501.15(e)(1)

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Natfuelbilll

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This section of the Code is confusing, or, I am a blockhead.

The area is C1D2.

Question 1
"The sealing fitting shall comply with 501.15(B)(I). Multiconductor cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be sealed in a listed fitting in the Division 2 location after removing the jacket and any other coverings."

Is the "shall be sealed in a listed fitting" phrase requiring the fitting to be only a conduit seal fitting, or is there some other type of cable fitting?



Question 2
Could one re-write the last sentence of 501.15(E)(1) "Multiconductor cables in conduit shall be sealed as described in 501.15(D)." as "Multiconductor cables in conduit , where the conduit enters an enclosure required to be explosionproof, shall be sealed as described in 501.15(D)." and be correct?



Question 3
For conduit equal or greater than 2" used in C1D2 to an enclosure that is not required to be explosionproof. Is there any scenario (non-boundary and non-ignition source) where the Code requires a seal because of the large 2" size and terminals, splices, or taps? ala 501.15(A)(1)(2) ?
 
Question 1
Yes, and the rest of the sentence specifies the method.

Question 2
What a great Proposal!

Apparently though, you and I are among the few people who fail to see a clear antecedent for last the sentence. I gave up trying to get CMP14 to change the current wording 10 years ago.

As far as I see, it is a stand alone statement that says, ?If it is ANY form of multiconductor cable, it must be sealed at the terminals whether the conduit itself inherently needs to be sealed or not;? the antecedent being the Section Title. This is especially problematic in light of Section 501.15 FPN No. 2, which doesn?t distinguish between Division 1 and 2. The FPN even worries about the ??interstices between the strands of standard stranded conductors larger than 2 AWG.? I tried to get CMP14 to tone down the FPNs concerns, especially for Division 2 with no avail. I know FPN?s aren?t ?enforceable? but they are a reasonable basis for a Section 90.4 ?interpretation.?

CMP 14 believes the context of the last sentence is clearly ?Multiconductor cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core entering enclosures that are required to be explosionproof.? ? That is what I think it should actually say rather than vaguely imply.

Question 3
No, not because an enclosure has a 2? or larger entrance with internal taps or splices.
 
Natfuelbilll said:
Question 1

Is the "shall be sealed in a listed fitting" phrase requiring the fitting to be only a conduit seal fitting, or is there some other type of cable fitting?



Question 2
Could one re-write the last sentence of 501.15(E)(1) "Multiconductor cables in conduit shall be sealed as described in 501.15(D)." as "Multiconductor cables in conduit , where the conduit enters an enclosure required to be explosionproof, shall be sealed as described in 501.15(D)." and be correct?



Question 3
For conduit equal or greater than 2" used in C1D2 to an enclosure that is not required to be explosionproof. Is there any scenario (non-boundary and non-ignition source) where the Code requires a seal because of the large 2" size and terminals, splices, or taps? ala 501.15(A)(1)(2) ?
Click to expand...

1. If your conduit seal also seals the cable as required, then that is the only seal that is required. An example where you might need a conduit seal and a cable seal would be.....Conduit is sealed at boundary. Cable jacket is impossible to strip at the boundary, so cable continues to the device/equipment. A few feet from the equipment you transition out of the conduit and run supported protected cable suitable for open wiring (TC-ER). At the termination you add a proper cable seal. Since the jacket of TC-ER is impermeable to gas/vapor, the cable seal becomes your boundary seal for for the cable and the previous conduit seal is the boundary seal for the conduit. This example would not apply to an enclosure required to be XP, enclosing arcing devices, etc. since the cable seal is not rated as XP. MC-HL cable with an XP seal would be required for that scenario.

2. Well shoot Bill, they already say that in the first sentence. :roll: Why would you want to make it clearer?

3. No. Seals not required in Div. 2 for splices, TB's etc.
 
501.15(e)(1)

Some thoughts

1.) Reference question 1... You don't mention the type of cable, but there are special fittings for use on some cables: uses epoxy compound.

http://www.crouse-hinds.com/catalog/PDFS/00074to00075.pdf

2.) I went over this a few years ago with a instrument and control cable manufacturer; they use to make what was listed as 'gas block cable' but was told that that particular manufacturer stopped making it since there was no call for it; contained additional fillers I undertand to prevent gas migration along the cable. Remember that this can only occur anyway when there is a pressure differential between the two ends of the cable. In most cases, our cables went from outdoors to outdoors, or pressurized / purged enclosure to outoors, or outdoors to a pressurzied control room, none of which is going to cause potentially hazardous gas migration in the cable. This is recognized in exception 1 to some degree.


