Instruments in a CL I DIV II GRP C and D

[rmitri]

I am installing instruments in a Class I Div II area. The instruments are classified for this area. do i need to seal the electrical connection to these instruments, what other provisions do I need tokep in mind when I wire these instruments. Where can I get good information on instrument installation in classified area.

 

[Rheinhardt]

We previously used safety barriers in a petroleum refinery, they acts as a isolation unit if there is excess capacitance or inductance.

You would also have to use spesifications on your instruments to do calculations of the capacitance and inductanse.

The instrument should be classified for your zone requirements. Idealy your source should be in a safe area with your barrier leading out to your zone area.

If i remember correctly you must also use Ex rated glands

Here is a good link describing the basics.

http://www.am.pepperl-fuchs.com/techresources/pdf/IS_in_a_nutshell-InTech-Dec2002.pdf

REMEMBER THAT YOU MUST CERTIFY THESE LOOPS with a certified explosion prevention authority

Hope it Helps

Regards

 

[resqcapt19]

501.15(B)(1) in the 2005 NEC only requires a seal at this instrument if the instrument is required to be in an explosion proof enclosure. Per the exception to 501.105(B)(2) most electronic instruments do not require an explosion proof enclosure. The 2002 code sections are 501.5(B)(1) and 501.3(B)(2) respectively.
Don

 

[jsummerfield]

Aren't seals are required where conduits travel from classified locations to general purpose areas? The NEC (NFPA 70) is a complex assembly of rules and exceptions to the rules.

Read Article 500 through 505 of the National Electrical Code. (Notice that the Class is a Roman Numeral and the Division is what we call an Arabic number, thus Class I Division 2.) Allow some time to digest this stuff.

John

 

[minimalibu]

If it's an IS instrument and you connect to it using the blue IS data cable which is a solid construction ie all airgaps filled with a gel or some other form of packer and there is an intrinsically safe barrier in the circuit in the safe area, and the callculations have been performed to determine that the cable length is ok, and you leave the safe area through a transit frame then you do not need a barrier. You really need to specify the details of the instrument,what zones you pass through etc. If you use conduit you should use barrier glands when transversing different areas.