Explosives Theory

(OPENING LECTURE) An explosive is a substance, made up up of various nitrates and chemicals, and when suitably stimulated, decomposes rapidly from a solid into a gas with the liberation of intense heat, resulting in a sudden and intense pressure causing violent disruption of the air and its immediate surroundings. I.E , one slab of TNT expands in the form of gas, in one second, approximately 18,000 times its own size in space.

This rate of change, from a solid to a gas, is worked out in meters per second and is known as the violence figure of the explosive, i.e., rate of change. For instance, TNT is approximately 18,-000 miles per hour.

THE CLASSIFICATION OF EXPLOSIVES can be divided into three groups.

(a) Speed of Reaction (MPS)

(b) According to its~Sensitivity.

(c) Service ClassificatlonT"""

The speed of reaction can also be divided into three groupst

{a) Combustion

(b) Explosion

(c) Detonation

Combustion. This is a chemical react-ion in whicFToxygen from the air is embodied, usually accompanied by heat and there is always a liberation of gasses, i.e., as in a petrol engine. The violence figure on speed of reaction i,s up to a third of a meter.

Explosion. This is a rapid form of combustion. The heat is intense and large quantities of gasses are produced suddenly, causing intense pressure and disruption, i.e., gunpowder, cordite and ballistite, etc. The violence figure is up to 3,000 meters per second. Both combustion and explosion can be produced by means of flash (spark flame), match, etc., and is mainly the expansion of burning gases, which rapidly requires room to expand and therefore gives a pushing or lifting effect to achieve this object.

Detonation. This is the ultra-rapid breaking down of a substance, proceeding through the explosive in the form of a wave, known as the "detonating wave". Detonation creates a cutting and shattering effect and depends on continuity. Therefore it will be halted by an air space. In detonation there is complete disintegration of any close object, so rapidly does it need to expand that it will cut through a substance or completely destroy it, in preference to moving it. Violence figure: 3,000 meters per second and upwards.

Up to 4,000 meters per second - Low Explosive

From 4,000 to 8,000 - High Explosive

From 8,000 and upwards - Very High Explosive

According to their sensitivity explosives are divided into three groups»

(a) Initiators

(b) Intermediaries

(c) Bulk Explosives

Initiators. An initiator represents a detonator or equivalent, such as fulminate of mercury.

Intermediaries. These are primers for boosting the detonating wave once it has been created, such as any of the sensitive explosives which can be initiated by detonator direct. (Gelignite or Nobel's 808) .

Bulk Explosives. These are main charge or fillings, representing a bulk explosive such as TNT or Wet Gun Cotton, etc. These are of the non-sensitive variety, which must have a primer to initiate them, and any of the above intermediaries can be used for doing this. It will be noted that all intermediary explosives (sensitive) should also be primed to obtain the best results and power. An example; Gelignite initiated by detenator alone has a violence figure approximately 3-4,000 meters per second, but when primed, will be raised in the region of 8,000 mps.

Service Classification. This can be divided ast

(a) Propellence.

(b) High Explosives.

(c) Miscellaneous.

The power of explosives is judged by two standards;

(a) The rate of combustion upon detonation (violence figure).

(b) The volume of gas produced in relation to an explosive such as Lyddite (power figure 100).

Sensitivity. This is the term used to determine the ease with which an explosive can be detonated; high sensitivity naturally involves danger.

Stability. All explosives, to a certain degree, are unstable, otherwise they would not explode. Most explosives used in military services are relatively safe, but under certain conditions some tend to break down and decompose, resulting in deterioration in efficiency and safety in handling. For instance, Gelignite is affected by heat and cold. Obviously, bulk explosives cannot be manufactured or transported safely if they have a high rate of sensitivity. Therefore, in order to initiate bulk explosives, a number of accessories are necessary, such as initiators and intermediaries.

Initiators. First, of combustion or flash»

(b) igniferous or percussion cap (flash cap).

(c) ampule or miner's igniter (chemically produced flash).

(d) friction igniter (German equivalent to a fuzee match).

(e) electric flash.

To prolong and carry the flash, giving a delay, safety fuse is used.

Burns under water.

