A few verticals like oil & gas and chemical processing industries need explosion-proof CCTV cameras because they function in hazardous conditions. The possibility of accidents such as a fire in an offshore or onshore oil rig, refineries, or even gas stations are high, and to secure such places, you will need cameras that are flame-proof and rugged. Even industries like grain storage and woodworking, where products are not highly flammable, should consider using intrinsically safe explosion-proof cameras because, in their dust form, such materials could be dangerous.
Several major manufacturers offer explosion-proof CCTV cameras. For customers, knowing key specifications and how they operate is necessary before purchasing them. This is especially relevant to those regions where there oil and gas play a critical role in the economy. In this article, we explore
what happens during an explosion, factors that make a camera explosionproof, and the standards to ensure quality.
How explosions occur
Explosions happen when three components come together – any kind of fuel, energy, and an oxidizer. Without even one of these, the explosion will not occur. A setting where an oxidizer like air comes near flammable stuff like gas or vapor is considered an explosive atmosphere. Energy or a source of
ignition is all that’s needed in such an atmosphere to trigger an explosion or fire.
This energy could come in the form of friction sparks, electromagnetic waves, surface heat, radiation, lightning, etc. The term “hazardous area” is used to denote such spaces where the risk of an explosion is high, and these are the areas where explosion-proof CCTV cameras should be used. The opposite of this is “safe areas” where normal video surveillance cameras can be deployed.
How explosion-proof CCTV cameras work
Now that we have seen how an explosion occurs let’s take a look at how cameras that are built to withstand explosions function. Three principles are fundamental to the ideal operation of these devices. In a white paper, Axis Communications defines them as prevention, segregation, and containment. Note that a single zone or area need not use all of these principles.
- Prevention: As the name suggests, the prevention principle works to ensure that thermal and electric energy remains at safe levels at all time. Intrinsically safe explosion-proof cameras use this principle.
- Segregation: The risk of an explosion decreases when electric surfaces are physically separated from the explosive atmosphere. Techniques such as encapsulation or pressurization are useful to achieve this.
- Containment: Limiting the impact of an explosion is crucial to minimizing damages. Any fire that breaks out after a blast should be contained to a defined space and not allowed to propagate to other areas. The use of explosion-proof housing or flame-proof enclosures on video surveillance cameras is necessary to enable containment.
Standards and certification
Testing and certification processes help customers make better purchase decisions. In most developed economies, electrical devices for use in hazardous environments and their installers should pass stiff requirements. Different certification terminology is used in different countries. The US uses the Class/Division system described in the National Electrical Code (NEC), article 500, to classify explosion-resistant electrical devices.
In Canada, the Canadian Electrical Code (CEC), section 18, is used. In other parts of the world, a zone system described in the IEC 60079 set of standards for the IECEx certification is mostly followed by some country-specific variations.
The specific marking indicates if a product has passed the certification tests. In the US, these devices should have a label with the name of the manufacturer, the certificate issuer and file number, and the marking according to NEC 500-506.
Europe mandates the CE label and the code number of a designated agency that monitors the manufacturer’s quality. There is also an ATEX Ex symbol, along with the Group, Category, and, if Group II equipment, whether the marking relates to gases (G) or dust (D). The labeling should also show the
type of protection, the temperature category, the group of apparatus, and the equipment protection level.
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