Diesel corrosion

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ZMiller
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Re: Diesel corrosion

Post by ZMiller » Sun Dec 18, 2016 4:43 pm

I'm replacing tank bottoms and bulkhead in tanks that are less than ten years old now. Some tanks with primary leaks in less than seven years. Recently replaced a rotted out motor riser bung in glass tank that was four years old.

So how long do we wait?

Please realize that all of a sudden customers have a bunch of tanks rotting away with say failing innards and leaking into secondary. You think hypothetically customers like UPS, 7-11 or CK are going to broadcast that their tanks are leaking?

Probably not.
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Re: Diesel corrosion

Post by bugbuster » Sun Dec 18, 2016 5:13 pm

That's exactly what I've been telling all who will listen. BTW, a couple of years ago, the Fiberglass Tank & Pipe Institute's (FTPI) legal counsel (who also happens to be PEI's and ILMA's - Independent Lubricant Manufacturers' Association) sent me a letter threatening that if I did not remove all documents that address FRP (fiber reinforced polymer - the generic name for Fiberglass) tank biodeterioration, the FTPI would sue me. Interestingly, at this year's PEI show, several companies showed samples of FRP tank biodeterioration (some had photos, others had actual sections of tank). During the same show, a colleague of mine had a conversation with a FTPI representative who was adamant about FRP biodeterioration being impossible; never happened; no evidence; blah, blah, blah... Pay no attention to any evidence to the contrary. What was that I wrote about denial being a most common approach to condition monitoring???

Like you, for nearly 40 years, I've been trying to convince site owners to just look for themselves. With rare exceptions, most have declined that invitation. I'm afraid that you and I will have to wait until the number of UST failures/year spikes. If you know the magic words to disabuse owners of their religious belief that nothing can possibly go wrong, I'm all ears, Zane!

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Re: Diesel corrosion

Post by CherokeeUST » Tue Dec 20, 2016 9:16 am

Came across this paper on ethanol corrosion from 1983. Guess we knew when we added it to fuels it was a corrosive element.

http://papers.sae.org/831828/
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bugbuster
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Re: Diesel corrosion

Post by bugbuster » Tue Dec 20, 2016 11:20 am

Thanks, Zane.

I'll download a copy of the full manuscript.

ZMiller
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Re: Diesel corrosion

Post by ZMiller » Mon Mar 13, 2017 1:18 am

I don't think we have learned anything yet.
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Re: Diesel corrosion

Post by ZMiller » Fri Mar 24, 2017 9:28 am

I have had time to read and digest the EPA report and here is what I learned
1) There are microorganisms in diesel storage tanks that probably generate organic acids such as acetic and formic acids. They need oxygen and other chemicals such as alcohol and glycol to survive as well as other chemicals. The majority of the food stuffs that the organisms thrive on probably come from biodisel and improper cleaning of the tankers transporting the diesel fuel.
2) The study by the EPA is rather small and covered mostly tanks located above the Mason-Dixon line.It included a mixture of fiberglass and metal tanks of various sizes and greatly varying ages.
The reported degree of corrosion in the tanks that were examined was merely based on the opinion of those that observed it either firsthand or from videos and the EPA had the final say in categorizing the corrosion level.
3) Several things are suggested as ways to prevent or impede the corrosion. First, eliminating the level of water in the bottom of the tank which will take away the food source for the organisms. Second, blanketing the tank interior with Nitrogen which would remove the oxygen supply to the organisms. Third, reducing the humidity in the tanks which would reduce the condensation of the acid vapors on the metal parts above the fuel level. Fourth, addition of chemicals that would kill the organisms.
4) What might really work. If the tank is full of fuel and the airspace if filled with Nitrogen, which is heavier than air, the organisms would be deprived of their oxygen supply. However, as the fuel is pumped from the tank and the tank is open to the outside atmosphere, the airspace in the tank becomes mixed with Nitrogen and air containing Oxygen. So, how could you prevent that happening? It would seem possible to have the tank operate under a very slight positive pressure and with a regulator and supply of Nitrogen, keep the airspace essentially filled with Nitrogen. I have no idea if that would be allowed under safety criteria but it could be accomplished with minimal cost. I don't know what chemicals could be added to the tank that would kill the organisms and whether there are any that would be compatible with the fuel.
5) Things that you could recommend to your customers would be to pay a lot more attention to the water content of their tanks and try to keep it at a very minimum and if your product supplies Nitrogen to the tanks, that should be a very good selling point but it does have some limitations.

