Dissolved Gas Analysis-Gas Chromatography - Part 2

Now that we have extracted the sample of gas from the oil it must be injected into the chromatograph for analysis and identification of the gases. Gas chromatography machines use tubes packed with special material to separate the gases. These tubes are called columns. Columns come in varying lengths packed with varying materials depending on exactly what you’re looking for. You can’t just inject your gases into any old chromatograph and expect it to tell you what’s in the sample.  The column is in the “oven “section of the machine and it’s heated to a specified temperature. This allows the gases to expand and stratify within the tube.

After a period of time long enough for the gases to separate and stratify they are “pushed” through the tube with an inert gas (usually argon) and then burned at the end of the line.

The chromatograph prints out a line graph corresponding to temperature and time. It looks sort of like a pencil line drawing of a series of mountains.  Looking at time on the bottom horizontal axis tells you what gas you’re looking at (remember they stratified or layered and came out in a certain order). When you calculate the area under the peak you can evaluate the percentage of that particular gas.  Now all that remains is to translate all of that data into parts per million of dissolved gas in the sample using the total amount of oil used along with the amount of gas extracted. That part is simple math.

All of the above is chemistry and can be performed by any qualified technician. The real art is interpreting the results. This requires usage of several different methods of evaluation along with a good field knowledge of the equipment and other reasoning skills.

I like to use Rogers Ratio, Sacramento State, Dornenberg Ratios, Key Gas and any other method available to come up with then verify my conclusions. No one method works best or all of the time.  Conclusions need to be determined by gathering as much onsite physical data and equipment history as possible. In many cases when a problem is discovered it is only a snapshot.  Another snapshot (test) should be performed at a later date to verify the problem and the extent of it.  That could be as soon as a week or as long as six months depending on the problem.  

That’s all for today.

Please write or comment on any subjects that may interest you for further postings.

Thank you,

Bob

Today’s quote is from  Billy Connoly

"My definition of an intellectual is someone who can listen to the William Tell Overture without thinking of the Lone Ranger."

Dissolved Gas Analysis-Gas Chromatography

Dissolved Gas Analysis-Gas Chromatography

Gas Chromatography is always an interesting topic to write on. There is so much technology involved from sampling, to extracting and testing and analyzing it can fill volumes. 

I have gone over some sampling procedures in earlier posts so here I will only mention that the sample has to be obtained carefully and it’s a good idea to never let it be exposed directly to the atmosphere.

Extraction is a job in itself. Once a sample has reached the lab the testing technician has to extract the gases from the oil in order to be able to put them into the chromatograph for testing.  An accurate measure of the oil used for extraction is needed first. The tech will usually use 35 to 40 milligrams of oil. This is normally in a syringe which is easy to measure or sometimes in a steel bulb which is a little harder. Oil poured out from a bottle can be tested but exposure to the atmosphere can skew the results.

In the lab a measured amount of oil is injected into a glass vessel under vacuum. The oil is then stirred by means of a magnetic stirring device under the vessel. Observation shows the oil will foam like a bottle of ginger ale when first injected. It will continue to bubble while being stirred. The stirring action exposes all of the oil surface to the vacuum and helps force the gases out of the liquid faster.  It is very much akin to opening a bottle of ginger ale. The contents,  under pressure holds gas, carbon dioxide, in the liquid. When the pressure is removed by opening the bottle the gas bubbles form inside the liquid and float to the top. Since the gas is compressed into the liquid you don’t see a volume change.  Once equilibrium is reached the gases no longer bubble out and the ginger ale turns “flat”. Put it into a vacuum and it will again begin to bubble.  

Once the oil is “flat” and won’t give up any more gas the collection portion of the apparatus is sealed off with a valve. The extracted gas is then compressed using liquid mercury for a piston.  At a given pressure the volume is measured. This enables the technician to calculate how much gas was in the given amount of oil. This forms the base for the parts per million of total gas found in the sample.  Most of the gas is then extracted from the chamber using a syringe then immediately injected into the gas chromatograph.

Sounds simple, but when working with vacuum it is very difficult to keep leaks from forming. The glassware used has to be specially designed for the purpose, and all hazardous materials need to be contained and handled carefully.

