PWM for controlling liquid flow through a Solenoid Valve

[kunalvanjare]

Hello guys, I am looking to control the flowrate of water through a Solenoid Valve in a continuous closed-loop process.

I inquired about Proportional Flow Solenoid Valves and these are a little too expensive and only a handful of manufacturers are supplying those.

But I looked online for some PWM Controllers and found a few, but I don't really know much about this topic as this field is new to me (I am a machine designer by profession). I've come here to ask you guys for some guidance :)

So the application is to control the flow-rate using PWM. I was told that you need to purchase Solenoid Valves with PWM-specific coils and a Controller to convert the 0-20mA signal from the PLC into PWM signals.

How do I go about this? And could you'll advise which PWM Controller would work for an application like this?

Thanks,
KV

 

[anorlunda]

Proportional Flow Solenoid Valves is not your only possibility.

Closed loop control of flow can be accomplished with many kinds of valves. For example a motor operated valve with only ramp-up/ramp-down/hold-position modes. Positioning can be continuous although rate of change of position is discontinuous.

 

[kunalvanjare]

Proportional Flow Solenoid Valves is not your only possibility.

Closed loop control of flow can be accomplished with many kinds of valves. For example a motor operated valve with only ramp-up/ramp-down/hold-position modes. Positioning can be continuous although rate of change of position is discontinuous.

I checked Motorized Modulating type valves that work on 4-20mA. But their opening & closing times are nearly 15 seconds which is way more than what I can offer.

 

[anorlunda]

Please don't make us guess. Give us your complete list of specifications.

 

[kunalvanjare]

Please don't make us guess. Give us your complete list of specifications.

Alright. Here you go.

I have to introduce a coolant, flow-rates ranging from 500ml to 2000ml into my system where it has to mix downstream with a flow of water coming under gravity. The water shall be introduced into the system under gravity or through the plant's water supply line, due to which the flow-rate might fluctuate.

I need to control the flow of coolant to effectively match that of water in real-time so that my final mixture doesn't get affected with an accuracy of approx +- 0.5%.

Hope this info shall suffice. Feel free to let me know if you need any more details & parameters.

 

[anorlunda]

You started by saying some solutions are too expensive. How much are you willing to spend?

 

[AZFIREBALL]

What is the accuracy of the water inflow rate? How is it being measured?

 

[kunalvanjare]

What is the accuracy of the water inflow rate? How is it being measured?

It will be measured with a Turbine flow sensor installed in my system. Flow-rate of water is mostly constant, but there are occasional drops if the main water tanks run out of water. But this is usually monitored so doesn't happen very often. But in case if it does during operation of my system, I can have an interlock to shut-off the system at a minimum pre-set flowrate of water.

 

[kunalvanjare]

You started by saying some solutions are too expensive. How much are you willing to spend?

So, the one quotation I have received so far consists of the PWM enabled Solenoid Valve with a PWM Controller which amounted to a total of approx. 700 USD here in India. This is the product - https://www.asco.com/en-gb/Pages/accessories-series-603.aspx

I would ideally look for something cheaper than that, although I haven't really set a price in mind.

 

[AZFIREBALL]

Is the water flow rate measurement within +- 0.5%?
What method of mixing is provided?
How will the final mix percentage be measured?

 

[kunalvanjare]

Is the water flow rate measurement within +- 0.5%?
What method of mixing is provided?
How will the final mix percentage be measured?

Yes the flow-sensors have an accuracy of 0.5%

Mixing will happen with both streams(water & coolant) entering a Static Mixer together.

With a refractometer.