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When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
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Re: Diesel corrosion

Post by ZMiller » Fri Mar 24, 2017 10:41 am

From data collected at nitrogen blanketed diesel and gasoline test site tanks exibiting ullage corrosion efects it was discovered that one dosen t even need continuous dry inert gas blanketing. Bring and drying the ullage atmosphere say once a week is enough to control acidic effects and control exposed surface wetting.

The real advantage for dry inert gas blanketing is the ability to continuously monitor and test the tank top fittings for leaks. With application of continuous or regulated low pressure water ingress is all but eliminated. Saying this by now most realize that a tight tank is a rare bird when found. Tight tanks from survey data collected rarely show signs of corrosion, a point ironac that Battell and CRC left out of their reports.
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
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Re: Diesel corrosion

Post by bugbuster » Fri Mar 24, 2017 11:41 am

Hi, Zane:

I agree with most of your comments.

As I think I've commented before, most statisticians consider 10% of the population to be the minimum needed for a representative sampling. If there are 200,000 ULSD UST in the US, the sample set would have to include 20,000 UST. 40 is 0.2% of the minimum number of UST needed to make up a representative set of inspected tanks. With a sample population that small, it is possible to conclude whatever you like. It's a variation on the theme of chicken little and his interpretation of the significance of a single acorn landing on his head. In fairness to the report's authors, they did acknowledge the study's limitations and warned against unwarranted extrapolation.

Speak of assumptions, you make quite a few about the impact of nitrogen blanketing on both corrosion and microbial contamination. I'm not disagreeing with any of your stated assumptions, but suggest that they should be treated as hypotheses which need to be subjected to a well designed field evaluation.

Cheers,
Fred
Last edited by bugbuster on Fri Mar 24, 2017 11:53 am, edited 1 time in total.

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Re: Diesel corrosion

Post by bugbuster » Fri Mar 24, 2017 11:52 am

Zane:

I'll comment to tight tanks separately here.

Again, no disagreement that water-free, tight tanks have a dramatically lower risk of corrosion - either abiotic or MIC. The trick is to inspire industry stakeholders to invest in best design and to follow best practices for PdM.

Although biodiesel blends are generally are more vulnerable than conventional diesel (even ULSD) to microbial attack, let's not forget that the fuel microbiology literature goes back to 1885 - that's 132 years of fuel microbiology literature about bugs attacking fuel and fuel systems in gasoline (all grades including ethanol blends) and diesel (again, all grades: high, low and ultralow sulfur; marine, kerosene and jet). In 1996, I did my first fuel microbiology literature review. At the time, I discovered >3,000 papers on the topic. In 2013 I published a review of "only" papers published since 1980. I cited >200 papers. The truth is that we still don't know what we don't know about fuel and fuel system microbiology. Or as Mr. Rumsfeld put it, we have the unknown unknowns...

This is one reason why I LOVE being a microbiologist!

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Re: Diesel corrosion

Post by ZMiller » Fri Mar 24, 2017 12:17 pm

I have always presented options for adding amines to control microbial colonization in tanks to customers as part of a reasonable tank maintenance program. One problem I constantly run across in that customers don't seem to be bright enough to actually read or understand amine application instructions with a situation in a tank becoming that they do more harm than good.

As well standing with a customer they ask where's the corrosion in the sump is coming from? I say the tank and they say that's impossible because the tank has been tested and no leaks were found. I chuckle and ask where then do they think it might be coming from? Often they look around and then to the sky.

The receint a few posts back though was not my composition. I was more or less just agreeing.
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
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