(b) S.A. Commercial Safety, misc. packing. 24 ft. lengths.

(c) Bickford's Blue. Commercial Safety.

Burning speed of all three fuses, 2 ft. per minute.

Booby traps need no delay, consequently, instantaneous Orange fuse is used and is lighted with a naked flame {but never should be). Burning speed; 90 ft. per second.

More on Detonators: - three main types.

(1) No. 27 packed 25 to a tin, complete with rectifier. (8 tins to a box).

Rectifier: A device for converting alternating current to direct current.

(2) No. 8 commercial packed 100 per tin.

(3) No. 33 electric, packed 100 per tin.

No 24 detonator is a service detonator and consists of a solid drawn-out aluminum tube 1 3/4" x .26" in diameter. To use with safety fuse, the fuse is inserted into the open end of the detonator, which is crimped, attaching both firmly to each other. The detonator consists of .35 grammes A.S.A. (lead azide, lead stypnate and aluminum powder) which is a very sensitive mixture, and -which detonates .55 grammes of tetryl. The tetryl has the effect of amplifying the effect and power of the detonating wave set up by the A.S.A. From the open end inwards is a space of 7/8 c. which the fuse fitb in, then comes the A.S.A mixture and lastly the tetryl ( tetra. nit-ro-methyl analine). Very sensitive, the detonator is sensitive to friction and it supercedes the previous type, which was filled with fulminate of mercury. The commercial equivalent of the No, 27 detonator is the No. 8 Commercial and in fact, they are one and the same. But the No. 8 service detonator (now obsolete) is entirely different, being filled with fulminate of mercury and is considerably less powerful than the commercial No. 27.

No. 33 Detonator is the standard el-ectric detonator and it consists of an electric firing head crimped into the open end of a No. 27. detonator. A neo-

prene plug (rubber) seals the electric firing head in position and prevents moisture from entering and the electric firing head is a filament terminal of two wires. Lowest current fire is 8 amps and a 4.5 volt hell icon lamp is normally used.

Electric Fuse No. 31 is an indepen-dent firing head supplied for use in conjunction with a No. 27 or No. 8 detonator, by insertion in the end which normally receives the safety fuse. It is painted brown and one end is closed with a cork disc secured by shellac and between the cork disc and the filament is a small amount of guncotton. This is ignited by electricity and in turn ignites the A.S.A. which detonates the tetryl.

Commercial No. 8 submarine electric detonator is equivalent to the commercial No. 33, the detonating end (really a No. 8 A.S.A.) is exactly the same dimension as a No. 27 service detonator and can be used with a 1 oz. C.E. or D.G.B. primer. It is also aluminum in color. The filament is sealed in the detonator by adhesive tape, which renders it waterproof.

Intermediaries. Primers are used to boost the detonating wave set up by the detonation and is a large amount of less sensitive explosive. Two main types

of primers are: - rifle bullet and is susceptible to dam-

(1) dry guncotton primer, speed 7300 age by moisture.

mps. (meters per second). C.E. primers may be substituted for

(2) Composition explosive (C.E.) pri- outside dimensions, the powder is enclo-mer. Speed, 7500 mps. sed in a waterproof, waxed covering. The

D.G.B, primers MK II, weight 1 oz. central, or axial, perforation is not Slightly tapered cylinder of dry guncot- tapered and is lined with waxed paper, ton provided with an axial perforation Rectification would split the paper to take a detonator. Length 1 1/4" They and allow the powder to escape. To pre-are 1.35" x 1.15° diameter at the larger vent this, the axial perforation is made and smaller ends respectively. slightly larger than the detonator,

To differ from the obsolete MK I pri- which will therefore need to be packed mers, which are marked with red figures to insure a close fit. A piece of paper and have a smaller axial perforation, or even a blade of grass is usually ade-the MK TI is marked with black figures quate for the purpose.

and takes a No. 27 detonator comfortably. C.E. primers are packed in G.C. tins Packed 10 per black tin cylinder weigh- or trade packages, 10 per cylinder, ing 16 1/2 oz. Six cylinders are packed Trade cylinders are of waxed paper 12 in a box painted service color, the dim- 1/2" .x 1 3/8", weighing 1 lb. 3 oz. Ten ens ions 13 1/8 x 5" x 6", weighing 13 of these cylinders are packed in a card^ lbs. board box weighing 14 lbs.

