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By Moore Industries-International
At first glance, the concept of Intrinsically-Safe (I.S.) fieldbus is a study in opposing concepts. After all, fieldbus is about powering multiple devices, while the idea of I.S. is to limit energy flowing into hazardous areas. The fact that multiple devices can be powered from the same wire pair only adds to the design challenges that engineers face when developing their own systems. Typically, this can lead to complex installations schemes as users mix wiring methods such as Division 1 and Division 2 (Zones 0, 1 and 2) in order to accomplish their task.
The ideal solution allows users to connect multiple devices without compromising area requirements or using expensive installation methods. Until recently, this was a pipe dream. But recent breakthroughs in design have brought together many of the best features of different I.S. techniques. Specifically the use of the "high Powered I.S. Trunk: concept greatly simplifies the installation and footprint of intrinsically-safe segments.
The sections here provide an overview of the existing technologies and methods that fieldbus uses have at their disposal when they embark upon designing and installing fieldbus in hazardous areas. These sections assume that there is a general understanding of fieldbus segment topology and design.
The New Dimension of Intrinsic Safety
DART dramatically increases available power in explosion hazardous areas while maintaining intrinsically safe energy levels.
Intrinsic safety of an electric circuit with dramatically increased available power during normal operation is enabled by DART. In the case of an unwanted, potentially threatening condition such as opening or closing of the electric circuit, DART puts the circuit into a safe state before critical levels are reached. This redefi nes intrinsic safety where energy limitation is traditionally achieved through power limitation.