The glass vessel is then removed from the apparatus to dispose of the oil. The magnet is retrieved and put back into the vessel. The sealing edges of the vessel are then coated with vacuum grease. The apparatus is then tested to make sure it’s ready for the next sample.

Any comments or suggestions are always welcome. If you have a question my email address is: transformerbob@gmail.com

Quote of the month:

"My mom said she learned how to swim. Someone took her out in the lake and threw her off the boat. That's how she learned how to swim. I said, 'Mom, they weren't trying to teach you how to swim.' " --Paula Poundstone

Transformer Oil Reclaiming and Heat

Product News! Product News! Product News! Product News! Product News! Product News!

Before you read my blog….

Have you ever been to the doctor for a routine checkup and been given bad news?  If you’re at all like me the first thoughts that form in your mind will be “I’m going to get a second opinion!”  

Darn Right you are!

Because there’s a lot riding on it! And as we all know, doctors are only human, they are not infallible. Well the same holds true for your electrical equipment.  When your equipment gets an annual physical checkup from your testing company do the results sometimes come in less than good?  Along with those results do you get a list of options proposing “Major $urgery” on it?  Maybe it’s time to reach out for a second opinion.  Luckily you may not have to reach too far.  If you have my dissolved gas analysis program in your toolbox you can verify those results immediately…or not! Think about the upbeat calls you’ll get from your clients when you tell them that you’re going to “anesthetize” their transformer for a half day or so to perform major repairs . OR……Think about how cheery they’ll be if the analysis said it was okay and the unit blows up two weeks later.  Believe me it can and does happen.  All of the good engineers I know have an inborn instinct to minimize risk, and I’m sure that you are one.  One of the golden rules in preventive maintenance is maximizing safety and reliability along with minimizing costs.

Try this program today. The software is:

·         Simple to Operate

·         Easy to Understand

·         Confirms (or not!) Your test lab’s recommendations

·         Works on any windows compatible computer

From the comments that I’ve seen so far, this program is invaluable. Just click on the button below for your copy and your CD will be on the way!  All shipping within the states is free!

Thank You!

Quantities

1 copy $159.00 USD 10 copies $155.00 USD 25 copies $145.00 USD 50+ copies $125.00 USD

Attention:

Transformer Oil Reclamation Continued

Hot Topic

In this post we need to talk a bit about heat. Heat is an extremely critical element in transformer oil reclamation. The filtering media will strip the sludges and acids from the oil but unless the oil gets hot enough the sludge that is deposited on the interior surfaces of the equipment will stay there. If it is not removed it will harden and begin to crack along with the insulation that it has formed onto. Essentially hot oil melts the sludge deposits in the transformer.  The transformer oil aniline point is right around 160 degrees Fahrenheit. Aniline point meaning the point at which is begins to act as a solvent. Transformers are cleaned much the same as if you run clean water into a muddy bucket. The more water that you flush it with the cleaner it gets. Cold oil will dissolve sludges over time. Evidence of this is available from test results taken after an oil change in a dirty transformer. Over a period of time the new oil will pick up some of the sludge in solution and it will show up in the tests by a rapidly dropping IFT reading. I use the term rapidly relatively. It should take about two years for the IFT in a lightly loaded unit (25C) to stabilize. At that point the oil is usually saturated and you start deteriorating where you left off at the oil change. You can change the oil again but this is an expensive and wasteful way to clean one out.

Heating filtering and re-circulating really works best in this case. Keep re-circulsating until the test results stabilize on the oil and you will have rid the unit of most of the sludge contamination. The temperature of the oil coming out of the reclamation unit needs to be between 180 and 200 degrees. That because it’s going into colder oil and the entire apparatus needs to reach at least the 160 degree mark. Remember that the cooling fins are normally functioning while the transformer is being treated and they will cool the oil somewhat. Ideally your oil processer should block off the fins to delete any “cold” spots that would allow sludge to accumulate or not be dissolved.

Heat also makes the filtering elements more active. In the case of fullers earth it becomes much more active and efficient at removing acids at elevated temperatures. The same goes for the vacuum system that is removing the moisture from the system. Oil will hold more moisture in solution at elevated temperatures and therefore is likely to change the equilibrium reached inside the unit between the oil and the cellulosic insulation. That can cause the insulation to unlock and give up some of it’s moisture to the oil. That oil then goes back to the processing equipment to be vacuumed.