D.G.C. primers will initiate detonat- Main Charges or Disruptions, ion in any high explosive, provided the Wet Guncotton Slab. Violence figure: contact is good and failures that may 5500 mps. Power figure: Approximately 60. occur are usuall'y due to absorption of Packingi - 1 lb. slab. 6" x 3" x 1 1/2". moisture. To prevent this, they are 14 per tin case 14 1/4 x 8' x 8 3/8", coated with acetone, although the sides (airtight).

may easily become cracked or chipped. Composition: - Tri-nitro-cellulose, pre-

When in goad condition and undamaged, pared by treating cellulose with nitric sensitivity will be retained even under and sulphuric acids. When prepared, it wet conditions for six hours, but spec- is treated or processed into blocks and ial precautions are necessary if primers then treated with carbolic acid to pre-are to be left in water for any length vent growth of fungus, and chalk to ab-of time. Dry G.B. primers burn very rea- sorb any free acid remaining. A block dily if ignited, though detonation by contains 13% to 14% water, heat alone is unlikely. It should never Properties. It is extremely insensitive be cut or rubbed with steel, as friction and a primer must be used. When dry, it may cause burning. will burn extremely violently, on deto-

If it is necessary to provide a wider nation, large quantities of carbon di-detonation hole, it is quite feasible to oxide are given off and therefore, it widen the axial perforation without sp- should never be used in confined spaces litting, as the primer being of G.B. is such as mines or underground tunnels, of a fibrous nature. A rectifier is pro- When two or more crates are placed vided with each tin of detonators and in together, ond one is detonated, the the absence of a rectifier, a thin pen- detonating wave will not normally pass cil is a good substitute. through the one remaining. But the det-

MK I primers can be used with Service onating wave will pass through the tin No. 27 detonators, although they were seperately. One slab of W.G.B, will originally designed for use with the No. blast a hole its own si2e through 1" of 8 detonators. If used with a No. 27 det- steel, 10" of wood and 20" masonary. It onator, considerable rectification is is a high explosive with a good cutting necessary. Even so, it will be impossi- power.

ble to insert a detonator more than 1/2 1 slab cuts 1" steel, 10" wood, 20" inch. This amount of contact is adaquate.masonary.

Dry G.B has been known to be detonated 4 slabs cuts 2" steel, 20" wood, 40" by a rifle bullet and care should be ta- masonary.

ken to minimize the chances of this hap- 9 slabs cuts 3" steel, 30" wood, 60" pening. masonary.

C.E. Primers (composite explosive) is Guncotton is an extremely safe ex-the service nomenclature for tetra-ni- plosive to handle and will absorb up to tro-methyl-aniline and it is also known 30% moisture, but detonation is then as tetryl. Pale yellow in color, it is rather unreliable and very much reduced, sensitive enough to be detonated by a If used under wet conditions, it should be protected by "bags" of G.C., 25 lbs. ignite (5C% N3) consisting of a jelly of MK II or "bags" of G.C. , 5 lbs. MK III. 7% collodion cotton in nitroglycerine A slab reguires a primer to iniate deto- mixed with 5C% of nitrate of soda, nation and the primer fits into tapered it has the power of NS Gelignite and hole in the center of the block. Italian its sensitivity to detonation is not equivalent: Fulmi-Catony. rapidly affected by moisture. Continued

TNT Slab or Flake. Violence figure storage under wet conditions or prolon-7500 mps. Power figure 65 d immersion in water, however, causes

.Packing: - Slabs. 15 per wooden box the nitrate of soda to dissolve and weighing 26 lbs. 14»x9»x8" or 14 per G.C.forit1s a Solution which exud^s from the

1/ J619 9 ' explosive. This solution is not danger-

Flake. 50 lbs. per wooden box. troglycerine. This may be detecyed by

Compositions tri-nitro-toluene. its oil nature. It is only these drops

Properties. Very stable if pure but of ^ which are dangerous and under liable to explode if in impure state. these circumstances, gelignite should

Not very liable to sympathetic detona- be handled with Care.

tion (set off by nearby detonations). when used for borehole charges, Gel-

Light yellow in color. Each slab is ignite should not be removed from its painted with acetone to protect against and tamping should be done moisture. The primer its in a central eirmly and tl with a wooden rammer, tapered hole as with the W.G.C. (wet gun squeezing and pressing the explosive cotton) slab, which is approximately the into potion, not on any account same in power, sometimes known as tetryl. thumping or using blows.

