An explosion at a hazardous production facility (HIF) for the storage and processing of vegetable raw materials occurs due to the contact of combustible dust/air mixtures and an ignition source in a confined space. All of these factors cannot be completely eliminated in food production and product transport. Risks can be reduced by complying with the safety regulations for hazardous areas and by providing explosion prevention systems, explosion protection.
The dangers of plant-based raw material sites
HIFs are plants where hazardous substances are present. This is defined in Directive 2012/18/EC on the control of major accidents. Hazardous substances include, among others, substances and mixtures with explosive properties, flammable gases and aerosols.
Places of storage, transportation and processing of plant raw materials of agro-companies, food production facilities are also hazardous sites. The main risk of such sites is associated with the formation of explosive dust/air mixtures.
Directive 2012/18/EC divides hazardous industrial facilities into two hazard classes, lower and higher, according to the probability of an accident with destructive consequences. The assignment to one of these is based on several criteria: the presence of certain substances and mixtures, their quantities, the proximity of other plants and social and residential areas.
The most hazardous in terms of accident probability and consequences are elevators and sites of flour, cereals and feed production.
Important. Hazards only become hazardous when they are incorporated in the process, by human interaction with them. Cocoa powder does not cause harm when stored in a warehouse. But if there are sources of draughts that blow dust into the air, and people with a cigarette, a lighter, a welding machine show up, the likelihood of an explosion is multiplied.
Typical accidents and their causes
According to publicly available statistics, 400-500 explosions occur each year at grain storage and processing facilities: grain elevators, bakeries, flour mills and cereal mills. Here are examples of the largest ones.
- 1981 - explosion and subsequent fire in the building of a high-quality mill of the bakery in Kalinin (now Tver), USSR. The six-storey building was completely destroyed. There were 10 victims and 10 wounded. Caused by an explosion of flour dust.
- 1992 - an accident at Balakleya fodder mill, Savintsy village, Kharkov region, Ukraine. Two floors of the main building and the outer bearing structures were destroyed. There were 11 fatalities and 18 seriously injured. The cause was a dust explosion.
- 2005 - explosion in a port grain silo in Latakia, Syria. A two-storey building, a seven-storey tower and a grain delivery conveyor were completely destroyed. One person was killed and 20 injured.
- 2013 - explosion at an oil and fats plant in Irkutsk, Russia. A grain elevator workshop was destroyed. There were 4 casualties. Caused by flour dust combustion.
This is just a small part of the accidents at grain elevators and bakeries, the main cause of which is dust mixtures explosion.
Grain, mixed fodder, silage, flour, dry food products are a source of organic dust. It accumulates both on the surface of technological equipment and inside it. In combination with oxygen or air as an oxidiser, the dust forms a combustible dust/air mixture.
If initiated by an ignition source (spark, static electricity or self-ignition due to overheating) it will ignite and cause a local explosion. This in turn instantly increases the temperature and pressure in the confined space. This leads to a secondary explosion, which is devastating to equipment, buildings and people. Such a catastrophe can turn a workshop or building to rubble in 1-2 minutes.
Important. The main causes of sources of ignition and explosion initiation in grain, foodstuffs storage areas:
- obsolete or faulty equipment;
- violation of its operating rules;
- non-compliance with fire safety requirements;
- violation of rules for handling plant raw materials;
- poor organization of works at the HIF.
In other words, the probability of an explosion is determined by three factors: technological, organisational and human.
The possibility of primary explosions due to accidental equipment failures or errors by operating personnel cannot be completely ruled out. Technical solutions can help reduce the risk of explosions in granaries and food processing plants.
Preventing explosions at a hazardous industrial site
Preventing an accident at a hazardous agricultural or food production facility means, among other things, ensuring that the site is explosion-proof:
- eliminate the possibility of an explosion of flammable dust/air mixtures;
- contain the accident in order to avoid devastating consequences and loss of life.
This is achieved by applying explosion protection and explosion prevention measures. Various methods are used for this purpose.
Explosion prevention is aimed at eliminating sources of ignition, dust accumulation; early detection of ignitions. Proper organisation of the technological process, industrial control at a HFI, training of employees in safe work practices, and the use of automatic detection and warning systems work here.
Explosion protection involves localising an explosion and limiting its spread. For this purpose technical solutions are used: fire and check valves, flame arresters, supply of inert gases and phlegmatisers to the equipment.
Important. There is no one-size-fits-all solution for every HIF. All plants are individual and explosion protection systems are tailored to their specific characteristics. There are general solutions in national and international standards. The parameters of specific equipment depend on the operating conditions of the individual HIF.
ATEX.CENTER offers effective explosion protection systems for explosive storage and processing facilities:
- explosion suppression equipment (HRD System).
- equipment for its release - explosion vent panels, flame arresters.
- explosion prevention equipment - non-return valve, gate valve, HRD barrier to cut-off.
- Explosion protection of bucket elevators (Elevex) - diaphragms, flame arrestor, check valve, HRD suppression or cut-off system.
Our experience is based on current Russian and international standards, knowledge of the specific development and spread of explosions of organic dust-air mixtures.
ATEX.CENTER experts will assess the risks, make the necessary calculations and assess the explosion hazard of the equipment and select an effective solution for its explosion protection in strict compliance with the applicable regulations.