Flowmeter blues...

Hi guys, long time...

I've been recently tasked to get some new mag flowmeters working in our Paint Mix room, and we ran into problems because the new paint that we are using has nearly zero conductivity. Oops...

So, now I'm trying to come up with something different. My ChemE buddy suggests going ghetto and rolling our own orfice plate flowmeters. Based on the info below, what size orfice would you suggest?

And the math formula for calculating the flow would really be nice as well.


BTW, the piping is 1", flow is between 10 - 25 GPM, and pressure is usually around 150 PSI. But all we really care about is flow.

As for accuracy, it's not that important. Even 25% off isn't any big deal.

I've included the paint specs (sorry about the excel spreadsheet, trying to post it within the message didn't work out so well).

If you need any other info, just let me know.


Thanks in advance,

John

Orifice sensing is differential pressure technology.

The impulse lines from the flange unions to the dp meter are dead headed, no flow through them. Is there the possibility of the paint aging or curing and blocking the impulse line?

Will you have to clean the impulse tubes/pipes between batches to keep any residue from mixing?

Dp's work great on media like steam, water, heating oil, gases, that doesn't clog or need cleaning. Does paint qualify?

Is the CPS column the viscosity values?

#2 is clearly different than the others.

Without a sizing program it's difficult to say how far off you're going to be for any different product from the design conditions.

By the time you buy a dp meter, orifice flange union, & an orifice plate, you aren't that far off from the cost of a thermal flow meter which is tube with a couple small protrusions in it, not that different than a magmeter.


Or even a paddle wheel meter (note the fairly significant pressure drop)
http://www.koboldusa.com/flow/us_df-k.htm

We use a turbine type flowmeter from Great Plains Industries that is very reliable and accurate, and extremely simple.


Our application is water, but their website claims a wide variety of fluid applications.

Here is a range of liquid flow switchs I have used that may suit you, one has a basic analog output, as well as a switch operation.

Its effeectively 2 thermistors as a differtial temperature sensor, one is in touch with the stainless steel tip, whilst the other is near, but is insulated from the tip, so the greater the flow the greater the temperature difference.


http://www.ifm-electronic.co.uk/ifmuk/web/pselect2!2_30_10_30.html

rootboy said:

BTW, the piping is 1", flow is between 10 - 25 GPM, and pressure is usually around 150 PSI. But all we really care about is flow.

As for accuracy, it's not that important. Even 25% off isn't any big deal.

Click to expand...

John
I ask mostly out of curiosity.
Other than confirming the pump is pumping what are you going to use this data for? A tolerance of 25% does not seem to justify the time trouble or cost.

Dan Bentler

If all you need is flow then a low cost mecchanical meter with a pulse output will probably be fine but a higher spec instrument could open up all sorts of possibilities for improved control. A good coriolis meter could give you pressure, temperature and viscosity readings as well as flow so the extra expense might be worth considering.
Andybr

I think of paint as high solids and potentially plugging orifice or any similar differential pressure type meter. How about ultrasonic? There are strap on ones available so you may not need to penetrate the pipe.

Ultrasonics are pretty expensive. As long as the line is never open to the air I would go with a turbine meter and pickup arrangement or a thermal flow meter as already suggested. A coriolis is the cadillac solution but its also one of the most expensive.

I think orifice and dp will have clogging problems with paint pigment build-up so I wouldnt go that route, or any route involving small holes and differential pressure impulse lines.
Simple and cheap there is always a rotameter with an external sensor arrangement. Theyre nort particularly accurate but they are cheap!

Last and by no means least theres always a PD meter. They seem able to cope with pretty much anything you throw at them and theyre pretty cheap and super accurate.

danw said:

Orifice sensing is differential pressure technology.

The impulse lines from the flange unions to the dp meter are dead headed, no flow through them. Is there the possibility of the paint aging or curing and blocking the impulse line?

Click to expand...

Not generally, no. But the meter is directly ahead of the filter anyways.

danw said:

Will you have to clean the impulse tubes/pipes between batches to keep any residue from mixing?

Click to expand...

