Transformer oil leaks, How to repair it ? 5

[sparky1976]

Guys,
I have 6 transformers each about 60 MW leaking. all transformer below 5 years old. and all leaks from flanges gasket. I already contact the XFMR manufacturer and no good answer.
I read on some papers that to fix leaks thats not big just use coumpound like glue around the gaskets,
Can anyone advise me with brand, manufacturer or web adresses, adhesives that works on fixing oil leaks ?

thanks
Pitat

 

[electricpete]

We have successfully used a product called Devcon.

 

[wbd]

What flanges are you referring to, bushing? If bushing, I would look at was it installed properly in the field. Have you tried tightening the flange bolts to the proper torque spec? Is the gasket material correct for the application, ie is there heating going on that exceeds the temperature rating?

For a txf leak repair kit, use a product by ITW/Devcon. They make a complete kit called a Leak Repair Kit, Stock #DE120. ITW Devcon is in Danvers, MA and the Technical Service phone number is 1-800-933-8266.

wbd

 

[SphincterBoy]

Not so fast. I think 'Yamin" wants to repair the leaky
gaskets by putting an oil additive into the oil, w/o
shutting down or draining the transformer (i.e.--a quick fix).

I checked on Devcon, and it is an adhesive to place on the
transformer gaskets, assuming the transformer is out of service and drained. I would never compromise the integrety of the winding insulation with an 'oil additive'.

For all practical purposes, you'll have to take the
transformer out of service, and have it sent to a repair
facility to have new gaskets put on.

Our specifications are pretty stringent, and we can usually
award a bid contract to only the best manufacturers.

In U.S., the best (manufacturer) is Waukesha Electric Systems (Five year warranty).

Five years is pathetic. Normally, we expect new substation
transformers to go for 20-30 years w/o major fixes.

 

[electricpete]

In our use of Devcon we applied it with transformer in service. The leak was at the bottom of the cooler, where tubes penetrate the tube sheet. We put the liquid gook into the accessible areas from the back (suction) side of the cooler and it flowed around the tubes and then hardened later. A flange would be more challenging geometry to hold the gook in place while it sets... but I have heard it can be done. The product is thick enough that I don't think very much can possibly get through small leak holes into the transformer oil (although I agree it's a calculated risk).

 

[sparky1976]

Guys,
We like to repair without drain the XFMR but we can afford to shutdown the XFMR.
Another question, if I drain the transformer should I purify the oil before I put back into the XFMR ? (the risk of moisture content above the permitted level)

 

[SphincterBoy]

If you are going to shutdown the transformer, then
you should go ahead a replace the gaskets, especially if the cooling fins are leaking.

The external patch 'dope' is less desireable than replacing the gaskets.

When we replace or add oil to our transformers, we always
filter the oil first.

The oil should really be drained in a factory setting, and
ideally, it should be done under very dry conditions, to
reduce moisture absorption by the cellulose insulation.

I heard a report where a utility received a new transformer from Virginia Transformer, in which the semi driver reported that the factory had to drain the oil from
the tank, in order to make the unit light enough to lift
onto the semi bed, then re-filled with oil. The utility
rejected the transformer when they heard this, for the reason the insulation may have been compromised during the time there was no oil in the tank.

If you can, try to keep the tank filled with oil, and
close the isolation valves on the cooling fins before remove the fins.

Can you tell me the manufacturer of your crappy transformer? I would like to report this to another
utility, so as we can avoid buying their product.

I have traveled to the factories several times to witness impulse tests, and perform my own mini QC check, before
OKing the unit for shipping. The manufacturers can be pretty sloppy anymore. You would be amazed at the crap I see.

 

[SMLD]

We had a leak on an inlet fin of one of our 24mW station xfmrs 5 years ago. A service company called United Power Group(UPG) located in Brockton MA, actually pulled a vacuum on the xfmr and repaired the leak, filtered the oil, and performed a disolved gas analysis. This was all done in the field with the xfmr taken out of service.

 

[sparky1976]

I agree to Sphincterboy Change the gasket is more preferable, but Guys I live/work for A Power Plant In a very remote island in a third world, near the equator line and ambient temperature is about 33 to 36 degree celcius.(to have internet line here is a miracle).
Without load My Xfmr on midday sunshine the temperature reach 55 degree C.
To get a Purifier company on site would be very expensive, compare to try first with "patch dope".
If Patch dope donot work, I have to change the gaskets,Now My XFMR have "Granulated cork bonded with medium nitrile butadiene rubber" gaskets. I believe this kind of gasket is for flat of flat surface, and if i want to change the gasket to more temperature proof like Viton is that acceptable ?
Does anyone have experience with XFMR with Viton Gasket ?
wbd, I cant find stock # DE120 on Devcon web site,
Sphincterboy I can tell you the manucfaqcturer name here, but When I try to get their service engineer on site to see and resolve the problem, I said will pay for the engineer and ask them to name the price, they said no, we donot want to come to site. I like the word crappy.

 

[electricpete]

SMLD - pulled a vacuum on the transfomrer and opened an [unisolable?] flange without taking it out of service? I have heard stories about putting just enough vacuum over the oil to prevent oil from coming out when the flange is opened up. Is that what they did?

(it sounds totally whacko to me.... if the bubbles coming out of solution don't get you the bubbles coming from the open flange will)

 

[SphincterBoy]

Yamin, it looks like you're stuck.

As I see it:

1. You cannot get service from the manufacturer.
2. You cannot drain the transformer (too humid/hot).
3. You cannot afford to hire repair services.

