Hazardous Area Instrumentation Protection Techniques, Codes of Practice and Design Aspects of Intrinsic Safety

摘要

Over the years various techniques have been developed for electrical and instrumentation for use in hazardous area. Each type of protectoin technique can only be used for specific application. There are some limitations on the level of the protection offered by any method. To apply any of the protection technique proper engineering judgemt is required. In the field of instrumentation most popularly applied techniques are: Flameproof or Explosion proof enclosers, Purging (for analyzers & panels), and the intrinsic safety. The intrinsic safety is applicable to the circuits where current and voltage levels of the circuit are low. This is not applicable for the circuits handling high voltage and current. Most of the instrument circuits operate on low levels of current and voltage and hence the intrinsic safety is becoming inereasingly popular in instrumentation. However, in some cases where the circuits handle high levels of voltages, explosion proof enclosures are the best choice. This paper describes different protection techniques and their limitations for specific applications. As intrinsic safety is most popularly used protection technique in instrumentation and hence the design and engineering aspects of intrisnically safe barriers have been explained in detail.