There are still a few engineers out there who are not proponents of energized processing. Since this has been done successfully on a regular basis since the 1960’s I don’t agree with them. Energized processing gives you the extra boost of the internal heat generated by the transformer, and that helps drive moisture out of the insulation into the oil to be removed in the processer. As soon as you shut the unit down the moisture in solution will start to migrate over to the insulation degrading the integrity of it. It may not be much but with today’s design criteria it doesn’t take much.

As for those who think it’s bad business to circulate oil in a running transformer, I suggest that you look inside the next time your sampling technician takes the top off of a small energized unit with cooling fins (especially a hot one).  You can actually see the oil moving through the unit. As the oil is heated by the core and coils it rises to the top and then as it passes into the cooling fins becoming more dense as it cools it drops to the bottom only to repeat the process. If it weren’t ok to move the oil around in a transformer the big ones wouldn’t have circulation pumps in the cooling fins. The trick is to keep the level constant with a relatively gentle flow. As long as you don’t get gas bubbles you will be ok. I should also note here that the oil is drawn into the processor from the bottom of the transformer and reintroduced through the top. Drawing from the bottom alleviates the problem of stirring up sediment. In most cases it goes into the processer to be removed and never gets stirred up around the current carrying parts of the equipment. Energized hot oil processing is safe and effective when performed on qualified equipment by experienced technicians.

That’s about all I have for today.

Any comments or suggestions are always welcome. If you have a question my email address is: transformerbob@gmail.com

Today’s quote comes from the boss-

“Employees are like mules, Some you stand in front of and coax along with a carrot. Some you stand behind And kick them in the ass. The key to management is knowing which mules are which!”

Don’t forget to order a copy of my transformer oil gas analysis program. It’s a great tool to have. You won’t regret it. When you need it,  it will be there.

Thanks,

Bob

Reclaiming Oil

Reclaimed Oil?

  In the past I have had many engineers ask me just how good is reclaimed oil? My answer is that it depends. When using reclaimed oil several things have to be taken into account.

1.     It goes without saying that the oil must be PCB free. Only a small amount can contaminate anything that it gets mixed with. On this issue we must look to the future and assume that sometime any PCB’s will be totally banned and we will have to dispose of them. In that case there’s no need to create any additional problems by adding it to non-contaminated oil.

2.     Where did the oil come from? Assuming that it is PCB free if it came from an OCB and has not had all of the carbon filtered out it may do more harm than good.

3.     What is the before level of moisture in PPM. After?

4.     How was the oil reclaimed? Was it just pumped through a filter press? Was it vacuum dried? Did it pass through a bed of active alumina or fullers earth? Know what the process is before you use it.

5.     What is the history of the unit that it was in? Did it explode? Was it very old? Why was this oil available to reclaim?

6.     How long since it has been processed and how was it stored?

These are just a few of the things that you should be thinking about before using or reclaiming oil. Properly reclaimed oil should perform as well or better than new oil if it has had the correct chemicals added such as oxygen inhibitors to slow down the oxidation process. DBPC is what has generally been used over the years. It has to be injected into heated oil as it will not dissolve into the oil at normal temperatures. Oil that is 20, 30, 40 years or older is actually a higher quality base product than the oil processed today.

A quick check of the internet can turn up several oil reprocessors that will come out to your site to perform the work. Since they usually come from quite a ways it takes quite a bit of oil to make it worth your while. You can always buy your own machine but unless you perform this function daily it’s best to leave it to the experts. If you do own your own machine you will find it harder not to cross contaminate your oils, another reason to leave it to those experts.

I have already mentioned PCB contamination in this article in addition to that danger you should also be aware of moisture contamination. Most processors won’t tell you that the adsorbent media that they use (fullers earth) can transfer moisture into the oil. In the reclamation process the oil first goes through a heating cycle, then it passes into a vacuum chamber that degasses and boils off any moisture that may be dissolved in the oil. The final stage for the oil is to be passed through an adsorbent bed of fullers earth to remove acids and sludges that have built up over time. If the moisture content of the fullers earth is greater than that of the oil…guess what! You’ve got it! The moisture level balances out and the oil can be returned with more dissolved water than it had to start with. This is not a good situation if you are having a tank of oil reclaimed. It’s downright disastrous if you are having the oil in a transformer reclaimed. When reintroduced into the equipment the moisture will immediately go into the paper insulation as it is much more hygroscopic than the oil.

