Thread: Mineral oil in a transformer

Hello,

I'm curious as to what happens to mineral oil in a transformer. I suspect that most transformers use some sort of other transformer oil, but surely some of the earliest transformers used mineral oil, before PCBs..

Anyway, my question is, specifically, must the transformer be vented in some fashion, if it's filled with mineral oil? Presupposing venting is necessary, why? Does the mineral oil produce some sort of gas in there? Is that gas, if any, dangerous?

Let's say I want to create a dummy load can, which is vacuum sealed and contains mineral oil. Does the sealed container, electrical current plus mineral oil cause a dangerous combination? How about in the climate-changed summer sun?


Thanks!!

-Joshua

Originally Posted by joshwrale

Hello,

I'm curious as to what happens to mineral oil in a transformer. I suspect that most transformers use some sort of other transformer oil, but surely some of the earliest transformers used mineral oil, before PCBs..

Anyway, my question is, specifically, must the transformer be vented in some fashion, if it's filled with mineral oil? Presupposing venting is necessary, why? Does the mineral oil produce some sort of gas in there? Is that gas, if any, dangerous?

Let's say I want to create a dummy load can, which is vacuum sealed and contains mineral oil. Does the sealed container, electrical current plus mineral oil cause a dangerous combination? How about in the climate-changed summer sun?


Thanks!!

-Joshua

Venting is not normally used because vents would allow moisture to accumulate within the transformer (although some transformers have a one-time safety relief pressure valve; once it pops, you must take the transformer out of service). Careful processing to eliminate volatiles is used instead. Big transformers use pressure-fuses that disconnect transformers that are evolving gas.

Mineral oil is pretty stable, and many transformers still use it. Its flashpoint is pretty high, and if you've processed all the water out of it (and keep water out of it), it'll do just fine under normal conditions. Just avoid internal arcover, which can break down the oil and generate gases.

How does the similarity exist for oil-immersed switching elements opening and closing high-current circuits? Obviously, venting is necessary. Moisture entering collects at the bottom, to be removed routinely? Automatically? Some amazing videos are available made in switchyards of high-voltage switching events, including dangerous overload switching and electrical explosions. jocular

Originally Posted by jocular

How does the similarity exist for oil-immersed switching elements opening and closing high-current circuits? Obviously, venting is necessary. Moisture entering collects at the bottom, to be removed routinely? Automatically? Some amazing videos are available made in switchyards of high-voltage switching events, including dangerous overload switching and electrical explosions. jocular

There's no sump pump, drain pan for water, or other such thing, because there's not supposed to be any water there in the first place. If there were, the transformer would suffer a rapid death from arcing/flashover/etc. That's why vents are a no-go. The manufacturing process painstakingly removes water, and the transformer is then sealed.

Originally Posted by tk421

Originally Posted by jocular

How does the similarity exist for oil-immersed switching elements opening and closing high-current circuits? Obviously, venting is necessary. Moisture entering collects at the bottom, to be removed routinely? Automatically? Some amazing videos are available made in switchyards of high-voltage switching events, including dangerous overload switching and electrical explosions. jocular

There's no sump pump, drain pan for water, or other such thing, because there's not supposed to be any water there in the first place. If there were, the transformer would suffer a rapid death from arcing/flashover/etc. That's why vents are a no-go. The manufacturing process painstakingly removes water, and the transformer is then sealed.

Er., I wrote oil-immersed switching elements making and breaking high current flow............not a transformer, a SWITCH. jocular

Originally Posted by jocular

Originally Posted by tk421

Originally Posted by jocular

How does the similarity exist for oil-immersed switching elements opening and closing high-current circuits? Obviously, venting is necessary. Moisture entering collects at the bottom, to be removed routinely? Automatically? Some amazing videos are available made in switchyards of high-voltage switching events, including dangerous overload switching and electrical explosions. jocular

There's no sump pump, drain pan for water, or other such thing, because there's not supposed to be any water there in the first place. If there were, the transformer would suffer a rapid death from arcing/flashover/etc. That's why vents are a no-go. The manufacturing process painstakingly removes water, and the transformer is then sealed.

