Transformer Oil Leaks

Hello TomHaRa

You have not advised the size of your transformer, in kVA or MVA, or given a picture of the leaking flange, or position of that flange.

It would be helpful if yyou could do so in your reply.

Large Power Transformers operating temperature generally remains within a small variable area, and there is never much change except for the Winter/Summer variations, which you don't really have at your location.

OK, so what has happened is that the gasket compound used to coat both sides of the cork-type gasket in the transformer has aged, lost elasticity, and thus cracked as it cooled much further than it's normal operating range, allowing transformer oil to seep along the cracks to become a visible leak.

I would urge you to ensure you have replacement gasketing materials to hand, along with proper gasketing compound, withdraw the transformer from service, lower the oil level and clean up the flanges, renew both the gasket and gasket compound, ensuring both sides of the gasket and flange are covered with the compound and that compound allowed to get 'tacky' for the required amount, befor bolting up the flange bolts, in proper order to avoid flange distortion.

Do NOT attempt to re-use the actual gasket, it will be damaged.

I always found that "Heldite" gasket compounds were best and you can locate the Heldite Website here: http://www.heldite.com/html/home.html

Heldite will certainly have a supplier in Malaysia, and you can use the http://www.heldite.com/html/contact_us.html link to locate you nearest supplier.

I have assumed your transformer is a medium-sized unit, weighing between 5 tons to 25 tons, with each of the flange steel thickness/es between 1/4 inch and 1 inch.

Reply here, with

Kind Regards....

Sparks,

I'm not familiar with Heldite, and the website was a little vague. Does this product require any cure time prior to refilling the transformer? Most of the products I've used must completely set before exposure, lest the mineral oil will wash away the compound.

Hello pwr2thepeople

I haven't used Heldite for some 20 years, and do not know if the present formulation of the product is the same.

Prior to that, I used it for almost every gasket seal job - Transformers, car engines, gearboxes, motorcycle engines, and so much more.

The Heldite I used was a dark brown liquid, with quite an aromatic sweet smell, I cannot identify the solvent/s used, and appeared to have finely ground-up mica flakes, which "sparkled in the light", as it was stirred, in the liquid.

It had to be vigorously stirred before application, and for large applications, stirred during use, as the solids sank to the bottom of the liquid, similar to paints with heavy suspended particles.

It was applied via paint brush, in steady strokes, and immediately started to go "tacky".

The gasket flange, both sides of the gasket and the opposing metal flange were all coated and allowed to go "tacky" which was normally between 4 - 6 minutes = 5 minutes was stated on the tin.

Once that occurred, parts were assembled immediately, and bolted up.

The "bolting up order" for large transformers was always carefully chosen, normally diagonally opposites from the central bolts on the long sides, outwards, so flange distortion and gasket movement was minimised.

Square Gasket flanges were started in the central bolt for each side, diagonally opposite, until the last bolt, at each corner, was tightened fully.

Bolts were always re-tightened after an hour, to correct Torque level, before the Transformer was placed into service.

Transformers were up to 70 tons empty weight, before filling with transformer oil.

Gaskets were from 1/32 inch thick in gearboxes, up to 1 inch thick for large transformers with 1 inch thick steel plate flanges.

The original Heldite did the job, every time.

No good for copper Head Gaskets on a car, as temperature sometimes too hot.

Trust that assists you.

Kind Regards....

As Sparky says, BUT one warning!!!

If its an old transformer it may still be filled with PCB a well known carcinogenic oil...

Please take all necessary measure to stop the leaking oil get into the public water supply, of indeed any supply!!!

Get a qualified company to remove and empty the transformer before attempting any form of repair...

John.

PCB is not carcinogenic. It is as close to a completely inert compound as man can create. It reacts with nothing under normal conditions. Unlike oil, askerel & other PCB compounds are heavier than water and will sink to the bottom of any water supply, below well pump suctions or river intakes. The weight of PCB also makes it difficult for the fluid to be sucked into pumps designed for water.

PCB was designed as a non-flammable replacement for mineral oil. Unfortunately, because it is so non-reactive, it tends to decompose, rather than combust, in high temperature conditions. The primary decomposition byproduct is dioxin, which IS highly carcinogenic.

Hello Electroman

Good Point about old transformers.

We never knew about the toxicity of PCB's in the older days, and no precautions were thought needed.

That stuff coated my arms and overalls often in my early days, from transformers, tap-changers, OCB's and more.

Perhaps one reason I contracted Cancer many years later.

Kind Regards....

dear TomHaRa,

I think ur transformer is not properly laminated. If it is laminated well then eddy current and corresponding heating becomes low. I think the leakage can easily eliminated by inserting the transformer to a body that can hold coolant.

Hello Guest,

Sorry to advise you that is the strangest "explanation" I have ever heard of.

Perhaps you are jesting.

Kind Regards....

Dear Mr. TomHARA,

Please check th silicagel breather. It should be clogged enough to build up back pressure to exhale and inhale of air with variation of day night temperature around 10 degree cent. or more in Malaysia

We have observed Pressure relief device operation, Rupturing of OLTC barrier board and at times the transparent body of breather it self

Regards

V S Rathore

Dear Mr. TomHaRa,

Please check silica gel breather. It is clogged probably and apparantly in good condition( Silica gel- Blue in color, because of throttled breathing)

Regards,

VS Rathore

Dear All,

thanks a lot for your supporting respond on this issue. the problem has been solve yesterday. the action taken is only to tighten all the flange and oli valve connection. we found that the screw not tighten enough. but the still has minor leak at one of the flange and suspected the o ring not performing well. the leak criticality also at very low level. we still energize the tranformer and at the same time will moniter the leak. as result for now, the no more leak at the site.

thanks guys.

Hello TomHaRa

Thank you for your reply post, with advice re the cause of the leaking oil.

So often problems are presented on the Forum, mainly by that elusive Poster: "Guest", and we never get any feedback.

So pleased your problem has been solved, without any damaged equipment.

Kind Regards....

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