Tuning in on Explosion Protection: Wireless Equipment in Ex–Zones

Related Vendors

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

TRM Filter d.o.o.

Donadon SDD Srl

R. STAHL Schaltgeräte GmbH

Notably, radio communication is also an integral part of intelligent systems within the “Internet of Things”. In addition, setting up and maintaining a wireless network is usually less expensive and easier to carry out than deploying an extensive cable installation. However, for a scenario involving hazardous area applications, the extra cost and effort for explosion protection measures must be factored in as well.

Radio: An Invisible Hazard?

Radio and wireless systems such as WiFi access points, mobile telecommunication components or RFID readers harbour potential ignition risks including transient voltages. Generally, a transmitter’s electromagnetic field cannot directly ignite an explosive atmosphere, provided the radio source does not have a transmission power of several hundred Watts. There is, however, a risk of sparking because of currents induced in metallic objects or in electronic circuits with insufficient electromagnetic compatibility.

First issued in 2004, the international standard IEC EN 60079-0 defines protection levels and limit value requirements for radio signals in hazardous areas. In addition to observing the limits during normal operation, this standard also requires the consideration of device malfunctions in zone 1: short circuits, electrical shunts, or interruptions must not constitute an explosion risk either.

Intrinsically Safe Signals

Using electrical isolation, the 9730 HF Isolator prevents low-frequency signals from leaving the protective (for example Ex d) enclosure of a wireless component altogether. Shielding the surrounding atmosphere from possible ignition risks associated with device malfunctions, the isolator instead transmits an intrinsically safe signal (Ex ia IIC) to the external antenna. In addition to its superior safety gain, the HF Isolator ensures easy handling during installation and operation: radio systems and their external antennas no longer need to be connected via fixed lines without plug connectors. Instead, any standard antenna for industrial use can be installed with customisable cables fitted with plug connectors. These cables can be easily replaced at any time to reposition an antenna or move the device to another spot.

In addition to the type 9730 HF Isolators, manufacturer R. Stahl provides a wide range of other Ex d and Ex p enclosures for radio systems and wireless solutions in hazardous areas.

* * The author is Product Manager Automation at R. Stahl, Waldenburg/Germany.

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