Hermetically-Sealed Distribution Transformers

You Can't ....That's the whole point of Hermetically Sealing them...They are sealed.

Sapper

Sealed means - Sealed.

My dear friend u cannot drain out any oil sample for testing, you have to ask for tests conducted by the manufacturer and believe them.

Hello "Guest",

Here is the very brief description which you asked for:

1. Isolate the Transformer
2. Earth HV and LV Connections/cables
3. Disconnect control and monitoring cables- Make all safe
4. Disconnect the Transformer from HV + LV connections
   
5. Disconnect Transformer Chassis/Casing Earth
6. Arrange Transformer shipping back to Maker's Factory
7. Attach Official Order for them to remove & test the oil, then Maker's to replace the extracted oil quantity and reseal the Transformer
   
8. Expect a large Account from the Makers
9. Receive re-sealed Transformer back from Makers
10. Install Transformer in correct location
11. Insulation Test Transformer
12. Connect Transformer Frame/Case Earth
13. Remove Earthing for control and monitoring cables
14. Connect control and monitoring cables
15. Test above (14) for correct function of protection and Discrimination Relays etc
    
16. Connect HV + LV Cables, after Insulation tests - If OK, then (17) below:
    
17. Test Transformer, and if OK, then Step (8) below:
18. Full function check of all systems
    
19. Place back into service
20. Pay the Maker's Invoice

As you may be aware, there are some extra subsidiary steps, and of course you should know those, if you intend to arrange for this work.
Trust you have been assisted.

Kind Regards....

Hi Sparkstation ,

Good advice. I shall request you to kindly add one small point. Let him carry out the job under the supervision of a qualified and licenced electrical engineer and observe all safety rules as this being not the job of an amature.

Regards.

V.I.Abraham

Your Point should, of course, be added to the above.

It is unfortunate I am unable to Edit my earlier post.

from me

For noting that very important extra point.

Kind Regards....

Hi Abraham,

is it possible for Guest to be a qualified and licenced electrical engineer as you said

above by giving some questions in CR4 ? this CR4 useful to add knowledge, isn't it ?

Thank You & best regards

Dear Mr. Guru,

Thanks for your guide lines.However you should have simply advised in one line that send the Tr to vendor. That is exactly I would be doing if I do not receive any proper procedure to take oil sample and fill up the oil for such Trs.

Regards

Hello "Guest",

I did give you the Brief description of procedure you asked for, in my earlier Post.

Please remember with all hermetically sealed transformers that if they are unsealed except in the Maker's factory, or under the direct supervision of the Electrical Engineer of the Makers, your unsealing will breach all Warranties on the transformer.

If you are "unsure" about the transformer, or the quality of the contained oil, best to contact the Makers, and arrange for the unsealing, decanting of oil, and refilling to be done on-site under the direct supervision of the Electrical Engineer as supplied by the Makers.

The Makers would normally make a charge for this, including transport/accommodation etc of the Engineer.

It would be in your own interests and also that of the transformer owners, to contact the Makers and accept their best advice.

After all, they will be hoping that they will sell further equipment to your Location and Company.

In the situation you find yourself in, having suspicions re the oil, it is advisable when decanting oil under the direct supervision of the Maker's Engineer, to also obtain extra oil which can be placed into "clean sterilized sealed after filling" containers, and sent to an independent Testing Laboratory for analysis.

That way, you have independent verification from the Testing Laboratory, in case of a dispute or further action, as necessary.

Kind Regards....

Dear Mr. Guru,

Thanks a lot for guidance/advice.

Regards

What type of hermetically sealed. Is there is a inert gas cushion or fully filled with oil?Normally unless u have had a fault or lightening strike u neeed not resort to sampling the oil

Thanks for the relavent question.

It is fully filled with oil except little space to show the oil level on the oil level glass-cum-pressure switch (but not gass filled). It has air venting as well as oil filling provision at the top cover.( Of course with screwed cap and screwed vent pug). Also a oil drain valve at the bottom of the tank.

