Do the tapered threads on conduit fittings listed for hazardous locations need to comply with all aspects of ASME B1.20.1? I've found that the female threaded hubs on conduit outlet bodies are sometimes tapped much larger than allowed under ASME B1.20.1. When checked with a NPT plug gage, the gage stops as much as 3 threads beyond the "L1" notch, i.e. 2 threads over tolerance. In such cases, a properly threaded male fitting can bottom out in the cast portion of the hub before the threads become even hand tight. I've also checked the male threads with a ring gage on conduit fittings and found similar non-compliance. My concern is that such problems might prevent sealing in wet locations, and perhaps compromise the flame path.
Should XP fitting threads gage to ASME B1.20.1?
- Thread starter depiertm
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- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Assuming your findings are accurate, your concerns are valid. I do find it a bit hard to believe these are factory or UL certified shop made threads though.
If these are field threads then they are non compliant with [2005] 500.8(D) and 500.8(D)(1). Depending on the area classification they may also be non-compliant with 501.4(A)(1)(a)
If these are field threads then they are non compliant with [2005] 500.8(D) and 500.8(D)(1). Depending on the area classification they may also be non-compliant with 501.4(A)(1)(a)
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
The basic standard is 500.8(D) and (D)(1) as I stated originally. But they must merely be wrench tight.
Only in Division 1 is the number of threads specifically mentioned and there the standard is number of threads "engaged" rather than the number of turns needed. The "wrench-tight" requirement is still in place of course.
Since these are tapered threads the must "bottom-out" eventually.
If you still find "wench-tight" is loose, then contact the manufacturer. If they don't provide a satisfactory response, UL has a compliance review procedure that you may use to resolve the issue.
Only in Division 1 is the number of threads specifically mentioned and there the standard is number of threads "engaged" rather than the number of turns needed. The "wrench-tight" requirement is still in place of course.
Since these are tapered threads the must "bottom-out" eventually.
If you still find "wench-tight" is loose, then contact the manufacturer. If they don't provide a satisfactory response, UL has a compliance review procedure that you may use to resolve the issue.
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