Hi..
I found some toroidal transformers.
There are small drops inside. I opened one, got the drops on my fingers. My fingers seem to be vaguely sticky afterward. Is this water ? Or do manufacturers put something inside what looks like water ?
If its water, any change this will dry enough to be safe again ?
-- hihihi is the username, wanadoo the domain, nl the country.
Yes, it looks like water. The moisture has condensed on the clear tape because its environment was cooler than inside the windings.
Put it in the oven after it has been used to roast the Sunday joint but turn the heat to off. Leave it there until everything is back to room temperature, say 4 hours. Don't have the oven too hot to start with, say 85ºC, or the insulation may suffer.
Where did you get the txfmr from?
-- -- Graham W http://www.gcw.org.uk/ XP1800+ Page added, Graphics Tutorial WIMBORNE http://www.wessex-astro.org.uk/ Wessex Astro Society's Website Dorset UK Info, Meeting Dates, Sites & Maps
Thanks for the tip.
Scrapyard, 16 trafos +/-30 volt, 3 ampere, for 17 euro.
The problem might be more serious. After i wrote the previous message, I have removed the outer plastic, and am busy unwinding the wire of the first level of one of the 16 trafos, which is the secondary side. Below there is a second layer of plastic, below which is the primary side. With also water drops.
It is possibly the trafos have been in the rain for a long time. Could be a bad buy. Happens sometimes. :-)
Well, now i will see the inside of a toroidal transformer, which is interesting in its self.
And i have not given up hope.
-- hihihi is the username, wanadoo the domain, nl the country.
hihihi wrote in news:46c8849a$0$302$ snipped-for-privacy@news.wanadoo.nl:
Damn good score. Don't worry about the water unless you see visible corrosion, which I doubt you will, wire enamelling being what it is. Just bake them for a few hours, a day perhaps, at 80°C. The omly possible risk of that is that the cost might make the transformers look less of a good deal. >:) So maybe put them in a black-painted biscuit tin and put the lot out in the sun for a couple of days. Just bring them in at nights. Just wait till you can test by putting them in a fridge or freezer and no longer see condensation form on the inside of the tape layer.
Good tip.
I have them currently in a green house type of thing, to get higher temperatures. This morning the outside of one trafo was at least 40 degree Celsius. With your blackbox idea this temperature will go up.
Good tip.
I had a theoretical idea. Put trafos in vacuum box. Suck air out, with it the moist in the air. Slowly add air again, while heating the air inside to 80 degree Celsius. The hot dry air will then go deep inside the trafos. Part of the water will evaporate into the dry air. Suck the moist air out of vacuum box again. Repeat process until all water is removed from trafos.
Problem is, i do not have a vacuum box. Allthough my mind is itching, how can i make one, with nothing :-))
-- hihihi is the username, wanadoo the domain, nl the country.
hihihi wrote in news:46c89acd$0$293$ snipped-for-privacy@news.wanadoo.nl:
Vacuum and cold are closely related, so you could try a peltier. :) Best not though, far too awkward, and the cold trap will just cool your box...
A better idea is to buy a cheap paper bag of granulated sugar and seal that in the box with the transformers. Except on a really dry day, in which case placing the lid with a small air gap will be enough.
Because of the many layers, it's difficult to dry the transformer. There are some methods to accelerate the draining. Just vacuum is one method (no need for high temperature). But I think that 40°C for a week is enough. The difficult part is to know if it's dry or not. Vacuum is a method for evaluation. If you put vacuum, and close the stopcock, the vacuum will drop because of added moisture (or increase, depending on how you measure). If the vacuum drops it shows wet. If the vacuum stop dropping the transformer will be dry.
-- Yianni
9jir snipped-for-privacy@yahoo.gr (Remove the number nine from my email address to send me email)
"Yianni" wrote in news:1187568901.703727@athprx04:
I agree that long term at lower temperature is ok, but not many people have access to vacuum stuff. As I said, vacuum correlates closely to cold, so a good way to test is to put it in a freezer while it's still at 40°C or more. If it's anything less than bone dry inside, the outer mylar tape will cloud on the inside.
80°C is definitely better than 40°C, the molecules of water will be more energetic and will find their way out of the deepest coil sooner. Much sooner than a week at 40.
Good idea for evaluation if it's dry!!
-- Yianni 9jir_2006@yahoo.gr (Remove the number nine from my email address to send me email)
It does not have to be vacuum.
I just did a little experiment with a 60 mL syringe. Put 10 mL air in the syringe. Hold your thumb on the syringe to seal the exit. Then pull until it is on 60 mL. This can be done easily. You could do it with a electro motor for example.
The pressure then will be: V1 = 10 mL volume. V2 = 60 mL volume. P1 = start pressure. P2 = end pressure.
P1 / P2 = V2 / V1 P1 / P2 = 60 /10 = 6 P2 = P1 / 6 This way you can reduce the air pressure to 1/6 th. Which means about 80 percent of the moist air has left the trafo.
Put the trafo in a plastic bag, which will act as the pressure chamber :-) Use the big syringe with a electro motor as air pump. You need a few valves to control the directions and timing of the air.
Suck air out until pressure is 1/6. Then about 80 percent of the moist air in the trafo comes out of the trafo. The add normal air to the bag, to re-pressurize. Part of remaining water in trafo will evaporate into the new normal air. Suck the air out, again. Repeat this process.
I think this can be done by hobbyists. Question remains, how long is it gonna take to remove the water. This depends on the size of surface contact of the water with the air. Which is impossible to determine.
-- hihihi is the username, wanadoo the domain, nl the country.