BONUS QUESTION!!!!!
A question for those of you who are familiar with reclaiming transformer oil.

Name one of the ways to stop oil from foaming too heavily in the vacuum chamber.

A correct answer will net you 10 points!

I will continue information on reclaimed oil in my next post. I will also be dealing with energized oil processing.

If you have any questions or comments, please let me know.

If you haven’t yet purchased your copy of my gas analysis program now is a good time. Just fill in the data below. All of the comments that I have received have been positive so that’s a good endorsement from you the users.

Don't forget to leave any comments or suggestions that you may have. To contact me directly just email me at transformerbob@gmail.com. I want you to know that I do appreciate my loyal readers and I will continue to produce content that you are piques your interest.

Today’s Quote: “The towels were so thick there, I could hardly close my suitcase” – Yogi Berra

Best Regards,

Bob

Product News! Product News! Product News! Product News! Product News! Product News!

I just finished the customer version of my GC analysis program.  When I was working I always used my own program to verify the lab’s gas analysis test results.  Now I have a copy that you can use too.  This program is:

·         Simple to Operate

·         Easy to Understand

·         Confirms (or not!) Your test lab’s recommendations

·         Works on any windows compatible computer

From the comments that I’ve gotten, this program is well worth it. Just click on the button below for your copy. As soon as I get the word your CD will be on the way!  All shipping within the states is included in the cost of the program!

Thank You!

Bob

Quantities

1 copy $159.00 USD 10 copies $155.00 USD 25 copies $145.00 USD 50+ copies $125.00 USD

Sampling Procedures for Oil Screening Tests Continued…

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

Quantities

1 copy $159.00 USD 10 copies $155.00 USD 25 copies $145.00 USD 50+ copies $125.00 USD

Attention:

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

 

Sampling Procedures for Oil Screening Tests

Before you read my blog………

I have some great news concerning Dissolved Gas Analysis for transformer engineers! This is a tool that every electric utility engineer needs to keep in his tool box! Eliminate misdiagnoses! Confirm that your results are right! It only takes a few seconds to check up on your oil test results and verify the judgments that your testing vendor has made concerning the condition of your transformers.  Continuous delivery of power to your customers is so extremely critical today due to the economic environment that exists. They can’t shut down for any extended period and you can’t keep spares sitting around for their benefit.  

Have you ever gotten a set of gas analysis results from your testing lab and had some questions about their diagnosis?

Why would you do that?

Maybe because you have seen some misdiagnosed problems in the past?

 Maybe because you have to justify that shutdown of a critical piece of equipment for repair? 

Maybe you just don’t really buy into what the test lab is telling you.

And..

If credibility isn’t a problem, maybe you would just like to have a second opinion!

Our new program on Dissolved Gas Analysis will affirm your decision making!  In the past you’ve had to rely on the findings of someone who sits at a desk all day, does a three minute review of your test results, and issues a canned evaluation based on some favorite method.  In some cases they can overlook potential hazards and in others cause you to shutdown and use valuable labor resources to investigate a non existent problem.  Remember the old Russian proverb “Trust but verify”!  Verify results using your own judgment!

Our computer program is:

·         Simple to operate

·         Easy to understand

·         Utilizes  most of the methods in use today for dissolved gas analysis evaluations

And the best part it doesn’t cost much more than the test itself, and you can use it over and over again, every time you receive lab results to confirm them. One incident can end up costing hundreds of thousands…if not more.  A wise decision would be to budget this tool for your toolbox before the end of the year.

The program runs on windows compatible PC’s and is available on CD now!!

Just click on the button below to get your copy!

Peace of mind and confidence will be well worth it and your customers’ will thank you for it.

For little more than the cost of a test you can confirm your results! This is a tool that you need! This is a tool that will add certainty to your decision making! One that you can't afford to do without! Be smart, Be certain!Get it now!

Thank you,
Bob

Quantities

1 copy $159.00 USD 10 copies $155.00 USD 25 copies $145.00 USD 50+ copies $125.00 USD

Attention:

And Now to the current post of my blog…..