3.) As tight as standard cables are 'packed', I can't believe there is any chance of gas migration unless the pressure differential is high

4.) Remember that conduit seal fittings are designed for arresting / containing the explosion flame front to within the explosion proof enclosure; the compound used is rigid and does not adhere well to the thermoplastic wire or cable jacket so I question if as gas block can be effectively attained with a standard 'EYS' and Chico compond. There is reference in 501.15(e)(2) that some leakage is permitted.

5.) As far as stripping jacket and the separating the conductors; even using the 'X' sized seals (40% fill rated as opposed to the standard seals that are 25% fill rated) , this does not work well.

Even more difficult is the spreading of the pairs on a shielded pair/ overall shield (SPOS) multipair instrument cable that I have seen places try to do; you can't do this and A) not break through the overall shield and lose that benefit, or B) keep the Mylar insulated foil shield on the individual pairs from getting scratched/ torn / shorted resulting in signal noise. This is recognized in exception 2...but I have not found an 'approved means' for PLTC cable which is what most SPOS cable is.

I do agree this subject is confusing and has lead to many different types of installations.
 
The cable is TC. Not TC-ER.

The tray cable leaves the tray and goes into conduit. The conduit is installed with a seal fitting and then finished in a myers hub or factory thread.

The CH engineer said the epoxy product in the link that you provided is not list or identified for tray cable.

So... I think the best i can do with these materials is to seal around the outer jacket in the seal fitting and apply the epoxy to the end of the de-sheathed cable end inside the enclosure required to be XP. Comments?

Excuse me, while I finish pulling out my hair...
 
TC or TC-ER is irrelevant

How do you finish the conduit in a Meyer?s hub if the enclosure is required to be explosionproof? (Just a question)

Whether the antecedent is clear or not you are still required to go back to 501.15(D). You are essentially describing an application of 501.15(D)(2) Exception. The key word in the exception is approved. Neither approved nor identified automatically mean listed or labeled in the NEC. See their definitions in Article 100. Unfortunately they generally do mean listed or labeled in FedOSHA terms. See the definitions in 29CFR1910 Section 399. However, if you sell your local AHJ, FedOSHA will usually buy it.
 
501.15(e)(1)

Regarding 'Meyers' hubs question (and I think rbalex is curious too) so I am going to state something to make sure we are all in agreement.

Hubs CANNOT be used on a threaded enclosure and maintain the explosion proof rating required for Cl I Div 1;
Hubs can only be used on sheet metal or composite enlosures and are commonly used in non-hazardous and Cl 1 Div 2 installations.

I think the only reasons I have ever seen a seal on a hub entry to an enclosure was to :

A) seal the cable for gas migration ...as this thread is about...and I have seldom seen this done

B) maintain purge / pressurization per NFPA 496 in the enclosure (and a seal is not required by code and this can be achieved in other ways)

C) the contractor was not sure one was needed and put one in just in case
 
501.15(e)(1)

Looking around there is another thread under 'class 1 cable end sealing' that is going on...

The one member brings up a good point again... Gas will only 'migrate' if there is sufficient differential pressure between the two points

The code says 'cables that are capable of transmitting gasses or vapors' and I don't see where most cables are installed in such an situation that puts a cable in such an exposure since there is not usually a differential pressure present involving a hazardous gas. The pressure they describe for acceptable seal gas leakage is at 6" which is almost a 1/4 PSIG..applying that standard to a cable installation, .you don't normally have this kind of pressure differential even presented in a pressurized enclosure !

For example; the one instance I have think of that meets such a criteria for sealing a cable is a thermocouple in a thermowell in a high pressure pipe and the thermowell fails pushing hazardous gas back up the thermocouple extension cable...in which case putting in an intermediate JB with vents on the enclosure is the more sure solution and an added layer of protection.
 
