Selection of explosion-proof and intrinsically safe types for field instruments
Thread Content
This post was last edited by leiyinnit on 2017-7-25 at 10:07. Some of the field instruments are installed in Zone 0, while others are in Zone 1; the wiring components and transmitters are located in Zone 1, such as those used in guided-wave radar level gauges and magnetostrictive level gauges. So, should this instrument be selected as a intrinsically safe type or an explosion-proof type? What is the basis for the selection?
It’s not necessary to choose flameproof instruments for meters – they are expensive and bulky, and the price difference isn’t that significant. Intrinsic safety type is suitable for all hazardous areas – use it with confidence
What do you think? Just take a look at the specifications and you’ll know.
Zone 0 devices must be intrinsically safe, while Zone 1 devices can be either intrinsically safe or explosion-proof.
I have an intrinsically safe proximity switch with 24V two-wire wiring on site; I need to transmit its signal to the control cabinet. Should this circuit be designed as a regular proximity switch, or are there any modifications needed in the design?
Is yours controlled by a PLC in the field control cabinet, or is it sent to a DCS system?
If it’s new equipment, including the intrinsically safe cable circuits and safety barriers, then of course intrinsically safe is the best option. However, in some older facilities, the communication lines are long, and intrinsically safe cable trays that meet the standards are not used, which makes it difficult to separate signals from interference. Since there is no budget for making changes, explosion-proof solutions have to be used instead.
It is best to add a safety barrier between the PLC and the proximity switch
If it’s clear from the specifications, I won’t ask. And this was suggested by the reviewing experts.