Shields Scotty

Inquiry

What impacts do rejuvenation fluids have on the conductor and insulation shields?

Response

With Star Trek Into Darkness in the theaters it was appropriate to revisit the question of shields. Not the shields that deflect Klingon disrupter blasts, but the conductor and insulation shields used to smooth electrical stress in underground power cable. When rejuvenation technology was first introduced about 25 years ago, that was one of the first questions that had to be resolved.

The table below provides some publically available data from a report prepared by Cable Technology Laboratories titled “Testing of VEPCO 35kV cable 5 Years After Upgrading,” dated May 28, 1999. The data examined the impact of a 70:30 mixture of phenylmethyldimethoxysilane and trimethylmethoxysilane (the white phase) and dimethyldimethoxysilane (the blue phase) in an application at Virginia Electric Power, compared to the untreated control (the green phase).

In short, both rejuvenation fluids show slight, but insignificant increases in volume resistivities of the conductor and insulation shields, four year after treatment at both 22°C and 90°C. In all cases, the increase is well below the limit set for cables of that vintage. The more modern limit is even more forgiving than the 1971 values. Dozens of such measurements were made in the last century, but they ceased to be interesting, because the impact was repeatedly insignificant.

Between Orange and Lemon Juice

Wikipedia defines “Fear mongering (or scaremongering or scare tactics) [as] the use of fear to influence the opinions and actions of others towards some specific end. The feared object is sometimes exaggerated, …”

The “feared object” is Novinium’s patented acid catalyst. U.S. Patent 7,770,871 (together with its foreign equivalents) demonstrates the tremendous benefits of this leap forward in rejuvenation technology. This advance, patented on April 20, 2010, largely makes the previous generation of technology irrelevant. So naturally the tactic of fear mongering is utilized by the purveyors of the over two-decade-old approach. 

The purpose of this post is to explore whether one should be concerned about the patented acid catalyst in Novinium brand Ultrinium and Perficio fluids. To take a guided tour on the subject, click on the presentation link below. For best results …

1. click on the full screen icon in the lower right corner of the slide frame,

2. click the “Allow” button to accept full screen mode, and

3. click on the play icon in the lower left corner to start the presentation.

 Between orange and lemon juice  

The presentation transcript follows …

01: What danger lies between orange juice and lemon juice? {Advance}

02: To answer this pressing question we have to understand what alkaline and acid mean. In water, chemists use the “pH” scale to delineate alkalinity and acidity. Technically pH is the negative logarithm of the hydrogen ion concentration, but you don’t have to understand logarithms or chemistry to understand alkalinity and acidity, because we experience most of the range of the alkaline-acid scale in our everyday lives. {Advance}

03: Let’s start with the alkaline portion of the scale. Anything with a pH greater than 7 is alkaline. Near the top of the list is liquid drain cleaner. If you get drain cleaner on your skin, wash it off immediately with copious water. While the word “acid” gets the rap for being dangerous, highly alkaline is just as bad as highly acidic. Moving down the scale, chlorine bleach is not nearly as irritating, but don’t leave bleach on your skin for too long … wash it off too. As we move down the pH scale the level of irritation becomes less and less. Soapy water left on your skin for a long time can be quite irritating too. In fact, our skin is acidic so all alkaline materials create some irritation over long enough time periods. {Advance}

04: Now consider acids. Human skin and black coffee share the same pH … about 5. We regularly drink tomato juice and orange juice at pH of 4 and 3 respectively. And we squeeze lemon juice into water or onto our fish, but for most people’s tastes, lemon juice is a bit too sour, or too acidic, to be drunk without some sugar added. In any case, these drinks don’t provide any problems to our bodies, because our stomach acid has a still lower pH. Let’s focus on that lemon juice for a moment longer … {Advance}

05: Did you know that over 6 million people die each year from lemon juice burns? … Just kidding … I was checking to see if you were engaged. The worst thing that can happen with lemon juice is a squirt to the eye. That can sting, but your eye will recover. {Advance}

06: Why does the word acid have such a bad rap? Is it the burning of skin from the acid in a lead-acid battery? Is it 30-weight-percent laboratory acid like hydrochloric acid with a pH of negative-one? {Advance}

07: Or is it alien blood, so acidic that it eats rapidly through metal floors on Hollywood movie sets? {Advance}

