Dosing control help.

[itsmoked]

I am trying to deliver a pressure profiled dose of water.

About 3 oz or 90ml per minute.

I have tried a very small expensive gear pump and I'm entirely dissatisfied with the static leakage thru it.

I have about 30 psi of feedwater to the system and I want to be able to provide about 1.5oz over about 1/2 a minute with a pressure of anywhere between zero and 130psi.

With my current pump/system I am faced with 30psi to 130psi and the difference in flow is only about 1:2 over the leak thru verses 130psi.

Any suggestions of systems or techniques I should be looking at? I am not having much luck with search terms either.

I can actually have a recharge period of a few seconds per dose if that broadens the field of choices. Syringe/piston style??

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Hi Keith,
I'm a little confused by your description.
Why not use a diaphragm type metering pump c/w back-pressure valve?
If you pick one that will deliver say 200# and have a 50# back-pressure valve the line pressure would have minimal effect on the flow.
You can operate the metering pump on 4-20 mA or a pulse from a PLC
e.g. 0.1 oz per pulse at 15 pulses per minute. If you need a smoother flow use smaller increments at higher frequency.

Brooks make small mass flow controllers that might work, I have only used the gas type but I'm fairly certain they have a liquid one also.
Regards
Roy

 

[itsmoked]

Hi Roy,
I was hoping you would come by.

That sounds excellent. Especially with the back pressure valve.

So let me see if I get it. I have to run a regulator in front of the diaphragm pump to limit incoming pressure to, say, 30psi.

Then the pump.

Then the back pressure valve(BPV) with, say, a 50psi spring/ball setup.

So nothing flows until the 50psi is reached.

I can then control the pressure after the BPV because there will be a restriction at the delivery point. This means I could actually have 2,3 5, 20psi after the BPV as controlled by the flow and the exit restriction?

See any difficulties with 200F and this scheme?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[AntonTRN]

I have used about 5 years back a coriolis based mass flow controller brand 'bronkhorst' it was working fine.
last year I bought some dosing pumps, giving a certain quantity per stroke, these where expansive and bad functioning.

http://www.bronkhorst.com

 

[roydm]

Keith,
Yes,. I would drop the pressure right down or use a small tank.
Check out accessories under the following link, it gives a good description of the back-ressure valve.
AntronTRN is right metering pumps can be a bit of a pain, but they are a way cheaper than a regular meter, control valve setup. We use them quite often.
I will look into other options as well.
I see another thread on metering pumps, check that as well

http://www.lmipumps.com/corp/details/0,,CLI1_DIV12_ETI3738,00.html

Regards
Roy

 

[roydm]

Keith,
Check out the coreolis mass flow controllers from Brooks, one of those might fill the bill. I'm pretty sure I have seen a thermal mass for liquid also.
If you do a web search under mass flow controllers you should find a bunch of other brands.
The nice thing about these they have a meter, control valve anf PID function all in one tiny package.
As I said I have only used them on gas, so if you go that way make sure you hve a filter upstream.

http://www.brooksinstrument.com/category1.asp

Regards
Roy

 

[itsmoked]

Thanks Roy, AntonTRN.

Let me digest this.

BTW The last mass flow controller I purchased was tiny (1/4 tubing) and cost $5,100!!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Keith,
About Canadian $1700 here for a Cole Palmer suitable for water.
If you want to send me a few more details on what you are trying to do I may be able to suggest something better. rmatson at noram-eng dot com

Roy