Before you read my blog………
Since I have retired from the transformer business I thought it might be a good idea to make some of the tools that I developed for myself available to operations people out in the field. One of my most useful tools was my dissolved gas analysis program.
It was used to analyze the test results generated from the gas chromatography test on transformer oil. All of the testing labs will give you a conclusion with the numbers generated from the test but I never had complete faith in their analysis. They never tell you how they reached their conclusion or what method they used. I used all of the major methods and then made decisions based on data from all of the major methods of analysis in use today. What I found most of the time was that inevitably one ore more methods might point to a potential problem while the others ignored it, or said that it was insignificant.
I have rewritten the program to make it easy for you to use and simple to understand. I am making it available to you on CD for Windows compatible computers. With this program you will be reassured that the data you are getting has been thoroughly scrutinized and the judgments that you make concerning the data are sound. Isn’t it always more comfortable to have a second opinion?
Normally tests are performed yearly and with this in your toolbox you can instantly verify any potential problems or normal running equipment.
All you have to do to get your copy is click on the button below. I will send it to you immediately. If you want to order additional copies for people on your staff or at satellite locations quantity discounts do apply.
For not much more than the cost of a test you can have peace of mind. Isn’t that something that can make your job just a tad easier?
Thanks,
Bob
And Now to the current post of my blog…..
Sampling Procedures for Oil Screening Tests Continued…
We are pretty close to being able to draw the oil sample here but I just want to mention a word about PCB contamination. The tech who is doing your sampling should be bringing in clean, PCB free accessories to obtain the oil sample. First of all you should know which transformers have levels of PCB’s and the quantity in parts per million. The tech SHOULD be using new tubing and a siphoning device. They don’t cost very much and will assure that you do not contaminate your equipment further with PCB’s from someone else’s site. I feel that it’s best to set this up when the tech calls you for scheduling. Tell him or her that you expect them to be packing new tubing, siphoning devices and if not new, alt least washed out fittings and nipples to screw into the valves. They can be washed out with an appropriate solvent and your substation escort should check them to verify the fact. Make a route map for the escort and leave all of the transformers that do not have valves and require siphoning for last. Then make a route for them that starts with the lowest level of PCB contamination and ends with the highest. For the larger units that require fittings and nipples, make sure that the tech flushes everything adequately.Most transformers come equipped with standard brass gate valves at the bottom for filtering and draining. That is where the sample should be drawn from. If a tech uses a small sampling port on the side odf a large valve he is just being lazy. To get an accurate sample the main valve should be used. Breaking this down into steps first the technician has to remove the plug in the valve. Normally oil has seeped through and there will be a small amount that runs out from the valve body that should be discarded in a waste oil container. Then the technician will probably screw in a reducer with a ¼ inch nipple attached. The tech must then flush the valve THOROUGHLY. This means at least three times the volume of oil that would fill the valve cavity along with any piping that is attached. This way he is assured that the sample comes out of the tank itself and not the connections between the tank and the valve. Another reason for this is to flush any condensation that could have been deposited in the valve cavity due to temperature changes. It only goes without saying the contained used needs to be clean. After the valve is thoroughly flushed the sample container should be half filled with oil from the valve, shaken and then emptied…twice to assure a clean sample. After that the container needs to be filled, capped tightly, identified, and stored for testing within a few days. Sample containers should be clear or at least translucent. The technician needs to hold the sample up and take a good look at it before putting it away and moving to the next unit. Samples should be allowed to “rest” and settle for at least a few minutes before being stored. Any sediment, free water, or debris observed in the sample dictate that another sample must be taken following all of the above procedures for flushing out the valve. It should be marked as a second sample and stored with the first. This will help to eliminate any questionable data that might be observed with just a single sample. At the end of the day when the samples are allowed to cool they should be checked again for any sediment or free water. If anything is observed and there is no second sample there is always time to go get a second one.
A good tech will clean up and leave the substation spotless, double check that the valve handles are tight, tighten any loose packing nuts and generally leave things looking better than when she or he arrived. You as the owner should take charge of all of the waste oil and waste product. This can prevent any problems that could arise later if someone ends up dumping the waste in the wrong area due to ignorance or negligence. You are legally responsible for the waste. It is more convenient for the technician if you take it as well. Make sure that you get everything. The tubing used and the siphoning device as well. These are inexpensive and the tech should have spares.
If the oil is being shipped to a central lab, check the packaging to make sure that no incidents can occur. You may also want to eyeball the labeling to make sure that it has been properly sealed and marked assuring that none of the samples are mixed up.
Test results should come out to you within two weeks. If it takes any longer than that either the lab is backed up and the samples sat around longer than they should have or the lab is disorganized. Check thae data printed on the sheets and compare it with your escort’s notes carefully. If any problems, other than high acidity/low IFT, are noted check to see whether or not the tech drew another sample. If he/she didn’t, make sure that you ask for a freebie retest for verification. (note: also if the acid/IFT numbers are not close to the previous test result ask for a freebie retest).
I think I have covered almost all of the standard procedures in sampling for oil screen tests. If you have a question regarding any unusual cases (or if you just have a question) please email me at transformerbob@gmail.com.
Please send some feedback and let me know what you would like to be covered in the next post.
Oh Yeah! Don’t forget to order your Dissolved Gas Analysis evaluation CD. I guarantee you it’s well worth it. Just send an email to transformerbob@gmail.com. It’s your decision but remember it’s a small investment for a large tool in your toolboxes. I have already received some very positive comments on it. Just use the shopping cart button at the top of the blog. And Thank you!
Regards,
Bob
Quote of the day:
“An investment in knowledge pays the best interest”
He also said:
“A countryman between two lawyers is like a fish between two cats. “Benjamin Franklin