08: It might come as a surprise to some, but that is not really possible. A close examination of the Hollywood special effect demonstrates that the “metal” is really Styrofoam^® and the acid is really an organic solvent. You can try this at home with some Styrofoam and gasoline. Drip the gasoline from well above the Styrofoam to get the cool splatter effect. {Advance}

09: I am not entirely sure why acid is a scary word, but let’s examine the space between orange juice and lemon juice. {Advance}

10: Two fluids that occupy that space are Coca-Cola^® Classic – the Real Thing^®, and another real thing, Novinium brand Ultrinium™ and Perficio™ fluids. Make sure you don’t spill either on a metal floor … they eat right through it like alien blood! {Advance}

11: So what danger does fall between orange juice and lemon juice? Advance the view again to summarize the answer … {Advance} Maintain healthy skepticism of what you learn from Hollywood and from fear mongers.

Methanolic Corrosion of Aluminum

Inquiry

I understand that there was some issue with CableCURE^®/XL fluid when deployed in Germany in aluminum stranded cables. How do Novinium’s Ultrinium 732 or 733 fluids interact with aluminum stranded cables?

Response

It is true that about 1% of cables treated in Germany in 2002 with CableCURE/XL fluid failed because of the methanolic corrosion of aluminum. Even though the incidence of failures was quite low, the failure mode was dramatic as illustrated nearby. See the image labeled “German Cable Failure” taken from Bertini, “Failures in Silicone-treated German Cables Due to an unusual Aluminum-Methanol Reaction,” (ICC October 29, 2002). In the illustration the grey material between the strands is aluminum methoxylate, the profuse formation of which caused the insulation to bulge. The bulge is described as similar to when a snake eats a rat. An analgous phenomenon occurs in low voltage cables in the presence of water. In both cases, the bulging occurs because the aluminum hydroxide or aluminum methoxylate has a very low density, or put another way, takes up a great deal of volume. Because rejuvenation is utilized to improve the reliability of power distribution cables, even a 1% induced failure rate is unacceptable.

Novinium was founded in 2003, so we enjoyed the benefit of hindsight into the methanolic corrosion of aluminum and hence we addressed this issue in all of our Ultrinium and Perficio technologies. Novinium has not had a single incident of methanolic aluminum corrosion.

To demonstrate why Novinium technology avoids methanolic corrosion, it is useful to understand the mechanism of methanolic corrosion. One compound and one element are required for methanolic corrosion to occur … the compound is methanol; the element is aluminum.

Compound

CableCURE/XL fluid, Perficio 011 fluid, and Ultrinium 732 fluid all include methoxy silanes, which react with encountered water and produce methanol as a by-product. Ultrinium 733 fluid and CableCURE/DMDB do not produce methanol as by-products, instead these fluids produce larger, less chemically reactive higher boiling point alcohols, namely 2-ethylhexanol and n-butanol.

The reaction of methanol with native aluminum (methoxylation) proceeds at a rate proportional to the concentration of the methanol. The concentration of methanol in the strands of a treated cable is influenced by four factors:

1. The amount of water that is present in the strands and the strand-shield. Less water means less methanol; more water yields more methanol.

2. The stoichiometry of the silane water reaction. Stoichiometry is chemist-speak for the ratios at which materials react. For the CableCURE/XL fluid and Perficio 011 fluids, which utilize the same monomeric silane, the maximum possible methanol concentration is about 25% by weight. For Ultrinium 732 fluid the maximum is about 20% by weight. All other things being equal, Ultrinium would enjoy about a 20% lower methoxylation rate because of the superior stoichiometry.

3. The rate at which methanol diffuses from the strand area out of the cable. The diffusion of methanol is quite fast, so the risk of methoxylation decreases rapidly for all technologies. Higher temperature accelerates the diffusion and dissipation of methanol.

4. The use of non-methanol-based alkoxysilanes reduces methanol concentration beyond the 20% stoichiometric advantage described in factor 2 above. In a patented process (U.S. patent 7,611,748 and its foreign equivalents) Novinium adjusts the formulation with more and more non-methanol-based Ultrinium 733 fluid as the anticipated temperature of the treated cable rises.

Element

Except for copper stranded cables that are immune to methanolic corrosion, at first blush it appears obvious that elemental aluminum is available in an aluminum stranded cable, but it is not. As soon as aluminum strands are drawn and laid into a strand bundle on the factory floor, the outside layer of aluminum reacts with oxygen to form aluminum oxide (Al₂O₃). Aluminum oxide forms a dense barrier that protects the underlying native aluminum metal. This aluminum oxide layer is called a patina and it protects the underlying aluminum from further corrosion.

