Intrinsically Safe vs Explosion Proof- What’s the Difference?|
Article - January, 29 2018 By LarsonElectronics.com
Intrinsically Safe vs Explosion Proof- What’s the Difference?
Hazardous locations call for specially-engineered lighting systems that can reduce the risks of ignition. For lighting systems and other industrial equipment, the most common types of protection include explosion proof and intrinsically safe.
The two vary greatly, from methods of protection to the way they are regulated by global safety institutions. This article explores the differences between the two, as well as their ratings and applications in industrial markets.
Designs and Features
Intrinsically safe refers to a type of protection that leverages low power currents to prevent the combustion of flammable compounds in the hazardous location. This technique is effective during normal operations, as well as fault or abnormal conditions. Intrinsically safe, wired equipment relies on an isolator or protective barrier to regulate power, preventing the occurrence of power surges that could (if present) ignite volatile substances. When used with other equipment in the hazardous location, the intrinsically safe barrier, which consists of resistors and fuses, should be separated from components that are not protected intrinsically, such as wires, in order to reduce the possibility of uncalculated connections.
Unlike intrinsically safe methods, explosion proof mechanisms allow ignitions to take place internally. Using heavy-duty conduits and seals, combustions are contained within the unit, ensuring they don’t escape and cause large fires, accidents or chain reactions. To reduce ignition temperatures, volatile gas is pushed through the system, forcing it to cool and expand safely before it is reintroduced back into the external environment.
In an intrinsically safe system, the main focus is power, which is heavily regulated and kept low to prevent the formation of sparks. Furthermore, this method does not utilize conduit and seals for protection – simply because it doesn’t need them. The main issue with intrinsically safe protection is its limitations in handling high-powered devices and equipment. Because low currents are required, this type of protection is not suitable for high power. For example, a camera with a flash cannot be intrinsically safe, because flashing requires bursts of high energy. Explosion proof protection would be more suitable for cameras, as well as fixed gas detection systems, sensors and industrial lighting (note: not handheld lighting), in hazardous locations.
Comparing the two options, explosion proof designs are required to mitigate surface temperatures, ensuring they don’t surpass ignition temperature thresholds of flammable compounds in the hazardous location. Since intrinsically safe devices can function safely in hazardous locations, they don’t need to take such factors into consideration. Additionally, explosion proof systems typically use high-strength materials during construction, such as cast aluminum or stainless steel.
From a cost perspective, explosion proof systems are most expensive to acquire and implement due to the use of heavy-duty components (conduits, enclosures, seals and more). But in some cases, like the use of high-powered devices, explosion proof is the only choice, as it caters to a wider range of equipment.
Compliance and Regulation
Intrinsically safe and explosion proof compliance can sometimes be complicated, due to varying standards between regions or countries. For instance, an intrinsically safe device in Europe is technically not intrinsically safe in the US or Canada, due to different regulatory standards and processes used when rating the product (just like how a local US driver’s license [note: not a US-issued International Driving Permit] is not valid in Japan, for example, but this doesn’t mean the US driver’s license holder doesn’t possess the necessary skills to drive in Japan – it’s basically an acknowledgement issue).
It is best practice to always adhere to the local standards of the hazardous location when matching equipment ratings with industrial safety regulations.
With this in mind, let’s take a closer look at how such ratings differ between safety institutions. The ATEX Directive, which is mostly used in Europe, certifies intrinsically safe equipment as Ex ia and Ex ib. The first classification is applicable to Zone 0, Zone 1 and Zone 2 explosive locations, while the latter is applicable to Zone 1 or Zone 2. This is similar to NEC’s Division 1 and a Division 2 explosion proof ratings for the US, in a sense that Ex ia is recommended for hazardous locations where volatile compounds are present at all times and exist (Division 1); and EX ib is recommended for hazardous locations where explosive compounds may exist (or have the potential to) sometimes or under abnormal conditions (Division 2).
From a global standpoint, IECEx standards are used for international certification, derived from IEC 60079-0. The key difference between ATEX and IECEx is that ATEX is only accepted in the EU and IECEx is accepted worldwide. However, this does not mean IEC standards can fully replace local regulations governing a hazardous location. In the EU, ATEX is mandatory – there’s no way around it. In practice, this means ATEX certification could technically be furnished using results from an IECEx test document. But in reverse, ATEX results cannot support IECEx certification. Because of this, it is common for products that require intrinsically safe or explosion proof protection to feature multiple markings (shared descriptions).
There are several regions and countries that acknowledge IECEx standards, such as the following: the US, Russia, Canada, China, Europe, Australia and South Africa.
The difference in standards between the governing institutions are great, in some aspects. For example, referring to ATEX, the gap of the flame path that is required in explosion proof equipment is considerable larger than what is required to meet US standards. This means that an explosive gas inside an ATEX-rated device will cool down faster, compared to the same device that is manufactured according to US explosion proof standards.