Taking fieldbus into hazardous areas

Two different approaches are taken to installing instrumentation in hazardous areas.

• Using instrinsic safety or non-incendive field wiring - no gas clearance needed for live working
  

• Using flameproof/explosionproof or non-arcing - requires gas clearance for live working

As end users have invested heavily in design, installation and maintenance of instrumentation based on their selected hazardous area protection methods, it is recommended that they use the same methods or site standards for the fieldbus network as they use for conventional instrumentation.

Two technically different approaches have emerged for interconnecting intrinsically safe and non-incendive fieldbus instruments:

• Energy Limited Trunk networks - where fieldbus trunk and spurs are live workable

• High Energy Trunk networks - where only the spurs are live workable

Finally, for flameproof/explosionproof or non-arcing instruments there is:

• High Energy Trunk networks - with no live working