501.15(B)(2) (Div 2 to unclassified boundaries require conduit seals within +/-10') - Exception No. 4. What is a conduit segment?

[MRKN]

Hi,

Compliance with 501.15(B)(2) can be costly to the owner in existing environments if changing the Div 2 boundary (e.g. due to installation of new source of release, or demo of existing) results in conduit seals (or lack thereof) that now do not appear to meet the +/-10' requirement of 501.15(B)(2). This flexibility is ultimately desired for low cost EAC drawing maintenance. I've done some searching on this forum and have concluded that it is typical to not require such a boundary conduit seal at all. The one that catches my eye is Exception No. 4, however, it is unclear what a conduit segment is defined as. I did not see a definition.

What is a conduit segment defined as?

Can one create segments of conduit by adding a conduit seal at any arbitrary location? If so, it would appear that the best practice for locating conduit seals in outdoor industrial environments would be once at the equipment/enclosure (and as further required by Exception No. 4 (4)), and once near the source, leaving room in between for the exact Div 2 boundary to vary.

Would a tree-like conduit system (typical of LV lighting) count as one conduit segment?

 

[rbalex]

I'm somewhat proud/ashamed to say I was the author of the original API SOEE text for the Exception 4 Proposal before it was heavily wordsmithed by people enamored by new IEC concepts at the time. It was written for the benefit of another SOEE member to permit outdoor pipeways to avoid adding seals if parts of the pipeway location needed to be reclassified for new process considerations.

A "segment" was basically sections of a raceway system between two termination or pull points.

 

[MRKN]

I found this definition of a conduit segment, as addressed in a rejection of a proposal, while browsing through the documentation of changes over the years. FYI. From 1998 ROPA.

“Exception No 4 applies only to that part or “segment” of a complete aboveground conduit system between the last enclosure in the Division 2 location and the unclassified location. This is a segment of the complete conduit system, not the complete system as would be the case with the change proposed”.