You most likely have to apply the external sealant.

You should call the Devcon telephone number, if the stock number is not listed on the Devcon website. At any rate, get the stuff! You may have to repeatedly apply the dope, to keep everything kosher.

If you insist/want to change gaskets w/o draining the tank,
then focus on the radiator gaskets, and top primary/secondary gaskets. Make certain no rain water (a tent?) comes in through the top bushing holes. The bushings should have draw leads.

You should (gasp) plan on purchasing a replacement unit
right away, since leaky gaskets might not be the only part/item wrong with the transformer. If you need specifications, I can e-mail you some fairly decent specs., which will get you, in all probability, a Waukesha Electric System transformer. Also, you should reserve a factory visit, to witness testing. A thought: you
might contact Waukesha Electric Systems at 1-800-835-2732
to discuss your issue with them, to see if they may be able to help.

I am very sorry for your situation. I wish ANSI would
raise their standards to cover such issues as warranties and service, and manufacturing standards. As I see it, ANSI is bare minimum, to allow even the worst manufacturers
to squeak by.

 

[wbd]

Yamin,
I called Devcon and they still make that repair kit, stock #DE120. They said they do not have all their products on the website. Use the website to find a distributor near you.

I have drained txf's down to make repairs and then had a oil processor onsite to hot oil clean, draw vacuum, dry out transformer and re-fill with no adverse affects.

I have used Viton to replace cork/Buna N gaskets. You need to find the right grade of Viton for your temperatures. I would change your txf spec to make sure the manufacturer uses Viton gaskets for high temp areas or if it is a silicone filled txf.

good luck
wbd

 

[SphincterBoy]

WBD,

Thanks for the info. on Viton. I am changing my
transformer specifications for Viton gaskets right
away.

Thanks!

 

[sparky1976]

WBD and Sphincterboy thanks for your helpful post,
I'm going to buy Devcon product.
If both of you have spec or table of gaskets including viton please send the information to me ledig18@yahoo.com.

again thanks for your helpful post.

Regards
Yamin

 

[prc]

Transformer leaks are a mess itself!
Let us look at the Devcon product.These are basically quick setting epoxy compounds which fills the gasket space or the crevices in gasket so that oil sealing is achieved.But its efficacy is limited and is only a temporary solution.Most important in its application is that oil leak has to be stopped temporarily during the glue application.If the leak is not profuse,you can achieve this by creating a vacuum over the conservator top (check whether the conservator can with stand vacuum!) Otherwise you have to drain oil. Then there is the option of gasket replacement .Then wipe off oil from leaking points ,clean the area and apply the sealant as per the combination recommended by the manufacturer.Release vacuum after the setting time furnished by the maker.
In transformers different types of gaskets are used.All are quiet effective ,provided material of proper specifications is used and flange surfaces are properly designed and suitable limitators or grooves are provided to avoid overcompression and setting of gasket/oil seal.Agood designer will normally take care of all these and leak proof trfs can be easily achieved.

1) Gaskets. These are of rectangular section 1/4 or 3/8 inch thickness and of width 10-25 mm effective width(width helping the leak)Most commonly used gasket is of cork -rubber
(made of nitrile rubber and cork granules 50:50 ratio)Compression is to be limited to 30-40% by metal limiters or grooves in the flange.This is quite adequate to a temp of 90-100 degree centigrade.Where higher temp is expected (bottom of high current bushings)synthetic rubber gaskets -silicon rubber or viton is preferred.Viton is also used where ambient temp is below minus 20 degree centigrade or when silicon oil is used.
When rubber gaskets are used ,instead of rectangular section,circular (O-rings) or chords are also used.

Find out which type is used in the leaky trf and evolve replacement strategy.One easy way is to use 10mm thick 15 mm wide viton gaskets,even though costly.In Indian subcontinent viton costs nearly 7 times more than nitrile rubber. Dont forget to apply rubber sealing paste over the gasket surface.
There is absolutely no need for specifying viton sealings for trfs as cork -rubber or nitrile rubber gaskets are quite effective for the purpose and proved their worth for the last several decades.

 

[electricpete]

Once again a mention of drawing vacuum on top of oil (prc).

I was always taught this was strictly forbidden. The danger would be that gases start to come out of solution during the vacuum. If you don't drain and refill under vacuum, it's tough to assure yourself there are no residual bubbles within the windings.

It may be an overblown fear, but it was the stict practice of a large utility that I used to work for.

 

[sparky1976]

Guys,
Before prc post I got the impression from Electricpete post that devcon can be applied on oily surface or not stopping the leak or drain the transformer.

 

[prc]

elecricpete's learning was correct-normally vaccum pulling over oil level in a trf should be avoided,for fear of gas bubble sticking in to windings.But when there is a leak rectification (eg welding leak)this is the only solution known to me.But we must give a settling time of atleast 24 hours before energising the trf so as to get the bubbles dissolved in to oil.
There are products that claim application in the oily condition itself-but I have no experience and also compatibility with trf oil is to be checked.If some body can try,well and good.One such claim-

http://www.durmetal.com

Durmetal AG ,Switzerland

 

[sparky1976]

Anyone have experience with Durmetal ?

 

[wbd]

A note of caution on welding to repair a leak - make sure to have a inert gas (nitrogen) in the gas space. I would have a bottle connected to maintain the gas and also probably do a couple of gas space purges with N2 prior to welding to ensure any explosive gases have been removed.