Mine Action - Five Pillars of Mine Action - Stockpile Destruction - Pre-Process Technology

Pre-Process Technology

It is may be necessary to disassemble or breakdown anti-personnel mines prior to the destruction process. This is necessary because of limitations on the amount of contained explosive that can be incinerated, the anti-personnel mine design or the requirement for different components to have separate destruction methods. All of these methods require the movement of exposed bare explosive to the final destruction facility. Available technology includes: manual disassembly, mechanical disassembly (pull apart, defuzing and depriming), robotic disassembly, mechanical breakdown (bandsaw, guillotine, cracker mill, rock crusher, punch), cryofracture, hydro abrasive cutting, laser cutting, and microwave explosive melt-out. The following are brief descriptions of these techniques:

Manual Disassembly

This technique implies the use of human resources to physically dismantle APM by manual labour using simple hand tools. It has the advantage of requiring limited capital investment required, but is a labour intensive process which results in relatively slow production rates. This method requires well-trained, yet semi-skilled staff.

Mechanical disassembly

The use of mechanically operated systems to dismantle APM. The different technologies are available, as noted above are: Pull Apart, Defuzing and Depriming. In contrast to manual disassembly, mechanical disassembly has the advantages of high production rates, it is an efficient system of work and has low staff requirements. It is environmentally friendly for this stage of the demilitarisation cycle and the technology is readily available. A major disadvantage, however, is the requirement for high capital investment. This is further complicated by the need for a wide range of equipment necessary to cope with all pre-processing requirements.

Robotic disassembly

A fully automated disassembly system. Similar advantages and disadvantages to mechanical disassembly, however the initial capital costs are much greater. This system would only be economically efficient for very large production runs due to the high start-up costs.

Mechanical breakdown

This process is mainly concerned with techniques required to expose the explosive fillings of APMs prior to the destruction phase. There are low staff requirements for mechanical breakdown, and it is an environmentally friendly operation during this stage of the demilitarisation cycle. The technology is now readily available and there is no secondary waste stream, which reduces scrap salvage and disposal costs. A major disadvantage is the requirement for high capital investment. This is further complicated by the need for a wide range of equipment necessary to cope with all pre-processing requirements. Production rates per machine can be slow and there is always te danger of induced initiation of the target APM during processing.

Cryofracture

This process is used to break down an APM into small enough pieces to be processed through an incineration destruction method. It involves the use of liquid nitrogen to change the mechanical properties of the munition casing to a more brittle phase by cooling it to -130 C. The munition can then be easily shattered using simple mechanical shear or press techniques. A cryogenic wash out system is in the early stages of development. The principle is similar to cryogenic fracture; except that the filling is attacked with liquid nitrogen in order to make its removal easier.

Cryofracture is an environmentally friendly technique during this stage of the demilitarisation cycle with low staff requirements. The technique can also be used for any other type of munition, explosive or propellant with limited pre-preparation of the munition required. There is no secondary waste stream, hence cutting final disposal costs. In financial terms low capital investment only is required for set up costs. Sensitivity tests have shown that even at -196C there is little change to the insensitiveness of the munition.

The disadvantage of high operating costs for liquid nitrogen usage must also be considered, however. Unfotunately, today there is only one proven production system in place. APMs with metal or aluminium casings are not susceptible to embrittlement and variations in the shear forces or pressures are required to fracture the munition casing. Further trials are necessary, as analysis has shown that the failure modes for the munition casings involved a mixture of brittle fracture, plastic deformation and shearing. Results are currently unpredictable and there is an obvious low temperature hazard to personnel.

Hydro abrasive cutting (HAC)

The use of water and abrasives at pressures from 240 to 1000 BAR to cut open APM bodies by an erosive process. There are two distinct technologies; 1) "entrainment" or 2) "direct injection". Research has now proven that the direct injection technology should be the preferred option for safety reasons. There are low staff requirements for HAC systems and a wide range of target munitions can be attacked. The explosive safety of systems is well proven and it is a cost effective technique in comparison to other pre-processing methods.The major disadvantage is the requirement for initial high capital investment for infrastructure. The systems also produce contaminated waste-water, which requires a complex filtration system to clean it up. In terms of post-process operations, the explosive content is "grit sensitised" and requires careful handling during any further processing or destruction.

Laser cutting

Still in the research phase in the USA.

Microwave melt-out

This technology is also under development in the USA. It utilises microwaves to heat up TNT based explosive fillings. It is a rapid, clean technique but has one major disadvantage, the lack of control over heating can lead to the formation of "hot spots" with a resultant initiation of the filling. Work continues on its development, but it is not yet a feasible production technique. It is more energy efficient that steam and improves the value of any recovered explosives.