What to Consider When Installing Wireless Networks in Hazardous Areas

Today’s processing industries demand that workers be connected to wireless devices for all manner of reasons:

• Site wide communication
• Condition monitoring
• VOIP for on-location Wi-Fi calling
• Worker safety
• Asset tracking
• E-permitting
• Remote mentor
• Equipment maintenance and inspection

The list goes on.

However, for hazardous area wireless products they must first be certified to the required standards. Installing wireless networks in hazardous areas requires careful, expert planning and execution.

This article explains the hazards posed by radio frequency (RF) sources, the issues involved when installing wireless networks in hazardous areas, and how to minimise the potential risk.

The Challenge for Hazardous Area Wireless

The RF spectrum covers a wide range from radio waves to gamma rays, but the agreed area of RF under the explosion protection standards only considers the range from 9KHz to 60GHz.

It has always been understood that RF can cause ignition in the right set of circumstances, but when the early radios and pagers were first introduced to the process plants there was little information or guidance in the Explosion Protected (Ex)- type approval standards to clarify what was a safe amount of RF power to be allowed in the different types of hazardous area.

Today, RF devices are used widely across many hazardous and industrial environments. Many people don’t realise that RF is a hazard. Many users ask, “why do we need a certified antenna when it is only fed with RF?” This common misconception is understandable, as there are still very few certified wireless devices on the market.

Radio Frequency Hazards in Explosive Atmospheres

There are several ways RF can be a potential hazard in explosive atmospheres. We know that radio waves and microwaves induce currents in metallic structures such as cranes, pipes and other plant structures, which can cause sparking if there is a suitable gap in the structure.

The power dissipated in the spark may be sufficient to ignite a flammable atmosphere if the radio wave is powerful enough. For some applications, such as pulsed radio transmissions in radar, the amount of power may be higher than these levels, but only for a relatively short amount of time. It is possible, in these circumstances, to use another limit based on threshold energy.

Fortunately, much of the latest wireless technology that is of great interest to users to deploy in their plants such as WiFi or RFID has RF power levels lower than the 2W limit. Providing antenna gain does not cause these levels to be exceeded, and they are installed in certified protection, such as Ex d enclosures, they can be used in a hazardous area without restrictions.

Hazardous Area Wireless

The main danger with wireless networking devices is associated with the electrical hazard from the transmitter and its power supply, as well as from the RF output stage. The hazard posed by electrical equipment has been catered for over many decades with the earliest standards and protection concepts now over 50 years old.

The two main dangers are the risk of a spark when a device short circuits due to inadequate creepage and clearances, or from a foreign body entering a piece of equipment.

Ignition can also be caused by the heating effect of components, under fault conditions, conducting electrical current which are not adequately power rated. Also, a non-battery powered radio transceiver is ultimately connected to mains voltage and thus under fault conditions this voltage could be transferred through to an antenna. If that antenna does not have suitable creepage and clearance, or be of a suitably robust construction, it could cause a spark or become dangerously hot.

This means that either the RF stage must have an intrinsically safe output or that antennas must meet a range of stringent mechanical, constructional, and thermal requirements to ensure that the installation is safe should any of the above events occur.

Extronics Wireless Access Point Enclosures

Extronics has been leading the way in hazardous area wireless since the launch of our first ATEX certified wireless solution in 2005. We are continually building on this experience and have formed technical partnerships with providers such as Cisco, Aruba, Siemens, ProSoft, Rajant and more.

iWAP series

You to choose your access point from leading vendors like Cisco, Aruba, Siemens, and more, and Extronics make if suitable for use in hazardous areas with our iWAP series of enclosure systems, specifically designed for wireless networking.

iSOLATE technology

Protecting against AC, DC, and dangerous transient faults, the iSOLATE501 makes RF outputs intrinsically safe. Working with sister product iSOLATE-CT, it allows you to use simple apparatus antennas in hazardous areas and hot swap them, too.

iANT range

Fully assessed by Extronics engineers as ‘simple apparatus’ under intrinsic safety standards, the iANT range gives a wide choice of antennas for use with our iWAP series to suit multiple applications.

Please contact our team of experts today to discuss your use case. Contact us using the form below, email info@extronics.com, or call +44 845 277 5000