Total acid number tests

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Hi,
I am looking for information on total acid number tests for transformer insulation oils. I am a novice to this so all information is welcome.
Firstly what colour indicators are used for ASTM D974 and D1534 TAN measurement. I have read that these colour titrations are difficult to read for dark oils. Are the solutions to overcome this difficult.
These are labour intensive so is there any simple indicator system like a litmus type indicator out there which could be used to give total acid number or am i just confusing pH with TAN if so how different are they as a corrosive test and could you measure pH to give an accurate indicator as to the corrosiveness/acidity of transformer oil.
I have been looking at FTIR methods for measureing TAN how reliable are these compared to the titration method in anyones experience.
I have also read research on experiments using VIS-Near Infra red spectroscopy to try and obtain TAN.Similar to FTIR but using cheaper optical components to try and measure the weaker absorpption bands.I have my doubts about it as to why there isnt a commercial product out there yet if it was actually possible. Has anyone looked at this method, is there any merit to it and any supplier of such a system which i may not have seen?
Thanks for any info on either of my long winded questions.

6/10/089:24 AM

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rogerdaviesMember

Testing of transformer oil, electrical oil is normally subject to some structure.
For example in the UK testing methods are stipulated and a British standard exists for tests to be conducted and includes some rejection limits (BS 5730) .Similar standards exist in Europe.
Classic methods are employed and currently little or no use for FTIR.

6/11/088:15 AM

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renewaMember

TRANS,

TAN is measuring the weak organic acid concentration by titrating against a known concentration of standard alkali (caustic)such as KOH - it's normally a weak caboxlyic acid that is in the oil. pH measures the acidity which is different to TAN measuring the concentration of the weak acid species and what you are doing is monitoring the increase in these acidic by products. It's due to the acidic by products laying sludge and varnish which can block oil ways and reduce the cooling effect of the oil. It can also damage celluose material. The oxidation by products can also conduct electrical charge so reducing the insulating properties of the transformer oil.

I have come across both ASTM D664 and D974 to measure TAN. I am not familiar with any quick test kits. Given when a transformer goes, the downtime can be lengthy with expensive repairs, transformer oil condition monitoring is vital.

The FTIR does not measure the TAN, it uses a complex mathematical model (algorithms) to predict the TAN. From my understanding, there are only recent movements towards using FTIR to predict the TAN - so not many labs are doing it as it's labour intensive in setting up the models. It's very important to ensure that the correct chemical models are used to predict the TAN.

Most commercial labs do offer a range of test suites to test transformer oil. You best solution will be to use a reputable lab preferably one that routinely does transformer oil analysis.

6/15/089:00 PM

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micbialMember

I have used both of Dexsil Corp's test kits (TBN and TAN)over the years and alway's had great success with them. By the time you get to the final reading the original opaqueness of the oil is gone, having been filtered out earlier in the test process. Quoted from the TAN test kit description "Oil color will not interfere with the test because the colorimetric end point is carried out in the aqueous phase."

As stated above the best solution is to use a reputable lab. However for expedient field test the Dexsil test kit's can't be beat.

Information about Dexsil Corp. can be found right here on Noria's website. http://www.noria.com/buyersguide/dexsil.asp Here's a link to Dexsil Corp's site with links for both the TBN and TAN test kits as well as their HydroScout moisture test kit. http://www.dexsil.com/products/detail.php?family_id=4&a...t.y=10&submit=Search

6/20/0810:08 PM

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