Interpretation: 501.140.B (5)

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Ingenieur said:
by 'continuous length' does this mean no splices?
thnx
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(5) Be of continuous length. Where 501.140(A)(5) is applied,
cords shall be of continuous length from the power
source to the temporary portable assembly and from the
temporary portable assembly to the utilization equipment.
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That would seem to be the case. I wonder why they added the word length in there.
 
petersonra said:
That would seem to be the case. I wonder why they added the word length in there.
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thanks, I agree

when you look in 400.9 (non-haz areas, flex cords), they DO allow splices >#16
they omit that section in 501
I have to assume they do not permit it in haz-areas

I am building a court case
 
You may wish to consider Section 90.3 which states Chapter 5 supplements or modifies the general rules of Chapters 1-4.

Also note Section 501.140 applies to both Division 1 and 2 without distinction. "General" splices are considered arc-making, especially in high vibration conditions where they may loosen without special precautions.
 
rbalex said:
You may wish to consider Section 90.3 which states Chapter 5 supplements or modifies the general rules of Chapters 1-4.

Also note Section 501.140 applies to both Division 1 and 2 without distinction. "General" splices are considered arc-making, especially in high vibration conditions where they may loosen without special precautions.
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I am meeting with our solicitor tomorrow
he thinks since both sections ref continuous, but the splicing portion is omitted from 501, that is intentional, and de facto splicing is not allowed

arcing is one concern
the other is ingress of gas thru the cable into an enclosure

do you have a ref for general splices are considered arc producing?
 
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Ingenieur said:
I am meeting with our solicitor tomorrow
he thinks since both sections ref continuous, but the splicing portion is omitted from 501, that is intentional, and de facto splicing is not allowed

arcing is one concern
the other is ingress of gas thru the cable into an enclosure

do you have a ref for general splices are considered arc producing?
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Ingress into cables at terminals is covered in the first sentence of Section 501.15(D)(1) for Division 1. Division 2 is a little different since there isn't supposed to be any gases in the first place and only enclosures required to be explosionproof are covered that way. In any case, Section 501.140 (B)(3) requires terminations for covered cables to be made such that there is no stress on the terminations.

Anti-arcing is from my IEC experience and the means by which Type "EX e" terminals are made. They are constructed such that the terminals are self-locking and vibration free. It was interesting that during the "Division 0" debates in the early to mid '90s, one of the proponents for Division 0 said that we used explosionproof enclosures in Division 1 because terminals were arc-making. I told the guy, we use explosionproof enclosures in Division 1, arc-making or not. I am only aware of the argument but can't find a specific document at the moment that memorializes this since I no longer have direct access to the IEC 60079 standards.

For the most part, Division 1 considers both normal and abnormal conditions for ignition sources since fuel can be present under normal conditions, Division 2 only considers normal ignition sources since fuel isn't supposed to be there under normal conditions.
 
my application is a mine
not covered by the nec but the nec is reference in our law

closest case is I2D
we have positive ventilation
but all equip is xp I1
cords are entered by threaded compression fittings with a packing gland

ingress not at the fitting but through an opening in the cable, and thru the cable into the enclos

we check the xp integrity weekly
many enclos contain arc producing relays/contactors
the thought is if gas enters the box and ignites it will be contained and the escaping gases cooled enough by the flame path to prevent ignition of amb gas

in addition
we monitor gas level
kill power at 2% (ch4 lel-uel 5-15) or upon loss of ventilation
coal dust is also a concern
rock dust to mitigate release into the air if there is an ignition
 
I have a fairly good idea how explosionproof enclosures work. Explosionproof enclosures leak through every threaded penetration - period; especially with methane. Leaking through the cable interstices is actually pretty trivial if the cable is sealed properly per Section 501.15(E).

If you’re monitoring your air-flow properly, gas detectors are pretty much a waste.

If you’re concerned about coal you might want to consider Section 502.5 as well with regard to explosionproof enclosures. It’s also Class II, Group F.

Is it State law or MSHA that’s requiring NEC compliance?
 
rbalex said:
I have a fairly good idea how explosionproof enclosures work. Explosionproof enclosures leak through every threaded penetration - period; especially with methane. Leaking through the cable interstices is actually pretty trivial if the cable is sealed properly per Section 501.15(E).

If you’re monitoring your air-flow properly, gas detectors are pretty much a waste.

If you’re concerned about coal you might want to consider Section 502.5 as well with regard to explosionproof enclosures. It’s also Class II, Group F.

Is it State law or MSHA that’s requiring NEC compliance?
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it's the little things that get you
we are making the case it MAY happen, and is less likely with an in-spliced cable

gas detectors are mandated by law and automatically shut the equipment down, they also monitor H2S, O2, CO

coal ignition is usually secondary in this case: gas ignites, blast wave blows coal dust off surfaces, then a secondary ignition
 
I suspect the original purpose of the gas detection system was/is more for toxicity than fire protection. Save the canaries. There are however some fairly rigorous requirements for applying combustible gas detection systems in Section 500.7(L). I suspect you are already meeting them.

Depending on the NEC edition in place, you may want to review Sections 501.15 (E)(3)&(4) as well. Not so much for boundary conditions in your case, but the opinion/philosophy of the CMP with regard to gases entering the cable at locations other than the terminations. Avoid the 2014 edition if you can, you will arrive at the same conclusions but it’s much more difficult to decipher. Except for type MI, no cable construction currently meets the requirements of Section 501.15(E)(2) although it does indicate the requirements for an adequate seal.

”May” is indeed the operative term for Class I, Division 2.
 
rbalex said:
I suspect the original purpose of the gas detection system was/is more for toxicity than fire protection. Save the canaries. There are however some fairly rigorous requirements for applying combustible gas detection systems in Section 500.7(L). I suspect you are already meeting them.

Depending on the NEC edition in place, you may want to review Sections 501.15 (E)(3)&(4) as well. Not so much for boundary conditions in your case, but the opinion/philosophy of the CMP with regard to gases entering the cable at locations other than the terminations. Avoid the 2014 edition if you can, you will arrive at the same conclusions but it’s much more difficult to decipher. Except for type MI, no cable construction currently meets the requirements of Section 501.15(E)(2) although it does indicate the requirements for an adequate seal.

”May” is indeed the operative term for Class I, Division 2.
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no, fire/explosion protection
the machines auto shutdown on 2% methane

they use CO detectors on the belts to trip the deluge system

the nec does not apply to mining, but in our case we are allowed to use relevant national/international standards to make our case
 
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