Jet Fuel Bulk Storage 6

[FredGarvin]

I was wondering if anyone here has experience with jet fuels and bulk storage of them.

I have a engine performance gremlin that I have been trying to track down for some time. One theory has been presented that involves stratification of JET-A in our storage tanks. Some people here have taken to the idea that JET-A stratifies in both our above ground and below ground tanks because we do not stir them and the resulting light ends seperating from the heavies is causing problems.

I personally am not convinced that this can happen as quickly as it is being presented, if at all. However, I am anything but a chemist.

Can anyone shed a little light on the possibilities of this "problem" or know of anyone I can contact?

Thanks for the help!

S.H.

 

[rmw]

Automotive diesel fuels are blended to accomodate seasonal changes. Winter diesel is blended more toward a #1 diesel, especially in the colder climates, and, in the coldest of climates, #1 diesel is sold outright.

The danger to a diesel passenger vehicle owner is in where he buys his fuel. Some either don't hear, nor do they heed the recommendation to only fuel at places that have high turnover rates, like truck stops, rather than 'mom and pop' service stations that might still be pumping from a tank of fuel delivered some months ago, when the climate is different.

Adding to that, depending upon where you live, and where your particular service station supplier obtains its fuel from, in our part of the country, one of the chief sources of petroleum products is a product pipeline that stretches from the gulf coast to the northern USA border. What that means for me as a diesel vehicle owner, is that the fuel flowing in the product pipeline today, in mid summer is the fuel that will be transported, delivered to the bulk storage facility, and then subsequently delivered out to the truck stops and farms next fall and winter.

Back before the laws changed regarding adding color to fuel to designate that it was a winter blend (Texaco, for example used to advertise around their "red" winterized fuel) it was not uncommon at all to see colorized fuel in the summertime here in the deep south.

Same thing about getting a load of next summers fuel on a bitterly (such as that might be in the deep south, but still occasionally cold enough to give fuel gelling problems, if trying to burn summer fuel) cold day.

Therefore it is beneficial to know who buys from jobbers that buy, in turn, from local refineries, that are blending more toward local conditions.

Now, SH, I said all that as background to ask this question. Since you mention a seasonal variation in the problem, is there any thing remotely similar going on in the "Jet A" world.

When you said "timeframe" that thought jumped out at me, since we don't seem to be boring in on any one culprit in particular.

rmw

 

[rmw]

SH,

You state that you are a jet engine designer/mfg, so that puts you in a pretty small club. Therefore, I don't know if the link I am going to give here is one from your company, or is from a competitor of yours, but it is publicly available, and has several papers on fuel issues, including distillate, pertaining to your industrial cousins.

http://www.gepower.com/prod_serv/products/tech_docs/en/all_gers.htm

I hope it has something that will help you.

rmw

 

[FredGarvin]

I noticed back in JMW's post in the referenced thread about Bunker C, his concerns regarding viscocity as a reliable measure of quality with heavy oil fuels.

Does this hold true for other fuel types? We base our daily inspections on specific gravity. My thought is that if it is a good indicator, perhaps we should be testing for viscocity as well.

RMW, thanks for the link.

 

[saxon]

FredGarvin, Just as an aside, could this possible be a problem with fuel injection at the test stand as opposed to a general fuel specification problem and every one's just pointing the finger at the fuel?

saxon

 

[FredGarvin]

Saxon,
without going into much detail about our fuel system on the engines, we have gone over each engine each time this has happened. We have yet to find any discrepancies in engine hardware that could explain this. However, I am not counting that out. I am taking parallel paths to figure out what is going on.

The thing I am doing now is to keep collecting data and wait until it happens again.

 

[rmw]

FredGarvin or SH,

You are welcome for the link. I go there a lot for a variety of reasons, but never your problem that I can remember.

I am still curious about the possibility of seasonal variations in the fuel that I asked about in the diatribe I did prior to the one where I gave the link.

If not, what is the nature of the periodic fluctuation or variation or whatever it was that you mentioned above?

rmw

 

[scorcher]

Hi,
Jet engines are a long way from my line of work, but this similar thread thread995-85538 might be relevent.

You stated the problems with brand new engines. Perhaps the problem is to do with a change in the cleaning regime (even seasonal changes here)

I know this is off the stratification theory you are persuing on this thread and you are looking at other possibilities of which i am sure this is one.

Is the small timeframe season/weather related (unseasonal weather seems to be how it is in the UK)

 

[FredGarvin]

RMW,

I too am very interested in the seasonal variations. I am in the process of trying to obtain the past fuel data to start doing the comparisons. Unfortunately our production facility is in another part of the country, so progress in that area is slow. I am not giving up on that.

