SLC 500 horizontal tank formula

remington · Feb 22, 2009

Hi Everyone,
I need some help with a formula on a horizontal tank. I need to write ladder logic for a horizontal tank that is 288" long. Diameter 100", minor radius of 17.75 ". I am using 3277ma for my zero and 16383 ma for my 100% full. I have tried a few formulas and it is still not right. I can get close but not accurate. Any help would be greatly appreciated! Thanks

Mickey · Feb 22, 2009

http://www.arachnoid.com/tank_volume/

http://www.red-bag.com/engintools/hortankvol.php

http://www.plctalk.net/qanda/showthread.php?t=42400&highlight=horizontal+tank

TheStarr · Feb 22, 2009

I haven't figured out the PLC implementation yet, got to let the brain chew on it for awhile.

Here is a calculator that helps visualize the problem.

http://www.visualtrig.com/circles.aspx

remington · Feb 22, 2009

Thank you for your interest

Thank you for your interest. I forgot to mention on my original post that I am also trying to convert it to lbs at 8.45. I have tried a formula on arachnoid and I am close but not good from 45 % on up.

Mickey · Feb 22, 2009

Is the tank perfectly level?

remington · Feb 22, 2009

level

The tank is darn close less than a qtr inch.

TheStarr · Feb 22, 2009

It seems like the theory has two parts. Between 0% and 50% you calculate how much fluid is in the tank. Between 50% and 100% you calculate the air space and then subtract that from 100%.

Mickey · Feb 22, 2009

More link on the subject.

http://www.plctalk.net/qanda/showthread.php?t=26220&highlight=horizontal+tank

http://www.plctalk.net/qanda/showthread.php?t=25694&highlight=horizontal+tank

http://www.plctalk.net/qanda/showthread.php?t=25255&highlight=horizontal+tank

http://www.plctalk.net/qanda/showthread.php?t=1397&highlight=horizontal+tank

(8{)} ( .) · Feb 23, 2009

Can't you just use a look-up table?

I've done this in the past and it's not incredibly complicated
but a look-up table is so much easier and faster.

Good luck,

(8{)}

.)

Tom Jenkins · Feb 23, 2009

The problem with the formula in the above link, like so many things with round parts, is it requires either trig functions or square roots to do the calculations. Many PLCs don't have tehm available. On the other hand, squares and cubes are easy with even four function math, although you really need floating point math to make it work easily.

I took the tables below from data by Panner Bailin. You can either create a look-up table and interpolate, or use the formulas I obtained by using a spreadsheet to do a linear regression on the tables. (This is a very good technique for all kinds of obtuse and complex functions.)

d/D = Depth/Diameter
Volume fraction Vf (that is, %/100)

d/D Vf
0 0
0.05 0.01869
0.1 0.05204
0.15 0.09406
0.2 0.14238
0.25 0.1955
0.3 0.25231
0.35 0.31192
0.4 0.37353
0.45 0.43644
0.5 0.5
0.55 0.56356
0.6 0.62647
0.65 0.68808
0.7 0.74769
0.75 0.8045
0.8 0.85762
0.85 0.90594
0.9 0.94796
0.95 0.98131
1 1
0 0

Vf = (0.4055 x d/D) + (1.7764 x (d/D)^2) + (-1.17839 x (d/D)^3)

Dished Head Volume
d/D Vf
0 0
0.06 0.0104
0.12 0.0397
0.18 0.0855
0.24 0.1451
0.3 0.216
0.36 0.295
0.42 0.381
0.48 0.47
0.54 0.56
0.6 0.648
0.66 0.732
0.72 0.8087
0.78 0.8761
0.84 0.9314
0.9 0.972
0.96 0.9953
1 1

Vf = (-0.0009478 x d/D) + (3.00269 x (d/D)^2) + (-2.00179 x (d/D)^3)

TConnolly · Feb 23, 2009

Tom Jenkins said:
The problem with the formula in the above link, like so many things with round parts, is it requires either trig functions or square roots to do the calculations.

Also, even though the SLC has trig functions available, the trig functions use radians, so you have make you set up your formulas correctly.

What caught my attention in this thread however is this:

remington said:
Thank you for your interest. I forgot to mention on my original post that I am also trying to convert it to lbs at 8.45. I have tried a formula on arachnoid and I am close but not good from 45 % on up.

Since you need pounds then just mount the tank on load cells. Then you get what you want in the first place and don't need cpu hogging calculations.

remington · Feb 23, 2009

Thank you

Thank you for the information. First a look up table is something I may try to incorporate. The putting it on load cells is out of question since half the tank is inside a building other half is outside. I have re done the program with the help of you guys and I am very accurate until half full, but the top half gets off quite a bit.

Kevdogg329 · Feb 23, 2009

remington said:
Hi Everyone,
I need some help with a formula on a horizontal tank. I need to write ladder logic for a horizontal tank that is 288" long. Diameter 100", minor radius of 17.75 ". I am using 3277ma for my zero and 16383 ma for my 100% full. I have tried a few formulas and it is still not right. I can get close but not accurate. Any help would be greatly appreciated! Thanks

why can't you use a Scale with parameters to your setpoints, scale them to 0 and 100%??

Tom Jenkins · Feb 23, 2009

If you calculate the volume correctly, and you have the correct density of the liquid, then the calculation must work correctly.

What is the liquid? Note that the density of water is 62.4 lbs per cu ft or 8.34 lbs per gallon or 0.27 lb per cu in

TConnolly · Feb 23, 2009

Remington, can you post what you have so far? Zip up your .RSS file and attach it to a post. The more eyes the better the chance of spotting a mistake.

SLC 500 horizontal tank formula

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