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Jet Fuel Bulk Storage
6

Jet Fuel Bulk Storage

Jet Fuel Bulk Storage

(OP)
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.

RE: Jet Fuel Bulk Storage

Hmm, it reminds me of similar problem we have had just a few months ago.

Check for microbial growth and water content (emulsified + dissolved); compare the IFT values before and after "stratification".



RE: Jet Fuel Bulk Storage

(OP)
Thanks for the tip. I will do that.

RE: Jet Fuel Bulk Storage

You don't say how many engines are using fuel from the same source.

Aviation fuel is blended for certain characteristics and the other parameters are pretty much a consequence of what refinery processes are running. There is no control over density or viscosity, for example.

Aviation fuels are usually bridged into segregated storage because the density from one batch to another, even sequenctial batches from the same refiner, can show significant variation (the key to interface detection). Of course, the main concern is the fuelled up weight of the aircraft and with many more fuelling bowsers equipped with density meters to correct the volumetric flowmeters this is probably not the problem it once was. Even so, co-mingling batches may lead to stratification.
But will it affect the fuels combustion properties?

Viscosity can also vary measureably. Viscosity affects the spray pattern and it is also affected by temperature. Significantly so? I doubt it, though when testing diesel engines fuel density and viscosity are required for the SAE J??? power factor correction, but i think this as much relates to engines tested cold as to anything else.

In any event, it should not be a problem to take top middle and bottom samples from storage and to take samples from the fuel lines to the engine under test, both when there is a problem and when not, and have an analysis done. This will confirm the fuel meets it specification. But apart from that, unless specific tests are called for, contaminants will not be discovered.

One thing more that can e done is to review any recent maintenance operations that occured at around the time the problems where noticed and to focus on the engine and any installation unique to the engine with a problem. For example, if someone has fitted the wrong seal material or gasket etc then this could be contaminating the fuel locally.
If there are several engines and only one has the problem, if possible exchange it with an engine in another installation and see if the problem moves with the engine or stays with the installation.

It sthe old story, once you have eleiminated what it isn't, what it is, should be easier to track down.

JMW
www.viscoanalyser.com
Eng-Tips: Pro bono publico, by engineers, for engineers.

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RE: Jet Fuel Bulk Storage

Moisture as well as microbiological growth would be exacerbated in your above ground tanks, if you are in an ambient where the atmosphere goes below the dew point on a regular basis.

The tanks heat up during the day time sun, breath out, and cool down at night, breathing in the most moisture laden air of the daily cycle.

Do you feed from above ground tanks to the underground tanks?, and do you sample your tanks, for moisture collection in the bottoms, and/or drain regularily??

Do you test and take fuel from the tanks immediately after a fuel delivery.  All the stuff in the bottom of the tank, the free moisture, and the slime caused by micro growth gets stirred up, and can be picked up and be transported to your filters, plugging them, and affecting engine performance.

If it were possible to keep the above ground tanks as full as possible as long as possible, in order to minimize the vapor space above the liquid level for atmospheric air to breath into and out of (leaving behind its moisture load when the tank wall is below dew point) you could minimize the breathing problems.  If you ever come out on a cool morning and see the above ground tanks "sweating", know that the inside of the tank is just as "sweaty," if there is any moisture inside.  And, of course, the condensation of this moisture creates a vacuum, drawing in more wet air to replace the volume change of the vapor to liquid.

Do you have breather valves on the vents, or are they just open vented to the atmosphere.  Breather valves will reduce the amount of diffusion of air into and out of the vapor spaces, as well as lessen losses of product vapors.

Your tanks are no different than every gasoline station and/or diesel trucker out there.  Attention to breathing problems is essential.  Some of this problem is mitigated, the lighter the fraction gets, the reason that gasoline car owners don't have the same problems as diesel owners, the vapor pressure of the gasoline is higher than diesel, so the gasoline vapors tends to fill the space above the liquid, while diesel does not have this benefit.

I am not going to to look it up, but I suspect Jet-A is more similar to diesel than gasoline in that regard.  If I am wrong, someone will post a correction, I am sure.

And, in the case of diesel, for long term bulk storage, certain additives are recommend to fight bugs and slime from growing in the fuel, as well as to coalesce the water so that it can be brought to collection points, traps, and filters, and removed before the engines 'eat' it.

Good luck,

rmw

RE: Jet Fuel Bulk Storage

Re RMWs comment "I suspect Jet-A is more similar to diesel than gasoline in that regard" prompts me to wonder about fuel degradation with time.Somewhere in one of these threads I posted a link to an article about diesel fuel breakdown with time. Perhaps this is a possibility here also?

JMW
www.viscoanalyser.com
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RE: Jet Fuel Bulk Storage

One excellent link on the topic was in Thread483-90990 titled "Bunker C" in a post I did on March 27, 2004 from Power Engineering Mag, and I think that is where your (JMW) comments on the subject were as well.

rmw

RE: Jet Fuel Bulk Storage

JMW,

Besides being too lazy to copy and paste the link again, I posted the thread number, so that the readers could see your remarks in that thread as well, which I thought were excellent, and especially since you had brought it back to my attention.  Your memory is better than mine.

