Discussion on explosion protection ratings
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For the same instrument, is the intrinsically safe version more expensive or the flameproof version? For example, are the explosion-proof versions of flowmeters such as E*a IIc T4 and Ex d IIc T4 more expensive? What is the best explosion protection rating? We’re puzzled: for instrument selection in the company, intrinsically safe types were originally used but were later changed to explosion-proof types, allegedly because they are cheaper.
Ex d is flameproof, so it won’t be cheap. Explosion-proof instrument enclosures are generally quite thick. For two-wire instruments, the explosion-proof and intrinsically safe versions appear similar in appearance; the only difference is that an isolation barrier must be added to the circuit for intrinsically safe versions. It is estimated that your table uses a two-wire system; in that case, explosion-proof tables are cheaper as they eliminate the need for a safety barrier.
For a single unit, it’s generally the explosion-proof version that is more expensive; the casing is what makes it costly. If intrinsically safe instruments are more expensive than flameproof ones, it’s because the former have an additional safety barrier, while the latter may not even be from the same manufacturer at all, so they aren’t comparable. If they are similar for one family, the explosion-proof version will definitely be more expensive.
When the hazard zone classification is the same, for example both are Zone 1 or Zone 2, when should we use intrinsically safe devices? When should an explosion-proof type be chosen? From what perspectives should the selection be considered?
It doesn’t matter whether the DCS has a safety barrier; if there is no safety barrier, then explosion protection is provided. The issue isn’t that all types of tables have explosion protection; by emphasizing explosion protection, it’s likely to become something exclusive.
Since not all types are flameproof, and intrinsically safe ones have been chosen, do I then necessarily need some safety barriers in my control room?
This post was last edited and replied to by *aoliu516 on 2011-7-13 14:50. Reply 1# meng*ao*a001: Intrinsic safety means it is of the intrinsically safe type； The main difference from the flameproof type lies in the internal circuit design – it features a design concept that prevents the occurrence of dangerous currents. . Therefore, the requirements regarding manufacturing processes are higher than those for explosion protection. As for the casing, whether it is thick or thin, the cost difference is negligible compared to that of the internal circuits and components. . Therefore, for an intrinsically safe instrument circuit compared to an explosion-proof instrument circuit, the intrinsically safe option is more expensive.
I tend to agree with the statement “Author: mao”
Personally, I prefer intrinsically safe instruments; unless the client requires intrinsically safe design, it is possible to omit the safety barrier, and 4-wire instruments are rarely intrinsically safe.