 1830, when Moses Shaw was granted a USP at for a similar device in which charges of gunpowder were fired simultaneously by elec current through the use of a priming compn containing fulminating silver and gunpowder. The device was not satisfactory and Shaw, with the assistance of Dr R.Hare, constructed another device which was the first "low tension" cap. It contained a fine wire, which was heated to incandescence by means of elec current from a battery. As batteries were not convenient for

Compound Cap t- Metallic Cap Reinforcing Cap


Priming Charge

Base Charge field use, Baron von Ebner of Austria, in the 1850's, invented the first elec friction machine suitable for field use. The machine was improved in 1869 by H.J.Smith of Boston and was used in the blasting of the Hoosac tunnel. Mowbray modified it and called it a "Powder Keg".* but it was not as good as the original device of Smith. The first magneto-electric apparatus was invented in 1856 by Sir C.Wheatstone while working for Sir F.Abel

A) High Tension Cap contains a sensitive priming mixt packed around a break(gap) between two pieces of wire; the outside ends of the wires are connected to two poles of a magnet or other app producing a high tension current. When the circuit is closed, a spark jumps across the gap between the wires and ignites the primary mixt. These caps have been practically superseded by:

B)Low Tension Caps. Electric blasting caps presently used in the USA consist of a cylindrical metal shell containing a detonating base chge, an ignition compn and an elec firing device having a high-resistance wire(bridge) between the two leg wires of the firing circuit. When the current is applied to the elec circuit(either by blasting machine or from a circuit connected to a power line), the bridge is heated to incandescence thus firing the ignition compn. This in turn acts on the initiating compn(such as MF, LA, etc) and this detonates the base chge, such as Tetryl, RDX or PETN. Sometimes, as in the "bridge plug type* caps, base and initiator chges are combined in one chge(see below). Because of the danger of detonation from stray ground currents, strong radio frequency impulses, ar accidental closing of the elec circuit, elec cap leads and circuits are always short-circuited until immediately before firing

Burrows et al of DuPont Co(Refs 9 & 10) describe the following types of elec caps:; a)Bridge Plug Type (Type 1) contains base chge (such as Tetryl, RDX, or PETN) combined with priming expl(such as LA). On top is placed plastic ignition chge(such as Ag or Hg salt of chlorinated azidocarbonamidine in NS gelatinized with aroyi acetate; Pb picrate or LSt or Ag azide in NS jelly; mixt of Cu acetylide, K chlorate & carbon in collodion). A high resistance bridge wire, connected to two leading (leg) wires of the firing circuit, is imbedded in the mixt. These wires are held in a fixed space relationship by means of a plug, usually shaped like a truncated cone. A waterproofing compn, covered with cast sulfur, is placed on top of the cone. In order to prevent the cap from accidentally being fired by static electricity developed in the human body, from friction or from stray radio frequency waves, one of the leading wires touches the wall of the cap at some distance from the ignition compn b) Concave Plug Type (Type 2) contains a base chge (usually Tetryl, RDX or PETN) in the bottom of the cap, covered with a smaller chge of initiating expl(such as MF or LA). The bridge wire is imbedded in an ellipsiod consisting of a cemented ignition compn which is generally in a plastic condition when applied and hardens on drying(See Type 1 Cap). In order to facilitate the application of this compn to the bridge wire, the smaller base of the conical plug holding the bridge wires is made concave c)Match-head Type (Type 3) contains in the bottom of the cap, a base chge(such as Tetryl, RDX or PETN) covered with an initiating chge(MF or LA). The ignition device consists usually of a flat strip of insulating material, the two faces of which are covered with metallic foil each soldered to a leading wire. A bridge wire passes around the end of the strip and connects to the ends of the leading wires. After this, the bridge wire is dipped into a plastic ignition compn which dries to form a hard, tear-drop shaped pellet similar in appearance to an ordinary matchhead. For this may be used Cu acetylide or Ag azide or LSt(yel variety) in NS gelatinized with amyl acetate; mixt of Cu acetylide K chlorate & carbon in collodion. The remaining parts are the same as in Types 1 and 2 (See also Ref 8)

See Figure next page Copper brass and aluminum may be used as material for the cap(shell) itself

Many other ignition compns have been patented such as: bis-triethyl lead styphnate, triethyl lead -basic lead styphnate, triethyl lead azide, mono -triethyl lead azo-aminotetrazole, bis-triethyl lead azoaminotetrazole, triethyl lead azidodithio-carbonate, diethyl lead diazide & bis-basic diethyl lead styphnate, etc. The ignition compns mentioned above have an "overall lag" of less than 0.0009 sees when fired at 12 amps, but in some cases this lag is even smaller, viz, 0.0002, 0.0003, 0.0004, 0.0005 or 0.0006secs

In addn to the initiating compds mentioned above(MF and LA) the following may also be used: LSt, DADNPh, TATNB, Cyanuric Triazide, Tetracene or a mixt of LA 80-90 & K chlorate 20 -10%(See also Additional References on Blasting Cap Compositions, which are given below) A special blasting cap, particularly suitable in

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