Burning of PVC coating of Mettalic conduit carrying data cables
Burning of PVC coating of Mettalic conduit carrying data cables
(OP)
I have encountered following problem at one of our site. Unable to think of a possible reason. Request for your valuable inputs
Problem: Outer PVC sheath of metallic conduit carrying data/voice cable burnt.
Problem ocured at a site where the distribution of data/voice cables is thru a metallic (MS powder coated}duct as a trunk route.
Each work station is fed 4 nos of cat6 cables from data duct to the work station thru a GI flexible PVC coated conduit with brass glands at either end. On one end this conduit terminates in the data duct and at the other end the conduit terminates in the data box on the work station.(No contact between the gland and the metalic encloser on either side, as the outer cover of conduit is PVC). (One of the cables cater to voice, one cater to data and other two are spare)
One day suddenly outer PVC sheath for one of the locations burnt heavily.
The affected nodes were 'dropped' from the data switch.
Problem: Outer PVC sheath of metallic conduit carrying data/voice cable burnt.
Problem ocured at a site where the distribution of data/voice cables is thru a metallic (MS powder coated}duct as a trunk route.
Each work station is fed 4 nos of cat6 cables from data duct to the work station thru a GI flexible PVC coated conduit with brass glands at either end. On one end this conduit terminates in the data duct and at the other end the conduit terminates in the data box on the work station.(No contact between the gland and the metalic encloser on either side, as the outer cover of conduit is PVC). (One of the cables cater to voice, one cater to data and other two are spare)
One day suddenly outer PVC sheath for one of the locations burnt heavily.
The affected nodes were 'dropped' from the data switch.





RE: Burning of PVC coating of Mettalic conduit carrying data cables
Is the work station grounded and is the grounding system intact?
In North America, most glands for flexible cable have an inner insert to support and ground the metalic flex.
If the burning was the result of electrical heating you will expect to see the damage uniform over the length of the flexible conduit.
If the damage is not uniform from end to end, look for an external source of heat.
respectfully
RE: Burning of PVC coating of Mettalic conduit carrying data cables
2. No failure of any power strip on the desk.
3. Workstations are not grounded and are placed on carpet.
4. The burning was not uniform through out the length.
5. The burning is definitely not due to any fault current as no breaker has tripped any where
Any co-relation to High Frequency (Radio Frequency) induction heating ?
RE: Burning of PVC coating of Mettalic conduit carrying data cables
There are conditions where a lot of damage may be done without blowing a breaker. One example is with an ungrounded work station or consul when a hot wire contacts the frame. With a good ground connection the breaker will trip. If there is an "accidental" ground of high resistance the high resistance area will get hot, possibly red hot.
Possible but probably not. It takes a relatively high amount of heat energy to do the type of damage you describe. Only a very small amount of the total RF energy radiated from a device is typically involved in incidents such as this. Most RF sources in an office radiate such low levels of power that they are completely incapable of doing any damage. Do you have any equipment nearby that radiates thousands of watts of RF power? Furthermore, enough stray RF to do such damage may also cause severe burns in nearby human bodies.Have you considered chemical burning? A possible spill of a cleaning chemical.
respectfully
RE: Burning of PVC coating of Mettalic conduit carrying data cables
The cause was not definitely known but was supposed to have been a work light left in close proximity to the cables by a worker who may have quietly taken his lamp and left when he realized the damage he had caused.
Just a thought.
respectfully
RE: Burning of PVC coating of Mettalic conduit carrying data cables