Hazardous Area Electrical Installation

Can using Steel Wire Armoured cables cancel out the need of using IS Barriers completely

Not in any American ATEX or European IEC standard I am aware of. Armouring of the cable is not acceptable on its own as a substitute for a purely intrinsic safety protection.

What can be the reason or am I missing out some thing??

Perhaps the equipment in the hazardous area is being installed in Ex d flame proof or Ex p pressurised enclosures (which provides the level of protection necessary instead of Ex i intrinsic safety). Perhaps the PLC I/O has an intrinsic safety rating and so doesn't require the additional barriers the old installation had (this is more common nowdays).

Since there could be a number of valid reasons for this perhaps you should ask the site system design engineer (or whoever is in charge of the hazardous area design), we can only guess (which is never a good idea when hazardous area design is involved).

Thanks for the info. May be I will check the PLC I/O. But out of curosity,in general will SWA cable prevent arching or is it just for the sake of durability.

SWA cable is common on hazardous area sites and is used to provide an extra level of cable protection compared to unarmoured or unscreened cable. Its use really depends on the application, cable position, existing cable protection (cable tray/cable conduit, etc) and site-specific and company standards.

It's there to give mechanical protection to the cable. There is no absolute need to use it. One could use various styles of conduit instead, for example.

There would be no incendive sparks were the cable to be correctly installed on an EEx i circuit, whether subjected to mechanical abuse or not.

The PLC I/O is irrelevant.

Hi,Guest,

Quite apart from any governmental standards requirement regarding cabling,glands,junction boxes etc. - the whole idea of Intrinsically Safe Barriers is to prevent ANY Voltage/Current combination reaching the instrumentation/control gear within the hazardous area. Steel-shrouded cable will not prevent sparking or overheating if, say, 12v DC finds it's way back from a defective temperature controller to a thermocouple element. Look at the original installation with this in view - you'll see why the I.S. barriers were fitted in the first place.

The original poster hasn't mentioned the protection concept of intrinsic safety so far.

Intrinsic safety is not confined specifically to 12VDC circuits. 28VDC is possible within the hazardous area under EEx i, for example, as would be a range of AC systems.

That’s a very valid concern. Using Steel Wire Armoured (SWA) cables does not cancel out the need for intrinsic safety (IS) barriers on its own. The SWA cable mainly offers mechanical protection and grounding, but it doesn’t limit electrical energy, which is the key function of IS barriers in hazardous areas.

You might have been advised to omit barriers because the new installation could be designed under a different protection concept, such as Ex d (flameproof) or Ex p (pressurised). These systems contain or isolate potential ignition sources, allowing higher energy levels without the need for barriers. However, this is only valid if every device, enclosure, and junction box in the hazardous area is appropriately rated for that protection type.

In similar industrial setups managed by Electrician Singapore, engineers first perform a hazardous area classification and confirm all protection methods before installation. This ensures compliance with local and international safety standards, especially in facilities handling flammable or volatile materials.

It’s strongly recommended to review the project’s hazardous area drawings and confirm with the design or safety engineer before proceeding. When it comes to explosive atmospheres, verifying every protection method is essential to maintaining both compliance and on-site safety.