As compared to smaller multiconductor TC, it appears that larger multiconductor may not be able to meet all the requirements of each of 515.15(1) (last sentence), 501.15(D)(1) (second sentence), and the accessibility requirement contained in 501.15(C)(1) (last sentence).

Can the internal spaces of a seal fitting be defined as accessible in the Code?

I know there is a 25% conductor fill maximum in 501.15(C)(6).

I have read elsewhere in this forum that separating the conductors of a TC in a fitting is nearly impossible. I don't know if they were speaking of a properly sized conduit seal fitting or not.

I suppose that there is nothing in the code to limit how large a seal fitting can be sized. If a 2" conduit was bushed up to a 4" seal fitting that there would be more space (accessibility) than in a 3" seal fitting to work the individual conductors in preparation of the compound.

How could conduit seal accessibility be defined?
 
I would suggest contacting the cable manufacturer, explaining the problem, and see if they can assist you in any way. (in case you have not already done so).
 
501.15(e)(1)

Seal fittings are available to meet the 40% fill as I indicated in an earlier reply; these are oversize compared to normal fittings we were use to over the years, and when the listing oversight was recognized about 10 years ago, ( and that oversight went all the way back in the code to when the conduit fill was raised form 25% to 40% decades ago) manufaturers reponded with the 'X' suffix fitting to accomdate the 40% fill..ie EYSX in lieu of the EYS. essentially they are the next size fitting body with smaller taps. These still are marginally adequate with large count cables of small conductor sizes..

The question then raised is do you use the area of the entire cable at 53% max fill or the sum of the areas of the individual conductors at 40% to size the fitting; I believe it is dependant upon if you split the cable and pack the individual conductors. Since even the X fittings are listed for 40% fill, then there is a possibility of for example needing a 4" seal with reducers to 2" to get the right volume for example.

Anyway, as far as sealing the cable ends; suggest you read the 'Zone' concept rules; specifically 505.16(c)(2)(c) . Zone 2 is basically Div 2
This paragraph states my assertion (a pressure differential must exsist for there to be an issue) that normal installations of cables in a CL1 Div 2 areas are not requiring a seal on the conductors, and such an exception should be inserted in 501 to normalize and clarify the code chapters.
 
WaltF said:
The question then raised is do you use the area of the entire cable at 53% max fill or the sum of the areas of the individual conductors at 40% to size the fitting; I believe it is dependant upon if you split the cable and pack the individual conductors.
Click to expand...

I think that my earlier post of leaving the sheath on, inside the seal fitting, is not the intention of the code. 501.15(D)(1) is pretty clear. Except for shielded and twpr cables, the sheath must be removed.

It also seems to make the most sense to use as large a seal fitting as is needed or as possible. The minimum required seal fitting still may not be large enough to perform the separation.

I have not personally had the experience of separating the conductors inside a seal fitting, but it must be a real bugger.

I suppose the cable would need to be fed from the enclosure required to be explosionproof. With sufficient cable installed to the 'line' side, then the cable sheath could be removed and conductors separated. Then the cable could be pulled in the additional amount to place the separated conductors inside the seal fitting. Is this how you did it in the past?

When applied to terminations in an enclosure required to be explosionproof, is it correct that 501.15(2) and 501.15(3) do not lessen or remove the requirements of 501.15(1) ?
 
The text and intent of 501.15(E)(3) and 505.16(c)(2)(c) are virtually identical except they refer back to different Sections for explosionproof/flameproof enclosures in context of their respective electrical area classification scheme.

Note: the specified pressures and flowrates for these Sections and thier preceeding Sections (501.15(E)(3) and 505.16(c)(2)(b) are not very much.
 
A seal is a fitting which makes it part of a wiring method. This makes Accessible (as applied to wiring methods) the relevant definition. The italicized terms are defined in Article 100.
 
Perhaps a 'suitability' requirement would require a larger seal in the conduit attached to an enclosure required to be explosionproof.

Searching.... searching....

Next time, the cables to an enclosure required to be explosionproof will be MC-HL, and not in conduit.
 
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