Maltese engineers to the rescue

Following the latest fireworks accidents, the Chamber of Engineers feels the need to a positive, constructive reaction. One of its roles in Maltese society is to provide a networking platform not just for engineers but also for the Maltese society in general.

Fireworks or pyrotechnics manufacturing plants form only a small percentage of the explosive atmospheres present in the world. Offshore platforms, petrochemical plants, mines, flour mills, semiconductor and pharmaceutical industry are all areas where a potentially explosive atmosphere may be present. Yet, good design and risk management can lower the risk substantially, protecting human life, the environment and the business operation itself.

As from 2006, organisations in EU countries had to follow two EU directives: Atex 95 Equipment Directive (94/9/EC) and Atex 137 Workplace Directive (99/92/EC). Atex stands for Appareils destinés à être utilisés en ATmosphères Explosibles, or equipment intended to be used in explosive atmospheres.

If I had to mention a single word that would apply to the situation of the pyrotechnics industry in Malta, Atex would be it. In brief, Atex classifies areas of hazardous explosive atmospheres into zones. There are two particular types of zones: 0, 1 and 2 for gas-vapour mix and 20, 21 and 22 for dust. These have to be protected from an effective source of ignition. Effective ignition sources are: lightning strikes; open flames (ranging from cigarettes to welding activity); mechanically generated impact sparks (such as blowing a hammer); mechanically generated friction sparks (such as those encountered during lifting or transport operations); electric sparks (faulty equipment, switching on/off); high surface temperatures (could be generated from machining processes); electro static discharge – ESD; radiation and adiabatic compression (pumping air into a tyre).

Thank God that the engineering community in Malta is adequately prepared to mitigate this risk. Good lightning protection can deviate thunder strikes from dangerous areas. Common sense and discipline should ensure that no cigarettes are lit in such zones.

Mechanical activity inside these zones should be restricted to the indispensable and should be carried out in a strict manner using a strict range of materials that do not generate sparks. For example, a mechanical pump can be replaced by vacuum, thereby eliminating risk of explosion.

Electrical appliances must be properly selected. This, of course, comes at a price. A light fitting costing under €50 might end up costing €500 to be Atex compliant, however, life is protected. The same applies to socket outlets.

Lifting and transport is also key. The Maltese market is already catering for such hazards. Fork lift trucks designed for such locations are available for sale/hire. To mention a few details, these fork lifters, as called by the locals, have: stainless steel forks to suppress mechanically generated sparks (compares to their steel equivalent; pre-wired batteries to reduce the chance of sparks or high temperatures from loose contacts; compressed air starters and muffling of the exhaust if diesel operated.

Coming from the semi-conductor industry, I am well acquainted with ESD. In electronics, ESD is known as the “silent killer”. Lightning is a full-scale ESD phenomenon. Through everyday operations, our body, particularly our hands, rubs clothing material together generating a static charge. When in contact with a conductor connected to the ground, this energy is discharged at once and a small spark is generated.

In everyday life, most of us would have experienced a “shock” from a car. Combing your hair or just moving your feet can generate 25,000 volts! If you undress cotton underwear in a dark room, you might be lucky enough to see your underwear glittering through ESD generated sparks. The effect of ESD on the Hindenburg airships on May 6, 1937 was so tragic it ended the era of hydrogen airships.

ESD can be handled in various ways. Properly designed overalls incorporate carbon conductive strips or grids to inhibit the formation of charge. Flooring and worktops are selected from a material that is neither conductive nor insulating. In such a way, an eventual discharge would be slow enough to reduce the current.

In the case of fireworks, humidity has to be considered. Low humidity means the air is an insulator. Thus, it is easier for static charges to build up just by common motions (like a cloud gaining static charge through friction with the wind). Unless there is specific process requirements, humidity should not go below 40 per cent. This is achieved through air handling units equipped with humidifiers. Taking a closer look at fireworks explosions, there is a tendency for low humidity periods during dry heatwaves. A controlled air handling unit can provide constant temperature, constant humidity and filtered fresh air and get rid of air carrying explosive dust.

High humidity, on the other hand, is not desirable. All of us who studied O level chemistry remember the classic experiment of burning sodium by just dropping it in the water. If such elements exist in pyrotechnics, these will react with water.

Other nuisances are the clogging effect of humidity on fine dust and the weakening of the packaging.

Humidity must therefore be maintained within a tight window, say 40-50 per cent. This calls for tight control, which is easily attainable with an air handling unit. Another advantage of such a unit is the possibility of extruding all the air. Thus, any dangerous dust will be expelled immediately from the plant. Another option is the use of mini-environments. All air is expelled and a nitrogen environment is used. Since no oxygen is present, an explosion is prevented. (Do you remember the fire triangle fuel+oxygen+heat?)

Needless to say, the roles of other professions, like architects and industrial chemists, are also crucial. Proper design exists for explosion prone buildings including collapsible structures. Qualified industrial chemists should be like the maestro leading all the musicians.

I will not debate whether we should stop manufacturing pyrotechnics. For sure, we cannot manufacture fireworks in an uncontrolled environment. As a Maltese engineer, worker and citizen I am proud we have overcome technological and economical challenges with flying colours. Malta has managed not just to retain but to expand its semiconductor and pharmaceutical manufacturing facilities, even when faced with high competition from our Chinese counterparts. This is only due to the ability of the entire Maltese community made up of workers, technicians, engineers, architects, chemists, entrepreneurs and managers, all operating within a controlled strategy. Why not adopt this approach and methodology to pyrotechnics?

Above is a historical event of explosions, outlining maximum temperature and minimum humidity. Statistics are not yet complete; however, there is an indication that humidity extremes promote explosions.

A warranted engineer with over 15 years’ experience, the author worked at STMicroelectronics both in production and in plant facilities, following which he joined MTS as a consultant. He is also a freelance consultant and treasurer of the Chamber of Engineers.