Patina

If you take a piece of aluminum and scrape off the patina with a knife, you will see bright and shiny native aluminum underneath. In the presence of oxygen, the patina begins to reform immediately. The shiny surface will soon return to its dull grey appearance. Of course, in a power cable there are no knives scraping off the protective patina, so how did the CableCURE/XL fluid penetrate the patina? One problem with CableCURE/XL fluid and CableCURE/DMDB is the use of a condensation catalyst called titanium (IV) isopropoxide.  Also known as tetraisopropyltitanate, we will call it TIP. Over the course of Novinium’s research we learned that TIP facilitates the degradation of the patina. Novinium does not use TIP in its Perficio or Ultrinium formulations. Novinium uses a patented catalyst (U.S. Patent 7,700,871 and its foreign equivalents) that does not suffer the same problem.

A second way that the patina can be damaged is bubble nucleation or boiling. Bubbles form in microscopic cracks in the patina and their rapid expansion and sudden disappearance mechanically perturb the patina. In the discussion above we learned that Ultrinium 732 fluids enjoy about 20% less stoichiometric methanol and hence the boiling point of the mixture is higher. Put another way, it takes a greater temperature escalation for Ultrinium to produce bubble nucleation than for CableCURE/XL and Perficio fluids. The patented silanes (U.S. Patents 7,658,808 and 8,101,034 and their foreign equivalents) included in Ultrinium fluids by Novinium and our partners enjoy improved stoichiometry, mitigating methanolic corrosion. CableCURE/XL fluid is particularly egregious in this dimension, because it includes an ingredient called trimethylmethoxysilane (TMMS) that has a boiling point even lower than methanol. To mitigate the aggressive bubble nucleation of 2002 vintage CableCURE/XL fluid UTILX Corporation reduced the concentration of TMMS in CableCURE/XL by a factor of between 3 and 6. This problem with TMMS is well documented by U.S. Patent Application 2009/0114882 and its international equivalent WO 2006/119196. Besides attacking the patina the TMMS creates a fire and explosion hazard. Novinium does not use TMMS in Ultrinium or Perficio fluids.

In addition to mitigating the causes of patina damage, Novinium utilizes a patina stabilizer from BASF^®, called Tinuvin^® 123 hindered amine light stabilizer. In experiments undertaken at Novinium, Tinuvin 123 outperformed all other patina stabilizers by at least a factor of two. Tinuvin 123 has other beneficial performance attributes to extend cable life and is included in Ultrinium and Perficio fluids and its use is protected by U.S. Patents 7,658,808 and 8,101,034 and their foreign equivalents.  In a patented process (U.S. patent 7,611,748 and its foreign equivalents) Novinium increases the supply of Tinuvin 123 by increasing Ultrinium 212 fluid as the anticipated temperature of the treated cable rises.

Summary 

Novinium substantially reduces the methanol concentration using proprietary silanes, does not use low boiling and highly flammable TMMS demonstrated to cause bubble nucleation even at moderate temperatures, eliminates a patina attacking catalyst utilized in the offending formulations, and adds a patina stabilizing compound to all but prevent methanolic corrosion of aluminum in its Ultrinium formulations. Perficio technology includes the improved catalyst and patina stabilization, and does not use low boiling TMMS. Perficio suffers from a higher methanol concentration than Ultrinium technology. Perficio technology should not be utilized in high temperature aluminum-conductor applications.

Neutral Corrosion & Novinium Warranty

Dear Informed Frog-

I have been asked to pursue something in writing concerning the 50% neutral corrosion and Novinium’s warranty. I respectfully request to have this from Novinium by quitting time this Friday, January 25, 2013. Thank you in advance for your cooperation in this matter and feel free to call me with questions or problems.

Signed,

Corrosion Concern in Colorado

Dear Concerned-

Short Answer

Go to …

http://www.novinium.com/Warranty.aspx

… and search for the word “corrosion” … you won’t find it! The warranty is purposely silent on neutral corrosion.

Less Short Answer

To understand why the short answer is so short, it is really useful to understand the purpose of the neutral and the consequences of various levels of neutral corrosion on the performance and reliability of the cable. To this end, view the recording of the September 2012 Webinar or read the webinar’s companion paper, “Neutral Corrosion – Significance, Causes & Mitigation”  prepared and presented by some of the cable experts at the Insulated Conductors Committee of the IEEE that created IEEE 1617™, the IEEE "Guide for the Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium Voltage Underground Cables."