We don't do "batches", each color has its own tank to pull from (the color change is done in the robots). So it shouldn't be a problem.

danw said:

Dp's work great on media like steam, water, heating oil, gases, that doesn't clog or need cleaning. Does paint qualify?

Click to expand...

Pretty much, but our low flow rate and our high viscosity seems to be a problem (to the meter salesmen at least).

danw said:

Is the CPS column the viscosity values?

Click to expand...

Yes.

danw said:

#2 is clearly different than the others.

Click to expand...

It's a Fisher #2 cup measurement. It's a cup with a hole in the bottom that restricts the paint as it drains out. The value is the number of seconds that it takes for the cup to empty.

danw said:

Without a sizing program it's difficult to say how far off you're going to be for any different product from the design conditions.

Click to expand...

It's going to be trial and error, especially if we make our own. But we do have the textbooks here that have the formulas...

danw said:

By the time you buy a dp meter, orifice flange union, & an orifice plate, you aren't that far off from the cost of a thermal flow meter which is tube with a couple small protrusions in it, not that different than a magmeter.

Click to expand...

I just got off of the phone with a thermal flowmeter apps guy. They don't have a solution for anything other than gas. I've got a call in to a different company, and I should hear from them tomorrow.

danw said:

Or even a paddle wheel meter (note the fairly significant pressure drop)
http://www.koboldusa.com/flow/us_df-k.htm

Click to expand...

That's what our competitor up the road uses.


Thanks for the help, I'm hoping that the thermal flowmeter works for us.

OkiePC said:

We use a turbine type flowmeter from Great Plains Industries that is very reliable and accurate, and extremely simple.


Our application is water, but their website claims a wide variety of fluid applications.

Click to expand...

Thanks

I gave them a call, but it's after hours. I'll try again tomorrow.

http://www.c-a-m.com/content/vm/flo/index.cfm

MEASUREMENT SYSTEMS
REGIONAL SALES OFFICE
302 TOLEDO DRIVE
LAFAYETTE, LA 70506
UNITED STATES
Contact: DANNY MCFARLAND
Phone-1: 337-234-1824
Fax: 337-232-1580

I dont think they service your area but this guy can probably help you see if they have something that will work in your application.

Gil47 said:

Here is a range of liquid flow switchs I have used that may suit you, one has a basic analog output, as well as a switch operation.

Its effeectively 2 thermistors as a differtial temperature sensor, one is in touch with the stainless steel tip, whilst the other is near, but is insulated from the tip, so the greater the flow the greater the temperature difference.


http://www.ifm-electronic.co.uk/ifmuk/web/pselect2!2_30_10_30.html

Click to expand...

Which one was the thermal flowmeter? I found the mag meter.

The vibration meter for the motor looks interesting (different app obviously).

Thanks!

leitmotif said:

John
I ask mostly out of curiosity.
Other than confirming the pump is pumping what are you going to use this data for? A tolerance of 25% does not seem to justify the time trouble or cost.

Dan Bentler

Click to expand...

That's the $64K question. Do we really need this info, or is it a leftover from the way that we used to do business? I haven't got an answer to that one as of yet.

As for 25%, that's more of a reality-based threshold than anything else. I'm willing to let the accuracy suffer for something that will work for us.

Good question though, now if my bosses would just come up with an answer for it...

Andybr said:

If all you need is flow then a low cost mecchanical meter with a pulse output will probably be fine but a higher spec instrument could open up all sorts of possibilities for improved control. A good coriolis meter could give you pressure, temperature and viscosity readings as well as flow so the extra expense might be worth considering.
Andybr

Click to expand...

I had the MicroMotion (coriolis) guy down here today. It would be perfect, but at a cost of $7500 each (ouch).

Thanks.

Tom Jenkins said:

I think of paint as high solids and potentially plugging orifice or any similar differential pressure type meter. How about ultrasonic? There are strap on ones available so you may not need to penetrate the pipe.

Click to expand...

I was told that the ultrasonic requires a goop not unlike what the doctor uses for an ultrasound.

Since it's a clean-room environment, that's a non-starter for use (if we located it outside of the Paint Mix room then that would be another story).

Thanks.