German China India

Wireless Transmission in Ex D Zone

Simple and Safe Wireless Hart Communication? Yes, we Can!

| Author / Editor: Sabrina Weiland, Dirk Heyden* / Dr. Jörg Kempf

The WirelessHart adapter “Bullet” features a flameproof Ex d enclosure and is suitable for use in explosion-hazardous areas up to Zone 1.
The WirelessHart adapter “Bullet” features a flameproof Ex d enclosure and is suitable for use in explosion-hazardous areas up to Zone 1. (Picture: Pepperl+Fuchs; © Sergey Nivens, © fotomek - Fotolia; [M]Tscherwitschke)

Wireless provision of status, process, and diagnostics data for Ex d field devices — Is it possible to communicate data regarding measurements, diagnostics, and parametrization from flameproof 4…20 mA and Hart field devices in a completely wireless process? Yes it is!

When it comes to transferring a signal from an explosion-hazardous area, the particular type of protection a device offers can have significant influence. Previously, if a plant was equipped with Ex d field devices, a wired solution was used for signal transfer, since only intrinsically safe adapters were available for wireless data transfer. If the plant operator wished to establish a wireless connection to the process control system, the flameproof field devices had to be connected via an Ex-d-to-Ex-i configuration.

These setups often turn out to be costly and complex. This complexity comes from the fact that, with Ex d field devices, the circuits are not galvanically isolated, and in many cases the internal capacitance is not known.

Due to the risk of energy feedback in the event of a fault in the Ex d field device, it is not possible to connect an intrinsically safe adapter for WirelessHart without additional effort.

Various approaches exist for configuring Ex d to Ex i:

  • First approach: In the rare case that the capacitance of the Ex d field device is known and intrinsically safe outputs are available, the circuit can be calculated and designed according to Ex i.
  • Second approach: Another possible approach is to position the WirelessHart adapter outside of the explosion-hazardous area, though this solution results in costs for implementing, routing, and protecting cables using conduits, as well as for installing the adapter.
  • Third approach: A third alternative approach is to make the circuit between the Ex d field device and the Ex i adapter intrinsically safe by using a Zener barrier. In this case, the field device is connected to an Ex d switch box and the Zener barrier integrated in there via a flameproof cable duct and a conduit. There is then another intrinsically safe field connection on the other side of the switch box and Zener barrier, enabling the Ex i adapter to be connected.
Additional Information
 
The world’s only Ex-d-certified WirelessHart adapter

All of the alternatives outlined are laborious to some extent and result in increased costs and significant effort. In contrast to these options, wireless connection with a flameproof WirelessHart adapter represents a much more convenient and cost-effective solution.

Content of the Article:

Comments are being loaded ....

Leave a comment

The comment is checked by an editor and will be released soon.

  1. Avatar
    Avatar
    Edited by at
    Edited by at
    1. Avatar
      Avatar
      Edited by at
      Edited by at

Comments are being loaded ....

Report comment

Kommentar Freigeben

Der untenstehende Text wird an den Kommentator gesendet, falls dieser eine Email-hinterlegt hat.

Freigabe entfernen

Der untenstehende Text wird an den Kommentator gesendet, falls dieser eine Email-hinterlegt hat.

copyright

This article is protected by copyright. You want to use it for your own purpose? Contact us via: support.vogel.de/ (ID: 43841190 / Control & Automation)