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On February 7, 2008 a huge combustible dust explosion and fire at the Imperial Sugar refinery in Port Wentworth, Georgia caused 14 deaths and 38 injuries, including almost half with serious and life threatening burns. The reason for the dust explosion: inadequately designed processes, equipment and safety practices. The effects of explosions without protective systems therefore represent a significant hazard and appropriate measures and guidelines are required to keep the probability of occurrence and the extent of damage as low as possible.

Why do explosions occur?

When a combustible material, an ignition source and atmospheric oxygen collide in a confined space, the result is an explosion. Preventive Explosion Safety measures aim to stop this potentially lethal mixture from occurring. However, in practice, the vast number of potential ignition sources alone almost always makes this impossible. Consequently, the most important safety features for industrial companies are protection measures that minimize the damage caused by an explosion. Industrial plants must always be protected against the consequences of explosions to ensure that employees are safe and production can be resumed quickly. After all, every hour of lost production costs money. In most cases, explosion safety can be provided cost-effectively through explosion venting and explosion suppression.
Explosion Safety Pentagon
The Explosion Pentagon:
The five requirements for a dust explosion.

Avoiding explosions

As part of a comprehensive and company-oriented risk assessment, suitable protective systems and measures that contribute to protection against explosions caused by hazardous substances as an ignition source must therefore be defined and implemented. Preventive explosion protection is about avoiding such a collision. However, due to the large number of possible ignition sources alone, this is almost always impossible in practice. That is why constructive explosion protection, which reduces the effects of an explosion, is the be-all and end-all for industrial companies in terms of safety. Industrial systems must always be protected from the consequences of an explosion in such a way that, even in the event of an incident, the safety of the employees and a rapid continuation of production are guaranteed because every hour of lost production is costly. In most cases, explosion pressure relief and explosion suppression measures can be used to efficiently and effectively provide constructive explosion protection.

We would be happy to show you solutions tailored to your process, which limit the effects of an explosion to a harmless level and ensure that production can be resumed quickly after an explosion event.

Why is explosion safety so crucial?

Higher – faster – further: not just the objective in sport but also in the development of industrial plant technology. Twenty-first century machinery has long been optimized and is running at high speeds. However, as plants approach their maximum capacity, the risk of an explosion also increases. Rising levels of fine particles produced by fast-running machines are one of the main reasons that the probability of an explosion has increased – these explosions almost always cost human lives. Even if nobody is harmed, an explosion in an inadequately protected industrial plant can still cause immense structural and financial damage.

History shows that explosions in unprotected plants have driven companies to bankruptcy time and time again. After all, every day of lost production puts the company’s existence at risk. Explosion safety concepts usually enable businesses to eliminate production downtime entirely or at the very least reduce it dramatically – and with REMBE® products it is always more affordable than you think.

What are hazardous areas?

Areas in which there is a dangerous explosive atmosphere, i.e. explosive gas/vapour/mist/air mixtures or dust/air mixtures or hybrid mixtures of air and combustible substances can occur, are referred to as potentially explosive areas. They must be divided into zones. For gas-air mixtures, these are zones 0, 1 and 2, for dust-air mixtures zones 20, 21 and 22. The highest number in each case means that an explosive atmosphere does not normally occur or only occurs for a short time. However, it does not mean that these zones are less dangerous.

EX zones for gas-explosive areas

For gas-explosive areas there is a zone classification which defines 3 zones:
  • Zone 0 is classified as an area in which there is a permanent or long-term presence of an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapor or mist.
  • Zone 1 is classified as an area where said reaction is likely to occur during normal operation.
  • Zone 2 is classified as an area where said reaction is not expected to occur, and if it does occur, it is infrequent and temporary.
Source: Directive 2014/34/EU(ATEX)

EX zones for gas-explosive areas

Areas with combustible dust are also divided into 3 zones:
  • Zone 20 contains areas in which an explosive atmosphere in the form of a cloud of combustible dust in the air is present continuously, for a long time or frequently.
  • Zone 21 contains areas where this is only occasionally to be expected during normal operation.
  • Zone 22 defines areas in which an explosive atmosphere in the form of a cloud of combustible dust in air is not to be expected during normal operation, but if it does occur, it is only for a short time.
Source: Directive 2014/34/EU(ATEX)

The 3 key features of a modern protection concept

1. Reliability and Productivity
Protective systems must be permanently available and operational. The potential for false triggers must be eliminated as much as possible since they reduce the productivity of the plant.

2. Compliance
Modern protective systems must satisfy all legal requirements and thus guarantee legal compliance for plant operators.

3. Cost-effectiveness
Protective systems must be as simple as possible to install and require a minimum investment of time and financial resources. The total cost of ownership of the systems must also be kept as low as possible.

All safety concepts from REMBE® meet these requirements. That's a promise!

3 steps to make your processes safer

1. Risk assessment
A risk assessment determines the probability that an explosive mixture of dust and air will come into contact with an effective ignition source. If there is a danger of an explosion occurring, you must take steps to prevent, or at least reduce, the probability of this happening (see step 2). Alternatively, you must implement protective systems that reduces explosion damages to an acceptable level (see Step 3).
2. Prevention and organisational measures
Technical measures
Effective dust extraction systems reduce the build-up of explosive atmospheres. Inert gas blanketing is also recommended to reduce oxygen levels.
Eliminate effective ignition sources
Use only the appropriate equipment (e.g. category 1D) and prevent foreign objects from entering the product stream.
Organizational Measures
Employees should always receive comprehensive training. Documented cleaning procedures and hot-work permitting programs create an additional level of safety.

