arpadveress Valve might come as a valve, but it might come as a motor operated unit…
Only difference in that case it belongs to those which shall be certified according to Ex standards.
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Thumb rule for spread of movement forex certification is 1 ft/sec. since the MOVs are normally operated slower, mostly certification is may not be mandatory. Even for the SDVs Ex certification in most cases the valve actuator asssembly may not require certification. However some valve vendors are providing certification and in 99% of the cases based on my experiences I have observed that valve certification becomes a non issue. Certification engineer needs to ascertain the certification requirements and document why the certification is not applicable
There are many reasons going for an Ex cert, anyway more & more endusers request it to be supplied with. But your comment is fully correct.
One more point pls read the ATEX Guideline – contains some imterestimg points related