Based upon IEEE 1617 and the aforementioned webinar many circuit owners have chosen 50% corrosion as their cutoff point for rejuvenation. But you get to make that determination yourself. You need only to communicate your wishes to the Novinium masters that proide your services. If you would like to discuss your choice with an expert … you can find them at Novinium. As you will learn in the webinar the 50% rule-of-thumb is a “glass half-full” proposition, because the rate of corrosion in direct buried cables declines over time. The pessimistic “glass half empty” perspective is not supported by observation.

Even if you have the occasional neutral corrosion in excess of 50%, don’t despair. The corrosion can be pinpointed and repaired, generally at a fraction of the cost of replacement. The webinar explains that option too.

Neutral on neutrals,

Thermo

A Cable Too Long

Dear Felicitous Frog,

I am currently reviewing a URD circuit with a cable segment that is 6,200' per our one-line and GIS.  It is our regular #2 db [direct buried] cable.  I am considering the installation of pull-boxes to break up the many long segments prior to attempting injection. What is the practical limit to TDR [time-domain reflectometer] testing?

What is the practical injection limit?   I assume in the best case that there at least a construction splice every 2000 feet, but there may be more that have to be replaced. 

Curious about cable  

Dear Curious- 

For background on how TDRs work, check out my October 1, 2011 post, “Reflections on a TDR”. A TDR sends a radar-like pulse down a cable. Like radar, a portion of the pulse is reflected when it “hits” objects along the cable path. Objects are anything that has a modestly different impedance (resistance, capacitance, and/or inductance) from that of the cable. Splices, cable ends, and neutral corrosion are generally identifiable. These objects are often called impedance anomalies, because the impedance varies locally from that of the cable.

There are two phenomena that reduce the acuity of the TDR – attenuation and dispersion. In the image nearby I illustrate the practical effects of attenuation and dispersion. As a wave travels along a cable its amplitude decays because no cable is without loss. When a male bullfrog croaks into a pipe, the volume decreases with distance because the sound wave amplitude attenuates. The attenuation is due to the imperfections in the molecular collisions. A portion of the sound waves are converted to heat. The same thing happens in the cable as electrons bounce among the cloud of conductor d-orbitals.

The second effect is dispersion and it too is the result of imperfections. Instead of loosing energy, dispersion smears energy because the rate that the signal moves through the cable is not uniform through its cross section. Skin effects and twisted stranding act to disperse the wave. Copper tape neutrals have a particularly nasty dispersion.

Simply recognizing these two effects helps the skilled operator interpret the observed wave shapes. Longer cables and those with more splices or corrosion will have shorter and more dispersed reflections.

Tactics to Improve Acuity

Of course the operator can use the TDR from both ends of the cable. This tactic effectively doubles the TDR’s resolution.

The next choice in the operator’s toolbox is to increase the pulse width. At the expense of resolving smaller or closely spaced impedance anomalies, wider pulse widths are the brute-force way to overcome both attenuation and dispersion.

A third choice is to divide and conquer.  Each construction or repair splice that is excavated provides an opportunity to TDR the two subsegments of cable from the splice in each direction.

Every cable is different, but more than likely the TDR should be able to identify all of the splices on a 6,200-foot run of No.2 URD cable employing just one or two of the aforementioned tactics.

Injection Length Limits

At Novinium, we know no bounds. We have a variety of patented injection paradigms to address long cable lengths. The preferred method for such a cable is sustained pressure rejuvenation (SPR). With SPR subsegments of cable are injected from termination-to-splice and from splice-to-splice. As you suggest, the longest run would likely be 2000 feet, the typical length of a cable reel. We have a model that allows us to predict injection times with great precision. Assuming your No.2 cable has round strands and 175 mils of XLPE insulation, a 2000-foot run utilizing SPR would require about 46 hours of injection time. We have treated cable subsegments that are several miles long and we have additional tools available for the most challenging circumstances.

With SPR the cable subsegments are typically deenergized during the injection process. If having the circuit deenergized for several days is not palatable, Novinium has still more tools at its disposable including flow-though splice technology that supports SPR. Of course, your suggestion of creating shorter subsegments by installing intermediate pull-boxes is another choice that can reduce the injection time.

Flow through really long runs of cable using older approaches is problematic. The challenges and the solution for really long cables, like submarine cables, are included in U.S. Patent 7,976,747 and in the paper, “Advances in Chemical Rejuvenation of Submarine Cables” presented at the Jicable conference in Versailles France in June 2007. To review this paper click here.