Scorcher,
Thanks for the link. I will check on that aspect as well. The small timeframe is indeed weather related. It tends to happen at the time of year when it first starts to get really cold.

 

[saxon]

FredGarvin, Fluid viscosity is temp. dependant; lower temp. higher viscosities. Pump output is viscosity dependant; higher vis. lower output. This may be your problem if the engine is exhibiting symptoms of fuel starving.

Hope this helps.
saxon

 

[rmw]

Aha!!, A clue, and a good one.

Just when it starts to get cold, huh? Well, Here is my conjecture. Just as the weather starts to turn colder, either you, from what remains in your own storage, or your fuel supplier from his storage tanks, or even his supplier, is still pumping down the last of the "summer" fuel, blended for summer temperatures when things like pour point, wax content, etc., aren't critical. Obviously, these things matter in winter, not only to a trucker in Minnesota, but to an air plane pilot sitting on the tarmac in Minnesota.

Could be that he is actually delivering winter fuel, but you have enough residual summer fuel in your tanks to "blend" his winter fuel back up to closer to a summer blend.

Maybe he is still "blending up" to winter conditions, and your residual summer fuel is "blending down" the mixture, bringing the total fuel more close to a summer blend for a short period of time.

So, as It turns colder, this quasi-summer fuel gels up, maybe a little, maybe a lot, and plugs your filters impeding the flow. Can you get fuel filter differential pressure data from the time frame in question??

And then, by the time you think this thing is eating your lunch, you get some fuel turnover via a new delivery that either replaces or dilutes your quasi-summer fuel, and the problem goes away, and everybody forgets about it until next fall, when it all happens again.

Believe you me, I became a believer one December 6th in Louisiana, when it was 6 F outside, rare for LA, and when a neighbor (older widow woman) asked me to bring my big old powerful diesel pickup truck down to her house to jump off her poor little Mercedes diesel. (It did not have fuel problems, just a dead battery. ran like a top when I jumped it, after grazing a fire plug by her driveway while distracted by fuel tank switching described below)

Problem was I don't use the pickup truck regularily, so it was sitting there with summer fuel, and not plugged up. The fuel filters plugged solid immediately. It is the only time I have ever seen the warning light activated by high differential pressure across the fuel filter, ever. The engine ran terribly, if you can call what it did running at all.

I quickly threw a heavy dose of fuel treatment, which contained pour point depressants among other things, into the almost empty tank, and, I swear I could tell when that treated fuel hit the filter/engine. It smoothed out, and purred like the kitten that it is. Since this tank was almost empty, and I live in a hilly area, and was concerned about the fuel pickup in the empty tank sucking air, and losing prime, as it had before at low fuel levels in that particular tank, so I had to keep switching back and forth between the empty tank, with its load of heavily treated summer fuel, which the engine would run on, and the full tank, which had summer fuel also, but with no treatment, which made the engine run terrible.

I had to nurse this combination of treated/untreated summer fuel to a service station several miles away, after jumping her off, where I knew their fuel was obtained from a local refinery in the area, and would be seasonally adjusted for the current winter conditions.

I told that anecdote to say that fuel gelling is real, and fuel seasonal blending is real. And, the wrong fuel for the season can wreak havoc.

Isn't the prist you mentioned just a water problem solver?? Isn't it an alcohol that serves as a water transporter, and an antifreeze for the water that might be in the fuel???? I thought I remembered your saying that is all you use. You might want to look into an additive that would give you a pour point depressant, and a wax problem solver. At least for the period when you suspect that this might be a problem.

Other than that, I have no idea what might be your problem.

Keep us posted.

rmw

 

[jmw]

FredGarvin,
I think a detailed response to your comment on viscosity is probably outside the scope of this thread so i will post it as a separate thread.

JMW

http://www.viscoanalyser.com

Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[jmw]

I need to make a correction to my previous comments.

I was at Europes 7th largest refinery this week and speaking to one of the engineers who was in the team that pioneered "MIC" (I think he called it), Measuring Instrument Certification. He explained that for products like gasolene (petrol), diesel and aviation fuels they inline blend direct to the client (road/rail tankers, pipeline marine terminal) and not into intermediate holding tanks. The fuel certificates are generated based on the online instrumentation and not on laboratory measurements. He further stated that the inline measurements are more accurate.

So anyway, one of the key instruments is the densitometer. While density is not a defining parameter they none the less work to a density tolerance. All other prime quality factors being met they then control the density to the minimum value consistent with meeting the other quality parameters as this helps reduce the "give-away".

While the fuel is blended for the principal quality factors, density may also be controlled.
That doesn't mean, necessarily, that the density will be consistent from one batch to another; as i indicated above, the density of aviation fuels can vary significantly. IT means that I was wrong to say that density isn't measured or controlled. As part of the MIC instrumentation there should also be a density specification in the certification for the fuels supplied; or as part of lab instrument based certification if that is still done.


