DC Furnace Arc Problems
DC Furnace Arc Problems
(OP)
I work in a structural steel mill which uses a DC Electric Arc Furnace (13.8 kV). We have been having problems for quite some time with the electrode arcing to the furnace roof and damaging the water cooled panels. I am currently researching ways that I can electrically isolate the roof from the body of the furnace. I have considered using an insulating ring made of muscovite or phlogopite which would be attached to the underside of the roof rim. However, I have doubts as to whether this material could withstand the heat (~2800F) for an extended period of time or if it will even serve as an effective electrical isolator. Has anyone else ever dealt with this problem, and if so can you give me any advice?






RE: DC Furnace Arc Problems
Also, do you have any contacts in AISE/ISS? There may also be information available from their conference proceedings (especially in the EAF conferences).
~NiM
RE: DC Furnace Arc Problems
~NiM
RE: DC Furnace Arc Problems
RE: DC Furnace Arc Problems
RE: DC Furnace Arc Problems
Beginning with the power supply, it has to be "floating", the P and N bus should not be solidly grounded. They are grounded through a resistor array. The reason is to let either the P or the N bus to touch a grounded point without damage.
On the furnace, the anode has to be "isolated" from the shell. This is probably the most important issue. The anode will be connected to the P bus which is floating.
The shell and the roof are solidly grounded.
Having this configuration, you will avoid roof arcing.
You will probably have more doubts. If you can give me your e-mail, I can send you a couple of skethes to explain in detail.
RE: DC Furnace Arc Problems
I would definitely like more info. I'm not electrical, I'm mechanical, so some of the explanation may be a bit over my head. However, I can have one of our EEs look at it with me and try to help me understand it. My email is 'daphne@sphynxter.com' I really appreciate your help.
Daphne
RE: DC Furnace Arc Problems
Did you succeed in fixing arcing problem on the roof? Our customer (DC EAF) not long ago has damaged a roof panel supplied by us just after 4 days of operation.
Appreciate your help.
SR
RE: DC Furnace Arc Problems
Do you have some findings on how the roof panel was damaged?
RE: DC Furnace Arc Problems
I didn’t see it myself, but they describe it as a pit hole – damage caused by the arc strike in the area closest to the electrode and possibly through the contact with the scrap. This problem is quite common here. It even reflected in the name of the panel: so called “sacrificial panel” or “protection ring”. Panel itself is quite narrow, only 8 pipes going around the delta. Roof is not solidly grounded, only through the contact with the shell.
Why do you recommend roof to be solidly grounded? Doesn’t it create electric potential difference between electrode and a roof (scrap – roof) and, inevitably, arcing? I don’t really understand how grounding the roof will prevent electrode-roof (scrap-roof) arcing. Furnace manufacturers have different views on roof grounding, judging by my observations of EAF in different plants, AC and DC.
SR
RE: DC Furnace Arc Problems