Methods, intrinsic safety and the use of flameproof enclosure ensure safety from fire hazard. How do they compare?
Intrinsically safe instruments do not need expensive enclosures and are cheaper as compared to flameproof systems. It is possible to calibrate intrinsically safe instruments even in hazardous areas since there is no restriction in opening the enclosure and doing the settings. They are often the first choice if available. The design of intrinsically safe circuits depends upon the availability of low power devices and circuit design skills. It may not be possible to restrict power to the circuits in all the cases. Flameproof systems use the standard circuits and neither depends on special low power devices, nor it is necessary to restrict the power to the instrument. Their operation and performance is not hampered due to restriction of power input, as in the case of intrinsically safe units. The flame proof housing design is however bulky and costly and the instrument cover cannot be opened in the hazardous area for wiring, calibration, or maintenance when the plant is in operation.
