I am having a hard time finding any definitive rules on this subject. My employer is attempting to operate a 50L reactor with a motorized stirrer, a temperature readout, and speed control within a Class I Div I area. Now based on my very limited knowledge of the CFR, this is not ok. I have spoken with my safety manager, and she said something about if the volume of air that the HVAC handles is x/hour, then they do not need to have XP/IS equipment in the booth. I understand that having sufficient air handling may drop the area to a lower class, but that is not what she is saying. She is saying that even though it is still classified as Class I Div I, is the air handling is to a certain degree, we can have non rated equipment in there. I don't think this is correct, but lack the knowledge to refute it. Can anyone help me out?

 

The objective of classifying an area is to establish the level of safety that is required.

You should not rely on the opinions of others as to the appropriateness of equipment. I recommend that you review the National Electric Code, chapter 5, Sections 500 thru 510. You will find the answers that you need within these sections.

If you need a little more specific information, please reply as such and we can point to a the code, by chapter and verse.

 

It is hard to say anything definitive without knowing more about how your equipment is configured.

It is true that a C1D1 area has to use a protection technology approved for that area classification.

It is also true that sometimes you can create via pressurization and purging a volume within a C1D1 area that is considered to have a lower hazard classification or even be unclassifed.

I have never seen it done, but I think that there are at least some limited cases where a combination of ventialtion and gas detectors is an accepted means of protection. But don't quote me on that.

It is also possible that the area was over classified and really should not be C1D1 in the first place.

Area classification is not something for trying to judge via a mailing list. Nor is the proper protection technique.

--
Bob

 

Thank you for the info. To clarify, I am not an engineer trying to determine the proper classifications. I am a chemical operator trying to find out if what my employer is asking me to do is safe.

 

> Thank you for the info. To clarify, I am not an engineer trying to determine the proper classifications. I am a chemical operator trying
> to find out if what my employer is asking me to do is safe.

Unfortunately, area classification is something that is often not easy to do. There are guidelines found in the NEC, but they have to be tempered with many other guidelines published by recognized standards agencies, along with operating experience. Many times insurance companies have a say in it as well. I do not think there is anyway anyone on list can tell you much more than that.

The advice given to apply the appropriate articles in the NEC given by another poster is OK as far as it goes, but the proper application of those articles is often debated by even those with many years of experience in the field.

Once an area is properly classified, and keep in mind many times areas are over classified, it is relatively straightforward to apply an appropriate protection technique. But, even that is something that is not easily described in a short blurb on an email list.

I wish there was a better answer that we could give you, but there just is not.

One thing that may be of some assistance to you is that often there is a height limit to the classified area. If so, this would be noted on the drawing(s) that defines the classified areas in your plant. It might be possible that the equipment you are concerned about is located high enough above floor level that it is above but not in the classified area. The only way to know with any certainty just what volume of space the classified area consists of is to have that drawing.