Firework Types & Explosives & how they work Part 3

High Explosives

Alfred Nobel showed that by careful adjustment of the grain size of gunpowder and suitable confinement of the reaction, that a detonation wave could be produced. The speed of combustion has been so accelerated that it has broken the sound barrier and gone super sonic. You are now in the realms of high explosive.

Deflagatory explosives decompose energetically by a process of chemical combustion; high explosives decompose energetically by a process of physical destruction. A detonator produces a super- sonic shock wave which scythes through the inter-atomic bonds that hold the molecules of the high explosive together. The released energy from these broken bonds then travels out to propagate the reaction.

The force of the high explosives is not dependent on the production of hot gases, but by the creation of a physical shock wave.

Basic high explosives are single substances and, since oxidising agents do not play a part in their decomposition, many can be quite safely ignited and they will burn like wood or paper.

High explosives can of course be mixed together, Lyddite, Gelignite are examples of mixed explosives.

It should be noted that Aluminium Nitrate can be used as an oxidising agent as well as a high explosive and is used in the manufacture of Amatol to get rid of the clouds of black smoke produced by the detonation of TNT.

Nuclear

Whereas high explosives involve the breaking down of molecules into atoms, nuclear explosions involve breaking down atoms into their sub-atomic particles

Nuclear explosions are Matter/Anti-matter reactions in which the Matter (Electrons, Protons, Neutrons etc.) are destroyed to produce Anti- matter (pure energy).

Fire precautions involving nuclear explosions are beyond the scope of this course.

The Keeping and Storage of Explosives

It is likely that Operators will at some stage need to keep explosives in temporary storage before a display, or after it in the case of unused items-

Explosives Act requirements

The Act requires explosives, including fireworks, to be kept in a factory or magazine licensed by the HSE, or in premises registered with the Local Authority. The quantities and types that may be kept will depend on the particulars of the licence.

Exceptions to this are where explosives are delivered to a site for use on that day, or where they are stored privately in accordance with the Control of Explosives Regulations 1991, as below.

Control of Explosives Regulations 1991

These Regulations allow, among other things, the storage of an unlimited quantity of fireworks on private premises for up to fourteen days before private use. This concession is however of no value to Operators who are giving commercial public displays.

Special Requirements for Fireworks

Operators are likely to require licensed or registered storage. In the latter case, the quantities that may be stored will vary according to the authorisation, and may range from a few kilos up to several tonnes.

The storage will need to be within easy road reach site, so that the items can be delivered and set up within the day.

MSER

Now in force took many of the older and less known explosives regulations (some of them listed) and wrapped them up into one all encompassing piece of legislation. It governs every aspect of Firework Storage, Manufacture & Use. Storage is determined by Hazard Type, Distance and an assessment of the pros and cons of any one site, the ACOP that accompanies the legislation is designed to help you interpret and put into place safe working practices.

Manufacture of Fireworks

Wherever they are manufactured, only fireworks designed and manufactured with care should be used for displays-

Main sources of Supply

Fireworks factories were set up in European countries and in the United States during the last few hundred years, producing fireworks for private and public use, and for the manufacture of other pyrotechnic articles such as signal flares, line-throwing rockets, etc.

However, after the Second World War, labour costs in the industrialised world raised to the point where the manufacture of fireworks in many cases became uneconomic, and a large proportion of the activity shifted to areas of the world where labour costs are low.

Imports into the UK

Imported fireworks have to be authorised and classified by the HSE, and this represents some restriction to ensure that fireworks of unknown or unsatisfactory composition and performance cannot legally be held or used.