I hope SH or FredGarvin finds some useful information there.

rmw

RE: Jet Fuel Bulk Storage

Just to satisfy anyones curiosity, the standard i was thinking of is SAE J1995. I think. (there are plenty to choose from on the www.SAE.org web site and all I recall is several years ago commissioning an inline digital viscometer to measure the base density and viscosity so they could ease up on the intensive lab work in a diesel engine plant somewhere in the south, NC I think.

Anyway, the standard applies to IC and SI engines excluding aero and marine versions and jets, and though i guess there may be some similar standard, I didn't look to far for it.

http://www.sae.org/servlets/productDetail?PROD_TYP=STD&PROD_CD=J1995_199506

JMW
www.viscoanalyser.com
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RE: Jet Fuel Bulk Storage

PS kind words about my "rant", thanks RMW. Let's hope that interested parties will take the time to look at several of these threads.

JMW
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RE: Jet Fuel Bulk Storage

(OP)
Thanks for the input all.

To get a bit more specific, we are a jet engine designer/manufacturer. The variation we see is in two places. The first is in one of our test facilities that draws off of the bottom of above ground tanks that are 300 gal. The second place we see it is in our production ATP test cell that draws off of a float system on an underground 10,000 gal tank. Each tank has one engine running at any time. We do test every load we get, but we wait for 24 hours before doing so to allow for settling. When we see our variation in performance we always retake our fuel samples as well as a full engineering analysis of the engine in question. To date, we have not been able to find a smoking gun.

I can readily see issues with the small above ground tanks. Especially with the temperature swings we see. The one fact that I see that helps us here is that our turn over rate on the fuel in them is pretty high. That fuel does not stay put for long periods.

We monitor all of our fuels' net heat of combustion as well as other parameters. Over the years we have seen an approximate 3% variation in API gravity and an even less variation in net heat of combustion. Always the fuel must, and does, meet specs set forth in ASTM D 1665. RMW, your assumption about jet fuel being closer to deisel is a correct one. They are not too terribly different. We do include inhibitors and and an anti-icing additive.

Our below ground tanks are indeed vented and do not have breather valves. That is definitely something I will look into.

The big thing I was hoping to get a feel for is the rate at which a tank can stratify. We have some people quoting time spans that I have no idea are possible or not. Does anyone have an idea of what kind of ballpark time it should take for a large tank to stratify? Are we talking hours, days, weeks?

Thanks again for all of the info and the links.

RE: Jet Fuel Bulk Storage

About all i can do is suggest a logical "truth table" type structured investigation to isolate what the most probable causes and focus the investigation on these.

Unless you are buying very special fuel or your installation and storage follow unique design and operation, one would suspect that a detailed investigation of these aspects is not yet warranted.

For example, can we conclude that more than one engine uses the same fuel but not all engines exhibit the problem?
If so, one would tend to believe the fuel in storage is OK. As a check, when there is a problem, possibly you have the means to supply fuel to the problem engine from a different source, i.e. fuel that does not, apparently, cause a problem with other engines when used in other test beds. Maybe you can even tanker some fuel from one facility to the facility in question. (You don't say how these tanks are filled or if the smaller tanks are direct filled from the fuel supplier or a fuelled from your own bulk storage).

You say you see the problem in two places. Is it always the same two places? Does it effect several different engines tested in these places? Some of them or all of them? One type of engine or any type? Have you been able to move a problem engine from to a trouble free test bed to see if the problem persists?

If the problem is localised, I would suspect one possibility is something in the installation unique to each of these two places. Presumably these are installation where there has been a history of good performance, i.e. the problem is not with the system design but may be due to a change in the system e.g. new component or something done during maintenance or service, or a change in the way the system is operated.

It is at this point I would start to look at anything that could provide localised contamination. You did not sy if you test fuel samples taken from the problem locations. If you do, it may be worth having a more extensive investigation made. You would be looking for a rogue contaminant and possibly a transient contaminant i.e. not always present if not all engines are effected.

JMW
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RE: Jet Fuel Bulk Storage

(OP)
We are indeed in the middle of a very similar process. This thought on stratification in our tanks was simply a question that makes up the rest of the investigation.

Thanks again.

RE: Jet Fuel Bulk Storage

SH,

First, I will state a few of my qualifications:
(1) Certified DOD/GSA Fuels Inspector
(2) 1 patent for increasing octane via catalyst enhancement
(3) 1 patent for removing sulfur from diesel/mineral spirits cut (jet fuel)
(4) 1 patent for preventing oxidation of Jet Fuel in storage tanks!!!
(5) Test Cell Engineer for variety of Gas Turbine Engines
(6) Sold bulk fuel additives, such as anti-oxidants, biocides, etc.

