Flexible conduit use in hazardous area 1

[Dodger_Fan123]

Hello

We are installing a couple of 12 meter high lightpoles in an oil and gas plant and were told to use flexible conduits wherever the unarmored cables are in the open. The cables run through the inside of the poles from the JB below to the 400W exd light fixtures on the top. The cables are in the open when it exits the pole into the light fixture and we can only fix the Kopex glands on the light fixture and not on the pole side. Is it necessary to use a flexible conduit in this scenario?

 

[waross]

Basically
10 Rem

... were told to use flexible conduits wherever the unarmored cables are in the open.

20 Rem

Is it necessary to use a flexible conduit in this scenario?

30 Rem Yes.
40 goto 10

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Dodger_Fan123]

I was hoping to know the reasoning behind this comment.

 

[waross]

Mechanical protection? The designer misunderstood the code? Are you using liquid tight flexible cable? The designer may have wanted the cables protected from rain.
The designer may have wanted the cables protected from birds.
The designer may not have realized that some unarmoured cables in the open were protected by 40 feet of elevation.
In the oil and gas industry it will take something a lot more serious than that to get the attention of the designer.
Basically: 10 Rem "... were told to use flexible conduits wherever the unarmored cables are in the open." Just do it. If you have a chance to ask an engineer why, you may get an answer. Don't argue, just do it. see line 10
10 Rem "... were told to use flexible conduits wherever the unarmored cables are in the open."
A revision to the prints may cost more than the flexible conduit. It's not worth the worry.

One of the issues that I was able to prevail:
If we follow the prints and connect the far corner of the gradient control mat to the ground grid, we will defeat the purpose of the gradient control mat and possibly kill a lineman.
That one did get a revision. Safety gets more attention than dollars in the oil patch.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Dodger_Fan123]

Thanks for the detailed reply. Yeah we already did the work but I wanted to know the reason. I am eager to learn and this has been bugging me...

Yes its a liquid tight flexible cable but the point I was trying make across was we were only connecting one end of the conduit using a liquid tight connector, the other end will just follow the cable just a couple of meters inside. It would have made sense to me if both ends were connected using a liquid tight connector. Ah well..

 

[waross]

In the Canadian code, short lengths of conduit (The code does not specify rigid, thinwall, or flexible) may be used for protection mechanical without complying with other sections of the code such as wire fill.
In some instances neither end need be terminated in a gland connector.
I suspect that this is a site wide requirement for mechanical protection of non-armoured cables and it is not worth the time and supervision to make an exception for a few cables that may be considered protected by elevation.
Alternatively, there may have been past damage to non-armoured cables by sunlight and the flex provides UV protection.
Sometimes the spec seems silly, but we just do it (but we may talk about it later).
Examples: A Chain Hoist trolly running on a 4" x 6" beam. The end of the beam was solidly, 100%, welded to the flange of a larger wide flange beam.
We drilled and tapped the beams and installed 1/4" bolts and #6 AWG bonding jumpers across the welded joint.
Same project; four x 40 ton skid mounted MG sets welded to a steel deck. (One 3000 HP induction motor driving 5 DC generators.)
We drilled and tapped the skids and the floor and installed 1/4" bolts and #6 AWG bonding jumpers.
The code accepted connection to a grounded structure as adequate bonding, but don't argue, just do it and cash the pay check.
Yes I understand your reason for asking.
It all comes back to the Authority Having Jurisdiction. In this case the designer.
See line 10 Rem "We were told..."

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

By the way, the little routine in my first post is basically all of the "Beginners' All-purpose Symbolic Instruction Code" language that I remember.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Dodger_Fan123]

Thanks a lot sir. You were very helpful.

 

[srini1785]

It would help to know under which zone these poles fall under inside the plant?. Zone 1 or Zone 2. The general philosophy of design in Explosive areas is to continue with the same protection method as the equipment until the safe area. So if Ex d was used in the Lighting fixture and JB then the conduit should also follow the same. Other methods like Purging (Ex p) can also be thought off but would be too cumbersome to use inside a flexible hose. Needless to mention that the hose needs to be properly grounded to avoid any static.

 

[waross]

The gland connector will ground the flexible conduit.
If the flexible conduit is used for mechanical protection, short lengths may be used without seals as long as the flex does not cross any boundaries between Zones.
This according to Canadian Code and practice.
I don't know what code either you or Dodger_Fan123 work under and so different rules may apply.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Dodger_Fan123]

"It would help to know under which zone these poles fall under inside the plant?." - zone 2

Both fixture and JB are ex d rated.

"Needless to mention that the hose needs to be properly grounded to avoid any static." - Right now, grounded at one end (where liquid tight connector is used).

"If the flexible conduit is used for mechanical protection, short lengths may be used without seals as long as the flex does not cross any boundaries between Zones."

We cannot connect using gland on one end, so thanks for this.

"I don't know what code either you or Dodger_Fan123 work under and so different rules may apply." - Haha, this project is in the middle east, lets just say, codes are often ignored.

Thanks again for replying.