In short, we have many tools to address every conceivable situation. Talk to our crack field engineering team to explore all the options, or write back to me with more details and constraints. Check out our senior field Engineer Norm Keitges splashing in Puget Sound. He must have thought for a moment that he was a frog, because we generally frown on humans swimming on the job.

Bending boundaries,

T. B. Frog

Merry Masters

Oh festive frog-

It was a pleasure corresponding with you this year, toward a better understanding of cable rejuvenation. I also appreciate all the material you provided regarding cable testing.

I wanted to take this opportunity to personally wish you and your adoptive family a Merry Christmas and a healthy and happy New Year.

Emily

Dear Emily-

Thank you for the kind sentiments. I am hopeful that your holiday season will be filled with great times with those who you love. I’ll take this opportunity to wish all of mankind and creature-kind a wondrous holiday season and a prosperous 2013.

A glance at our Novinium Christmas tree reveals elements that you would expect to see.  Presents donated by our masters going to foster children to brighten their holidays. Unblinking white lights symbolizing electrical reliability delivered with unrivaled craftsmanship. Candy canes to satiate the sweet tooth for all those Novinium masters who were good boys and girls. Dennis, no candy cane for you until you quit smoking – because we love you.

A closer examination, however, reveals ornaments fashioned out of power cables. The cables are of many constructions and from all over the world. An even closer examination reveals that the tree-top star is fashioned from the fanned-conductor-strands of a feeder cable. You might think that our star is kind of cheesy, but then being born in a manger was not a glamorous affair. I was born in a swamp! That makeshift star reminds us that it isn’t the brightness of our lights that makes us good – it is the warmth we harbor in our souls. At least to this frog, Christmas is a time to thank God for Her good will.

Green Christmas wishes,

Thermo B. Frog

Third Party

Dear Alert Amphibian-

Can you provide third party data demonstrating that cable injection will extend the life cycle of underground cables? My colleagues and I are preparing for a rate filing with the OEB and we are looking for some firepower, facts and figures to bolster our case for additional cable injection monies for 2014 and beyond.

Seeking help,

Organizing in Ontario

Dear Organized-

I can think of four “flavors” of third-party data.

Flavor 1

Flavor 1 includes data gathered by third parties at the behest of a firm engaged in rejuvenation. The third party is independent, and is generally working for the technology supplier. There is an ample supply of this type of data, spanning over two-and-a-half decades. As an example of this type of data, consider Figure 3 of the paper published by my colleagues at the IEEE International Symposium on Electrical Insulation in September 2004…

New Developments in Solid Dielectric Life Extension Technology 

Figure 3 shows the substantial improvement in AC break-down performance seven days after injection at Cable Technology Laboratories. There is an abundance similar Flavor 1 third-party data. A compilation of that data can be found in the bibliography presented at the NETA Powertest Electrical Conference on March 17, 2008.

History and Status of Silicone Injection Technology with Bibliography

This paper provides 50 references including flavors 1, 2, and 3 of third-party data.

Flavor 2

The second flavor of third-party data are results reported by end-users. There have been several North American utilities that have reported their post-rejuvenation reliability over multiyear periods. The IEEE’s Insulated Conductor’s Committee (ICC) Discussion Group C30 is compiling several of these case studies as part of its efforts to craft a Guide entitled, “Extending the Life of Power Cables in the Field.” One exemplary data set was published by Northeast Utilities at the spring 2008 ICC. I have attached an excerpt of the ICC meeting minutes below. Over a nine year period from 1999 to 2007, the failure rate of the post-rejuvenated cable was 0.7% and the failure rate of the non-rejuvenated cable was 12%. Novinium’s failure rate is about half of the failure rate enjoyed with this older technology – see flavor 3.

R.Vencus. Cable Injection Program CL-P 2008.pdf (8.13 kb)

Flavor 3

The third flavor of third-party data is the overall failure rate of rejuvenated cables. Circuit owners have an incentive to report their post-injection reliability issues as they get cash for doing so! Novinium transparently publishes these statistics at …

http://www.novinium.com/Lessons.aspx

Novinium’s post rejuvenation failure rate is less than that of new cable! Check out my March 23, 2012 post, “Better Than New” to learn more.

