Isolation Transformer Giving Abnormal Sound

The cause is ....magnetostriction,

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Something may have worked itself loose or delaminated and it now making the vibration more apparent.

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Your plan to observe should be fine. From what you have stated so far, this isn't something that calls for immediate shutdown.... if probably won't require much beyond inspection when you do have a regularly scheduled maintenance shut down.

This isolation transformer 240V/240V feeding to critical load in our plant (petrochemical), To shutdown the plant is very big decision. but to keep it online also. we have to concern about safety (risk of heat, fire or spark). We have to give clearance if it is safe to keep it online for six month-eight month until our scheduled plant shutdown.

if anybody have same experience or idea will be useful information for us.

Thaks a lot

Plan a short shut down during a weekend, disconnect both incomming and load lines, perform an AC hipot testing at at least twice the rated voltage plus 1000 for 3 seconds, if it's OK, use polyester resin to hold any loose insulator or laminations, check mounting and chassis hardware.

Make sure you're not drawing more 125 Amps. and the transformer is not overheating.

Your dear Guru

There is an alternative to shutdown, but this must only be done by qualified plant electricians under engineering supervision, and only if it is in a non-classified area of the plant.

You could obtain an identical transformer, proper leads, taps, circuit protection, etc., and after ensuring that the polarities on all leads are identical to the existing transformer, connect it in parallel with it, then disconnect the suspect transformer.

I am deliberately leaving out the exact details of how to do this since they are known to qualified personnel experienced with this power level.

For use by properly trained personnel only! Do not try this at home!!!

JUST TURN THE RADIO UP, till you can't hear the noise.

That'll be as good as taking advice from total strangers regarding an unknown, undefined symptom that you cannot characterize adequately.

Your "scheduled shutdown" has gone from two months to six to eight months in two minutes which means to me that you won't do anything until the plant shuts down or blows up.

Get a (PAID) service tech on-site and don't try to get free advice and trouble shooting help from a forum who has no idea of the scope, age, or level of maintenance the equipment has had.

Hire a competent service tech to look at this, or turn the radio up.

'... and don't try to get free advice and trouble shooting help from a forum who has no idea of the scope, age, or level of......'

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That was very nice of you to offer that advice, especially free of charge.

Free advice is worth what you pay for it.

False modesty?

I don't think you would have written it if you didn't think there was some value in writing it.

Noise from transformers might come from loose coils , the steel plates or the frame that holds the steel plates together.

It should be possible with an isolated stick to find out which part is loose.

If it is the coils You can risk an isolation failure to the steel plates, not good.

If it is a single steelplate that swings give it som resin.

If it is the frame , then tighten the 4 bolts that probably holds it all together.

Remember your safety tools. Gloves - shields etc.