Meyer R., Koehler J., Homburg A. Explosives. Wiley-VCH, 2002 / Explosives 5th ed by Koehler, Meyer, and Homburg (2002)

Octol

A mixture of Octogen (NMX) and TNT 70/30 and 75/25. Performance values:

Oxidizer

Sauerstoffträger; comburant

All explosive materials contain oxygen, which is needed for the explosive reaction to take place. The oxygen can be introduced by chemical reactions (nitration) or by mechanical incorporation of materials containing bound oxygen. The most important solid-state oxidizers are nitrates, especially W Ammonium Nitrate and W Sodium Nitrate for explosives; W Potassium Nitrate for W Black Powder and ion exchanged W Permitted Explosives; potassium chlorate for W Chlorate Explosives and for pyrotechnical compositions; W Ammonium Perchlorate (APC) for W Composite Propellants.

Important liquid oxidizers for liquid fuel rocket motors include liquid oxygen (LOX), highly concentrated nitric acid, liquid N2O4, liquid fluorine, and halogen fluorides. See also W Oxygen Balance.

Paraffin

CH3-(CH2)x-CH3

Paraffin serves to impregnate explosive cartridges against moisture. The technical product may contain ceresin, wax, or fat.

Specifications

Parallel Connection

Parallelschaltung; branchement en parall`ele

In multiple blastings with electric priming, W Bridgewire Detonators are usually connected in series to the priming line. If the boreholes are very wet, and there is a real danger of voltage loss, the charges are connected in parallel. Since only a very small fraction of the electric energy employed is then actuated in the primer bridges (the bulk of the energy is dissipated in the lead wires), parallel connections require special high-energy-supplying blasting machines.

plasticizers. Depending on the additives they contain, the plastic explosives are denoted as PE-1, PE-2 or PE-3 (W also Plastic Explosives and PBX).

Pellet Powder

Black powder pressed into cylindrical pellets 2 inches in length and 1 1/4 to 2 inches in diameter.

In the United Kingdom, pellet powder is the term used for rounded black powder for hunting ammunition.

Pellets

Explosives in the form of round-shaped granules, e.g., of TNT, used for filling the residual vacant spaces in boreholes.

Pelonit D

Trade name of a cartridged powder form explosive containing aluminum powder, distributed in Austria by DYNAMIT NOBEL WIEN.

density of cartridge: 1.0 g/cm3 weight strength: 80 %

detonation velocity at cartridge density, confined: 3500 m/s = 11 500 ft/s

Pentaerythritol Trinitrate

Pentaerythrittrinitrat; trinitrate de penta´erythrite; PETRIN

empirical formula: C5H9N3O10 molecular weight: 271.1

energy of formation: – 470.2 kcal/kg = –1967 kJ/kg enthalpy of formation: – 494.2 kcal/kg = – 2069 kJ/kg oxygen balance: – 26.5 %

nitrogen content: 15.5 % density: 1.54 g/cm3

volume of explosion gases: 902 l/kg heat of explosion

(H2O liq.): 1250 kcal/kg = 5230 kJ/kg (H2O gas): 1142 kcal/kg = 4777 kJ/kg specific energy: 125 mt/kg = 1227 kJ/kg

The compound is prepared by cautious partial nitration of pentaerythritol.

The free hydroxyl group can react with an acid, e.g., acrylic acid; the polymer PETRIN acrylate serves as a binder with its own active oxygen in composite propellant formulations, e.g. composition NM:

The percentage of APC can be lower than in formulations with fuel binders.

Pentastit

Name for W PETN phlegmatized with 7 % wax.

detonation velocity, confined:

7720 m/s = 23 700 ft/s at r = 1.59 g/cm3 deflagration point: 192 –194 °C = 378 – 390 °F impact sensitivity: 3 kp m = 29 N m

friction sensitivity: crackling at 24 kp = 240 N pistil load

critical diameter of steel sleeve test: begins to explode at 4 mm P.

Pentolite

Pourable mixtures of W TNT and PETN, used for shaped charges and for cast boosters (for initiation of insensitive explosives, such as ANFO). A 50 : 50 mixture has a density of 1.65 g/cm3; the detonation rate is 7400 m/s = 24 300 ft/s.

Perchlorate Explosives

Perchlorat-Sprengstoffe; explosifs perchlorates

In these explosives, the main oxidizer is sodium, potassium, or ammonium perchlorate; the combustible components consist of organic nitro compounds, hydrocarbons, waxes, and other carbon carriers. Nowadays, these explosives are uneconomical and are no longer industrially produced.

A mixture of 75 % KClO4 and 25 % asphalt pitch, melted together under the name of Galcit, was used as a rocket propellant and was thus a precursor of the modern W Composite Propellants, in which ammonium perchlorate, in the capacity of the oxidizer, is embedded in a plastic material and acts like an oxidizer.

Percussion Cap

Anzündhütchen; amorce

Percussion caps serve as primers for propellant charges. In mechanical percussion caps, a friction-sensitive or impact-sensitive priming charge (containing, e.g., mercury fulminate with chlorates or lead trinitroresorcinate with Tetrazene) is ignited by the mechanical action of a firing pin.

Percussion Primer = Percussion-actuated initiator.