Gelignite. Violence figurei- 6000 mps Gelignite can be reliably initiated Power figure 80 with any detonator or detonating fuse.

Packing 1 - 4 oz. and 8 oz. cartridges But best results are obtained by using packed in cardboard boxes weighing 5 a primer, which must always be used lbs., 10 boxes to a 50 lb. wooden box. with explosive when used as a cutting The explosive is wrapped in waxed paper charge, to prevent actual contact with the other cartridges. Ammonal.

Composition:- Nitroglycerine 40/603i. The of ^o^i « applied both to cerUin blasting cxplo-Sodium potassium nitrate 20*. Wood meal which ^^ aluminum and lo miliUry wploilivei( bQsed or collodion cotton 40/20*. upon immonium nitniU/ which conUin thi, meUl. Miliiary an»-

Properties: - Liable to exude nitro- ^^ are briBant and powerfui explosive which explode with glycerine at extremes of temperature. m bHght flaah They are hygroe<50piCi but the flake aluminum

Primers should be used , but will deto- which thcy cont6in KtMXvhfki in the manner of the nate without. It is more sensitive than thingl« on a woi and helps materially to exclude moisture. At any other normal service explosive. Be- |h> ^^ of the firBt World War the Germans were using longing to the nitroglycerine group, ge- j» ^r caliber .hells an ammonal having the first of the com-lignite is largely used commercially for ^ |jtted ^ Aftcr thc War had adyanced and TNT borehole charges and they may be freq- ^

uently met in service. It burns quietly Cmman axmonu. Fknck in small quantities in the open. But if I II ammoxm.

confined or if the cartridges are bulked Ammooiumniir«u m 72 sa

, . Trinitrotoluene 30 12

together, detonation may occur. AJumiaum fUkM is 1« a

All types of of the gelignite group Siwic add a are liable to cause headaches if bare ... ... , .

explosive is handled. It is sensitive to hftd b<come more Bcarce' oi the Reconrt formula was friction. It is liable to detonate if adopted. The French al«o u«d ammonal in major caliber shells struck by a rifle bullet. during the first World War. All three of the above-listed explo it is issued in two typesi- Firstly, »ives were loaded by compresaion. Experiments have been tried its freezing point is many degrees below with M »mmonal containing ammonium thiocyanate; the mix-0p centigrade. Second type, not of low ture WM melted, and loaded by pounng but was found to be freezing point with a disadvantage of unsatisfactory because of its rapid decomposition. Ammonal freezing at 46° F , in which state they ^^ * 1Ulw which " particularly hot, and consequently gives are dangerous to handle and use. For ao unduly high mult in Uis Trausl load block test, these reasons, Commercial gelignites are Ammonal is also largely used commer-not ideal for service use, but their cially and such types are generally plastic form makes them suitable for use more sensitive than the military varie-in boreholes. The most common NG explo- ty and many are liable to be detonated sive likely to be met is Polar. NS Gel- hy a rifle bullet. Such Ammonals need only a detonator or detonating fuse for small for the average British detonator iniation. But a primer should always be as the detonators intended for use are used on service Ammonal to insure deto- fulminate detonators used only with ful-nation. minate of mercury contained in a copper

The commercial equivalent most like- tube. Violence figure 7250 mps. Power ly to be met with is No. 704 in 25 lb. figure 100. tins, two tins per box, weighing 60 lbs. It contains no charcoal, being light green in color and has the same power and characteristics as military Ammonal.

The above are the main types likely to be met with. Following are some of the lesser used bulk explosives and their compositions. They are often used in smaller quantities or in cooperation with others.

