Diesel corrosion

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ZMiller
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Re: Diesel corrosion

Post by ZMiller » Sun Dec 22, 2019 12:26 pm

I have given up on saving and or pointing out integrity issues due to corrosion in vessels that store fuel. In all likelihood it is as with trying to refloat the Titanic and way to late to reverse the damage. The problem being nobody yet can see a whole picture for resolution.

The recipe for this disaster is defined by changes in storage tank Use and Regulations without consideration of system operational changes, fuel formulation, dynamics or consequences.
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Re: Diesel corrosion

Post by PatSmyth » Sat Feb 29, 2020 1:54 pm

Just catching up on the posts.

Regarding Re: Diesel corrosion
Unread post by CherokeeUST » Mon Sep 16, 2019 11:13 am
Ethanol is not the cause of corrosion???

Ethanol is mentioned 50+ times in the 2016 EPA corrosion report. One simple possible reason that trace ethanol is found in ulsd biodiesel blends is that both biodiesel and ethanol are polar molecules, so will be attracted to each other. If so, there should be trace biodiesel in gasoline blended with ethanol. Has anyone looked for biodiesel in ethanol blended gasoline?

A new paper has just been released that monitors corrosion in B20 storage over a years timeframe. This is the first long term, in situ study, and shows the increased levels of MIC over time. It is a very good read. I'm interested as it ties in water and MIC. Dry the fuel, control the MIC. Two ways of control is removal of water, with SAE J1488 filtration, and prevention of water absorption with nitrogen blanketing. I understand that water can also be removed using heated nitrogen.

This latest paper (Feb 20 2020) studied 6 tanks at two United States Air Force (USAF) bases for a year. It is coauthored by Dr. Bradley Stevenson, Associate Professor of Microbiology, Dept. of Microbiology and Plant Biology, University of Oklahoma.

This peer reviewed paper was just published in Frontiers in Microbiology, "a leading journal in its field, publishing rigorously peer-reviewed research across the entire spectrum of microbiology."

https://www.frontiersin.org/articles/10 ... 00167/full

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Re: Diesel corrosion

Post by CherokeeUST » Wed Mar 04, 2020 7:53 am

Thank You Pat. Nice report on B20.
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ZMiller
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Re: Diesel corrosion

Post by ZMiller » Wed Mar 04, 2020 7:57 pm

A doubling of a nitrogen mass flow drying diesel (Hennery and Fick's laws) cuts drying proportionally in half the time. Heating to say 60c forgoes the need to increase mass flow. An example being water at 500ppm could reasonably and predictably be groomed down to say 80ppm. Depending on the percentage of bio diesel blended in the last 80 to 40 ppm at the initial mass flow is tough to bump out. While between 40 and 80 ppm might be marginally acceptable it has been found that the same mass flow at 60c greatly decreases the drying time. Determining the polar bonding wall would depend on knowing the blend percentages.

Interestingly if one knows the blend percentages and the nitrogen mass flow temperature is gradually increased the the ppm reduction curve to less than 20 ppm can be seen more or less as a straight line.
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Re: Diesel corrosion

Post by ZMiller » Tue Apr 07, 2020 6:47 am

The Use of Nitrogen Enriched Air (NEA) to Dry, Monitor and Control Fuel Moisture and Oxidizing Atmospheres in Lubrication and Bulk Fuel Storage Tanks

Abstract:
A study of the process of removing water (moisture) from an above or below ground bulk fuel storage tank by pumping (purging) Nitrogen Enriched Air (NEA) into and through the tanks primary empty space (ullage). It is important to monitor and or control corrosive low PH and moist atmospheres in tanks to protect fuel storage tank containment boundary integrity and quality of fuel or product being stored. Study results reveal that the absorption of moisture by a NEA mass-controlled flow through a tanks empty space decreases the moisture content in the tanks primary empty space as well as in the fuel or lubrication product stored during the procedure. This effect being the expected and desired process study outcome. Due to the relatively dry NEA entering the ullage and displacing the moist air, reduction of the partial pressure of water at the fuel/ullage interface is realized. This shift in equilibrium condition forces water to evaporate from the fuel’s entire surface. The amount of water migrating from the fuel directly into the ullage was during the study significant and anticipated. The rate of decrease of the moisture content in the ullage is determined by the NEA mass flow rate and this was found to be the dominant contributor to the tanks ullage and stored fuel surface drying time. When pumping NEA directly into the ullage a significant decrease of moisture was realized even when the NEA is not pumped through the fuel. Realized as well, doubling the mass NEA flow rate halves the drying time. The studied process for removing moisture from stored fuel and a bulk fuel storage tanks primary empty space is particularly attractive as a method to preserve quality of product stored and control tank boundary integrity degradation requiring very little bulk storage tank design modification.

