Steel Wire Armoured (SWA) applications

[Junior Designer]

Hello All,

Can anyone tell me if if the use of steel wire armored cables and cable glands are acceptable for use in Class 1 Div 1 and Zone 1 applications.
I am working on the a boiler supply and installation project and the client has some additional requirements for interconnections between the new boiler and existing control system, the connections are to be made on junction box which is installed on the burner assembly, all vendor supplied instruments are connected to this junction box via rigid metal conduit. The client insists that with an explosion proof gland the use of SWA cable (which they have in their stock, probably from a previous in house project) will satisfy the code requirements. I am not sure that this is correct since the SWA is not a continuous metal sheath and if a cable gland is used directly on the junction box no seal fitting can be installed.
Any help will be appreciated.

 

[Smart $]

Hello All,

Can anyone tell me if if the use of steel wire armored cables and cable glands are acceptable for use in Class 1 Div 1 and Zone 1 applications.
I am working on the a boiler supply and installation project and the client has some additional requirements for interconnections between the new boiler and existing control system, the connections are to be made on junction box which is installed on the burner assembly, all vendor supplied instruments are connected to this junction box via rigid metal conduit. The client insists that with an explosion proof gland the use of SWA cable (which they have in their stock, probably from a previous in house project) will satisfy the code requirements. I am not sure that this is correct since the SWA is not a continuous metal sheath and if a cable gland is used directly on the junction box no seal fitting can be installed.
Any help will be appreciated.

If this installation is under NEC purview, TTBOMK, the SWA must be of a recognized wiring type and installed under an approved method. As to the type, the fact it is SWA is not enough for a cable-only type installation. As to approved wiring methods, there are only five types permitted: 1) threaded RMC, steel IMC; by Exception PVC, RTRC, 2) MI cable, 3) MC-HL cable, 4) ITC-HL cable, all per 501.10(A), and 5) flexible cords per 501.140.

 

[dha]

Thank you very much Sir for your response.
You mentioned that "the SWA must be of a recognized wiring type and installed under an approved method", I am assuming this is if the SWA has to be installed in a Cl 1 Div 1 location, can you explain a little bit further about what the approved method may be as I don't see any specific mention of it in the NEC, or is it that the seal fittings etc still need to be used?

Thanks again.

 

[Junior Designer]

Hello Smart $,

I have read through the NEC 501 and basically still have the same question regarding the use of the SWA. Is the SWA cable classified as flexible cord?
I looked also briefly at the IEC-60079 and this is also kind of vague on the application of SWA cable (not that we are mixing reference standards on the site, it was suggested by my boss for reference only).
Or, is it as mentioned by dha, are the seals required period, i.e. cable glands explosion proof are insufficient in Cl 1 Div 2?

 

[Smart $]

Thank you very much Sir for your response.
You mentioned that "the SWA must be of a recognized wiring type and installed under an approved method", I am assuming this is if the SWA has to be installed in a Cl 1 Div 1 location, can you explain a little bit further about what the approved method may be as I don't see any specific mention of it in the NEC, or is it that the seal fittings etc still need to be used?

Thanks again.

Hello Smart $,

I have read through the NEC 501 and basically still have the same question regarding the use of the SWA. Is the SWA cable classified as flexible cord?
I looked also briefly at the IEC-60079 and this is also kind of vague on the application of SWA cable (not that we are mixing reference standards on the site, it was suggested by my boss for reference only).
Or, is it as mentioned by dha, are the seals required period, i.e. cable glands explosion proof are insufficient in Cl 1 Div 2?

Its not a matter of seals, because sealing can be accomplished if cable is run exposed or in conduit.

I provided the five wiring methos acceptable under Article 501. It is very unlikely the SWA is of the MI, MC-HL, or ITC-HL cable type. That leaves running it in conduit for any lengthy run. It is unlikely the SWA is listed as flexible cord(cable)... but I'll leave that possibility open as I do not know the entire listing of the cable under discussion. Even if it is listed as a flexible, it has to be of a type of those tabled in Article 400. On top of that, it has to meet the conditions of usage itemized in 501.140.

If being run in conduit is to be the general wiring method, the contents of the conduit itself must also be of a type mentioned somewhere in Chapter 3. Type SWA is not mentioned specifically. However, it may fall under MV cable if so identified. Refer to Article 328 for specifics.

 

[rbalex]

First, I want to eliminate the two big sophistry exceptions – we are neither talking about intrinsically safe systems [Art 504] nor possible local permission by the AHJ [Section 90.2(C)]. We are only discussing US domestic applications as described in NEC [2008] Articles 500, 501, 505 and their relevant cross-references to other Sections.

There is NO cable armor recognized for Class I, Division 1 or Zone 1 except a “continuous corrugated metallic sheath.” The cable will be marked with a Type appended with an “-HL.”

For Class I, Division 2 or Zone 2 cable armor is not required at all although some form of cable protection is i.e., raceway, cable tray, location, etc. Specifically recognized cable armor is meta-clad (Type MC) which may be smooth metallic sheath, corrugated metallic sheath or interlocking metal tape armor. Type MC-HL is simply a specific case of corrugated metallic sheath.

In ANY Class I, Division 1 or Zone 1 location all cables of any type must be sealed at their terminations with terminations listed for the application. (This includes grounding/bonding if necessary)

In ANY class I, Division 2 or Zone 2 all cables entering enclosures that are required to be explosionproof [or flameproof in Zone 2’s case] must be terminated just as if they were in Division 1 or Zone 1. Otherwise, they must be terminated such that there is no stress in the termination. Note: While listing or labeling is not a general requirement for the cable terminations, it is usually the simplest way to determine Suitability for use in classified locations – See 500.8(A)(1) [good luck attempting to use (2) or (3)].

Steel Wire Armor (SWA) has NO general applicability in US domestic Classified locations. It may have an additional marking as another Type, such as TC or MV, in which case it would be acceptable in Division 2 or Zone 2, It is definitely NOT a “flexible cable.”

Note: I'm not sure which Part of IEC-60069 you are referencing; SWA is not only acceptable in IEC Zone 2, it is acceptable in Zone 1 as well. It just isn't acceptable in the NEC. [I told the Code Making Panel 15 years ago this was going to get confusing :grin:]

 

[dbuckley]

Do you chaps even have SWA in the USA? I thought it was a Europe-only type solution.

A standard SWA termination is not anything like gas tight, however, SWA is (obviosuly not in a NEC juristiction) widely used in boiler rooms.

 

[rbalex]

Do you chaps even have SWA in the USA? I thought it was a Europe-only type solution.

A standard SWA termination is not anything like gas tight, however, SWA is (obviosuly not in a NEC juristiction) widely used in boiler rooms.

It's available; its primarily used by utilities. It may occasionally be listed as Type MV or TC depending on the ultimate construction. Note: It can only be listed as Type TC when the armor is NOT one of the constuctions permitted by Type MC.