RTD's in Class 1 Div 1

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MikeShaw

Member
Location
Cypress, CA USA
Do RTD's require seal offs in Class 1 Div 1 areas?

I know that many manufacturers indicate in their documentation "seal off not required", and in general I have been treating them as "non sparking" devices for as long as I can remember. However, I have had a recent installation called into question and a request for a seal-off on the (RTD) device. This particular device indicates that it is rated for use in Class 1 Div 1, and per usual I installed without a seal-off. I don't have the documentation for this particular device (working on getting it now), so I don't know if the manufacturer states that a seal off is not required, but what I am looking for is a more general rule on RTD's. I have had no luck finding any good information on the actual classification of RTD's and whether or not they are ignition sources. I appreciate any assistance and/or code references.

Mike
 
Do RTD's require seal offs in Class 1 Div 1 areas?

I know that many manufacturers indicate in their documentation "seal off not required", and in general I have been treating them as "non sparking" devices for as long as I can remember. However, I have had a recent installation called into question and a request for a seal-off on the (RTD) device. This particular device indicates that it is rated for use in Class 1 Div 1, and per usual I installed without a seal-off. I don't have the documentation for this particular device (working on getting it now), so I don't know if the manufacturer states that a seal off is not required, but what I am looking for is a more general rule on RTD's. I have had no luck finding any good information on the actual classification of RTD's and whether or not they are ignition sources. I appreciate any assistance and/or code references.

Mike

I have a similar application in a natural gas processing unit. We have a Rosemount MVS and RTD installed inside a cabinet that is considered a Class 1 Div 1 area. The MVS is rated explosion proof for Class 1 Div 1 area and the RTD has and explosive proof conduit box on it. I used MC/HL cable to run between these devices and put a Crouse Hinds TMCX seal on both ends. I also struggled with the RTD because I didn't think it was capable of causing an arc or spark. My decision to seal both ends came from 501.15(D)(1) requires cables to be sealed at all terminations regardless of the type of equipment contained in the enclosure or the cable diameter in class 1 div 1 areas. Of course this is different than a conduit application.
 

kwired

Electron manager
Location
NE Nebraska
It would be my opinion that 501.15(A)(1) applies and seal fittings are not required.
I agree with that also. Seal is required within 18" of enclosures containing components that under normal operation can produce arcs/sparks, or operate at a temperature high enough to potentially ignite the hazardous material, unless the item in question is otherwise sealed in some way to make this unnecessary. Most RTD's would not introduce such hazard, and especially if already rated for C1D1, then should be suitable with no additional enclosure or sealing.

You still need boundary seals when leaving the classified location.
 

MikeShaw

Member
Location
Cypress, CA USA
RTD's and Classified Areas

RTD's and Classified Areas

Thanks for the replies....I guess this is just one of those areas where there is no definitive answer, and as such I guess in the future I will err on the other side and add the seal-off.

Mike
 
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