JMW

http://www.viscoanalyser.com

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[jmw]

It's not an "apple jelly" problem is it?

http://www.desc.dla.mil/DCM/Files/APPLEJEL.PDF

I just thought that some of the papers here, including on Apple Jelly, might provide some clues if you still have problems.

JMW

http://www.viscoanalyser.com

Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[FredGarvin]

Thanks JMW. I'm definitely going to have to read that and take a look around there. You have piqued my curiosity.

As an update, so far we have found one major culprit in the puzzle...of course it was the one thing the facility said would never EVER be the issue.......a manufacturing process change was made on a pretty important part. Of course, it has had the effect we were looking for. So the majority of our "issue" was not fuel related at all (which most of us were thinking to begin with). Through the process we have also brought up some differences in the way our two facilities handle fuel data, i.e. SG and LHV. So now I have the task of going back through historical data and rerunning calculations looking for any possible deviations in our constants.

Thanks to everyone who has helped with this. It surely was a good learning experience for me. Hopefully others benefitted as well.

 

[jmw]

Problem solving is one of the best learning experiences there is.

JMW

http://www.viscoanalyser.com

Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[peterwiens]

FredGarvin. Have you tried keeping track of the daily temperatures at the fuel level height in the tanks, the tank bottoms and about the middle of the bulk in the tanks to measure for differences?

The differences in the specific gravity of the fuels when drawn off the various depths of the storages were only noticeable when searching for those results. Jet fuels are more refined than diesel fuels. When the electric fuel pump on the farm drew away the heavier diesel fuel off the bottom over a few days of heavy use in the spring, lighter weight fuel seemed to be accessed eventually as the storage tank level dropped as there was noticeably lacking power and more volume consumption.
An aviation connection comes from the idea of possible settling processes in the storage on the farm related to settling possibilities at the airport's above ground tanks. Sweat on the outside is in a warming trend and sweat on the inside is in a cooling trend.
Waxbased fuel like diesel seems to have more variations than above ground gasoline storages from the upper levels to the lower levels of outside tanks. In your underground tank a high volume addition by refilling warmer fuel would likely often bring about a temperature difference(especially if you take delivery on a hot day). As lower temps are found below we assumed in our case on the farm that the heavier specific gravity and thus stronger horsepower fuel seemed to be linked and were at the bottom of the tank. This happened over and over again.
In the CFS (canada flight supplement) there is a chart that has a surprising difference in fuel weight for two extreme temperatures as well as two main weight groups of jet fuel listed. I wanted to show how 1000to2000lbs of cold fuel shaking around in the wings of a single engine turbine aircraft during approaches affects icing catchrate if it is either much warmer or much colder than the air or other aircraft metal.
In the process found that Jet A gets much heavier in the bitter cold than other types used in the peak temperatures in the summer.There's a lot more weight per volume in the winter and a lot more volume per weight in the summer. The lighter fuel from the very top(if in fact this turns out to be the case)will drain via funnel effect into your floating sump in each tank when any kind of separation exists. In our case the light fuel remained on top until it arrived at the bottom. I hope that helps.

 

[peterwiens]

Fred Garvin:

Are latent heat effects worth checking(water crystals etc)?

Parafin is a superior phase change material that can absorb heat or release it without changing temperature while it is in a certain state either during the cooling down or the heating up phase. The fact that its melting point is significantly higher than its solidification point has captured my interest. I wish to expose how fast the releasing latent heat of nearly frozen pure-water contained in compact snow (at its solidification point in the cooling phase) absorbs into parafin PCM in Jet A fuel(at the beginning of its melting point in the heating phase). The parafin and the water are only separated by the aluminum wing/fueltank hardware. The residually cold bulk fuel at -20C continously recoates the inner tank walls with a thin parafin film by the splash that is swished up in flight and manoevring. The wing is otherwise warmed to the outside atmosphere. The points below relate to an early winter cold/IFR weather-event that might aid in synthesizing my developing explanation.

1 Wing Ice - Re: Freezing wet-snow's heat conductivity-rate into JetA parafin based fuel separated from it only by a thin aluminum barrier, the laminar surface. A minimum jacketed high surface-to-volume-ratio nature of the wing tank walls seems to perpetuate a unique supercooling effect that is almost unperceivable in regards to the speed at which it appears to develope.

2 eng power - Re: Comparing various fuel nozzle spray patterns/temp, fuel supply line viscosity/density and air intake temp/humidity/pressure vs take off shaft horsepower variations

3 dense fuel - RE: Unplanned weight addition to max-payload for small air transportation application in the context of legal contingency fuel.

I will afford a new thread for latent heat parafin
unless its been explored elsewhere.
peter