Violation? Installing over 3m length Explosion proof flex conduit

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orange_blossom75728 said:
In class 1 div 1 D location, we are planing to install explosion proof flex conduits (over 3m length). Is it a code violation?
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For some reason, that product is called a flexible coupling and not flexible conduit.

They are very expensive with a 3/4" x 36" one costing about $250. I believe that the longest standard one is 36", but they can be custom made in lengths up to 12'.

Are you in a Class I, Division 1 location? In many cases standard liquidtight flexible metal conduit can be used in Class I, Division 2 locations, but if you have a division 1 location, you need the explosion proof flexible couplings.
 
They are "couplings" because of they are a entire factory assembly; that is, the terminations cannot be field installed.

UL does not restrict the maximum length; however, most manufacturers have a maximum that they can handle.
 
Thanks for ur advise. We are working in a maintenance aircraft hangar, and the place to be installing flex is specified as class 1 division 1 group D location. NFPA and/or NEC don't restrict the max length for explosionproof flex coupling, either?
 
In this case, if UL does not restrict it, NFPA/NEC won't either.

It will be incredibly expensive and you may still have support issues.

Unless you are doing painting, is difficult to believe that it is actually Class I, Division 1. It is also difficult to believe that this is an NEC rather than JIS installation.
 
It took me a while to find it but the UL application data is here. While there is no length restriction, there are other things to note. Personally, I think it's just a bad design.
 
Our project is under U.S. Contract, on U.S. military base in Japan . That's why we need to follow US regulations, and really tough to work w/o knowing them... The location of Class 1 Divi 1 is specified by the contract drawing. Thanks for many helps. I'm looking at UL data
 
Do the contract drawings specify explosionproof flexible couplings?

I still believe the contract drawings are using excessive classifications. This is a common problem for people who do not actually know how to classify an area; they over classify "just to be safe". The proper source is Article 513. Eventually, they will discover just how unbelievably expensive over-classification is.
 
The drawing dose not say about using explosionproof flexible couplings, but the under hangar floor and the above about 2 feet (I don't remember the exact number) from the hangar floor is classified as class 1 division 1. So our sponsor advises us to use explosionproof flex couplings.
 
I believe our sponsor will never allow to deviate from the contact drawing especially regarding to the safety matters such as hazardous locations even if the classification is over classified. Cuz they cannot (or don't want to) take responsibility for safety issues.
 
orange_blossom75728 said:
The drawing dose not say about using explosionproof flexible couplings, but the under hangar floor and the above about 2 feet (I don't remember the exact number) from the hangar floor is classified as class 1 division 1. So our sponsor advises us to use explosionproof flex couplings.
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Why do you need the flexible length that long? Why can't you install rigid conduit and just use the flexible coupling for the final equipment connection?
 
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