Totalizing pounds per hour on allen bradley panelview


Thread Starter


I am measuring pounds per hour steam flow in a boiler room. I get two 4 to 20 milliamp inputs from differential pressure, measured in inches, and pressure. I am currently reading steam flow in pounds per hour on panelview. I need a totalizer to keep up with total pph for readings and to look at efficiency. If you can help me with this frusterating problem please do.
First you will have to convert the DP signal to flow signal using square root conversion.

Then Preferrably scale the signal in Engineering units.

For totalizing first you will have to make a 100 ms timer. Divide the value by 36000 if your flow rate is in pounds per hour. add the present value to the previous value.

Check the conditions and see that you do not go to overflow.

It's not as simple as it sounds.
But you can do it. I assume the DP producer is on the saturated steam side. If on the superheat side, it's more involved. Anyway:
If the DP is an orifice plate, correctly installed and XTR calibrated correctly, the overall accuracy is around ± 0.6 % of reading. But better than 1 %. For acuracy around 0.25 % you would need a calibrated meter run [Canadian Meter, American Meter, Daniels ...]
Next, is staithforward:
In the mass-flow formula, pressure and diff pressure @ reference conditions give the net mass-flow. On the saturation line (assumed before), even small change in pressure affect the calculated mass-flow. So, from the operating pressure, you must calculate the steam weight density ( I have the formula).
Now, you have a corrected instantaneous steam mass-flow.
Your Panel View what it does, I have no idea ?
Technicaly you need:
Accumulate 'x' readings over a given time period, and equally spaced in time.
If you have enough readings (I can tell you also), you can perform a Romberg Integration.
This is the best numerical approximation for integration [in that application].
Note: generaly, in math packages, Romberg goes with functions defined by an equation. But it can be converted for discrete data set.
I have the full development as personal tool.
Let us know.
As the step above provides total mass-flow over a given period of time, for longer period, you would need repeat the process.
Romberg Integration is sensibly more accurate than simple Simpson. When applicable to math functions, the accuracy ranges in the 10 decimal places.

barrington marsh

You're already showing instantaneous flow rate in pounds per hour and need to integrate this with time to get the total useage value.

1)Examine the data base in PanelView to see which plc register you are displaying.
2)Write PLC code to divide the above register by 3600 to give instananeous value in pounds/second
3)Use the above value to update a register every second to give a total useage value. (Every second add the current instantaneous flow to the register)
4)Put a new display on the PV Screen to show the total useage stored in the above register
5) Add a button on the PV to reset the totalizer

Hope this makes sense

Jimmy Fletcher

I am metering liter per minute with a rosemount 8732c magnetic flow meter. We have been losing a lot of the chemical lately and nobody knows where its going. I want to meter it as it goes into the storage tank. I am using a slc 5/03 and I want to set up a totalizer on the panelview to display total liters loaded into the tank. Can someone send me some code to help me get started.