Er., I wrote oil-immersed switching elements making and breaking high current flow............not a transformer, a SWITCH. jocular

Sorry. I couldn't quite parse the slightly fractured English of your first sentence. Thanks for clarifying.

That said, I don't see why the considerations for switches should differ all that much from that of transformers. I don't recall all the details of the few very high-voltage switches I've encountered, but I don't believe that they had any provisions for draining water periodically. The philosophy in the utility industry is to make these things as maintenance-free as possible. They are just supposed to work, period.

Thanks! That is very helpful.

Another question: Are batteries safe to use if suspended in mineral oil?

I think they would be, with perhaps the exception of cases where the mineral oil breaks down the battery's casing. Something like a laptop battery or a AA battery is what I have in mind.

Thanks again,
Joshua

Originally Posted by joshwrale

Thanks! That is very helpful.

Another question: Are batteries safe to use if suspended in mineral oil?

I think they would be, with perhaps the exception of cases where the mineral oil breaks down the battery's casing. Something like a laptop battery or a AA battery is what I have in mind.

Thanks again,
Joshua

I've never tried this experiment, nor seen it carried out. Electrically, you're certainly fine. However, mineral oil is a solvent for many inks, so I'd expect the artwork on the battery casing to dissolve, for example. Whether such solvent action has more serious consequences for the scenario you describe, I do not know.

mineral oil should be safe in contact with batteries ---- but what for????????????

Originally Posted by fizzlooney

mineral oil should be safe in contact with batteries ---- but what for????????????

Thank you.

Cooling. Protection from the elements (moisture, extreme cold).

Originally Posted by joshwrale

Originally Posted by fizzlooney

mineral oil should be safe in contact with batteries ---- but what for????????????

Thank you.

Cooling. Protection from the elements (moisture, extreme cold).

When heated until some vaporization occurs, beyond that of normal room- or operating temperature vapor pressures, most all mineral-based oils will catch fire. This is the reason unknown tens or hundreds of thousands of power transformers worldwide were filled with Poly-Chlorinated Bi-Phenyls (PCBs) over a period of some 40 or more years. When a severe fault occurred, causing high-temperature arcing, mineral oils instantly heated sufficiently to burn explosively; PCBs being a synthetic chemical, oily and non-freezing, chemically-stable, non-supportive of burning, thermally conductive for cooling of transformers (and capacitors, and perhaps batteries in some high-duty applications {submarines?}, having very high electrical insulating qualities better than air, were PERFECT for such applications.

Today we know that the human body takes up PCBs when they are found in the food chain, where they remain chemically unchanged for decades, even, the most serious consequence being their chemically-close resemblence to humans' natural hormone estrogen. The body stores PCBs in the fatty tissues, tricking the 'hormone-messenger" system into thinking they are true estrogen. But, in excess, the hormonal imbalance created can wreak havoc on the usually-disregarded messenger system which regulates virtually all organ functions, including the brain. We think these hormone-disrupting synthetic chemicals may lie in part to blame for the unprecedented rates of sociological deterioration in obesity, aggressive behavior, and associated violence. jocular

Hi I manufacture transformers and I just wanted to get some verification as to whether or not my work is keeping my health's interests in mind. They take our transformers out of the vapor phase chambers and the plant is filled with smoke from the vapors of the transformer oil. Today my throat is soar the vapor in the air was so thick. Is this ok? Should i be voicing my concern to them?

Originally Posted by JJ731

Hi I manufacture transformers and I just wanted to get some verification as to whether or not my work is keeping my health's interests in mind. They take our transformers out of the vapor phase chambers and the plant is filled with smoke from the vapors of the transformer oil. Today my throat is soar the vapor in the air was so thick. Is this ok? Should i be voicing my concern to them?

You should look up the MSDS (or equivalent) information for that oil. That should give you some idea of whether you have a big worry or not.

This MSDS says there is an OSHA exposure limit of 5 mg/m³ of oil mist for Lubricant Base Oil (Petroleum)

http://www.marcnelsonoil.com/MSDS_PD...former_oil.pdf