Regards

If it has Drain & Fill Points and an Air Vent, It is not by definition Hermetically Sealed.

from your description above it simply an Oil Cooled transformer and any qualified contractor should be able to perform this task for you.

Regards,
Sapper

i want to ask you something i aiready perform maintainance on hermatically sealed transformer . and i will refill the transformer with oil with ou sealing.

note that the transformer cover with bolts and drain valve.

is it right to do so .

Then it in Not Hermetically sealed.....

It is simply an oil filled transformer and the ability to drain and refill it is a simple maintenance task.

If it was hermetically sealed, there would be threaded sealed plugs as they are not designed to be field maintained.

Regards,
Sapper

This is a expandable radiator type without conservator.So as in any transformer you can samples and do the testing Total oil filling ensures no moisture with expansion being accommodated in the radiators.Go ahead

Dear Nesubra,

Thanks a lot for your reply. I think you are correct . I also feel it is radiator expandable type but vendor document says it is hermatically sealed .By the way is it correct that such Trs.also can be named as hermatically sealed?

Why I asked this because after receiving the Tr. we found the oil leaking from radiator welding seems at 2-3 places( small just like dripping small drop by drop).So it is to be repared at site by specialist. We will call for vendor help at site.

Thanks once more for the correct guidance.

Hello again "Guest",

It appears that your transformer is actually not "Hermetically Sealed".

If this is so, then the Makers have misled you.

If the transformer is new, then the repairs are the Maker's responsibility, along with any damages accordingly.

You have yet to advise of the transformer size, but if there are places of "defective radiator welding in 2-3 places", you are within your rights to insist the Maker replace the faulty radiator/s at their expense using their own Engineer to do the job on-site.

Extra costs involved would include Out-of-Service costs, plus others costs as appropriate.

Ensure you receive a "New Warranty" from the Engineer, when he/she has completed the replacement/refill/test/reconnection.

Kind Regards....

.

Sparkstation,

can we prosecute The Maker That have mislead a company by Law Track ?

because we have Consumer Protection Law.

Thank You

Yes it is considered as hermetically sealed transformers.It is not a misnomer.I have seen and handled many such transformer which offer space saving.Wilson transformers of Australia have Joint venture in Malaysia and they make these kinds of transformers.The radiator fins form a part of the tank and can expend to accommodate oil expansion as there are no conservators.It has a pressure relief device and is filled to top with oil and top is bolted.You can take oil samples but ensure to top it up to level

Dear Nesubra,

Thanks a lot once again for such a vital and correct information.

Hope to get more help/information exchange of knowledge etc... henceforth from such a professional like you and keep in touch with you through this wonderfull forum.

Regards

Yes sir .It is heremetically sealed .It will have pressure relese valve also .Pl check.If radiator is leaking it is better to replace with a new one and manufacturers rep. should do it.It is possible in transit and handling some minor damg age might have occured.But when it is loaded the oil expands and expansion is accomadated in the fins .if it is leaking then u will have oil gushing out.So ensure leaks are arested before energising.Several of this type I have seen in Malaysia and Thailand.Wilson malaysia makes them.You can peruse lot of web sites for more details

have a good day, gentlemen

want to continue this topic. even after brilliant answer on the beginning I still have a doubt about getting sample from hermetic Trafo. - for example into manual of Pauwels International NV it is mentioned tt "oil sample may be drawn and send for testing" ones in 5 years- as per maintenance schedule.

is there any clear explanation - standard, norm or something like ?

If it is a hermetically sealed transformer it is not a conservator type unit. The transformer is filled with oil up to the top cover and it has a buchholtz relay, a pressure relief valve, a level indicator and usually with no drain valve. A transformer with conservator is not a hermetically sealed transformer. A hermetically sealed transformer is by design of the radiator and the hermetic materials used for sealing. Please read hermetically sealed transformer in the google web.

Boy Medellin

This is a type of hermetically sealed transformer and I have handled them. as I said it is not necessary to take samples as we don normal transformer.