Basics of explosion protection

Explosion protection is the basic element of the safety device in many potentially explosive areas. In all Ex zones there is an increased risk of explosions due to various atmospheric conditions or the handling of explosive and flammable substances. To ensure the highest possible level of safety in these areas, legislation in most countries has developed standards, ordinances and laws that operators must implement to prevent accidents.

What are Ex Zones?

Wherever flammable or explosive materials are manufactured, processed, transported or stored, safety plays a major role. We immediately think of explosives, oils and gases - but the danger of explosions also exists from many other substances and due to some other circumstances. A central question when evaluating an Ex zone is where ignitable environments occur or can occur.

Areas at risk of gas explosions can be divided into the following three zones:

Zone 0: Area in which an explosive atmosphere consisting of a mixture of air with flammable substances in the form of gas, steam or mist is present continuously or for a long time.
Zone 1: Area in which an explosive atmosphere consisting of a mixture of air with flammable substances in the form of gas, steam or mist is likely to occur during normal operation.
Zone 2: Area in which an explosive atmosphere consisting of a mixture of air with flammable substances in the form of gas, steam or mist is not to be expected during normal operation, and if so, then only rarely and only briefly.

In addition to explosive solids, liquids and gases, another common cause of explosive fires is combustible dust. With a small grain size (usually less than 0.5mm) and sufficient concentration in the air, a small electrical spark can be enough to trigger a devastating explosion. Even if the dust is not swirled in the air at the time of the sparking, smoldering nests can form, which rest for several hours and suddenly explode when the air is stirred up.

Basically, explosive areas with combustible dust can be assigned as follows:

Zone 20: Area in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, long-term or frequently.
Zone 21: Area in which an explosive atmosphere in the form of a cloud of combustible dust in air can occasionally occur during normal operation.
Zone 22: Area in which normal operation is unlikely to result in an explosive atmosphere in the form of a cloud of combustible dust in air, and if so, then only rarely and only briefly.

The North American division system only divides hazardous areas into two divisions. Division 1 describes the area in which ignitable gases, vapors or dust particles occur permanently or temporarily in normal operation. Comparable to zones 0 and 1. Division 2 includes areas in which ignitable mixtures are unlikely to occur in normal operation. Comparable to zone 2.

Explosion protection measures

Explosion protection measures can be divided into three stages depending on the approach. If possible, the primary explosion protection measures should already be taken to avoid explosions. This means to prevent the formation of a dangerous and explosive atmosphere or at least to limit it as well as possible.

If this is not possible due to the operational processes, then according to the measures for secondary explosion protection, effective ignition sources should be avoided. In rare cases, even that is not enough to make an area explosion-proof. In these cases, tertiary explosion protection must be used. This means the implementation of measures that limit the impact of an explosion to a safe minimum. One speaks here of constructive explosion protection.

Explosion protection for customer-specific applications

Input devices can also be sources of explosion because each time a key is pressed, a circuit is closed and a possible detonator is actuated. To prevent this, the devices can be built with different protective properties. We can support you in the implementation of explosion protection in your area by jointly developing customer-specific input systems.

In principle, as the responsible operator of an Ex area, it must be ensured that the devices used comply with Directive 2014/34 / EU (ATEX). We develop and produce customer-specific input systems, but we do not take over the certification, this would be handled by our customers if necessary.

Classification of devices that can be used in Ex zones

Devices that can be used in hazardous areas are divided into three groups, each with three sub-groups:

Group I: mines at risk of firedamp (coal mining) - the risk increases from A to C depending on the respective explosive substance.
Group II: explosive gases - sub-group A includes diesel, petrol, methane and carbon monoxide, B includes city gas, hydrogen sulfide and ethylene, and C hydrogen, acetylene and carbon disulphide.
Group III: Dusts - are divided into A for fibers, B for non-conductive dusts and C for conductive dusts.

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