Unrated RTD in Class 1 Div 2 area

[Slplsnts]

Thank you for taking the time to review this.
I have an unrated Platinum RTD rake probe being inserted into a liquid hydrogen tank. If the probe is welded into the tank, I believe the area above the weld is Class 1 Div2 for 25ft sphere.
If the probe is flange mounted to the tank, I believe the area around the flange is Class 1 Div 1 for a 3ft sphere.

As I understand, the RTDs would require an wiring method consistent with C1D1 such as IS Barrier, Armored Cable, Conduit and seal offs, mineral insulated...

If we are meeting C1D2 with unrated RTDs, can I install the same PLTC cable with rated glands etc. the same as we would use with other instrumentation or do I still need to use the C1D1 installation methods (most likely IS Barriers) since the RTDs are not rated for hazardous locations?

Any thoughts would be greatly appreciated.

 

[don_resqcapt19]

You need to start with the area classification drawings that are required by 500.4.

 

[Dsg319]

Also if the RTD is not rated for the location that and in of itself is an issue that any sealing method will not solve.

If I’m understanding you properly.

 

[Slplsnts]

Also if the RTD is not rated for the location that and in of itself is an issue that any sealing method will not solve.

If I’m understanding you properly.

You need to start with the area classification drawings that are required by 500.4.

Thank you both for reviewing.
The area classification has been set to C1 Div2, group B, outdoors. The installation I am referring to is new to the existing site and will add new C1 D1 locations due to bolted flanges. I believe in the case of Liquid Hydrogen, this is a 3' sphere around the flanges for C1 D1 and 25' Sphere for C1D2 I do not know if the RTD rake will be bolted flange or welded, although bolted flange makes more sense in this application.

The RTD rake is a series of platinum RTDs attached to a rod. As I understand NEC 500.8 (?), an RTD is considered a simple apparatus which does not require marking or a control drawing for use in an IS circuit. My comment of unrated was in reference to the fact that I do not have a control drawing, I do not know if the RTD manufacturer provides a hazardous classification rating in the literature.

The manufacturer of the probe is providing the wiring from the RTDs, there are no signal conditioners or active electronics on the probe.

I am currently assuming that I will need IS Barriers to meet C1 D1. If the probe is welded and the area around the probe is C1 D2, can we use PLTC cable wiring method?

 

[rbalex]

I’m sorry for my tardy reply.

Why do you believe, “The installation I am referring to is new to the existing site and will add new C1 D1 locations due to bolted flanges.”? That is an unnecessary inference of Section 500.5 (B)(2), IN No.2. That is, just because, “Piping without valves, checks, meters, and similar devices would not ordinarily introduce a hazardous condition even if used for flammable liquids or gases”, doesn’t necessarily mean piping with valves, checks, meters, and similar devices would ordinarily introduce a hazardous condition. Other considerations such as the pressure rating of the flange should be reviewed. In any case, unless there was an intentional leak point, such as a relief valve, it would rarely require a Division 1 location.

With regard to PLTC, what does Section 501.10(B)(1)(3) tell you?