Melinite. A standard French explo-sive, mainly composed of tri-nitro-phe-nol (picric acid). It should always be kept dry, as it reacts with most metals to form very sensitive Picric salts.

When moist it is vivid yellow in color. It should be handled with extreme care and it is liable to Sympathetic Detonation. Gases formed on detonation are very poisonous, and when mixed with air, are highly flammable. Therefore, Melinite should never be used for offensive mining.

It is obtainable in slab form or as a powder. Slabs are yellow-gray or brown in color. The powder consists of small, straw-oolored crystals, with a very bitter taste.

Melinite is not sensitive to shock and will burn in free air without detonation. The powdered form, known as pul-

verelent, is more sensitive than the French Melinite. The German equivalent slab form and is used either as a primer is Granate Fulling, Composition* Trior separately for the less sensitive nitro-phenol. Properties. It should al-slab form. ways be kept dry as it reacts with most

It is supplied in the following forms:metals to form sensitive Picric salts, (1) Cylindrical cartridge. Weight of liable to Sympathetis Detonation. Its 100 grammes. 3.22 oz. Total weight of gases are highly flammable when mixed package, 130 grams or 4.18 oz. It with air and"are also highly poisonous, is used for boreholes or in camouflets. violence figure 7250 mps. Power figure

Explosive, 135 grams. 4.35 oz. Total 100. weight 190 grams. 6.12 oz. Cutting or Fulminate of Mercury.

mined charges. These charges are also Composition. Precipitated when a sol-

manufactured in five more sizes, ending ution of mercury in nitric acid is heat-in 20 kg., 44 lbs. ed in methyl alcohol.

The cylindrical cartridge is composed Properties. Fine, sandy crystals. Ve-of the powdered form and needs only a ry sensitive when dry but comparatively detonator or detonating fuse to initiate insensitive when wet. Sensitivity in-detonation. The petards consist partly creases if compressed, it reacts with of slab Melinite and partly of the pow- metals to form sensitive metallic salts, dered form. A detonator or detonating Detonation will occur when dry if sub-fuse is therefore sufficient to initiate jected to friction, percussion or flame, the petards as well as the cartridges. Violence figure 4500 mps.

Both petards and cartridges are sup- Cap Composition. This is made from plied in sealed tins and the lids can Fulminate of mercury, potassium chlorate, easily be moved to gain access to the antimony sulphide and mealed gunpowder, detonator socket. This socket is too Properties. These give an igniferous camouflet (F. pron. ka-mO'tlit), n. [F., smoke puffed into a sleeper's faco; origin unknown.] Milt., a mine with u charge so small as not to produce any crator when explodod. .¡such a mine it«

often sunk In tho wall of earth between two parallel galleries, in order, by lilowln« the earth Into one of them» to suffocate or cut otf tho retreat of the miner who 1b at work in it. When need for this purpose it is also called a stiver.

petard (po-t&rd') An engine of war used to blow in a door or gate, form a breach, in a wall, etc. it came Into n*e In the sixteenth ecntury, and In It« early form« was a kind of mortar of Iron or bronze which was charged with about seven pounds of gunpowder, rammed down and wadded, and fixed by moan a of ring» to a stout plank, which was then attached to tlio surface to be blown In. The use of bomb« has rendered the petard almost obsolete, but as Btfll occasionally employed It is a cubical box of stout oak-wood, charged with twenty pounds or more of powder, and fired, like the older forme, oy a fuse.

Lyddite. This equivalent to the

Field Expedient Explosives
Peíanle« Firing & Retard.

flash only. Fulminate of mercury increa- seCond type is Known as "80/20" composi-ses the sensitivity of the composition. tion of which is, ammonium nitrate, 20%, Potassium chlorate, owing to its rich- TNT, 80%

ness in oxygen, increases the heat of Properties. 40/60 can be poured but the explosion. Antimony sulphide pro- 80/20 must be screw-filled with an Arch-longs the flash flame effect. Mealed emedian screw. A primer is essential, gunpowder diminishes the violence of This explosive is fairly stable, provi-

the explosion. ding the TOT is pure.

