Clearance between HV line and Sulphur Conveyor

[mastergate]

For a project in Morrocco, a solid sulphur conveyor is crossing under a HV line (63KV).

In my understanding we need 3 protections (please correct me if this is wrong):

1/ During normal operation: the HV line shall be kept out of touch (some minimum distance shall be kept between the line and the conveyor).
I want to know what is this distance per IEC and other standards.

2/ In case of line fault (arc, short-circuit, cable cut..):
As the conveyor line is classified ATEX, it is necessary to avoid creation of sparkling and over-heating near the conveyor, which can result in fire/explosion.
I need details and types of protections / safeguards for this case (if possible with reference standards).

3/ Effects of magnetic induction and capacitive coupling: can be resolved by a good earthing in the intersection area.

Please help.

 

[7anoter4]

I am not familiarized with ATEX classification of hazardous place[location].This hazardous place is 20,21 or 22 Zone classified, I guess. It can be similar with NEC class II Division 1 or 2 location group G [nor metallic powder neither coal dust is present].
An AHJ[the authority having jurisdiction] has to state the Zone classification. According to this you may find in ATEX recommendation what type of enclosure you have to employ.
The equipment-except intrinsically safe circuit-has to be enclose in approved [let's say NEMA Type 9 for class II Division 1 according to NEC].The temperature of enclosure-including motors –has to be lower than material ignition temperature, any way.
I don't think you need to keep more distance than is recommended in local electric safety code. In USA NESC- Rule 234 states-approximate- 1.5 m from the energized conductor at 63 kV up to a conveyer[no indication of material conveyed].

 

[mastergate]

Thanks for your answer.

I want just to clarify: the ATEX area is only the conveyor galery. So in normal operation, the HV line is in safe area.
You are right: the hazardous area classification was done by a Client & competent agency. All electrical equipments along conveyor are chosen for ATEX 22 area (category as per IEC & NF French standards).

My question is related to Line Faults and safeguards to protect the hazardous area.

Thanks.

 

[waross]

We often see conveyors that cross roadways and walkways enclosed to protect vehicles and persons passing underneath. Such a physical protection may be required to prevent a possible broken 63 kV conductor from contacting the conveyor. This would have the effect of containing the hazardous area to the space inside the enclosure.
The second option may be to dead-end the high line on either side of the conveyor and route it underground past the conveyor.
In normal operation the high line should be outside the hazardous area, but if you must consider the possibility of an accident where there may be falling sparks or falling conductors, these may be the only options.


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

 

[mastergate]

Thanks waross

Could you please give me more detail/example about these enclosures (types, material)?

Regarding the possibility of accident on the HV line, this is what I need: is there any standard describing similar case? Is there any benchmark?
I can't find any IEC or European standard for my case.
I've seen only some french standards:
- Some defining the clearances between HV lines and buildings ...
- Some prohibiting passing HV cable over some kind of forests (fire hazard)

For the option of passing HV line underground in the intersection area, there are some constraints: first is the risk of cable theft (public access area), then clashes with foundations, underground services, and some problem of guarantee and project scope of work.

thanks.

 

[7anoter4]

The voltage induced in conveyor gallery could be important only if the conveyor run parallel with the overhead line. If the line cross the conveyor the voltage by capacitance and induction is negligible. Conduction voltage transmission could occur in case of line-to-ground short circuit in the vicinity. The utility has to check the touch and step potentials around the poles to be under the maximum permissible.
However if you intend to protect the conveyor from a conductor
falling - the Utility has to provide a double suspension for all conductors above the conveyor ,no splicing in this location and –may be-a guard structure of two conductors-the same cross-section as the line conductor-at least-well grounded at the minimum permissible distance under the line.
A guard structure it is a structure built of poles and rope nets. It is used whenever conductors are being strung over roads, power lines, communications circuits, highways, or railroads, and is normally constructed in such a way as to prevent the conductor from falling onto or into any of these facilities in the event of conductor failure, loss of tension, etc.

 

[ScottyUK]

Near where I work the pipeline corridors crossed by HV lines are protected by metal frames designed to ensure that the line touches the frame before a pipe. The expectation is that the line will trip on earth fault before it damages the pipe and either causes a breach in the pipe wall or ignites the contents, or both. The frames aren't anything special - they appear to be sections of 3" or 4" pipe welded into a crude frame and erected vertically either side of the pipeline corridor. I don't know how successful they would be in practice, and given what is flowing up that route I'd be quite happy if I never find out.

 

[mastergate]

Thank you very much.
I think also that considering the high reliability of HV protections for earth faults, this can protect enough the conveyor line.

I was considering also that the hazardous area is contained inside the conveyor gallery and if a regular cleaning is done, then probability to have accumulated dust layer on the top of conveyor is almost zero.

I guess that few people have met this issue and there may be no clear requirements in IEC & NEC, NFPA standards.

 

[waross]

If this conveyor runs inside an enclosed gallery then the hazardous area may possibly not extend outside the enclosure.

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

 

[mastergate]

Exactly, but in practice it is not obvious to keep a good sealing and in case of abnormal condition (belt sway, maintenance work..)
An then with a large fault energy/overheating how to be sure of not having ignition of sulphur inside gallery.