Introduction:
A major consideration in the design of bulk fuel and lubricating fluid storage tanks is the purity of the product stored. The first line of defense is a region at the bottom of fuel or product storage tank where debris and water settle from the product being stored. Fuel storage systems also contain strainers and filters that monitor and or prevent large debris, sediment and water respectively, from entering the fueling delivery system and or consumers vehicle or equipment. Diesel, kerosene and lubricating fluids in bulk storage for example can absorb moisture which often enters the fuel tank ullage empty vapor space through the vent riser at the top of the tank.

Dissolved water (moisture) to a regulated degree is not considered to be a contaminant and is typically vaporized during combustion. During temperature and pressure fluctuations however, moisture can separate from the solution forming a water-in-fuel emulsion: small water droplets suspended in the fuel. Separated water is a contaminant and can cause several problems.

Water that is drawn into a fuel and or lubrication system can interrupt the smooth and efficient operation of the engines.

With temperature drops below product stability thresholds, free and entrapped water can gel or form ice, which can then attach onto the fuel lines and strainers introducing blockages.

Water also promotes the growth of bacteria, which can also block filters and create low PH and corrosive empty space atmospheres.

Due to the relatively greater density of water, these droplets gradually move down towards the tanks bottom forming a separate layer that may or may not be easily be removed from the system. The time of this settling process, as determined by the water and fuel density, viscosity and size of the water droplet and temporal condition can range from minutes to weeks. Such unpredictable and possible lengthy timescales are or can be unacceptable.

The main protocol for reducing the amount of moisture entering the fuel and or product storage tank is to reduce the tanks empty space, monitor and control the moisture in that space. Reducing the size of the ullage, and therefore, the amount of water vapor that can be dissolved into the fuel could be considered unreliable, as the fuel can also be contaminated with water during production and transport.

**The method being studied, and method suggested here involves pumping nitrogen enriched air (NEA) through a fuel or lubrication bulk storage tanks Empty (ullage) Space. The idea that, due to the absence of water in the NEA there will be absorption of any moisture in the empty primary storage space of the tank. ***NEA entering the ullage in a mass-controlled flow will exit the system through the tank vent riser carrying absorbed moisture (removing water) from the fuel tank.

The overall aims of the present study are to optimize a bulk fuel storage tanks ullage for a tank and fuel drying process that;
•Adequately monitors and removes moisture from the storage tanks primary empty space,
•Adequately monitors and controls excessive moisture dissolved in the product being stored.
•Adequately monitors and prevents in a tanks primary empty space, moisture and the formation of degradation low PH acidic atmospheres,
•Ultimately protecting and preserving quality of fuel or lubrication product being stored.

Objectives of Investigative Study and Testing:
Change in water (moisture) concentration in a fuel storage tanks ullage. The change in water concentration in the fuel storage tank away from equilibrium should be mitigated by the migration of water from the fuel at the fuel surface/ullage interface into the inert dry moisture purge gas flowing through and out of a tanks empty space. It is expected that the migration of moisture from the fuel at and over the fuel surface/ullage interface will reduce by evaporation the concentration of dissolved water (moisture) in the fuel itself.

Study and testing of theory will confirm that as reasonably expected, fuel drying times will correlate to a mass flow rate of dry inert gas (nitrogen) flowing through the empty space (ullage) of a fuel storage tank. As water concentration in fuel is reduced it is expected that a concentration difference between the ullage and fuel surface/ullage interface will be realized. Evaporation occurring on the entire fuel/ullage interface is the most important factor for the drying effect and reduction of water dissolved in stored fuel.

*Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase after reaching its boiling point. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other based on how they collide. When a molecule near the surface absorbs enough energy to overcome the vapor pressure it will "escape" and enter the surrounding air as a gas.

**Henry's law States that: At a constant temperature, the amount of a given gas dissolved in each type and volume of liquid is directly proportional to the partial pressures of that gas in equilibrium with that liquid.

