Metering Pump control with a flow meter

Hello, I have this project that I need to connect a flow meter (http://www.powogaz.com.pl/pliki/prod...l_K_52_420.pdf ) to control a metering pump from prominent gamma/ L Solenoid Diaphragm Metering Pump type).

The problem is that I need to program using Allen bradley rslogix 500 or 5000 plc for the flow meter to stop the pump let say after every 10 litres of flow. I guess the flow meter gives pulse so I could connect it to a digital input.
I do not have much experience in PLC programming and I would be glad if somebody can help me with an idea on how I should go about with the program.

I have no knowledge about metering pumps but this is what I am suppose to use: http://www.prominentfluid.com.au/upl...ng%20Pumps.pdf

Your comments are welcome.

I work with systems similar to this. We use them to control additive injection into gasoline and diesel. If you have a flow meter you really dont need to use a metering pump. You could use a standard pump, a meter and a solenoid to do this. Might save some money in the process as metering pumps are expensive.

To use the meter pulse, you will need a PLC that has a high speed DC input. All the Micrologix PLC's have high speed inputs on the DC input models so that is not a issue.

As for the PLC I/O You will need a digital input (DI) to count the meter pulses. A DI for a pump start command. A digital output (DO) to start the pump. It you use a solenoid you will need one more DO for it.

Programming: You will need to set up a High Speed Counter (HSC) in RsLogix. I would have it reset every time it counts to 1Liter. Every time the HSC resets you can add a 1 to a integer file (N7). This will keep track of the total number of liters you have run through the meter.

Set up a DO to close and start the pump when you get a DI. The meter will start counting and when the N7 file equals the number of liters you need to deliver you can stop the pump by opening the DO.

In my business we use a pump, meter and solenoid. We start the pump at the beginning of the load and wait for an inject signal from a separate loading meter. This happens about every 40 gallons. When we get that signal we open the solenoid and count the meter pulses. When we get the proper number of pulses we shut the solenoid and wait for the next injection signal. When the load is done we shut off the pump.

I hope this helps you get going. If I can help more let me know.
Chris

If you have a flow meter you really dont need to use a metering pump.

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True, and the converse could be true also: If you have a metering pump, you may not need a flowmeter. With a metering pump, you tell it how much to pump and let it "meter" the liquid, either a continuous rate, or until it gets to a set volume.

Overall, if given a choice, using a flowmeter and standard pump works best, because someone will want to see the total amount pumped on some display. For very small flows (drops per minute), a metering pump may work better than trying to use a flowmeter.

Very true Lancie1!! My expertise is in liquid measurement so it is strange to me to not use a meter

Thank you very much for the detailed information given from this forum.Actually the flow meter is mounted on a pipe which supply water into a big tank. The metering pump is acting as a dosing pump which supply some chemicals to this big tank. Now the so called metering pump is working manually and I want it to work automatically and the flow meter should cut the pump off, after some amount of liquid has been pumped into the tank.
I have got some idea from this forum and I will send the program code I have done with rslogix 5000 so that I can get some correction. Thanks a lot

VIRUZIE said:

Thank you very much for the detailed information given from this forum.Actually the flow meter is mounted on a pipe which supply water into a big tank. The metering pump is acting as a dosing pump which supply some chemicals to this big tank. Now the so called metering pump is working manually and I want it to work automatically and the flow meter should cut the pump off, after some amount of liquid has been pumped into the tank.
I have got some idea from this forum and I will send the program code I have done with rslogix 5000 so that I can get some correction. Thanks a lot

Click to expand...

As you are using Logix5000, (RSLogix5000 is the programming software), you may want to use an Event Task for counting the pulses from the flowmeter. This will make the counting completely independent of scan-time for any other code you may have in the controller (assuming the event task has the highest priority).

Configure the Event Task to be triggered by "Module Input Data Change"

Configure the Input module that the pulse from the meter is connected to, so that an Input Data State Change is detected on that input, and that input only, and only for Off-to-On transitions or you will count both the pulse coming on, and going off.

You can safely use an ADD instruction to count the pulses (Count=Count+1), as the code will only be executed once each time the pulse comes on. Or, if you use a CTU, remember to OTU the .CU bit, otherwise the counter will never increment more than once.

Since the code doesn't need to see the input off, you can configure the meter for a much smaller volume pulse (e.g. 0.01 litre), giving you much greater accuracy with your measurement. Strictly speaking, the code doesn't actually need to inspect the input at all, it will all work from the way you configure the "Change-of-State" in the input module.

Program Code for my flowmeter pump control

Hello guys, please this is the code I have been able to write concerning the flow meter controlling the pump. Please review it for me to know where I went wrong.

Thanks.

VIRUZIE said:

Hello guys, please this is the code I have been able to write concerning the flow meter controlling the pump. Please review it for me to know where I went wrong.

Thanks.

Click to expand...

There is not much in your code that helps to explain what your objectives are....

It looks like the "flow_meter" tag on the first rung is supposed to allow the pump to run for a specific time, but it is not time you need... you want the pump to dose a predefined volume.

You have set-up a 1 second timer, that repeats due to the RES on rung 1, and the counter on rung 2 is therefore just counting seconds.

You use the Counter .DN bit to reset the counter on rung 2, then on rung 3 try to use the Counter.DN bit to drive a bit called Pump_running.

Pump_running can never be true, because as soon as the counter .DN bit becomes true, you are resetting the counter, which resets the .DN bit. The following rung will not see the counter's .DN bit at all, ever.

So now I ask you to think why you need a timer at all ???

You only need to count the pulse inputs from the flowmeter while the pump is running, nothing else, there is no timing function needed, and when a preset count is reached, stop the pump.

Edit : Please thank your city for Sibelius

Hello Daba, I am so grateful for reviewing my code. my flow meter gives a pulse every 1 second which is equivalent of 1 litre and the metering pump gives a pulse for every 100 litres of flow from the flow meter. So that is why I brought the timer code there.