When Intrinsic Safety is essential for industrial displays

Many process plants have hazardous areas with explosive atmospheres. These can be ignited even by low levels of electrical or thermal energy such as arcing or sparks from electrical circuits. It’s therefore essential that any electrical equipment, such as industrial displays, intended for these environments is designed to prevent any such ignition opportunities.

Within Europe, the solution is usually to build products that are intrinsically safe; that is, their energy consumption and storage comply with international standards for safe level limits under specified fault conditions. All our semi-custom monochrome, OLED and TFT displays can now be customised to comply with these international Intrinsic Safety standards.

Intrinsic Safe Displays

Flat panel displays consume electrical energy, and are connected to an external power source. Arcing or sparks arising from short circuits or failures are therefore possible: these could cause an explosive atmosphere to ignite. Such atmospheres exist within hazardous areas found in many process plants including petrochemical, pharmaceutical, paint manufacture, pill coating, and battery manufacture where there is a presence of flammable liquids, gases or vapours.   Combustible dusts such as those in granaries and food processing are also potential hazards which can be ignited and cause an explosion.

One possible solution is to protect all hazardous area electronics by sealing it within a gastight, positively pressurised enclosure that isolates any possible source of electrical discharge from the area’s atmosphere. This approach is sometimes taken, but in Europe an Intrinsically Safe (IS) solution is used. To be classified as intrinsically safe within Europe, equipment must comply with international IECEx standards and the European ATEX Explosive Atmospheres Directive. This defines the maximum energy that may be transferred to or stored within the equipment under specified fault conditions. Equipment is considered intrinsically safe if it is incapable of generating sufficient electrical or thermal energy to cause an explosion in the  atmosphere of its environment.

A product’s intrinsic safety within a hazardous environment depends not only on its own performance but also that of any external power or signal I/O feeds. These must reach the product directly from a safety barrier located in a safe area. Such barriers usually include a series of diodes, resistors and fuses arranged and sized so as to limit the energy provided to the device in the field. It is always important to remember that no piece of equipment can be considered Intrinsically Safe under all conditions. Its IS status depends on how it is connected, where it is located geographically, and the class of hazardous environment it is to operate in.

Some special IS considerations apply to electronic equipment destined for hazardous areas, in addition to reducing or eliminating internal sparking. Component temperatures should be controlled, and component spacing that could allow dust to establish a short-circuit must be designed out. Safeguards such as current limiting by resistors and fuses must be used to ensure that under no circumstances can any component reach a temperature sufficient to cause autoignition of a combustible atmosphere. These issues have become increasingly critical as components, and the PCBs that hold them, have become ever more compact and higher in power density. Additionally, single component failure modes can be catered for by using multiple series resistors and Zener diodes.

At Anders we have experience in customising different display technologies, including semi-custom monochromeTFT and OLED. All our industrial displays of these types can be customised specifically to comply with the conditions of their destination country, the classification and type of their target hazardous environment, and the external system – if they are not a handheld device – they will be integrated in to.

If you need an IS display for your particular application, contact us to find out how an Anders flat panel display can be designed to comply with your target environment.

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