6.6 KV power Cable joint on open air Cable Tray in Hazardous area

[sramesh]

Good day to you

Our installation is LNG production plant(Oil and Gas)
We have a failure of a 6.6KV power cable near to the equipment located in Hazardous area IEC Zone 2. Planning to cut the faulty portion of the cable and splice it with a short piece ofnew cable.
We are debating on the safety aspect the location of the cable joint since it is inside hazardous area. We prefer to put the joint at the under ground portion of cable route considering cable joint will be the weak point/inside hazardous area, for this minimum 100mts of cable is required. The contractor proposal is to have the joint on the Cable tray with a small piece of cable of 10 mts.

We would request information/ suggestion from the forum on any international standard reference governing the cable joint location inside Hazardous area.

Thanks in advance for your quick input.

Regards
Ramesh

 

[Kiribanda]

sramesh,
In my opinion IEC 60079 series has nothing mentioned about such cable joints.
Whether you follow IEC (Zones)or NEC (Divsions) the main issue is whether the equipment is producing sparks or arcs. In Zone2 or Div2 the probabilty of simultaneous occurence of spark and gas leak is considered.
Therefore, that probabilty is there in Zone2 even with a new cable. Because of that we are not going to have "explosion proof" cables or "explosion proof" motors or JBs in Zone 2.If the cable is specified per IEC 60332, then it is not essential to have it in sand filled trenches.
Based on above, I cannot justify of putting the cable joint underground, because when you make a good joint it becomes a part of the existing cable.Therefore, I agree with above ground jointing.

 

[waross]

Will the joint be made with a splice kit approved for the location, or in a junction box approved for the location with approved glands?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rbulsara]

Furthermore, most Codes would require all joints and splices to be accessible for inspection.

Rafiq Bulsara

http://www.srengineersct.com

 

[rcw retired EE]

IMHO - A properly made splice with adequately connected shields and earth (ground wires) with proper jacketing such as a heat shrink jacket is just as reliable as a cable. Some codes like the NEC, (392.8(A)) allow approved splices in cable tray.

A splice in a tray is not much different than a splice on messenger supported overhead aerial cables. I have seen many splices like that within a Class 1 Div 2 location in refinery process areas. (Similar to Class 1 Zone 2).

The cause of the original cable failure might have some bearing on the decision or the type of splice used. Did a local process system spew acid on the cable or was there mechanical damage that could be expected to occur again?

 

[sramesh]

Thanks for all the replies, the cable is installed in the normal area, no acid or chemical handling area. We feel the failure is due to cable external damage happened during laying.

Thanks again

Ramesh