Hermetically Sealed Transformers

Well it all depends on ones point of view and just a little more information. Was this transformer hermetically sealed for operation or shipping? This will determine if you once had a problem or that you now have a problem. The good news is that you are doing maintenance. This implies two critical things here. First, regardless of either state you were in, you got away with operating it and not knowing if it should or should not be sealed. Second, doing maintenance implies that you have a maintenance procedure to follow that either came from your management or the transformer manufacturer. Follow this procedure to answer your question. If you don't have a maintenance procedure I offer this troubleshooting flow chart as a guide.

Image from

http://1heckofaguy.com/2006/09/24/troubleshooting-flow-chart-1/

In lieu of the instructions that might be found in the operators manual, red's flow chart is widely used in some industries.

Any reputable manufacturer will include operation and maintenance instructions with their equipment, and have a tech available to answer questions from their customers.

Any competent maintenance engineer will have these documents on file in their office and at the machine, if regular maintenance is required. Transformers should have such instructions also.

My advice is:

1. Read the manual

2. Read the manual again

3. If you don't understand the manual, call the supplier of the transformer.

And finally, Why was it hermetically sealed in the first place?

First of all why do you need to open up the hermetically seal transformer?

Second..What type of maintenance that you need to perform inside the hermetically seal transformer?.

If the transformer is working properly without any problem, the hermetically seal transformer should not be open up as there is no maintenance required inside the transformer.

I have aiready opened a hermatically sealed Transformer and perform the required Maintainance but I want to refill the transformer With oil with out sealing is there any problem for that

As long as you don't energize the transformer (what ever size it is) before preforming any of the required procedures to remove moisture and air that may have built up in both the oil and transformer it will be fine, if not then don't be surprised if the transformer fails prematurely.

You use the word "I" implying you were tasked with performing the maintenance, if you are not qualified AND you don't follow the manufactures's (and electrical standards) requirmements you will void any warrenty and may cause property damage.

What I mean that I will treat hermatically sealed transformer like Any other transformer of course I will remove moisture from the coils and Performe vacuuming for air remove is there Any other steps done specially on hermatically sealed transformers

Without more information on the transformer it is hard to say.

You need to consult the transformer manufacturer and supplied documentation least you void the transformer warranty.