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Old October 31st, 2019, 01:01 PM   #1
qwemx
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HMI - Volume of irregular shaped Tank

Hi experts

I got a last minute surprise when the customer told me that the tank is not uniform

I already have program which show this on scale of 0 to 100% but it has to be changed to actual Volume which is around 85 units of Volume (gallon)

The Customer has been using a float ball type Potentiometer based Level sensor it has an output of 0 to 5 Volts DC - and my module is 0 to 10 V DC analog input

this is being Used to measure the volume of fluid inside the tank, the tank is having a shape as shown in the picture
https://imgur.com/gallery/YcjIN9d
How do I tackle this issue?

Last edited by qwemx; October 31st, 2019 at 01:04 PM.
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Old October 31st, 2019, 01:08 PM   #2
widelto
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Is lower part a cylinder ??
Is upper part a cylinder ??
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Old October 31st, 2019, 01:10 PM   #3
Elcan
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You have to create a formula, calculating the volume for each of the tank sections, using an IF or a Greater Than condition.
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Old October 31st, 2019, 01:29 PM   #4
qwemx
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Quote:
Originally Posted by Elcan View Post
You have to create a formula, calculating the volume for each of the tank sections, using an IF or a Greater Than condition.
Something like this

IF output_from_the_sensor is less than height of smaller part THEN Volume :=((real value from sensor )/Real_Value_till_the_ball_is_inside_the_Lower_Part) *Total_height_of_lower_part*Volume_Per_Unit_Height ));
Else
Volume := (ReaL Value from sensor - Real_Value_till_the_ball_is_inside_the_Lower_Part) * Volume_of_upper_part_perunitheight)+ Total_volume_of_the_lower_Part.

Main variables to investigate

Till what height is the lower part, what reading it reads on the level sensor and what is the total volume of this part

What is the height of the Upper part
what value the Sensor reads on reaching 100%

Last edited by qwemx; October 31st, 2019 at 01:35 PM.
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Old October 31st, 2019, 01:30 PM   #5
qwemx
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Quote:
Originally Posted by widelto View Post
Is lower part a cylinder ??
Is upper part a cylinder ??
I will check the drawings. I did not receive anything yet.
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Old November 1st, 2019, 06:56 AM   #6
alfhuckett
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The float sensor gives 0-5V output, This is based purely on the height of liquid in tank.


Treat the tank as two sections, and work on the dimensions of each section.


e,g Lower Section A, 40% of Height; Upper Section B, 60% of height


If Sensor Output <2 Volt, Volume = V/2 x Volume A
If Sensor Output >2 Volt, Volume = ((V-2)/3) x Volume B)+ Volume A


Adjust the numbers to suit the relative heights of the sections.
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Old November 1st, 2019, 07:01 AM   #7
cjd1965
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you may need to pour in known amounts like 50 litre steps and record the potentiometer reading and then create a table in the PLC to lookup the values vs litres / gallons
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Old November 1st, 2019, 07:13 AM   #8
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Oh and when you say Gallon, you have to say US Gallon or Imperial Gallon, otherwise International Weights and Measures finds you and they do things to you.

cjd1965 has it right. At the very least you should test it like this.
0-5V potentiometer on a float sounds like it won't be linear either.
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Old November 1st, 2019, 07:27 AM   #9
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I use these mounted on top of tank facing down.
https://www.automationdirect.com/adc...suring/opt2011
They are much more accurate 0-10 v although as others have stated you will need
2 formulas to get the volume one for lower section and one for top. I would write 2 separate SCP's with a GTR to switch between them
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Old November 1st, 2019, 10:14 AM   #10
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Does the oddly shaped tank's mechanical drawings or documentation include a "sounding table"?

It's definitely not the same, but for quite a few of ballast tanks in ships, the manufacturer will supply you with this sort of table that lists volume per cm of liquid inside it. It's then fairly easy to detect transition points and come up with a formula to calculate the volume.
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Old November 1st, 2019, 10:57 AM   #11
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Yes I have a sounding table
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Old November 1st, 2019, 11:18 AM   #12
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Sorry Volume has to shown in Barrels .
more details in documents
sounding table and dead volume also because if the ball type sensor
https://www.dropbox.com/sh/w1awvao21...dzB8tHvVa?dl=0
Attached Files
File Type: xlsx sounding table.xlsx (40.8 KB, 7 views)
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Old November 2nd, 2019, 11:25 AM   #13
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Today i took the values from the module when it was at bottom and at top and also at the point where the surface area of the tank changes

I also created a block in ladder to do calculations all details are in attachment please see

pot is reading 0 to 4.22 volts dc because this pot is not the exact replacement of the required pot however i am using the INT values from the module and not the dc values to make calculations
https://www.dropbox.com/sh/w1awvao21...dzB8tHvVa?dl=0

Last edited by qwemx; November 2nd, 2019 at 11:29 AM.
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Old November 2nd, 2019, 07:30 PM   #14
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I used to work in a lot of tank farms in the oil industry and the tanks are not uniform. We had 40,000, 80,000 and 250,000 barrel tanks and other sizes. We had what are called "strapping tables". They basically measure the tank diameter at different heights. The tanks had gauges that used a steel tape to measure the liquid level, and just did a look up and temp compensation etc.
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Old November 3rd, 2019, 06:06 AM   #15
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Always going to be hard work....

Using "look-up" tables of height versus contents - how many points do you include ? The more you put in, the less the potential errors when interpolating between the upper and lower figures.

Using tank dimensions - how many tanks have the exact design dimensions ?


By far the easiest way, if it can be achieved in your case, is to put the tank on load cells and measure weight. A simple calculation can then be done to convert the weight to volume, based on the density of the contents, and temperature.
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