Corrosion Transformer

[brookster]

I have to look at an 11KV/415V transformer with an reported leak due to corrosion - bear in mind I have not seen the transformer but should be at some point tomorrow.
My initial thought on this are if corrosion has set in to this sort of level where leaks are becoming present the best thing to do would be to replace the transformer, any repairs would be temporary at best and would not be advisable in the med-to long term? can anyone tell me if such a repair would be a good course of action it's something I have never seen done.
Also to maintain the site power a generator will need to be installed to be run as a temp measure until works can be completed to replace the 220KVA transformer.
I cannot yet provide any more info on the level of corrosion will update hopefully tomorrow.

 

[Engineer54]

I have to look at an 11KV/415V transformer with an reported leak due to corrosion - bear in mind I have not seen the transformer but should be at some point tomorrow.
My initial thought on this are if corrosion has set in to this sort of level where leaks are becoming present the best thing to do would be to replace the transformer, any repairs would be temporary at best and would not be advisable in the med-to long term? can anyone tell me if such a repair would be a good course of action it's something I have never seen done.
Also to maintain the site power a generator will need to be installed to be run as a temp measure until works can be completed to replace the 220KVA transformer.
I cannot yet provide any more info on the level of corrosion will update hopefully tomorrow.

Depends where the corrosion and leak is. Best you take a look first and maybe post a photo or two. Yes repairs can and often do get made to transformer casings etc, the type/method of repair being based on the material involved. I've had a brand new 1.6MVA TX tank given weld repairs made on site, after being dropped by a fork lift driver...

At just 220KVA it's a bit of a baby, i guess it depends on just how bad the corrosion and the leak is, whether or not it's past it's useful life or not. The thing is, if oil is leaking out in any quantity, air and moisture could be getting in and contaminating the insulating oil. So maybe worth giving a sample of oil a breakdown test.

 

[Knobhead]

Without seeing it, it’s impossible to say.
Usual suspect points are the radiators and cable boxes. I can recommend a specialist repair company if you want. (Sorry wont mention them in open forum.)

 

[brookster]

An update for those who are interested,

Couldn't get the keys to the cage (AP on hols) but the transformer is in an absolute nic, according to reports today maintenance has not been done on it for over 30 years! I can only imagine what the oil inside is like acidity wise haha! Probably eating it inside out.



Leak is actually coming from the bottom of the tank, oil level is probably got 1.5-2 inches before it hits the actual transformer. So very dangerous times indeed.
It needs a new tranny will update more later sorry I couldn't get better pictures but I am more bothered about that than you

The whole area is a bunded area so no worries that way chaps, I'm sure you can also see there is NO oil in the sight glass!

I was agitated so I didn't take more pics but right round it spots of rust are everywhere.

 

[Jamzie]

Wow, she's a small 'un! Is the weep coming from the bottom of the tank adjacent to the radiator? Is it not possible to weld up?. Only seen a repair like this done the once, but a repair was far easier than disturbing the old paper lead cable that was attached to it. Although ensuring the inside was dry, so not a fire risk, whilst preventing the transformer from drying out was another issue...!

The oil, if as old as suggested will probably contain PCB's. Something to consider when mopping up.

Tony will be on later, about 0100-01300 hrs usually. He'll give his expert opion.

 

[brookster]

The leak is actually coming from right under the bottom, agree PCB's are highly probable.
It's not getting repaired its getting replaced.If cables need done they will get replaced too!
You can't really see from that pic but trust me it's not pretty.

 

[Knobhead]

Despite the rumours PCB’s aren’t that common in transformers. Normally found in power capacitors. Get a specialist in to check, not expensive. Less than £100 as of last week.

Regarding the leak, re-welding tanks is quite common if you get the right company, back flushing the tank would depend on the oil sample results.

Repair or replacement is up to the customer. It’s a baby, but 250KVA are 2[SUP]nd[/SUP] user stock items if you know where to look.

Top the oil up to give you the time to make a reasoned decision. I’ve had to keep a leaking transformer going for nine months before we could take it out of service. 3.3KV bushing leaking around the cable box.

The down side with this one is it doesn’t have conservator to make topping up easy.

 

[brookster]

Despite the rumours PCB’s aren’t that common in transformers. Normally found in power capacitors. Get a specialist in to check, not expensive. Less than £100 as of last week.

Regarding the leak, re-welding tanks is quite common if you get the right company, back flushing the tank would depend on the oil sample results.

Repair or replacement is up to the customer. It’s a baby, but 250KVA are 2[SUP]nd[/SUP] user stock items if you know where to look.

Top the oil up to give you the time to make a reasoned decision. I’ve had to keep a leaking transformer going for nine months before we could take it out of service. 3.3KV bushing leaking around the cable box.

The down side with this one is it doesn’t have conservator to make topping up easy.