Flavor 4

The fourth flavor of third-party data would be a Coke vs. Pepsi, side-by-side “taste test” of different rejuvenation technologies funded by electrical circuit owners and conducted by a third-party laboratory. There is good news, there is bad news, and some new that falls between good and bad. The good news is such a test was arranged by NEETRAC (National Electric Energy Testing, Research & Applications Center) sponsoring firms including: AEP, BG&E, ConEd, Oncor, FPL, Exelon, Southern Company, PEPCO, Southwire, and Snohomish Public Utility District. The bad news is that only Coke showed up for the taste test! The other technology supplier participated in the experimental design, but withdrew just as the testing was to commence citing, “Business and commercial reasons.” I will leave it for your contemplation why the other guys would not want to participate in a side-by-side test. The test proceeded with Novinium only. The news that is not bad, but not ideal is that even though the test was completed about two years ago, NEETRAC has not yet published the results in anything other than draft form. An excerpt of the draft NEETRAC report provides the bottom line of the testing:

“ … the stress at which the rejuvenated cables fail is higher than for the non rejuvenated cables: 26 kV/mm and 16 kV/mm, respectively. These stresses are taken at the 50^th percentile (median). Moreover, it would appear that the [Novinium] rejuvenated cables have a threshold for failure at 4.5 kV/mm whereas there is no threshold for the Non Rejuvenated cables."

The reported performance advantage was measured after about 18 months of accelerated aging – well beyond the originally planned twelve-month experimental plan. The electrical stress of a typical 175 mil insulated URD cable energized at about 8kV to ground is 1.8kV/mm. The treated failure threshold is 2.5-times typical operating voltages even after extended thermal and electrical accelerated aging.

Ready for any party,

Thermonuclear Frog

Wet, Wetter and Wettest

Dear Soggy Froggy,

I have two areas under consideration for rejuvenation next year.

• The first is a sub-division with 40 year-old cable that is in relatively dry sandy soil.
• The second sub-division has 15-20 year-old cable that is in very wet, swampy soil.

All other things being equal, which area would enjoy the greatest benefit from rejuvenation? Is there any data to support the recommendation? I hypothesize that the cables in the swampy soils should be injected first, since those cables are constantly in water and injecting them might yield the greatest benefit.

Wet, Wetter and Wettest

Dear Wettest-

It’s true that I have a personal preference for the swamp, but I won’t let that predilection alter my advice. This is a really great question because the wetness of the soil at one meter depth is not often discussed and often misunderstood. Fortunately one of my colleagues wrote a paper cited below that unearths the truth of the matter.

Bertini, “Molecular Thermodynamics of Water in Direct-Buried Power Cables,” IEEE Electrical Insulation Magazine, Nov/Dec 2006.

I would encourage my readers to review that paper in its entirety as it dispels many common myths. However, I asked the author to summarize the portion of the paper that relates specifically to your query and he has done so in a YouTube video. Watch this video and learn why both populations of cable are equally wet.

In your inquiry you say, “All other things being equal.” But are they really equal? I would suggest that the first criteria should be: Which of the two areas has had the greatest reliability issues per foot of installed cable? If reliability is equal, I would use age as the next best predictor of future performance.

Forever wet,

Thermo B. Frog

Flash Point Matters

Dear Ms. Yorker-

That’s a really interesting question and a great learning opportunity. I touched upon this subject in two previous posts in 2010 and 2011, but 2012 is a new year so let’s take a fresh and more comprehensive look.

Before we dive out of the frying pan and into the fire, I want to comment on the quip, “… unbreakable from a lineman’s viewpoint.” Linemen take great pride on being able to break anything, and as we shall see later, the fallibility of equipment, the inevitability of equipment failure (whether or not that failure is encouraged by rough handling of burley line-personnel), the certainty that fluid will one day be released into the confined volume of your pad-mounted transformer, are precisely why this issue is so important.

Let’s reproduce a table of closed cup flash points from the November 2, 2011 post, because the values are very important. The materials with a red background are defined as flammable liquids by OSHA 29 CFR 1910.1200(c) and DOT 49 CFR 173.115-120.

It’s also important to understand what a closed cup flash point represents. Referring to ASTM D93-10 (Standard Test Method for Flash Point by Pensky-Martens Closed Cup Tester), a sample of fluid is placed in a closed metal cup at a temperature well below its flash point. The fluid and the air/vapor space above the fluid are well mixed as the temperature of the cup and its contents are uniformly increased at a prescribed rate of 5 to 6°C (9 to 11°F) per minute. A small shutter is opened at each 1°C increment, and an ignition source is lowered quickly (0.5 seconds) into the vapor space of the test cup. The ignition source lingers in its lowered position for 1 second. It is then quickly raised and the shutter is closed. This process is repeated until the vapor-air mixture flashes. The ignition source might be a propane flame or a spark. The temperature of the ignition source has zero impact on the flash point. That’s right, it does not matter what the temperature of an arc is – it may be 35,000°F or 35 million. It’s the temperature of the fluid that determines whether an ignition occurs.

