Wet transformers....recovery?

[MartinJones]

I have power & output transformers that have been fully emersed in water. Would simply allowing them to dry-out be suffient? No previous experience of this. The story: dismantled my WAD 300PSEs to component parts for rebuild. Obviously cleaning B4 rebuild. Nephew (bless him) wanted to help, so placed in/out Txs into bucket of water. NB. they were not attached to any components as amps totally stripped down............any advice please

[NickG]

Maybe you could leave them in a warm for a couple of hours to get the final trace of moisture out.

Should be ok, the wire is insulated anyway. I guess if they are built with paper insulation and not varnished impregnated it will be a case of getting that paper dry.

[Greg.]

What about using an oven hotdrawer? (I mean for the Tx, not the nephew )

[Paul Barker]

If they aren't impregnated and baked I would say they would remain very dangerous for quite some time. I would leave them in a low oven, you will smell the house out, (I have my own oven in the cellar for this job) for hours on end, and still you might get fireworks.

At the best of times transformers can self ignight, I wouldn't help the process by wetting them.

[MartinJones]

Not sure of the internal construction. They are the original Txs from the WAD 300PSE dated 2000-1.

[steve s]

Iam with paul on the time frame.. intermitent use of a powerful hair drier or air line may help too

and test it on some old spekers..

i once spilled a cup of coffee over my laptop key board.. it took 2 days to get enough moisture out of it before it would work again.. and that took some doing..

[John Caswell]

I venture to suggest that a good baking in the oven for about a day at 80-100ºC and then get them insulation tested with a megger winding to winding would be a good way to start.
I think I am right in saying that all the WAD Txs were varnish dipped (as opposed to varnish vacuum impregnated) so you may be lucky that the water has not done too much damage. I think a lot will depend on how long they were in the water.

John aka Dr John

[Black Stuart]

Martin,
there may be another way but it's a long shot that you would know anyone in an appropriate company - freeze drying. Much fruit and veg undergoes this treatment. The suggestions for using heat may well work but eg. being an cycling enthusiast - it was always rec. that with steel framed bikes the best time to spray/apply oil to the inside of a bike frame was in the winter months when the air is actually drier. That way you might avoid trapping water/condensation beneath a film of oil. If you use the oven method you should ensure that when you remove the txs and they begin to cool you don't attract moisture/condensation back into the structures - just a thought.

Black Stuart

[MartinJones]

Thanks folks. Dr John: they were only submerged for a few minutes & were shaken & dried (not Mr Bond's style) then placed on a radiator for a couple of hours. Been cooking now for nearly 2hrs (not rising yet!). I take the point about moisture settling on cooling, & will reduce the temp then allow to cool inside oven, keeping door shut. I dont have access to a freeze drier nor a vacuum oven. However, it will be many days/weeks until the 300Bs are all back together & ready to 'fire-up', so I suspect that they would be throughly dried-out by that point.

[John Caswell]

Hi Martin,
Sounds promising. The best thing to do when you are ready to reinstal is to connect the tx to the mains supply, with absolutely nothing connected to any of the secondary windings, and measure the various voltages out of them.
If you have an ac ammeter you could place it in series with the primary to measure the ingoing magnetising current which should be quite low.
I will try to measure my two to get an idea of the magnitude.
If all seems OK then instal it or just wire it in on extended leads and check each winding as you go along. A bit long winded I know, but...
Any further problems write them here

John aka Dr John