Gas Tanks

The colour of the gas change with the volume. Only joking.

The stick is placed on the bottom of the tank. and the whetted mark is taken.

When the shape and dimensions are known the remaining volume can be calculated.

The tanks are mostly cylindrical - area of a cord x length = volume.

The stick can be calibrated for volume but usually it is just marked for linear measurement and because it is use regularly they start remembering the conversion relationship.

As I remember there was a material you would coat the end of the stick with. It would change color when it came in contact with water -- you could tell how much water was in the bottom of the tank below the fuel. The owner used to joke that he wanted to make sure he had enough water in the tank for the fish.

Time to Google 'dipstick'.

Once was a pump jockey when they actually pump gas for you and cleaned your windshields. If you have the dimensions of the tank the volume can be calculated. The wet mark on the rule will let you know the level and the volume can be calculated from that. But most look it up on a chart supplied by the tank manufacture.

Of course when dealing with a real rather than ideal gas tank, we have to take into consideration that they seem to be the last thing designed and have to fit around everything else in the vehicle! you should see some of the tank shapes that I've seen. A camaro for instance, has something akin to an upside-down triangle, so when the meter reads 1/2 tank, you really only have about 3 out of your total 11 gallons left!

It's gotten on my nerves so many times that I've wanted to design a translator circuit to better convert %depth to gallons remaining, but I can think of better uses of my time. Would make it a lot easier to calculate MPG if you weren't filling up all the way...

Another possibility is that the stick floats in the fuel, the more it sticks out of the tank the fuller it is. Please note that as an Australian I can't call the stuff in the tank "gas", we call it petrol. What do Americans call LPG (we call it gas)? Jeff

With me old Kingswood I had a half meter black 1/4 inch (or is that 8 mm) poly pipe as a dipstick. The gage was the only thing that never worked on this "Best Car Ever" and I could rely on the improvised method for years. We are talking real country here, but I wonder what your real problem is. Benchmarks is what you could google. Good Luck.

Butane

LPG is propane or butane or a mixture of the two in North America

Nicely done, hadn't thought about that one.

As far as the nomenclature for LPG, I've always called it LPG, most non-engineer non-mechanic people I think just call it (incorrectly) propane.

Stainless steel "Strapping tables" are welded to the sides of tanker trucks, kept on paper in binders on the shelves of offices in places with big storage tanks, etc. They tell you what is in the tank and what the freeboard remaining is for any depth liquid in the tank.

The man filling the tank at the gas station knew before he left the terminal how much was needed because he was automatically summoned and told how much by the electronics monitoring the entire operation. He was "sticking" the tank just to confirm what he'd been told.

Good luck.

The measuring stick used is like a ruler. It uses calibrated marks that correspond to the volume of the tank. When the stick is inserted into the tank, to the bottom, then removed, the wetted portion will indicate the amount of fuel in the tank.

If you know the total volume of the tank and stick the current level, it is only a subtraction problem.

Bill IMSE WVU 06'

That's true if the tank has a constant cross section - like a vertical axis cylinder or a rectangular tank.

What if the tank is a horizontal cylinder with elliptical heads - or rectangular and has slightly bulging sides because of the way it was made.. ?

With strapping tables the actual volume contained by the tank is typically listed for every 1/4" depth of liquid from the center bottom of the tank. These tables result from a part of the testing done by the tank maker. They reflect what is real - whether the tank ends up precisely as drawn, or has a slight unintended taper or whatever.

Any dipstick should be calibrated as per the tank it measures.

The way to calibrate a tank: You feel it up, bottom the stick in a certain known position, (if perpendicular is not possible,) and mark the dipstick full . Than start emptying it slowly say one or so gallons/liters at a time, make markings for each quantity until totally empty. same goes for floating stick, except it measures the quantity from the top rather than from the bottom. In any case this dipstick is only good for a specific tank! The best dipstick is made out of wood, because it absorbs gas/petrol (or whatever name you have for it.) and leave a clear mark.

This is a common practice in the airplane industry. When you buy a new or used general aviation airplane the dipstick comes as legal accessory.and indispensable part of the airplane.

Hope it helps.

Wangito.

Interesting idea. The strapping tables I referred to relate any measured liquid level to actual volume in the tank - and related freeboard remaining - the tables are specific to the individual tank being measured - and account not only for the geometry of the tank, but also the peculiarities of the tank. In the Chemical and Petroleum industries this is very standard.

Sounds like in your industry you have dipsticks with the strapping volumes on them - that's handy - only drawback is when it gets lost.

Many year ago when I did it, the stick was marked in inches. We knew that if the level was below a certain amount we could take a delivery. As we sold ethyl and regular in those days, and the truck would deliver both at the same time, we would wait until both storage tanks could take a full delivery.