The worrying thing is that the oil has not been changed in over 30 years, there is a whole lot of trannys being replaced over the coming years just so happens this one went ---- up.

 

[Engineer54]

The worrying thing is that the oil has not been changed in over 30 years, there is a whole lot of trannys being replaced over the coming years just so happens this one went ---- up.

As the oil is in a sealed environment, it shouldn't ever need changing, not unless there has been some internal fault or moisture has managed to enter and contaminate the oil. Typically every TX should be inspected regularly and oil samples taken to confirm it's insulation properties are within specification with no particles in suspension. How this TX has got to a point where oil levels are so low, it's not registering on the sight glass, means that it has been neglected for a very long time.

Don't be too bothered about rust spots, the tank and cooling pipes are thicker than you may think. Leaks are more likely to be found at bushings and at points of failed poorly made welds...

What do you mean, by this TX going ''---- up'' ??

 

[grantr37]

ok, I wouldn't touch that, now there is a company that makes a pot of epoxy stuff (about 50 pounds for 1Kg) that is a temporary patch intended for sort of up to 4 weeks service, it is not permanent and is really only to close off leaks until the thing gets removed.......this transformer looks to me to be from around 1955....don't let the paint fool you, they put lead, cadmium , arsenic and a few other chemicals in there so that it would look like that for 100 years, paint that is banned since about 1990..

This will have PCB's in it (Polychlorinated ByPhenals) which are a nasty long effect damaging poison, and should not be disturbed....what will need to happen is that the Electricity supply company will need to kill it with an axe, then kill it again just to make sure.....and a specialist chemical company will need to have the whole thing away and turf it into a blazing hot metal furnace, the gravel and the concrete around th base will need carting away as well to be chemically washed then disposed of legally.....

This Transformer is (due to the leak) going to cost about 50,000 pounds to get rid of, I don't think the sorbant sheets under it are doing much good...wouldn't touch it as it is a chemical waste issue, and it is a level of contamination that can lead to all sorts of issues, up to jail level...

I have seen a contractor fined 25,000pounds for spilling about 1 litre of oil, and that was after grabbing the phone and calling the environment agency within minutes, and doing everything they could to clean it up....there was a specialist contractor there after that to clean up and they were there for 2 weeks, testing soil and water nearby etc as well.....that had to be paid for too and apparently more than wiped out the whole value of their contract...so be warned...

 

[Knobhead]

I know of transformers installed in the 30’s sill in use today. They were babies at only 250KVA, no conservators or silica breathers fitted. I can only remember one having the oil filtered.

 

[Knobhead]

This will have PCB's in it (Polychlorinated ByPhenals) which are a nasty long effect damaging poison, and should not be disturbed....what will need to happen is that the Electricity supply company will need to kill it with an axe, then kill it again just to make sure.....and a specialist chemical company will need to have the whole thing away and turf it into a blazing hot metal furnace

Just what the job needs, a scare monger. How can you say it contains PCB’s without testing.

As for the disposal of PCB’s, steel works wouldn’t touch it. It mainly gets used as a fuel for cement kilns. Higher temperatures and high volatile gas flows with secondary combustion. The kiln also operates under negative pressure so air can only be drawn in and not under the positive pressure of a furnace with a slow moving burden where the gases can be expelled.

 

[grantr37]

the oldest transformer I remember seeing, was removed about 3 years ago, dated to about 1905, it was still live but the load had been removed/demolished back in the 1970's, the power company had it away when they were in the area re-poling.....

I am going to a place today or tomorrow possibly which has 80 year old power lines going for a distance of about 10 miles, chopped at both ends and just going from a to b with the village they used to power gone since just after the war.....I may take some photos of some of them if I get up there...I actually think they are so old that they are solid copper...the whole lot is bright green....

 

[Bobster]

Just what the job needs, a scare monger. How can you say it contains PCB’s without testing.

As for the disposal of PCB’s, steel works wouldn’t touch it. It mainly gets used as a fuel for cement kilns. Higher temperatures and high volatile gas flows with secondary combustion. The kiln also operates under negative pressure so air can only be drawn in and not under the positive pressure of a furnace with a slow moving burden where the gases can be expelled.

Most cement kilns are becoming waste disposal units with a byproduct of clinker nowadays.

 

[Engineer54]

I'm with Tony here, extremely unlikely that this TX contains PCB's. Relatively very few transformers were insulated with PCB's and i have personally never come across one myself!! For someone that's so jittery being around MV, makes me wonder what your doing in such work place environments?? lol!!


Decently manufactured transformer can have an unlimited lifespan, certainly measured in scores of years, provided it's maintained and it's not worked hard at the top end of it's rating for long periods etc. Most they would need is maybe a nitrogen top-up (depending on it's design) now and again and maybe an oil exchange in it's lifetime.... One of the most reliable electrical components ever made!!