Volume af cylindrical tanks lying down

JERA · Sep 19, 2017

I have to calculate the volume in cylindrical tanks lying down.
PLC = Siemens S7-300
Software = Step7 vers. 5.5 software (not TIA portal)

I have analog signal for liquid level height in the tank.

Does anyone have program for this calculation in a Siemens PLC, or the formula for the calculation?

Andybr · Sep 19, 2017

The formula is given on this page :-
http://mathworld.wolfram.com/HorizontalCylindricalSegment.html
As you can see this is a fairly heavy calculation for most PLC's and you might want to consider just using a look up table of volume against level at predetermined intervals (ie 1% intervals) instead. This would be much quicker.

JERA · Sep 19, 2017

Hi Andy

Thanks for your reply.

I can see that formula for calculation is difficult to make in a PLC.

Lookup table will probably be the solution, but it depends on the accuracy that I will find out with the customer

Christoff84 · Sep 19, 2017

Depending on the sensor used, you may be able to have the sensor do the scaling for you. We have this situation with an oil tank, and we put an Endrauss+Hauser ultrasonic sensor on it, that was smart enough to handle the scaling for us.

JRW · Sep 19, 2017

Jera
Looks like that formula is in the Oscat library
You ever use Oscat?

Tom Jenkins · Sep 19, 2017

In many cases like this I plot the function in an Excel chart and get the trend function to give me an equation. This is an example.

Bit_Bucket_07 · Sep 19, 2017

JERA said:
Hi Andy

Thanks for your reply.

I can see that formula for calculation is difficult to make in a PLC.

Lookup table will probably be the solution, but it depends on the accuracy that I will find out with the customer

If you decide to go with a lookup table, this site will do the number crunching for you: http://www.handymath.com/cgi-bin/circlevali25.cgi?submit=Entry

L D[AR2P#0.0] · Sep 19, 2017

SCL or STL implementations:

Code:

FUNCTION FC898:REAL
VAR_INPUT
R:REAL;    
h:REAL;
L:REAL;
END_VAR

VAR_TEMP
Term1: REAL;    
Term2:REAL;
END_VAR
Term1:=(R-h)*SQRT(2*R*h - h*h);
Term2:=R*R*ACOS((R-h)/R);
FC898:=L*(Term2 - Term1);
END_FUNCTION

Code:

FUNCTION FC 899 : REAL
TITLE =
VERSION : 0.1


VAR_INPUT
  R : REAL ;    
  h : REAL ;    
  L : REAL ;    
END_VAR
VAR_TEMP
  Term1 : REAL ;    
  Term2 : REAL ;    
  hsquared : REAL ;    
  tworh : REAL ;    
  rminush : REAL ;    
END_VAR
BEGIN
NETWORK
TITLE =

      L     #R; 
      L     #h; 
      -R    ; 
      T     #rminush; 
      L     #h; 
      L     #h; 
      *R    ; 
      T     #hsquared; 
      L     2.000000e+000; 
      L     #R; 
      *R    ; 
      L     #h; 
      *R    ; 
      L     #hsquared; 
      -R    ; 
      SQRT  ; 
      L     #rminush; 
      *R    ; 

      T     #Term1; 
//..
      L     #R; 
      L     #h; 
      -R    ; 
      L     #R; 
      /R    ; 
      ACOS  ; 
      L     #R; 
      *R    ; 
      L     #R; 
      *R    ; 
      T     #Term2; 
//..
      L     #Term1; 
      -R    ; 
      L     #L; 
      *R    ; 
      T     #RET_VAL; 

END_FUNCTION

JRW · Sep 19, 2017

Nice
JERA- you owe LD a few beers

JERA · Sep 20, 2017

Thank you to everyone for answers that have been of great help.

JRW - I know Oscat and have used their blocks a couple of times

Thanks to Tom Jenkins for the Excel sheets, that I will use to check for calculations.

L D [AR2, P # 0.0] Thank you for the code and if you come to Copenhagen one day, send me a PM and there will be some Danish beer

Volume af cylindrical tanks lying down

JERA

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Andybr

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JERA

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Christoff84

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JRW

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Tom Jenkins

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Bit_Bucket_07

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L D[AR2P#0.0]

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JRW

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JERA

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