Sparking- does Cu wire resting on forged Alloy steel shaft cause it?

[alwayslearning]

Dear All,


1) Does a copper cable (9 mm od- made of multi core fine drawn wires) riding freely on a rotating equipment shaft (made of Forged Alloy Steel) lead to sparking by friction alone?


2) Is it possible that the above cable (riding freely on the rotating shaft) can cause any grooves or damage to the shaft.

3)Is it possible that there is an electrical spark due to occasional lifting (for whatever reasons) of the copper cable from the shaft? The voltage difference can be up to 20 volts (measured using oscilloscope).

Let me explain this "riding freely" more clearly: We tied one end of the copper cable to the turbine casing and let the cable (about a foot long) rest freely on the shaft of a condensing steam turbine shaft to effectively "ground" the
shaft to eliminate the static charge generated. Having done this we in the plant are going through a debate about the safety aspect.

Is it at all possible that a spark is generated (either due to friction, or due to electrical contact) by the contact of the copper cable and shaft? Where in literature can i find a mention about such a possibility? Does NFPA mention any possibility of spark occurence due to contact of copper and steel etc.?

Any help would be most appreciated. Thanks

PS: I had posted this query on materials- other topics thread367-94192 and received some insightful responses. I just hope to hear from a wider members on this matter. I hope it is not breach of etiquette on this forum

 

[MintJulep]

1) Sparking occurs when an electrical charge travels across an air gap. Perhaps the wire is not really in firm contact with the shaft at all times.

2) Yes.

3) See 1.

There are various ground brush arrangements available for this purpose. Why not use something actually designed for what you need to do?