Here’s why that is the case. I think everybody is familiar with the “fire triangle,” I illustrate nearby. In order for a fire or explosion to occur, there must be three things: A source of ignition, fuel, and oxygen. Part of Ms. Yorker’s point is that in medium and high voltage environments, sources of ignition are common. Of course, oxygen is also ubiquitous and hence the only thing that is missing to create a fire or explosion is the fuel. But just having fuel is still not enough! As we discussed previously, a spill of fluid (fuel) is inevitable, despite Herculean engineering and procedural efforts to prevent that event. For now, let’s assume the spill does occur from a tank failure, a failure of one of the fittings, the tubing, or an injection elbow. What happens next?  Check out Frogograph 1 nearby. The fluid will flow to the lowest point of the transformer enclosure. There may be a puddle or perhaps just fluid-wetted soil.  In Frogograph 1, the temperature at the bottom of the transformer is lower than the flash point. The flash point is indicated by the red “FP” arrow. Because the temperature is well below the flash point, there will not be enough fluid evaporation to reach the lower explosive limit (LEL). I’m perfectly safe standing there drinking my coffee.

The situation changes in Frogograph 2 as the temperature just exceeds the flash point. Now in addition to the blue liquid layer, there are three other possible strata, labeled <LEL, Goldilocks, and >UEL. Let’s start from the bottom – the UEL is the upper explosive limit. All flammable fluids require a threshold amount of oxygen to burn. As a practical matter, this light green stratum is very, very shallow and since the likely sources of ignition are higher within the enclosure, its presence is largely irrelevant. Now let’s jump to the uppermost stratum left clear in the illustrations.  In this stratum there may be some molecules of evaporated fluid, but there simply is not enough to ignite in a self-propagating chain reaction. It’s the red stratum, the “Goldilocks” zone, where there is just enough (not too much and not too little) fuel (vaporized fluid) and just enough (not too much and not too little) oxygen to support combustion. Because the transformer enclosure is not well ventilated and because the flammable vapors are heavier than air, these strata form at the bottom as illustrated. When a fluid vaporizes, its volume increases about 1000-fold, so even a small spill has the potential to create a large Goldilocks stratum. The rate of fluid evaporation is related to the difference between the temperature at the bottom of the enclosure and the flash point. The higher the flash point, the lower the rate of evaporation will be. There are three things that mitigate an increase in depth of the Goldilocks zone. Gravity will draw the spilled fluid into the soil. Secondly, enclosures are not air-tight and hence restrained convection will remove some of the vapor. Thirdly, my favorite law of thermodynamics, the 2^nd law or entropy, helps disperse the spill. Both liquid and vapor diffuse through air and soil acting to reduce the concentration of the fluid vapors. The Goldilocks stratum is checked by these three phenomena. For a given spill, the depth of the Goldilocks stratum will be determined by the difference between the temperature at the bottom of the enclosure and the flash point.

In Frogograph 3 the temperature is well above the flash point and the Goldilocks stratum is much larger. In this illustration, we imagine that the neutral bleed wire to the elbow does not make an adequate electrical connection and discharges occur at that point. As the Goldilocks stratum enlarges it eventually reaches this discharge and the Goldilocks volume ignites. Because the transformer provides mechanical confinement an explosion occurs and the lid is blown open violently.  That is precisely what happened in the photograph nearby to an Ohio circuit owner. Fortunately, no tadpoles were playing nearby.

Now go back to the flash point table above. Does the temperature in your transformer enclosures ever exceed 55°F (13°C)? Unless you are on the North Slope of Alaska, the answer is probably yes. If Alaska Airlines asks if they can store one gallon of jet fuel A in each of your enclosures, would you say yes? The jet fuel would be safer than the low flash point injection fluids.

How many fires and explosions would be too many on your system? Some may be stammering, “But, … but, we have never had a fire or explosion with the flammable rejuvenation fluid we have used in the past.” Lucky you … others have! As a standards engineer you should demand that all suppliers provide a complete accounting of all fires and explosions its process and fluid have ever experienced. If a vendor is unwilling to comply with this most reasonable request, you can disqualify that supplier. Let me preemptively supply the Novinium list … boring as it may be.