A.S.A. Violence figure 4500 mps. Baratol. Violence figure 5000 mps.

Composition. A mixture of Lead azide, Power figure 85,

Lead stypnate and aluminum dust. Proper- Composition. Barium nitrate 20%, TNT ties. Used in conjunction with a small 80%. Properties. This explosive is some-quantity of composite explosive (Tetryl) times known as 20/80 Baratol and is ex-in modern detonators. Fairly sensitive. tremely stable.

Lead Azide. Violence figure 4500 mps. usea in powder form in grenades, mor Composition. Salt of hydrazoic acid, tar bombs and sometimes mines. Barium prepared by using soluble salts, such as nitrate being a heavy salt, packs very lead acetate with sodium azide. Lead az- veil and is unaffected by moisture or ide is precipitated out in fine white temperature.

crystals. A primer should be used but small

Properties. Initiated by flame. Not quantities will detonate without one. reliable by percussion or friction and Gunpowder. Composition. Potassium ni-

is fairly stable. It is fairly sensitive trate 75%, charcoal 15%, sulpher 10%. when compressed. Addition of water does (Percentages are by weight). Properties, not decrease sensitivity, and if exposed A lifting charge. It is black in color, to moisture for long periods, it decom- Ballistite. Composition. Soluble ni-poses and forma compounds liable to trocellulose and nitroglycerine soluble spontaneous combustion. in acetone. Properties. Produces a large

Lead Stypnate. Violence figure 4500 volume of gas. mps. Composition.Normal salt of stypnate Cordite. Composition. It is pure gun-acid is precipitated when lead acetate cotton dissolved in nitroglycerine, sta-and magnesium stypnate are mixed. Prop- bilized and formed into sticks. erties.Initiated by flame, it is fairly There are three main types of detona-insensitive. Addition of moisture does ting fuses, as opposed to fuses which not reduce insensivity but pressure does.detonate primers. They are Primacord,

Composite Explosive. Violence figure Cordtex and FID (Fuse Instantaneous Det-6000 mps. Composition." Tri-nitro-phenol- onating) .

nitromene, commonly known as tetryl. Fuse Instantaneous Detonating. Tatyl.

Properties, it is readily ignited by mk TIT. flash but if initiated by detonator, FID consists of a lead and tin alloy gives complete detonation. It is unaf- tube .23" in diameter filled with pure fected by moisture or temperature. TNT (Tatyl). This is wound on a metal

Penthrite. Violence figure (Cast) reel in 400 ft. lengths and contained in

6000 mps. (Powder) 6500 mps. a yellow tin cylinder weighing 46 lbs.

Properties. It is only used in deto- Violence figure 5000 mps.

nating fuses, such as primacord and tor- Principal uses, (1) To fire a number dite. It is sometimes called PETN (Pen- Qf charges simultaneously when firing by taerythrite tetranitrate), Used by the safety fuse. (2) To avoid excessive enemy (Italians) as a bulk explosive. It lengths of safety fuse, which would oth-can be detonated direct, also initiated erwise be required in certain denolit-by flash and will burn violently. ions. (3) As an adjunct to electrical

Shelllte. Violence figure 6800 mps. firing, where there are so many charges Power figure 85, to be fired that the detonators will be

Composition. A mixture of trinito- beyond the power of the exploder. (4) To phenol and dmitrophenol. Properties.Ve- avoid the use of detonators in boreholes ry stable when dry but liable to Sympa- or camouflets mined charges. (5) To wid-thetic Detonation. Internally reacts en the hole made by the camouflet equip-vith most metals to form a sensitive ment tube. FID is perfectly reliable salt, provided precautions are taken.