I suggest though that the professor is looking for a little more than the above. It is easy enough to calculate the submerged area of an endcap of the storage. Assuming the endcap is essentially flat, multiplying that area by the length of the tank would give the amount of fuel in cubic units, which could then be converted to gallons or liters.

A formula that does that is (pi*r^2)/2 - (r-h) * (2*h*r-h^2)^.5 - (r^2)*Arcsin((r-h)/r)

where h is the height of the fuel as measured by the stick and r is the radius of the tank. You would then multiply the result with the length of the tank.

I have this set up in Excel -- which is why it might not be the most efficient formula for calculating the result.

Your professor is nuts giving the young students such an idiotic problem. It is better to go and fill up every time you passby a cheaper gas station. Or go to certain level and fill a certain amount of gas depending your vallet and keep yourself worry free.

Nadeem

08302007

What!

You want us to do your homework for you, shame on you.

You get a failing mark on that assignment.

Sit down with your slide rule and do your calculations - oops, I forgot, we don't use slide rules any more. How many even know what a slide rule is, I believe that tool is forgotten. I hope we have not forgotten how to think, too.

Anyway, I never was blessed with Engineering 101, my major was physics/chemistry, double major. Physics has always been my first love. It was just be chance and the need to put some bread on the table that I worked in Mechanical Engineering and reached the level of 'principle' with a major engineering corporation. Learning never stops. One of my regularly visited links is MIT's open course ware, it should be yours, too. Another of my regular stops is The Edge, for a little philosophy.

Basic math: The tank has a given diameter. It also has a known length. Multiply the diameter squared by .7854 times length, and you have cubic area of the tank. Given the aforementioned, you can figure out the rest. Tip: The fuel level sticks are calibrated to the tank, using the above formula.

And what if the tank has an irregular shape? Almost all automotive fuel tanks have irregular shape.

Not a very smart answer.

Wangito

WRONG!

In the USA, almost all gasoline tanks are tubes with sealed ends, double walled, and tested to 1.5 times the expected maximum eternal pressures. The EPA and DOT have taken steps to remove all old, single walled tanks that so many of which have developed leaks and contaminated our ground water. Gas and liquid hydrocarbons as all stored in round tubes with either spherical or elliptical ends designed to hold the contents safely. These shapes are the strongest and most efficient for the purpose. Think PIPE!

Wrong?

what's wrong? That d2 x h is not the "Cubic area" of a cylinder? (what's that?) according to our poster, and it is only a good formula for a volume of a right cylinder, and that is not a good formula for an irregular shape tank?. "Think pipe"? Why? He was talking about an Exxon underground (so I guess,) fuel storage tank, How do you know what shape it is? If you are not sure about the formulas, go back and revise your middle school notes. The rest of your answer though true and interesting is totally off topic.

And BTW, I find the question to be middle school level, definitely not engineering 101. That's nobody's fault here, but it does raise a whole lot of other questions.

Wangito.

Wangito.

the wrong! was in reply to the multiple adn odd shapes statement made above, sorry I did not quote it as I should have. My bad.

Right on the mark about the education level - the trouble with the U.S. is there are no real standards in education - a high school diploma could represent a reasonable level of education in some places, and mean the kid can read little more than a stop sign in other places. The differences are even greater in colleges and universities.

There are always exceptions. A general question deserves a general answer, unless you are standing on your head. Here in the states, underground tanks are designed per specs approved by the powers in charge. The are, and the point made was how to come up with an answer. If it ain't round, then run the cubes,(any tank manufacturer already ran the usable volume calcs for you, (because of lawyers, don't you know) why re-invent the wheel) and dang, you got yourself an answer. It doesn't take a rocket scientist to tie shoes.

I love it, because so called Engineers like to make a career out of micromanaging a simple project, allowing me to make a quite comfortable living. Nobody really gives a damn how smart you are, can you make something that works, and won't cause the company grief!

At car service station, the labours used to evaluate the volume of gasoline tank with copper stick divided into centimeters (or inches) calibrated to define the exact volume of tank for each rising centimeter (or inch). The witted length represents how much exactly the volume of liquid.

Note: For open tanks designed for ambient pressure, we can not store any gas or liquid under pressure. And handling of LPG requiring special design of that vessel under a design pressure not less than 250 PSIG, which takes into consideration the higher vapour pressure of propane than of butane.

So, in Egypt you measure the quantity of liquid in cm (or inches)?

I thought it would be like here in Chile in liters (or gallons).

Wangito.

No, what he's saying is they use sticks marked with the liters or gallons represented by the various depths marked on the stick. This is similar to the use of strapping tables for a tank where the actual volume of the tank is laid out in tabular form corresponding to measured depths. This type of measure tends to be much more accurate than even using known formulas for known shaped tanks - because they result from testing the actual tank and include for all minor variations in the reality of the final tank shape.