Sampling Procedures for Oil Screening Tests

In this post I will discuss sampling procedures for the oil screening test. First I want to mention that samples should ONLY be taken by experienced qualified personnel who are fully aware of the dangers involved in being around high voltage equipment. This is by no means an instructional manual on how to sample transformer oil. It is meant only to educate and so that you the reader can know whether or not the tech that you brought in to perform the sampling has done an adequate job. I cannot be responsible for any yahoo that reads this and thinks he or she can do it themselves. Again, please leave the sampling up to the experts. They know what they’re doing and how to do it without injury. Even then I have seen several accidents occur when the tech lost his focus.
There are other liquids used in transformers but here we are only discussing those filled with mineral oil. Mineral oil being lighter than water, therefore the sample should be taken at the lowest point available on the transformer.
When first approaching the equipment the technician takes note of several things such as the weather, the location of possible sampling points, the overall conditions in the substation, the proximity of current carrying components, cleanliness, lighting, leaks etc. These conditions should be recorded and kept with the sample because they will figure in to the evaluation of the sample when testing is performed.
Weather- Is it rainy or sunny? If the tech isn’t willing to cash it in because of rain then use another company, chances are good the results will be fudged. For emergency purposes sampling can be performed in the rain but an uncontaminated sample is a lot less likely. Even if the substation is indoors rainy weather should be noted in case the sample containers got wet. Sampling in the rain for an outdoor substation is not recommended for other reasons as well. One never knows when a lightning strike may occur and if it does that’s not the time to be hanging out in a substation.  It really doesn’t take an Einstein to know that the best time to take a sample of oil is during dry sunny weather.
Note the ambient temperature. Is it hot or cold?  Cold weather can cause the oil to contract creating a vacuum in the tank. A good tech always takes note of the ambient temperature, then checks the temperature gauge on the equipment along with the red line on the gauge for the maximum temperature. Then the tech will carefully touch the tank with the back of his/her hand to confirm what the gauge says. In about 5% of the cases they don’t work. If there is no gauge present the back of the hand will have to do. The tech uses the back of his/her hand for a couple of reasons, 1. The skin on that part of your hand is more delicate and senses temperature better than the tough skin on the palm, 2. If there happens to be something like a grounding problem and the outside of the equipment is energized your muscles will contract. In that position your hand will not grasp anything that it could lock on to. The tech should be trained to use the right hand for this. Using the left could cause current to pass through the heart causing fibrillation and stopping the heart.
If the transformer is cool to the touch and the weather is cool as well it’s wise to check to see if the transformer is under a vacuum. Most of them have gauges that you can check. Don’t always believe what it says. Tap the gauge. Look at the tank, if it looks like it’s sucked in a bit then there could be a significant vacuum on it. There is usually a nipple under the vacuum gauge. First check to see if it’s dry because there could be water in it or debris that can be sucked in. While holding your finger over the nipple release the valve under the gauge to check for vacuum. If a vacuum does exist, get a tank of dry nitrogen along with a regulator and a clean clear plastic tube. Be careful how much that you add to the top airspace. Remember that if it’s very cold out the pressure will increase when it warms up. That could blow out some gaskets and cause leaks. Use your best judgment but in any case if it’s cold out never increase the pressure to any more than two lbs. preferably less.  If you should try to drain a sample with a vacuum on the top airspace the unit could suck air in from the bottom valve causing air to bubble up through the tank Causing  arcs and sparks (one of the functions of the oil is to contain the voltage). Worst case scenario could be an explosion. Also after a rain I have seen water collect in a valve if it has not been plugged. That water can get sucked in along with an air bubble and be immediately distributed through the system. Don’t think that this can’t happen because it has happened to me. I got as far away from that piece of equipment as possible until the water settled in the bottom of the tank. As an additional note don’t forget to check for sudden pressure change shutoff relays. These relays will kill the power at a sudden pressure change and can cause real problems if the transformer is powering equipment that runs on a continuous processing line (been there too!).
When the tech checks the redline on the temperature gauge, records it and resets it, he or she should also take note of leaks. Did the temperature rise so much that it pushed oil out through the gasketed portions? Does it look like the gaskets are still leaking? Check the oil level. First check the gauge then feel up the side of the tank for a temperature difference at about where the oil level should be. If it’s hot, is it below the top level of the cooling fins? Why? Where did the oil go?
Look for safety issues like limbs or plants growing across the power lines. Is there garbage in the substation? Most of these are fenced in, is there a lock or some method to restrict access to the substation?  Are the cooling fins free or is there something restricting the airflow? How about the condition with respect to corrosion? Is the paint all faded, is the unit rusty? What kind of paint is on it? If it’s a metallic paint such as a silver or aluminum color you can bet the transformer runs about ten degrees hotter than if it were painted with just white enamel.
Check the valve. What type is it? How does it look? Is the packing leaking? Is it a brass valve? The reason for this is that in older days many manufacturers used a “cider press “ valve. Just like the ones used on your gas line at home. They were meant for minimal use. The proper method of opening that type of valve is to loosen the nut underneath, then gently tap upwards on it loosening the tapered portion. Then it can be easily turned about ¼ turn with a crescent wrench from the top. A lazy or less than knowledgeable tech will just try and turn it from the top. Most of the time it will work but all it takes is once for the taper to shear off and your stuck with a gushing stream of oil that you’re not prepared to stop. It’s always good to be prepared with a “C” clamp that can be fitted around the top and bottom of this type of valve for a temporary field repair should a break occur.
If the unit does not have a valve on the bottom look for access at other locations. Most transformers have gauges that can be removed or plates near the top. In this case the technician needs a siphoning device attached to a tube that can reach the bottom of the tank. This is one the second worst scenario that you can encounter because it puts you in proximity of the wires. A very close friend of mine found a small plug that he could remove near the top of the transformer so he could feed a small tube in to siphon a sample. Problem was that the incoming lines were carrying over 7200 volts. As he cranked his crescent wrench down on the plug, his head dropped along with the rest of his body. He came too close to the wires and the power arced across the gap and blew off the bottom of his ear. Luckily he survived to tell the tale. Another reason that it’s worth every dime to have an experienced technician draw the sample. Finally if the unit does not have a valve or any other access if the bushings are not located on the top of the unit an experienced tech can remove the top and siphon out the sample. Believe me this is much easier said than done.
All of that said we are just about ready to draw an oil sample from the transformer, but as I’m looking at my watch I have run out of time and will have to leave that for the next posting. Looking at the previous two pages makes me wonder how many of you thought that it was this easy just to get to the point of drawing the sample?
As always if you have any questions, comments, input, or output please email me at transformerbob@gmail.com.  
The quote of the day is:
“I bet after seeing us, George Washington would sue us for calling him "father." Will Rogers