3. Protective Measures
Explosion pressure resistant or explosion proof vessels
These terms are used to describe vessels that are strong enough to withstand the maximum explosion pressure.
Conventional Explosion Venting
Explosion venting is a technique for protecting enclosed vessels to prevent the internal pressure from exceeding an allowable limit. Breaking points, such as explosion vents in the walls of the plant or vessel, rupture when the pressure reaches a predefined level, maintaining the internal pressure below enclosure strength.
Flameless Explosion Venting
This essentially uses the same principle as conventional explosion venting. However, it offers the advantage that the explosion can be safely vented indoors. The flame and pressure wave of the explosion is controlled which eliminates the risk of injury even when working in close proximity to the equipment.
Explosion suppression
Electronic sensors detect the initiation of an explosion inside a vessel. Within milliseconds, a system controller triggers the injection of pressurized dry inerting powder. This suppresses the developing explosion before it can reach damaging pressures.
Isolation These explosion protection measures must always be combined with explosion isolation to avoid the devastating effects of the explosion propagation and secondary explosions.

What is preventive explosion protection?

Preventive explosion protection describes all measures to reduce or eliminate the probability of an explosion. Per the 5 prerequisites (Explosion Pentagon) for the occurrence of an explosion- explosive gas or dust mixture, oxygen, source of ignition, confinement, dust distribution-to prevent an explosion from occurring, it is sufficient to remove one of these prerequisites. Finding the right protection against such an event will vary with each application and must be assessed very carefully. Thus, ignition can be life-threatening not only in a closed but also in an open process depending on the situation.

Before an explosion can occur, three things must come together: an ignition source, a combustible material, and oxygen. So for example, when handling flammable liquids or when filling devices with flammable dust, it is often sufficient to take preventive explosion protection measures, with the "avoidance of effective sources of ignition" being a priority.

Electrostatic charges are created on the surface by friction of chargeable materials. This charge remains until it either slowly dissipates or discharges by arcing on a conductor. The spark produced by this discharge can lead to ignition if an explosive atmosphere is present. To prevent this electrostatic charge and safely discharge any charges that arise, suitable grounding devices such as grounding clamps must be used on e.g. barrels, systems and pipes. Grounding clamps are particularly useful for mobile objects since the grounding clamps can be assembled and disassembled quickly.

What is flameless explosion venting?

Flameless explosion venting is based on a process in which flames are cooled extremely efficiently in the mesh filter of the flame arrestor and extinguished immediately. Neither flames nor pressure escape and the increase in pressure and noise pollution in the operating area that are typical of an explosion are reduced to a barely perceptible minimum. Likewise, the flameless vent design guarantees that no burned or unburned substances escape. So, the production plant can be set up in a process-optimized manner. In addition to reducing the effects of the explosion, this also ensures the highest level of protection for employees.
  • Pressure relief without flame and dust propagation.
  • process-optimized installation of the system.
  • Safest + most economical solution indoors.
The situation: Explosion vents are not sufficient to relieve the pressure on indoor plant components. The escaping dust and flames pose an enormous risk to personnel and the system. Secondary explosions caused by dust being thrown up are just one example. Vent ducts, also known as relief ducts, are often used to vent the pressure and flames of an explosion to the outside.

The problem: This solution prevents a process-optimized system design. The longer the vent duct is, the stronger and more stable the vent duct and the system itself must be built. This increases costs significantly. Why? The further away the explosion is from the source of the explosion, the more the pressure build up the duct and the system have to withstand increases.

What is explosion isolation?

When it comes to isolation, a distinction is made between active and passive systems:

Passive isolation systems react simply due to the explosion effect. Their structural design prevents flames and pressure waves from spreading

Active systems have detectors or sensors which register the pressure rise or flames and trigger countermeasures such as closing a valve.

The aim of isolation or decoupling is to protect adjacent parts of the plant and prevent the explosion from propagating. By sealing pipes and conveying equipment, the explosion does not propagate into other parts of the plant. Quench valves and mechanical isolation valves are used for explosion decoupling. Extinguishing the explosion flames using a chemical extinguishing agent barrier is also common. Valves and extinguishing barriers can isolate in both directions at the same time.

What is explosion suppression?

Explosion suppression is an explosion protection measure in which the combustion of an explosive atmosphere in a closed or essentially closed volume is detected and stopped in the initial phase, thus preventing destructive pressure increases. A controller initiates the sudden release of extinguishing powder from the extinguishing bootle into the volume to be protected in the shortest possible time. An explosion is considered suppressed if the explosion pressure does not exceed the engineered strength of the affected volume, or the degree of flame propagation remains within the specified limits and directed into safe open spaces.
These explosion protection measures must always be combined with explosion isolation to avoid the devastating effects of explosion propagation and secondary explosions.
Any Questions?
We would be happy to show you solutions tailored to your process that limit the effects of an explosion to a harmless level and ensure that production can be resumed quickly after an explosion event.
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