Need a Low Electrical Resistance and High Conductance Oil

I don't know why you'd use a conductive fluid for this. It won't work.

Find out what oil they use when performing electrical discharge machining and use that.

Good luck.

The combination of oil and electric welding will often make for uncontrolled fires. I think that you should instead consider either conductive brushes or rollers in your design.

no, this type of roll mounts already in market and my US branch is already using this. but i couldnt contact our engr overthere thats why i couldnt get which oil they are using.

also the oil is a non-burn one.

Maybe he doesn't work on Sunday's.

What's the emergency, that you can't wait?

Why would you ask total strangers for advice when you have an associate in the USA?

Bye bye.

hahaha.. i know but he is on leave for 15days. also i am looking for a very efficient oil than we are using in US.

Why can't you wait 15 days till the only person in your organization that can help you, "to incorporate resistance welding roll mount" gets back in the office??????

Search, search, search for the answer. Who is your present supplier? Why can't he help?

This is a situation where the OP won't say what he's trying to do. No details. Guessing at what he's after goes nowhere.

Thick indeed.

what is OP?? wht u r trying to say??

Hehe, we understand it!

hey i cant waste my time to wait until he comeback. thats y i am searching....

OP = Original Poster. In this case, that means you. I know there is a language barrier here, and that's understandable. The thing is, you don't give enough detail of what you are trying to accomplish. Details of the situation don't give us the big picture. The big picture is where you have to start to begin narrowing in on a solution.

Dong ma?

I suppose you mean high thermal conductance?

I don't think you'll find an electrically conducting oil. Oils are covalent compounds and don't have free electrons like metals. If your man on hol in USA knows better I'll stand corrected.

i am looking for the oil now. already i planned to use mercury.

I cannot see how Mercury could possibly be used in a situation like this from a company health and safety perspective (regardless of whether or not it would work). Mercury + (electrical discharge + heat) = Mercury vapour = serious health hazard.

This is an American site isn't it? Have you run this passed your Senior engineering and management team?

Surely there must be a better way (a special mineral oil perhaps). Have you searched the internet to see what the rest of the industry is using (I cannot imagine it would be Mercury).

Keep us posted on your findings (and don't use Mercury).

of course jack. i will keep you on posted. anyway we are not going to use mercury....

Let's dissect (take apart for the purpose of greater understanding) you post.

In our facility we are going to incorporate resistance welding roll mount.

What is resistance welding roll mount?

the main supply

Supply of what?

is connected to the body

Body of what?

and inside the body the shaft is rotating. end of shaft we connected copper welding wheel.

What is a copper welding wheel, and how did you connect it?

the shaft is immersed in a oil that has low resistance to electric current flow and has good conductance.

This statement is redundant. If it has low resistance, it, by definition has good conductance; that is, unless you mean good heat conductance.

i am looking for the oil now. already i planned to use mercury. but handling of mercury is little danger and harmful.

Hg is NOT an oil!!! It is extremely toxic, especially the vapor. Every time an electrical contact is made, some Hg is vaporized. That's why Hg switches are enclosed.

Now I'm yelling: IF YOU WANT SOME HELP, TELL US WHAT YOU ARE TRYING TO DO!!!

Noble effort but I seriously doubt that you're going to get any useful response here.

As we all know the most common form of electric welding involves arc production in many forms. To be completely accurate there is also a few forms of resistance welding but these are typically a form of spot welding or seam welding. In both a spot and a seam weld the electrodes are across the thin welded materials. To my knowledge, the very reason a resistance weld works is that the contact between electrodes is supposed to be a higher resistance than the electrodes themselves so that most of the power deposited will be melting the welding material and not the electrodes. So using a high conductive fluid between electrode and welding material seems to defeat the intended purpose.

IMHO the OP does not know how the machine works and has been sold a vanishing bottle of snake oil.

just see the pic you could have a better understanding.

the brass body with connected copper wheel at the right end....

the shaft and mercury are kept inside the brass body(shown in picture). fully sealed with rubber seals.

Of all trades, you clearly are not on the right wavelength with this fellow. Allow me a course correction for you.

Yes, mercury (or quicksilver in older use) was and still is in use in equipment, like thermometers, but also in thermostats, and power rectifiers, as thyratrons. These are tubes, capable rectifying very large currents, and medium voltages. It was done for at least 80 years on an industrial scale. Oil has nothing to do with it.

On the other hand, there are large current welding robots, like in the car chassis assembly line, that might fill your needs. They run dry, obviously, and their welding electrodes need to be swapped out a few times every work shift. Companies sell them in the open market. It seems to me, it might fit your needs too.

Good luck with it.

I suspect we are experiencing a terminology disconnect and what you are looking for is an electrically conductive fluid to achieve conduction across the rotary joint of a seam welder. Mercury was formerly used for these connections, but is no longer used because of health concerns. I'm not sure what the current options are but I think they are binary or ternary alloys of indium and/or gallium. I suggest a search under "low melting liquid metals".

Metal/ Carbon Film resister manufacturing "steel cap to copper leads" welding m/cs use mercury joint to supply high current to Tungsten Copper welding electrode wheel. current is about 20 to 50amps. If there is no space problem you can try by attaching many carbon brushes or phosper bronze brushes, instead of mercury or conducting oil. Most vegitable oils are conductive but if you pass current property of oil may change due to electrolysis.

?

One option is to use a ternary eutectic alloy composed of 66% Ga,20.5% In, 13.5% Sn. It has a liquidus temperature of 51.3 deg.f and a molten resistivity of 29.4e-6 ohm.cm.

Interesting alloy. The low tensile strength of those three metals will also mean that an accidental solidification while parts are moving will likely not cause any serious damage. I wouldn't call it an oil though. Likely our OP meant fluid or liquid but typed "oil" inadvertently.

I agree. I think the use of the word "oil" was a poor choice that led everyone in the wrong direction.

because our engr in US he mentioned in his mail, "we are using a special oil here". thats y....

Now this makes better sense to me. GA

Re: #32. Welderman's excellent suggestion started me thinking along a related line. That is surface wetting and heat expansion. I had to replace a number of mercury wetted contacts, as when oxide products and other contaminants collected on the surface, it became unreliable. High currents can make such an event in welding quite spectacular. Thyratrons are reliable performers, as they are radio tubes made in clean room conditions.

The other issue, that makes it a nontrivial exercise is surface wetting and heat expansion. No matter, what OP said, or shown in pictures, when a wettable shaft is mated with the wetting liquid metal, it will creep out under the seal in a few molecule thick layer, as soon as heat expansion occur in the liquid. Mercury is a potent poison in milligram amounts. If it is not forbidden yet at the workplace, it will be soon.

That may be the real crux of OP's question.

Ternary components are better, I think. But only by degree. Any liquid metal has a corresponding vapor phase. I am not sanguine about long term breathing of gallium, indium, tin or some such. Workers in tin smelters are known to get sick on the vapors. Then they need chelation treatment to remove the metal from their bodies, to return to some degree of health.

Yahlasit's note is correct. Brushes in oil bath may be a short lifetime item, but has none of the problems listed.

In the seam welding process, the weld current must be conducted across a rotating joint. Two conventional methods are: 1) running the rotating joint in a liquid metal such as mercury, or a low melting alloy, or 2) Operating a copper shaft between highly loaded silver brushes lubricated with Castor oil, e.g. see http://seedorffwelders.com/seamwelders/ Both of these methods have advantages and disadvantages.