Perforation of Oil Wells

Perforation von Erdölbohrlöchern; perforation des trous de sondage

In petroleum technology, shaped charges fired from special firing mechanisms (jet perforators) are lowered into the borehole down to the level of the oil horizon. Their purpose is to perforate the pipework and the cement work at the bottom of the borehole, so as to enable the oil to enter it.

Permissibles; Permitted Explosives

Wettersprengstoffe; explosifs antigrisouteux

1. Definition

Shotfiring in coal mines constitutes a risk in the presence of firedamp and coal dust. Permitted explosives are special compositions which produce short-lived detonation flames and do not ignite methane-air or coal-dust-air mixtures.

The methane oxidation

CH4 + 2O2 = CO2 +2 H2O

needs an “induction period”*) before the reaction proceeds. It the time required for ignition by the detonation flames is shorter than the induction period, then ignition of firedamp will not occur. Thus, the composition of permitted explosives must ensure that any secondary reactions with a rather long duration, which follow the primary reaction in the detonation front, are suppressed and that slow W Deflagration reactions are avoided (W Audibert Tube).

Such explosives are known as “permissibles” in the USA, as “permitted explosives” in the United Kingdom, as “Wettersprengstoffe” in Germany, as “explosifs antigrisouteux” in France, and as “explosifs S.G.P.” (securit´e´ grisou poussieres)` in Belgium.

Safety measures to avoid ignition of firedamp uses salt (NaCl) which is included in the usual compositions of commercial explosives. It lowers the W Explosion Temperature and shortens the detonation flame. Higher safety grades are achieved in ionexchange explosives in which the ammonium and sodium (or potassium) ions are exchanged; instead of

NH4NO3 + (inert) NaCl = N2 + 2 H2O +1/2O2 + (inert) NaCl the lifetime of the reaction is:

NH4Cl +NaNO3 (or KNO3) = N2 + 2 H2O +1/2O2 + NaCl (or kcl).

Thus, a flame-extinguishing smoke of very fine salt particles is produced by the decomposition reaction itself. Combinations of salt-pair reactions and “classic” detonation reactions quenched by adding salt are possible.

Permitted explosives with a higher grade of safety are powder explosives. They contain a minimum percentage of nitroglycerine-ni- troglycol to ensure reliable initiation and transmission of detonation and to exclude slow deflagration reactions. The mechanism of salt-pair

*Contrary to the delayed ignition, the oxidation of hydrogen with the salt-pair aid of an ignition source, 2 H2 + O2 = 2 H2O, is instantaneous.

detonation in confined and unconfined conditions is explained in W Detonation, Selective Detonation.

2. Testing galleries

Versuchsstrecken, Sprengstoffprüfstrecken; galeries d’essai.

All coal-mining countries have issued detailed regulations for the testing, approval, and use of explosives which are safe in firedamp. The main instrument for these tests is the testing gallery.

Fig. 18. Testing gallery with borehole cannon.

A test gallery consists of a steel cylinder which initates of an underground roadway; the cross sectional area is about 2 m2 (5 ft P; one end is closed by a shield of about 30 cm (1 ft) P, against which the cannon is placed. The other end of the chamber which has a volume of ca. 10 m3 (18 ft length) is closed by means of a paper screen. The remaining part of the tube length (10 m; 32 ft) behind the paper screen is left open to the atmosphere. (The gallery tube can be constructed in closed form if the noise of the test shots can be diminished.) After charging and positioning the cannon, the closed chamber is filled with a methane-air mixture (containing, e.g., 9.5 % CH4 to give the most dangerous composition), and the charge is fired. Whether or not ignition of the gas occurs is observed from a safe position.

Amongst the known types of mortars is the borehole cannon, as shown in Fig. 18. A steel cylinder about 1.5 m (5 ft) long and about 35 cm (1 –1/8 ft) in diameter has in it a borehole of 55 mm (2 –11/64 in.) diameter and 1.20 m (47 in.) length. The explosive to be tested is placed in the borehole, unstemmed or stemmed by a clay plug, and the detonator is introduced last in the hole (direct initiation). If the detonator is inserted first, followed by the train of cartridges, initiation is “inverse”. The required test conditions can be severe; ignition of the gas mixture is more probable to occur using unstemmed charges and inverse initiation than with stemmed charges and direct initiation. The different mortars are designed to simulate different underground conditions. The borehole cannon in the testing gallery illustrates the action

of a single shot in the roadway of gassy mines. The British break test and the slotted mortar in Poland imitate the exposure of a charge and, consequently, the more extended contact between the firing charge and the firedamp atmosphere where breaks in the strata intersect a shothole:

Fig. 19. Break test.

Two steel plates are held at a given distance by means of a closing angle and a plug. The lower plate has a groove for the cartridge train. The plate arrangement is covered with a polythene sheet laid upon two steel side walls; the gas-tight room is filled with the methane-air mixture after charging. The break test conditions are varied; permitted explosives which meet the most stringent test conditions belong to the British safety class P4.

The slotted mortar allows similar test procedures.

Fig. 20. Slotted mortar.

The slot does not extend over the whole length of the borehole and does not begin at the mouth of the hole.

A specially dangerous condition can arise when several shots are fired in one round by means of electric delay detonators. A preceding shot may then break the coal of another hole or even cut off the whole burden of the charge in question so that it is partly or completely exposed. This condition is simulated in the angle-mortar test.