A partial compilation of fires and explosions suffered by circuit owners utilizing flammable rejuvenation fluid can be found at …

http://www.novinium.com/pdf/papers/Rejuvenation_Hazards_Analysis.pdf

... in Addendum C of the Rejuvenation Hazards Analysis, beginning at section 2.3.3. Specific examples are illustrated at 2.3.3.1.3b, 2.3.3.1.3.1.2c, 2.3.3.2.1c, and 2.3.3.2.2c. There are many more.

Thankfully, most of us have never been in a head-on auto accident, but we take comfort in the PPE designed into our cars, namely the seat belts and air-bags. We pay more for these features on our cars, not because we have had a serious accident, but because we wish to avoid the terrible consequences of such an event should it occur. Even better than seat belts and air bags, imagine a system that eliminated the risk of collision altogether.

Such a system is available to circuit owners enjoying the capital efficiency of rejuvenation. My final illustration in this post is the “Hierarchy of Control” nearby. The upside-down pyramid illustrates that the most effective way to deal with safety risks is to eliminate them. At Novinium we embrace this hierarchy and you should too. Eliminate known risks, substitute safer materials and processes for those that are less safe. Apply concentrated engineering effort to prevent occurrences and mitigate the impact when unfortunate and inevitable incidents do occur. Implement, but depend the least on administrative, behavior-based, and PPE controls.

With flash points greater than 142°F for Novinium’s Perfico™ 011 fluid and Ultrinium ™ 732 fluids (both of which enjoy patented methods including U.S. patents 7,658,808, 7,700,871 and 8,101,034 together with their foreign equivalents), fires are extraordinarily unlikely. But we don’t stop there. With our improved unsustained pressure rejuvenation (iUPR) we eliminate the 60 to 90 day soak period employed by the two-decade-old approach altogether. That’s about a 60-fold reduction in the exposure to a leak in the first place. With our patented sustained pressure rejuvenation (SPR) process (U.S. patents 7,615,247 and 8,205,326 and foreign equivalents) and associated injection adaptors (U.S. patents 7,195,504, 7,538,274 and 7,683,260 and foreign equivalents), the possibility of a leak is entirely eliminated. There’s more – a lot more. To understand how technology has vastly improved the safety performance of rejuvenation technology, see …

So here is the bottom line in my longest ever post.  Flash points and the impact they have on safety are in the public domain.  What will you say on the witness stand in defense of your firm when somebody or some frog is hurt by using the least safe technology?  To help you on the stand, cut out the handy cheat-sheet below and check all that apply.

Better safe than sorry,

Thermonuclear Bull Frog

Galvanic Corrosion of Neutrals

Oh greenest of greens,

My copper neutrals look a lot like you – green! I was wondering if our practice of bonding neutrals to the rebar in our vault structures might lead to neutral corrosion.

Califorrosion

Dear Califorrosion-

Yes, copper carbonate does have similar hue to me ... a touch bluer though. And like me, copper carbonate is your friend. The copper carbonate patina protects the native copper underneath from corrosion. It’s also true that bonding two metals can cause corrosion under the right circumstances. In fact this type of corrosion, galvanic corrosion, is the first mechanism mentioned in IEEE 1617™ (Paragraph 6.1 of “IEEE Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables”). For galvanic corrosion to occur five conditions are required …

1. One of the two metals must be more anodic (inclined to be less negative). In your query that would be the steel rebar.

2. One of the two metals must be cathodic (inclined to be more negative). In your query that would be the copper neutral.

3. There must be a metallic connection. That would be the bonding hardware together with the neutrals and rebar.

4. There must be an environment for ions to flow. Wet soil provides such an environment, wet concrete works too, but not nearly as well.

5. Finally there has to be oxygen present. This last assumption is usually true unless the area is an anaerobic swamp.

The bottom line to your question is that the steel rebar is the anode and the copper is the cathode and hence any galvanic corrosion that does occur will occur to the detriment of the rebar. The rate of galvanic corrosion on the rebar will likely be quite slow, because concrete, even submerged concrete, does not allow for the rapid transport of ions.

My colleagues will be presenting a webinar on the subject: “Neutral Corrosion: Causes, identification & Mitigation” on September 21, 2012. To register for this learning opportunity navigate to www.novinium.com/events.aspx.

Green wishes,

Thermo