I would like to evaluate the amount of solvented paint deposited on a strip by measuring accurately the inflow and the outflow going to and from the coating head. Therefore I would like to find flowmeter type that could do the job. The requirements for such kind of flow measurement would be ideally :

outflow :
- Able to do gravity flow (the flow to be measured is the excess flow from the pan)
- Could run solvented paints
- Easy cleaning
- No calibration required for each paints (variability in chemistry,composition, viscosity, density,....)
- Really good accuracy
- Numeric output(able to be datalogged or analysed after....)
- Low maintenance
- Flow in the order of few liters/min (no really sure to be honest)

for inflow the same but without the requirement of gravity flow as it is pump fed and flow of 10-60 L/min

If any other information is required please do not hesitate

I would be grateful for all your input

 

You might want to look at a very small coriolis meter like Brooks
Instrument's Quantim, or a Rheotherm Very Low Flow meter.

Walt Boyes
Editor in Chief
Control and ControlGlobal.com
555 W. Pierce Rd Suite 301
Itasca, IL 60143

[email protected]
www.controlglobal.com
630-467-1300

 

Many years ago I had some experience with this sort of system, hopefully this might help.

If you are somehow controlling the amount of paint being applied, then you can remove the requirement for a flow measurement with a very low head. Also deriving a measurement from the difference in two flows is probably very noisy and not too accurate.

Do you manually control the paint deposit by adjusting the coating machine somehow, or do you add or reduce the amount of solvent in your paint supply?

The system we developed controlled the coating weight of solids onto a paper web, by forcing the machine to take the calculated quantity of coating mix.

We calculated the required flow from line speed and width and then fed this flow to a small recirculation tank. The return flow from the coating head was also collected in this tank and the mixture of new flow and the return was pumped to the coating head. Then we measured the level in this tank: if the level was rising the coating pick up was low, and if the level was falling the pickup was too high. We controlled this level which then controlled the coating weight.

There were a couple of ways we controlled the level in the re-circulating tank. In several systems we adjusted the air pressure in the "Air Knife" coating head. In another system we added more or less solvent (in our case this was water) to the recirculation tank. If you think about it, these systems not only controlled the overall coating weight but also the weight of each constituent of the coating mix. There was a complete material balance. If the paper tried to absorb more of one component in the mix then the re-circulated mix would be deficient in that component and the system would balance out.

The measurement of the new flow was quite easy as there was a decent head available from the coating preparation plant.

If the above description helps in any way, and you need more details, do not hesitate to contact me off list at pbg[at]wave.co.nz.

Regards
Peter Green

 

Coriolis might be a good bet if you can get the flow you need - head loss may be an issue for gravity flows.

Otherwise you might want to look at the FTI low flow ultrasonic meters.
The head loss will probably be very much more favourable.

All sizes (3mm tube to 6") to choose from here:
http://www.ftimeters.com/products/ultrasonic_flowmeters.htm

 

Look at McMillan Flow Meter, they have flow meters for such small flow rate applications.

 

You might also look at Rheotherm. They make what are called microflowmeters.

Walt Boyes
Editor in Chief
Control and ControlGlobal.com
555 W. Pierce Rd Suite 301
Itasca, IL 60143

wboyes [at] putman.net
www.controlglobal.com