Oh Yeah! Don’t forget to contact me to get your Dissolved Gas Analysis evaluation program. I guarantee you it’s well worth it.   It’s a small investment in your toolboxes.
Thank you,

Bob

A Word About Transformer Oil Color

A Word About Color

I need to add a few words about color here. Color is pretty much just an observation. It becomes more relevant when you compare it from previous years. Oil that has been heated during a reclamation process will usually show up at about a 2.0. The color will be just a bit off from the disk on the colorimeter because it’s been “roasted”. The acid and ift numbers will show up fine on these. If over a few years it starts to drop rapidly then you know that the oil reclamation process did not do a good job of cleaning out the sludge. Probably a result of too little exposure to the filtering media and hot oil. It could also be due to an incomplete draining during an oil change out. Again future tests will reveal the process.
I have seen some oils in that were new and they were at a 4.0 to 4.5 on the colorimeter. I remember the first time I ran across these and was mystified as to why the oil test results were showing up as good. It was explained to me that that was an oil produced for Westinghouse corporation and it was used in a lot of units. You can identify it first by the test results and second by the bluish cast that it has when held up in sunlight. Anytime you get an oil with a 4.0 or better color you still had better sniff it to assure no arcing or overheating.

For those of you that are visiting my blog I want to thank you and make an offer that you can’t refuse. I am currently working on a program that I can post on the blog site that you can use to evaluate your own oil screen test results oil screen consists of Acid, IFT, Color, Dielectric, Specific Gravity, Visual, and Sniff tests). If you send me your results at my e-mail address I will look at them for you for free and send you back a short evaluation sheet. Just send them to: transformerbob@gmail.com. Allow a little time for me to evaluate because I don’t open up my email every day.
Thanks and Best Regards,

Transformer Bob

“Good breeding consists in concealing how much we think of ourselves and how little we think of the other person.”

MARK TWAIN, Mark Twain's Notebook