There is one problem to look out for. If you take the cold trafo out of the freezer, the outside air will create moist on the cold outside of the trafo. This might look as if it is inside. Wipe the outside of the trafo dry before checking if there is cloud on the inside.
-- hihihi is the username, wanadoo the domain, nl the country.
hihihi wrote in news:46c962b1$0$286$ snipped-for-privacy@news.wanadoo.nl:
That's the sticking point. A LONG time. The idea of driving the energy up in the water molecules is that they'll move to a cooler region of unlimited volume on their own. If you're trying to captuer vapour laden air you'll have to capture and displace it for days, even if you use a large chamber.
Use heat.
hihihi wrote in news:46c9669d$0$278$ snipped-for-privacy@news.wanadoo.nl:
No need, the idea is you open the door and take a look after sealing it in there for ten minutes. I guarantee this will work, you will get a very good look at it before it can cloud on the outside. I doubt it will anyway, because you put it in warm, it will stay warmer than the ambient heat for a lot more than ten minutes.
Don't take my word for it, get a ceramic bowl, heat to 50°C, put a few drops of water in, then cover with clingfilm, then seal it in the freezer, then go back and look at it after ten minutes, and see how long it lets you see that the condensation is clearly INside, and not outside. I bet you'll have no trouble at all.
And removing the transformer from the freezer after testing will be fine, it won't be cold enough to get vapour back inside from the ambient air. If you thgink there IS a risk, on a humid day, or you forget to remove it, just seal it in a plastic bag before letting it warm up outside the freezer.
I think that heating to low temperatures (40 deg C) for a long time will not necessarily dry the transformer well, especially if the humidity of the environment is high (e.g. in an outdoor greenhouse or a gas oven). Also, the warm temperature may accelerate the corrosion cause by the water (e.g. the iron core).
If the transformer insulation is rated for e.g. 120 degrees C or higher, then it might be better to heat the transformer to say 105 degrees C (measured with an accurate thermometer!) for a while (allowing the core to reach that temperature), whereby all of the water should evaporate quickly.
The ideal solution would be to place the transformer in a vacuum chamber, which will cause the water to evaporate and be removed by the pump, even at room temperature. You should not need a very good vacuum, even a single stage pump should be adequate, especially if you pre-heat the transformer slightly. You can get old vacuum pumps on ebay though they are not very cheap (maybe 50 euros if you're lucky). Water vapour is not good for some vacuum pumps, though probably the cheap ones will not suffer as much damage as very high performance vacuum pumps. An old refrigerator compressor or airconditioning compressor also works as a vacuum pump (particularly the rotary type). The water vapour is not good for refrigerator compressors, but if it was being scrapped anyway then that may not be a problem. The local dump near me collects fridges but does not correctly recycle the CFCs anyway, though it would be good if they would, I gave them a full can of freon to recycle and they threw it straight in the scrap metal crusher - I should have kept it.
I would not suggest freezing the transformer, because the expansion due to freezing may cause damage to the insulation due to mechanical stresses.
Chris
Chris Jones wrote in news: snipped-for-privacy@corp.supernews.com:
Most of your other points were already made before you posted. And if you're suggesting my advice on use of a freezer is wrong, forget it, I'm not talking about turning it into an icepack, just creating a strong temperature difference across the tape layer for a few minutes to test for dryness after an 80°C bake.
If you read more, and decide less that all other posts before you arrived are wrong, irrelevent, or not even there, you might have made a better post.
Lostgallifreyan is right. You said about vacuum, so I thought you have a vacuum. A syringe with one or better two valves is a solution for pumping. But for making a 0.1 atm vacuum in a 2 liter jar you need about 100 "pumps" with a 60ml syringe. And the most difficult is to make an airtight jar (if there is even a little leakage you will make muscles pumping the air!). Trust me.
People dry fruits many years just using (low) heat (the outer dryed part makes the inside dries slower). May it needs 1 day, or 1 week or 1 month to dry. Freezer is a good idea for evaluate the drying.
-- Yianni
9jir snipped-for-privacy@yahoo.gr (Remove the number nine from my email address to send me email)"hihihi" wrote in message news:46c962b1$0$286$ snipped-for-privacy@news.wanadoo.nl...
The plan was to use a plastic bag, instead of a jar. Then you can push out a lot of air by hand. And you need to add just a little bit of air to get the inside back to room pressure. I have seen this method on tv where professionals glue two plates together under pressure in a plastic bag by sucking out the air.
I was allready worried about this :-)
-- hihihi is the username, wanadoo the domain, nl the country.
I just opened one trafo to the core. There was water in the secondary and primary windings. I have no way of knowing how long the trafos have been wet.
There is rust on the metal core.
This is a normal webcam picture of the core with rust.
This is the same picture, but improved with gthumb -> image -> equalize
I must assume the other 15 trafos can have the same or more rust.
My trust in the trafos is getting low. It looks wise to me NOT to use the trafos. Unless someone has a good reason why it is safe to use them for the long term.
-- hihihi is the username, wanadoo the domain, nl the country.
Like this :
-- hihihi is the username, wanadoo the domain, nl the country.
hihihi wrote in news:46cab6bb$0$87143$ snipped-for-privacy@news.wanadoo.nl:
I think it would have to get much worse than that before being bad. Most of the metal is fine, the rust is barely more than a stain there. I've seen E/I type transformer cores in a terrible state and still working ok, it's just ugly. Those toroids look ok to me. After drying, just make sure they stay that way. While they're in use it's unlikely that they'll get dampness in to do more. If the cores needed more protection against that rust it would have been applied before coils were wound on them.
If you want to use that one in a critical risk of damp, you could spray it with smooth Hammerite first, or the kind of paint used on engine blocks, before winding more wire on it.
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