Alternative to a Proportioning Motorized Valve?

[kdv1988]

Hey guys,

I'm looking for a way to control the opening of a valve as per feedback from an upstream flow meter. I have a motorized proportioning ball valve, but it takes about 10-15 seconds to complete it's rotation (one-way).

I need to find a way to expedite this so was wondering if there are any other type of valves (pneumatic or electrically actuated) that could do this in about half that much time?

I tried searching for some but couldn't find anything that fit my requirements. Please note that size & price is somewhat of a constraint.

Thanks,
KV

 

[LittleInch]

Well some details would help such as

Valve size
Pressure rating
Power limitations
time you need it to close
Why so vague about opening time now? 10 to 15 seconds is a 50% difference

A pneumatic controller can be much faster, but more as a typical control valve and globe valve / moveable plug.

Using a ball valve as a flow controller is not normally a great idea. Why?


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kdv1988]

Hey,

Here you go:-

Valve size - I need two sizes. 1/2" & 1"

Pressure rating - both gravity flows. They're not high pressure requirements.

Power limitations - None. The valves need to actuate on 4-20mA

time you need it to close - It is a mixing application. Two different streams pass through the two valves, get mixed downstream and are supplied to a tank. Once the required quantity of mixed liquid at output is reached, both valves need to shut.

Why so vague about opening time now? 10 to 15 seconds is a 50% difference : the range because it is a modulating type valve. So 50% opening takes around 10 seconds, while 65% takes around 15 seconds. And the same amount of time to close. I need this operation to be done much quicker.

I am all in for pneumatic controlled valves. But do you get modulating type control valves that run on 4-20mA?

 

[LittleInch]

4-20mA is a very common control signal input so I would have thought you wouldn't have any issues there.

1" and 1/2" are though quite small

but are you using these as controlling valves or just on/off?

What power are you using for the operation of the valves? 10 seconds to close a 1" valve 50% sounds like a very low powered motor to me

a solenoid /spring powered on/off valve may be more what you want

It's not making a lot of sense at the moment - when you say "much quicker" how much quicker?

0-50% in 5 seconds? 1 second? 0.5 seconds?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kdv1988]

I'm using them as controlling valves. The opening of the valves changes as per the concentration of mixed liquid required in the output. For operation of the valves I am using 24VDC.

Much quicker would be anything below 5 seconds. The 1/2" line contains the chemical that is mixed with the water in the 1" line. Since concentrations are being targeted in the range of 1-3%, very less chemical is fed to the system compared to flow of water. For that, I need the valve to open and close as fast as possible.

What type of spring loaded or solenoid powered valve do you recommend?

 

[LittleInch]

Well thinking a little outside the box here if you really want control over a mixing rate I would use some sort of metering pump arrangement.

If you have low differential pressure, any form of control valve doesn't work very well.

Any type of 24V solenoid valve will do you - just search online.

But you really need to sort out what you want these valve to do. Close / fine control over volume flow is not really compatible with sudden closure, so you may want two different types.

If your current set-up works but you just want fast closing then stick a solenoid valve in D/S the mixing valve.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kdv1988]

Yes, a metering pump to transfer chemical from a drum to the system is in our plans. Just that even with a metering pump, we may have to throttle the flow as per the final concentration of the mixed liquid (which will keep varying!).

A 24V solenoid valve will not have a modulating function though right? It will just be an ON/OFF valve. When you say sudden closure, are you referring to my required short ON & OFF timings (<5 seconds which I had mentioned).

A solenoid valve in downstream of the mixing valve will not work, because it is essential that the right amount of chemical gets mixed with water. Perhaps this would work if the flow-rates of both chemicals were constant.

I need something that adjusts the opening as per real-time conditions (concentration requried at outlet, incoming flow-rate). I guess I could do with a slightly slower speed of opening & closing of the valve. I haven't yet taken trials with my Motorized ball valve because I just have the one right now. But seeing the speed at which it operates, I am a little concerned about the accuracy of results. Hence my questions

 

[moltenmetal]

Pneumatic control valves will respond much faster than motor driven electric ones- full travel in under 1 second. But using control valves isn't the best solution when you could instead change the speed and/or stroke length of a metering pump instead.

 

[LittleInch]

I'm still not sure what you're trying to do here.

I think that what you have is a varying flow of water in your pipe of unknown size which you are metering the flow of.

Then you have either a 1/2" or 1" ball valve which is gravity fed which you're trying to get 1 to 3% of a mysterious chemical into the water. I assume the chemical flow is measured in someway?

There are many very easy ways to do this but a motorised ball valve isn't one of them.

You can get mechanical mixing meters which power the injection pump from the water flow to certain percentages. Metering pumps are often multi piston affairs - can take a 4-20 coming from you PlC no problem.

You can get quick acting air driven control valves - the speed of closure is limited mostly by the speed of your controller loop, but making it to fast means the valve is constantly moving up and down.

But using a very slow motorised ball valve??




Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kdv1988]

Here are replies to all your points :-

I'm still not sure what you're trying to do here.
I'm trying to build a liquid dispenser, where a cooling oil(water soluble) is mixed with water. The oil is pumped from a barrel and water comes under gravity. The concentration of mixing is defined by the user into my PLC. The PLC then decides to open the valves as per the existing flow-rate which is measured by the Flow sensors (upstream of the valve).

I think that what you have is a varying flow of water in your pipe of unknown size which you are metering the flow of.
Pipe size of water is 1", that of chemical is 0.5"

I assume the chemical flow is measured in someway?
I will be using a pump, either a AODD or a Gear pump to transfer liquid from the Barrel into my system. I still haven't decided on the type of pump though. Suction lift would be around 2 meters. Some help here would be appreciated as well!

You can get quick acting air driven control valves
I have spoken to representatives of Burkert & Tork for their Proportional Solenoid Valves. Link 1 -

https://www.burkert.com/en/type/6024

, Link 2 -

https://en.smstork.com/sp10-10-serie-direct-operated-proportional-solenoid-valve.html

but making it to fast means the valve is constantly moving up and down.
So this is going to be an on-demand dispensing system. I envision the system to be used when the concentration of coolant in the machine goes beyond a particular safe limit.

But using a very slow motorised ball valve??
I really wasn't keen on these. But it is just recently that I have found the quick acting solenoid valves. If you have any other suggestions on how to achieve this, that would be great!

P.S - I have seen similar products using PWM. I really have no experience or exposure to such systems though.

 

[danschwind]

kdv1988,

I concur with LittleInch. Why not just use a metering pump? There are metering pumps that are adjustable and can receive the signal from a PLC. Even a "dumb" metering pump can be controlled by installing a frequency inverter.

Also, depending on the flow rate, you may try to use a fuel addictive injection block (like a MiniPak 3000). They are often found on fuel distribution facilities, but maybe you can make it work for your application.