For some of you.The jet fuel tanks MUST be vented to atmosphere or you would be creating a pressurized vessel that would be full of jet fuel vapors and that would not be safe. Well, it was the thought that counts I guess.!!! :) (You still need to stay safe tho) 1st. Best of luck Mark and please keep us informed of your progress. These are the vents from the under gound tanks. Micky, it is more common than not for fuel tanks to be vented to atmosphere, all of ours on the ship are vented and if you go to your local gas station look on the side of the building and you will see many pipes running up the side of it. EXAMPLE INT or DINT or LONG MUL, DIV or use CPT Thanks for bring this problem to the forum, I never though of trying to figure out this scenario before so you have got my brain working and I will brush up on my math skills now so I too will be able to solve this if need be in the future. Others on the forum with more experience will be able to guide you as to the correct PLC instructions and math formulas to use. The instuctions I used here were for example only, I just spit this out and did not put alot of thought into it. So use a MUL instruction MUL Source A = N7:2 Source B= 0.004329 Dest = N7:3 (Total Gallons of Jet Fuel in Tank) Please take all that I have said with a grain of salt, as I am in no way a PLC or a Math expert, in fact I am pretty mediocre at both. Once you get to this final number after this equation you will have cubic inches of fuel in the tank so lets say the destination for this will be N7:2 Now you will need to convert the value of N7:2 (cubic inches of fuel) to Gallons. I am not familliar with the 1500 but TConnolly pointed out earlier that it does have limited math abilitys. From here you will need to get help from others with a much better grasp of math and the capabilties of the ML1500 you are using to compute this math calculation. df = depth of fluid (or Height) in the above linked formula so N7:1 would get moved into place anywhere the formula calls for df. Pressure/Specific Gravity = Height (I believe the SG of Jet Fuel is 0.82 you will need to check but lets use this # for now) DIV Source A = N7:0 Source B = 0.82 Dest = N7:1 So now N7:1 = Height in tank (in inches) Now that you have the Height of the tank known you can use a MOV instruction to place this variable into the larger equation. So you would then need to use a Divide instruction (DIV) to calculate Height of liquid in tank. Lets say this SCP will output to N7:0 So now N7:0 = PSI Inches of water column can be calculated with a known PSI and specific gravity of the liquid. (PSI of a liquid can be calculated in a linier manner so you could use an SCP instruction to scale the raw input value of the pressure transducer and scale it to PSI. If pressure transducer would work then it would give you PSI. But basically your tank size is a constant, so the main variable that will change in the equation is: What level is the liquid in the tank. lol I would agree that this is pretty confusing and higher math is not a strong point of mine either. ![]() So we are just killing fish not terrorist. Not on a military vessel, just a large At Sea Fishing Trawler / Processor. ![]() Hi Mark, Thanks for your kind comment's, although I am not really doing anything for you out here unless you eat a lot of fish. Anyway keep up the good fight, and please let us know how it turns out. We have a system that shoots a burst of air into the tank and a measurement is calculated from that. Also just a thought, is the pressure transducer you are using classified for hazardous locations / rated to be submerged in Jet Fuel? Onboard the ship I work on we are subject to a very strict criteria as to what we can and cannot use to measure level in our fuel tanks. ![]() ![]() Is the tank vented to atmospheric pressure or is it a sealed tank under pressure? What temperature fluctuations will the liquid in the tank be subject too? Is the tank perfectly level or slightly tilted toward the suction line of a pump? And as TConnolly pointed out the tank is probably not a perfect cylinder. From the reading I have done you will still have many factors that come in to play and can add variables to your calculation if your measurements have to be exacty precise. Hopefully others will be able to help you with specific questions, as I am still trying to wrap my head around this, its interesting though. Calculate WC from psi: Formula for Calculating Volume: Then you will still need to convert cubic inches into gallons. Here are a couple of links I found, hope they will help you out. Hello, The math on this one makes me crosseyed, once you get into a totally non linier vessel it seems to get very complicated.
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