Amatol. Violence figure 6500 mps. Thia particular mixture of TNT readi-

Power figure 114. These figures are for iy absorbs moisture, causing it to be-"40/60" compositions of which is as fol- Come insensitive. Consequently, 6" lowsi — 40% ammonium nitrate, 60% TNT. A should be cut off before starting to use the drum and 6" should always be left string can be used. Successful joints spare at initiating points and at junc- can also be made by using the cardboard t.ion boxes. Ends left for any length of outer container of the primer, the FID time should be sealed, taped with insu- being held between the primer and card-lation tape or closed by pinching the board. The three detonators method is cord out for approximately 1/4" and not sufficiently reliable using the No. sealing the lead sheath by squeezing to- 27 or No. 8 commercial detonator, gether. FID will initiate direct all explo-

The fuse can be used under water as sives that can be detonated alone. In the metal case provides adaquate protec- all other cases the end of the FID tion. It is perfectly safe to handle and should be capped with a primer. Where it is initiated either by a single primer is necessary to join two lengths of FID or by three detonators. The single pri- or to boost long lengths. (Boosting is mer method is easiest to use. The single required every 100 yards). A single primer method binds the primer to the primer should be used, as follows, end of the FID, leaving 6" to spare. Cordtex. This is a commercial deto-

Method of Initiating FID, Single Pri- nating fuse consisting of a sensitive mer. Rubber or adhesive tape makes the explosive (PETN) wrapped in a gray fab-best binding. But ordinary tape or ric tube, with or without cotton cover-

Ww2 Cordtex
¿WA yjt««

MSTtfC* Cfi iNt#TH49_ C oeftTfi*.

ing. Outside diameter is .19" and it may a situation where there is the least li-be issued on service in lieu of FID. klihood of impact. Drums of fuse are un-

A single strand of Cordtex is unlike- likely to be detonated if struck, ly to be detonated if struck by a rifle Cordtex is liable to damage by moist-bullet. Junction boxes of the fuse have, ure at the open ends and one foot should however, been detonated by impact of be cut off from the drum before use and bullets and should, therefore, be placed one foot left over spare at each point with care away from hard backings and in of initiation or junction.

C'ordtex is absolutely liable to detonate in hot climates and so should be stored in a cool place.

Cordtex is packed on wooden reels of <500 ft., weighing 9 1/2 lbs. Five reels per case weighing 67 lbs.

Cordtex can be initiated by a single No. 27 detonator, or equivalent, as shown.

Method of Initiating Cordtex. It is very important that a spare end be bent back, as otherwise there is a danger of the burning fuse igniting the Cordtex core and preventing detonation. It will initiate direct any of the AG group or PE2, but a primer is required for other explosives. Speed 6000 mps.

Primacord. Very similar to Cordtex in composition and use to a good quality Cordtex. It consists of a case of PETN surrounded by cotton braid and enclosed in a coat of bituminous x^aterproof ing compound, followed by a layer of pho-film tape and two layers of spirally applied cotton yarn, the whole being finished by a light-yellowish orange colored wax composition.

The external diameter of the fuse varies between .200" and .210" and it is wound on a wooden reel with a central hole for easy handling. It■comes in lengths of 500 ft., weight 12 lbs. and 1000 ft. 20 lbs.

A reel may contain one or more splices, which are as strong as unbroken lengths and will detonate properly under all normal conditions. The explosive core is liable to damage by moisture and one foot should be cut off from the drum before use and one foot spare at each point of ini.at.ion or junction. Ends can can be sealed by fixing empty detonators tubesonto the fuse by sealing compound and when sealed, the fuse is hiqlLLy resistant to water penetration.

The speed of detonation is approximately the same as that of Cordtex and is not less than 6000 mps.

While single strands of fuse are not likely to be detonated by a rifle bullet junction boxes should be protected and placed with care away from hard backings.

Primacord does not deteriorate quickly, even under unfavorable conditions of storage.

Primacord will initiate direct any of the NG group or PE2 but a primer is needed for all other explosives.

Joints are made in a similar manner to Cordtex, the most suitable being a reef knot for main lines and a clove hitch or two half hitches for branch lines. Branch lines, after leaving the main lines at right angles, should be led off in the general direction of the detonating wave, These joints permit considerable strain being put on the cord.

A fourth type of detonating fuse is Cardeau detoriaiit, which is similar to a service BID except that the tube is composed of lead instead of an alloy of tin and lead. Special care should be taken to see that there are no kinks or severe bend9 in the fuse. Any position where there is any doubt as to the severity of the bend should be boosted by tying on a detonator or a primer.

Petard Melinite


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