Flow Rate To Total Production

[Kabir]

This the problem guys
I am installing flow meters at different sections of the plant to measure %loss in production.
Since the flow meters are there I also want to use them to produce figures of production over each shift.
I would think that I should integrate the flow rate in order to obtain this figure.

How exactly do I write the ladder logic for this application.

Hardware: Allen Bradley PLC5 Enhanced
Software: RSLogix5

And if there is anyone with this information I also wanted to know what are some of the common errors that exist with this system

 

[randylud]

Need some info here!

You are probably measuring instantaneous flow with your meters. I would suppose you are getting values of flow rate in some engineering units that are consistent with your plant needs. You should convert the instantaneous readings to mass flow and then totalize them. You can do the conversion this way:

Qm= D x Qvol

where Qm = mass flow rate
D = Fluid density (mass per unit volume)
Qvol = volume flow rate ( ie: what you are already measuring)

Once you have the mass flow rate, then just keep a running total of the amount in the PLC data table. Your PLC code should sample the flow rate at some rate that is consistent with your needs and you may want to do a trial and error method on that depending on how much your rate changes over time. If it is fairly constant, then you can sample fewer times than if it is changing rate quickly. Be sure to use consistent units in the calculation above or you may get oranges when you are wanting apples.
Some of my learned colleagues here will doubtless have other suggestions for you but this might get you started.

 

[(8{)} ( .)]

Analog flow indicators generate an output based on Quantity/Time. For instance Gil/Fortnight.

Once we know the engineering units range it's easy to build a totalizer. Here's an example.

For our example we'll assume that your flow meter output is in a less common range, say Liter/Minute.

1) Designate a subroutine for the calculation
2) Call that subroutine 1/sec (as an STI if possible)
3) Add the following rung to the subroutine

------------- F8:0 = F8:0 + (AnalogIn/60.0)

Since the sensor gives it's reading in minutes and we call the subroutine once/second we add 1/60th of the current reading to the total. This is the simplest method I know and there are going to be some overflow issues (eventually) with the floating point data.

If the flow meter output was in the range of ??/hour you'd divide the analog input value by 3600.0. If you change the STI resolution the denominator will change accordingly.

Oh yea, note that I divided the AnalogIn value by 60.0 (float) and not by 60 (int). Do this to force the PLC to perform the division using FP math.

Hope this helps,

Good Luck,

(8{)} ( .)

 

[Fritz_frederix]

Hi,

What kind of flowtransmitter are you using, perhaps the totalizer is already there?

Rudi

 

[Ken Moore]

Most of the flow meters that I'm used to dealing with have more than one output. At my plant we use a pulse output to totalize, and a 4-20mA analog signal for flow rates. Uses more I/O, but is also easier to setup and trouble shoot.

Ken

 

[SHAMEER]

FOR TOTAL PRODUCTION CALCULATION

Just measure the pulse input from flow meter and convert the pulse into kg as you can set the flow meter pulse to any value. then add this kg unit in data block and monitor it an op panel.thats all

 

[DairyBoy]

I'm guessing he's probably done it by now...

 

[jkerekes]

Old thread Alert!

 

[Alamgir Hossain]

Most of the flow meters that I'm used to dealing with have more than one output. At my plant we use a pulse output to totalize, and a 4-20mA analog signal for flow rates. Uses more I/O, but is also easier to setup and trouble shoot.

Ken

Could you please share a PLC program using cx-programmer to count the output pulse of a mass flow meter?
We have a refrigerant gas charging machine in our factory. I am trying a lot to understand the concept of the mass flow meter plc program but can't succeed.
I need help from an expert.
Any assistance regarding this issue would be appreciated.

 

[Ken Moore]

Alamgir,
This a really old thread. Suggest you start a new one with your questions.