Flow Control for Solution System
Flow Control for Solution System
(OP)
Hi,
Need some advice on flow control for solution system.
I have a system that dispense fluid into a container and the dispense amount is determine by a fiX weight.
Currently, I am facing the problem in controlling the flow which resulted a wide fluid dispensing variance.
In the up stream, a diaphragm pump is use to supply the fluid.
During the dispensing, I observed that when the pump pump, the dispensing pressure and rate increase.
I am thinking of using a flow control valve to regulate the fluid flow.
Will that solve my problem? Is there a better way to regulate the flow regardless of the upstream pressure and flow? Thanks in advance for the advice.
Need some advice on flow control for solution system.
I have a system that dispense fluid into a container and the dispense amount is determine by a fiX weight.
Currently, I am facing the problem in controlling the flow which resulted a wide fluid dispensing variance.
In the up stream, a diaphragm pump is use to supply the fluid.
During the dispensing, I observed that when the pump pump, the dispensing pressure and rate increase.
I am thinking of using a flow control valve to regulate the fluid flow.
Will that solve my problem? Is there a better way to regulate the flow regardless of the upstream pressure and flow? Thanks in advance for the advice.





RE: Flow Control for Solution System
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Flow Control for Solution System
Thanks for the advice.
I had attached a schematic.
Not sure if I have got all the symbols are correct.
The dotted line are electrical input and output feedback line.
Best regards
Rickco
RE: Flow Control for Solution System
It is difficult to say much more without specifics, e.g. volume of the container, speed of delivery, accuracy of amount etc.
IN dispensing you sometime get a variable flow which slows down as the amount limit is approached tobe able to more accurately shut it off - a fairly simple logic loop in the PLC.
It's not entirely clear what your problem is so a bit difficult to say much more...
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Flow Control for Solution System
Details on weighment - how much - lbs, kg, liters, cc, grams?
From start to finish, how much time is used for the weighment?
What is the fluid? Water-like or high viscosity?
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Flow Control for Solution System
Another issue could be due to tubing design. Does a variable amount of fluid drain from the line after the valve closes?
RE: Flow Control for Solution System
Hi LittleInch, a pulsation damper would certainly help.
I am actually thinking of a system that can dispense accurately to +/- 1gram of water with a range of supply pressure.
For example, if the system is installed in plant A, with a water supply pressure of 1bar and the same system is installed in plant B, with a water supply pressure of 3bar. I would like the system to be able to dispense within +/- 1 gram. Dispensing time is not critical. With the same simple loop program, will I be able to achieve that? Or I will need to fine tune the program each time the supply pressure changes?
Hi Compositepro, currently the dispensing logic is similar. When the program is written, I tested using gravity feed supply, which seems fine.
When I add a pump into the system, the dispense amount overshoot. When water supply pressure is at 1 bar and at 3 bar, the amount dispense differ. So I am thinking if I can make it in such a way that the system can be operated between 0.5-4.0 bar without any changes to the program.
I am thinking if I could added a pressure transducer after the variable control valve before the pinch valve and make use of pressure feedback to control the amount of water flow through the variable control valve.
Once again, thanks for the advice, really appreciate it.
RE: Flow Control for Solution System
I'm with compositepro here - I would regulate flow rather than pressure and a you get to within say 90% of your target weight make the program reduce flow rate gradually by 50% or more so that you have very good control over the last bit and can shut off with higher accuracy without compromising the time taken to fill.
Regulating pressure might be enough, but with a pulsating inlet pressure you'll struggle to get smooth flow without some sort of pulsation damper.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Flow Control for Solution System
Got it, I will try that out.
Target weight is approximately 135g +/- 1g.
Thanks for all the advice.
RE: Flow Control for Solution System
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Flow Control for Solution System
As the control valve closes in to reduce the flow the pump (assuming it is fixed speed) is still trying to deliver the same volume of flow- increasing the line pressure which increases the flow.
A recycle line from thet discharge of the pump back to the tank that is used to control the pump discharge pressure would help, a variable speed pump would be better, replacing the diaphragm pump with something more controllable (peristaltic, or centrifugal) would be better still.
As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"
RE: Flow Control for Solution System
Unfortunately, we do not have the option to change the pump or add a return line to the tank.
From my understanding, a pulsation dampener needs to be install as close to the pump as possible.
What is the effect if I try to install the pulsation dampener near my equipment which maybe 500m away from the pump?
I am wondering, by adding a pressure transducer and a intelligent controller to automatically control the supply flow using a variable control valve could help to damper the change of pressure?
RE: Flow Control for Solution System
You really need to change something fundamental here otherwise it will just flow at the same rate an in slightly pulsating way.
The only other way perhaps is to pump into a local tank which is above your dispensing unit and use gravity to feed the dispenser?
So either change pump configuration, change pump type or introduce a break tank or feed it from the mains water supply.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Flow Control for Solution System
The local tank concept will definitely work, but I will need to add in features for sanitization.
Thanks for all the advice and idea.