PCB Filled Transformers 5

[nasmith]

The plant that I work at has several PCB transformers that we are planning to replace or retro-fill. I have heard some sketchy things about Retro-filling that make me question the process and end results.

I’m wondering what information or practical experience others have had with retro-filling?

More General Info that might be important:
The replaced X-fmrs are dry type.
Most transformers that need replacing are 6.9kV Y to 480V Delta (KW vary)
Some are in hard to reach locations.
Most transformers are in continual use.
Some are in pretty nice climates, but most are operated in a harsh temperature environment (100 + F).
All the transformers are about 20 years of age.

Thanks,
nasmith

 

[busbar]

In most cases, resolution depends a lot on region, site process, potential to public exposure, transformer operating status, vessel condition and concentration in insulating fluid.

One reference is

http://www.epa.gov/opptintr/pcb/

Contracting with a specialized service firm may be a cost-effective approach. Regulatory aspects have sort of “leveled off” in the last two decades but are still quite complex to the uninitiated.

 

[stevenal]

http://www.sdmyers.com/frameset.pcgi?fm_dir=2&fm_content=pcb_reclaim

 

[DanDel]

Retrofilling PCB transformers is not quite the end of the story, since the core insulation material (typically paper)is still saturated with PCBs. This is one of the reasons why regulations require frequent re-testing of PCB transformers and retrofilled units, since the PCB levels tend to increase again over time after the retrofill. Requirements and regulations for PCB contaminated equipment will never become less stringent, and there is some noise about them becoming more.
Replace them while it is still your choice.

 

[gordonl]

It is generally very difficult to impossible to retro-fill a PCB transformer. Once the oil isreplaced/filtered PCB will leach out of the core and coil to concentrations higher than allowable limits. It could take multiple retro-fills over several years, and the end result will always be a PCB contaminated transformer at best.

If the transformers are only contaminated, (ie mineral oil that was contaminated at some time) then retro filling is very economical, but still may take a couple of runs to get it below contaminated levels depending on level of contamination.

I would also suggest looking at Silicone or R-Temp filled transformers as replacements vs. dry type, they are generally cheaper and smaller, and less sensitive to enviromental conditions.

 

[jbartos]

Suggestion: Visit

http://www.nttworldwide.com/tech2308.htm

for PCB Dilemma

 

[nasmith]

I appreciate all the answers that I have received. I will look into other oil filled transformers for replacements and will ask our purchasing group why I haven’t heard that option mentioned. I’ll also talk to the person who had my job years before me about using other oil filled transformers as a replacement. And I’ll email our Environmental Engineers about the other oil filled, and see what they say.

Let me give some more information:
• Because of whom the company is owned by and because of what the generation plant is the goal for PCB reduction per transformer is less than 2 ppm.
• We have two other generating plants similar to the one I work at that have both have had PCB replacements (we have not). One done years ago and one done recently. The one done years ago has probably leached out above the PCB limit, since they no longer test the transformer oil I have no way of knowing. The one done recently was attached to the leaching device for a longer period of time (years). I have calls into my counter parts at both plants, but like the rest of the world, they are covered up and haven’t responded yet.
• Interesting enough the group we have been dealing with is not the website by Stevenal, and I was under the impression the company we are dealing with was the only company in the business. I’ll also ask our purchasing group if we have looked at SDMyers.
• I’ve been told by our design group and others that retro-filling will degrade our transformers, shorten the life, and will decrease the load our transformers can handle.

Please keep the comments coming, and if anyone has had a transformer retro-filled, I’d love to hear from you…

 

[gordonl]

Generally transformers that are retrofilled don't use mineral oil because of the fire hazzards. (That's why PCB was used in the first place) The replacement oils that have to be used have different properties (viscosity, heat transfer, lubrication for moving internal parts) so an evaluation of the transformer has to be done, and a reduction in rating may be required. With a limit of 2ppm I don't think you'll ever get there with retrofilling. But get samples from your other sites, then the truth will be seen.

See the follwing links:

http://www.cooperpower.com/library/pdf/92006.pdf

http://www.dowcorning.com/content/power/powerfire/default.asp

http://www.ecmweb.com/ar/electric_analyzing_transformer_insulating/

http://www.ec.gc.ca/pcb/eng/pub_e3.htm

 

[rlpuck]

Several things to consider about doing a retrofil, the "cleaning" agent, or interm fluid used for retrofil is perchlorethane?(or etylene cant remember)this is the same basic thing as dry cleaning fluid used by the dry cleaners. However this fluid is a hazardous wasted and special care needs to be taken while using this fluid, if a leak developes in a transformer with this fluid it will evaporate and your transformer can evaporate the liquid level down to a dangerous level. This fluid is non-combustible fluid and better heat transfer charateritics then PCB so that is good, it can be kept as a final fluid, but again it is a hazadous waste and subject to a whole other group of enviro laws. The final clean up success depends on the about of wood that is in the unit, PCBs leach out of the wood at a much slower rate then the paper of the winding. The final fluid if not percholr is often Silicon, the concerns with this fluid is that it is not as good at heat transfer and you will have to derate your unit, if it runs near full load this may not be an option. Also silicon is extremely hard to prevent from leaking, you must regasket a retrofill unit and using viton gasketing material. I would seriously consider replacement and not retrofil unless replacement is not an option. You should check out the cast coil design as a replacement.

 

[pablo02]

We decided to replace all of our PCB power transformers in the mid-1980's over 3 budget years and paid the money against the wishes of those who thought retrofil was the way to go.. we merged in the mid-90's with the neighboring utility who retro-filled -- several of the large transfomers kept leaching PCB's and they were retrofilled several times over a period of years trying to keep them below the contaiminated limit (50 ppm ?)-- got reassigned to a plant where the insurance company made us resample the retrofilled units -- samples came back at slightly over 500 ppm (?) -- as if they were never retrofilled....

I think replacing the transformers is the way to go -- a couple of items to check: a) if you retrofil, check the level of PCB's immediately after retrofil by an independent lab for acceptance (or as a double check) even though the retrofiller is a well known, establihed firm that will analyze the stuff [yeah, right -- if they know they'll be audited, you'll get a better job done]... b) check on viability of silicon, I've heard rumor that it (won't breakdown and) is being treated as hazardous also (our recycler wouldn't touch a silicon filled transformer)
c) if you select a dry type, make sure the environment it sits in is not detrimental to the insulating qualities of the transformer AND check the impedance of the proposed transformer -- those quoted to us were significantly different from the oil-filled