Horizontal Tank Volume vs Level

[Bullzi]

Hi Everyone,
I am trying to compute the tank volume vs level on a horizontal LP tank (capsule tank). I searched the forum and found a nice post that had a spread sheet on it by Tom Jenkins. http://www.plctalk.net/qanda/showthread.php?p=757739

I am trying to implement the algorithm that he posted and I seem to be having some issues. The Volume Factor for the Tank portion of the calculation does not seem to follow the chart that is in the Excel spreadsheet.

Could someone give me a sanity check on this? I am using ST in Studio 5000 v28 to do this calculation. Let me know what I am doing wrong.

Thanks for your time.

 

[Dirt]

Try

VF_TANK := (-1.17839 * (dD**3)) + (1.77642 * (dD**2)) + (0.40551 * dD);

instead of -1,7839 as in your screenshot. You missed the first decimal.

 

[Bullzi]

I double checked my equation and it is defiantly -1.17839. If I had used a comma instead of the decimal point I wouldn't be able to compile the code due to an error.

What I ended up doing was I found a web site that would let me put in the tank size info and a fill height and it would spit out a volume. I put in all the fill heights every 3" and recorded the volumes it gave me. I put those heights and volumes into the same spreadsheet to develop a curve and equation for that curve. I will put in that equation into the PLC.

Given these tanks were built in the 50's and any strapping charts are long gone this should be close enough. We are using a meter to load into the trucks so we don't have to worry about using the tank gauge for Custody Transfer. I just wanted to have a volume so I can display the Ullage on the HMI.

 

[Dirt]

I double checked my equation and it is defiantly -1.17839. If I had used a comma instead of the decimal point I wouldn't be able to compile the code due to an error.

Look at your own print screen. It's -1.7839 in your code instead of -1.17839. I tried your formula as in your print screen and got the same error.

When I tried the exact formula from the Excel file it checks out. Tom Jenkins Excel file is correct and working.

 

[Bullzi]

You are correct. I am sorry I was thinking that you were referring to me putting a comma separator in my code as apposed to a decimal point. I didnt even look at the actual number my apologies!!