You stated you have engine performance gremlins!  Let's start at your test cell;
(1) Are you using the same fuel pump on every class of gas turbine?
(2) Do you have any type of filter system prior to the fuel pump?
(3) Do you have a fuel preheater?
(4) What is the material of construction for the fuel storage tanks?
(5) What chemicals are you adding to your fuel?
(6) Who is the fuel supplier and what are the additives?
(7) Have you changed bulk fuel supplier within the past 6 to 12 months?
(8) Do you conduct visual inspection of fuel as part of check list prior to running each and every engine?
(9) What is BS&W of fuel in tanks?
(10) Do you have a fuel quality program in place?

Todd


 


Todd
www.oxilume.com

RE: Jet Fuel Bulk Storage

Are your tanks equipped with floating suction lines, which would avoid to pump out all the bottom sediments and water that we usualy find here???
An other solution to avoid moisture comming inside the product is to install an internal floating cover (for the aboveground only, of course!!!)

try this : www.larco.fr

RE: Jet Fuel Bulk Storage

Are the additives throughly mixed ? Additives in small dosages don't alter the main fuel properties, however they show sometimes adverse effects such as on water-separating properties. This is one other item for checking.

RE: Jet Fuel Bulk Storage

2
FredGarvin:

I have built several jet fuel reception, storage, treatment and distribution systems for airports and have never encountered a problem with short term stratification of fuels.  We follow guidelines that prohibit usage of fuel that has sat in storage (in-pipe or in-tank) over 30 days without pump around to thoroughly remix the fuel and then retest for specific gravity, color and particulate contamination.  Note that all tanks are sumped daily for removal of bottom solids and water.  Fresh fuel is accepted, settled for 24 hours and then tested for the parameters listed above.  IF a tank should sit for over 30 days, part of the recertification process is to compare current test results to initial results.  In the case of pipes which have not been used over 30 days, the pipes are flushed with a minimum of three pipe volumes of fresh fuel and then tested for particulate until samples meet specifications.  This procedure detects corrosion products from the piping/tankage that might be a problem as well as biological problems.  All flushed fuel is recycled within the system (i.e., passed through a filter/separator for particulate/water removal) and retested.  If it meets spec, it's added back into a tank of already accepted fuel.  If not, it goes into the slop fuel system for disposal.  

Have you taken a close look at the above ground tank pumpout configuration for bottoms removal?  Make sure it is removing all the condensed water.  Bottom product draw tanks are the worst problem for this because the water drawoff may be offset in favor of a centered product drawoff, thus hindering the effectiveness of sumping activities.  I also must agree with jmw, check and see if any recent maintenance activities have resulted in the use of gaskets, etc. which are not Jet A compatible.  Finally, I would have to agree with 25362 that the mixing of the additives should be checked as inadequate mixing could result in the types of problems you describe.  

RE: Jet Fuel Bulk Storage

(OP)
Thanks to everyone who has replied. I am going to need some time to digest all of the information and links given here.
Some very quick answers are:

1. We have used the same carrier for years. We have not changed.

2. We use float systems in the tanks which draw approx. 12" below the fuel level.

3. We monitor for water and contamination, both through the level monitoring system we use and weekly visual inspection.

4. Our only additive to Jet A is PRIST.

5. The engines we see the gremlins on are brand new engines, during their initial performance evaluations and only during a very small timeframe during the year (it has repeated and we noticed the trend).

6. All of our facilities use the same type of fuel pump, but in differing capacities depending on engine type.

7. We filter after the main pump.

8. We do not use preheat from the fuel farm, however the engine itself has a liquid to liquid cooler.

9. All fuel is inspected prior to offloading for water and contamination. We analyze for SG only on every load. Our suppliers are responsible for maintaining conformity to ASTM specifications.

Fizzhead: We have a similar program in place for our fuel storage. That is why I have a hard time believing the proponents for the fuel stratification theory.

Thanks to everyone again. I appreciate the assistance.

SH

RE: Jet Fuel Bulk Storage

Fizzhead merits a star for his useful post.

RE: Jet Fuel Bulk Storage

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

RE: Jet Fuel Bulk Storage

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

RE: Jet Fuel Bulk Storage

(OP)
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.

RE: Jet Fuel Bulk Storage

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

RE: Jet Fuel Bulk Storage

(OP)
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.

RE: Jet Fuel Bulk Storage

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

RE: Jet Fuel Bulk Storage

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)

RE: Jet Fuel Bulk Storage

(OP)
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.

RE: Jet Fuel Bulk Storage

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

RE: Jet Fuel Bulk Storage

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



RE: Jet Fuel Bulk Storage

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
www.viscoanalyser.com
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RE: Jet Fuel Bulk Storage

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
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RE: Jet Fuel Bulk Storage

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
www.viscoanalyser.com
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RE: Jet Fuel Bulk Storage

(OP)
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.

RE: Jet Fuel Bulk Storage

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

JMW
www.viscoanalyser.com
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RE: Jet Fuel Bulk Storage

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.  
   

RE: Jet Fuel Bulk Storage

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      

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