***Fick's law relates the diffusive flux to the concentration under the assumption of steady state. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low concentration across a concentration gradient.

****Raoult’s law states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature. This is called phase equilibrium, because the only thing changing is the phase that the substance is in. This leads to the conclusion that there is a vapor present above any liquid. The vapor pressure of a liquid is the pressure exerted by the vapor above the liquid.

HOW MUCH WATER IS OK?
The easiest answer would be none. All diesel contains some percentage of water. The most important thing is to keep the water below its saturation point so that it stays dissolved rather than entering equipment as free water. Equipment manufacturers specify that ZERO free water must reach the engine. Saturation points vary from roughly 50 ppm to 1800 ppm based on temperature and on the petroleum diesel/biodiesel ratio. As you can see on the chart following, biodiesel can hold significantly more water in saturation than its petroleum equivalent. Blending bio and petroleum diesel together, however, does not result in a mathematically proportional moisture content. The blend will hold less in solution that the sum of the parts, meaning that free water precipitation may occur when the two are mixed.

The best way to remove large volumes of settled water is to drain the tank. Ambient moisture and condensation can be prevented from entering the diesel fuel storage tank using good desiccant breathers in combination with and or a blanket of dry air (or nitrogen) fed into the tank's headspace and out through the vent riser. The relative humidity of the diesel will tend toward the relative humidity *** (or "dryness") of the air. Moisture in the diesel will, with time, be released back into the dry air until the diesel is just as dry as the air.

You can contact Zane Miller and Greg Young, authors of this article at admin@orvr.us or (770) 780-2700. You can also find more information at vaporless.com.
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ZMiller
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Re: Diesel corrosion

Post by ZMiller » Wed Apr 15, 2020 11:49 pm

Still can't figure it out can we?
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Re: Diesel corrosion

Post by CherokeeUST » Wed Apr 29, 2020 2:35 pm

Fuels Institute Launches Diesel Fuel Sampling Study

https://www.convenience.org/Media/Daily ... tudy_Fuels
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Re: Diesel corrosion

Post by bugbuster » Wed Apr 29, 2020 3:53 pm

I recall reading about the planned study and applaud the effort.

One tough issue to grapple with, is sample size. There are statistical tools that can be used to determine the size of a representative population - the number of tanks/dispensers from which samples must be collected and tested in order for the results to be considered representative of the total population. Typically 10 % is considered adequate if there isn't too much variability among samples.

Recent industry stats indicate that there are approximately 250,000 ULSD UST in the US. A 10 % sampling would include samples from 25,000. The original Clean Fuels Council study looked at samples from 7 UST. The more recent US EPA study looked at 50. If I recall accurately, the new study will include dispenser nozzle samples from 500 sites. The two aforementioned studies intended to assess the risk of UST and fuel system corrosion. The new study is focusing on fuel quality at the nozzle. If all of the fuel samples are in spec, that will tell an important story. If there's considerable variability among the samples, then any conclusions from a non-representative sampling will be indefinative. Still, 500 samples is ambitious and much better than any survey done previously.

I look forward to reading the results of this study.

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Re: Diesel corrosion

Post by ZMiller » Thu Jun 04, 2020 6:38 am

CherokeeUST wrote:
Wed Apr 29, 2020 2:35 pm
Fuels Institute Launches Diesel Fuel Sampling Study

https://www.convenience.org/Media/Daily ... tudy_Fuels
I'm somewhat puzzled as to why the 7 or 8 thousand problem predictive diesel samples collected and analyzed so far remain study irrelevant. Battelle, CRC and FI studies logically for insuring future study funding could only be inconclusive. It's almost like no body really wants to know.

Not being the least bit pessimistic I can only say "it's to little to late" in the game. Study in a more optimistic light needs now to be in dealing with storage tank and delivery system component containment integrity failures AND remediation of their surrounding environments.

On the Titanic's first trip across the Atlantic the 3rd class passengers and crew well below the main deck had a pretty good idea the ship was sinking long before passengers in First Class.
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Re: Diesel corrosion

Post by bugbuster » Thu Jun 04, 2020 10:41 am

Bummer, Zane:

I just wrote a reply to your last post. But if vaporized when I clicked "preview." Rather than rewrite the whole post I'll cut to my bottom line: New information can be very useful for indicating the most cost effective means of minimizing corrosion damage to fuel dispensing systems. However, stakeholders must be willing to act on new information/knowledge.

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