How can I achieve homogeneous in-line mixing of a Coolant (or Part Washer Cleaner) with Water?

[kdv1988]

Hello,

This is for a new product I am designing, which involves topping-up or refilling the liquid into a CNC Machine or Part Washer.

I have to mix about a Litre of the chemical (alkaline.. pH in the range of 8-12) with about 50 Litres of water. The water will be fed under gravity through a 1" pipe, while the chemical will be pumped either from a Chemical Barrel or a Tank.

Flow-rate of both the chemicals will be controlled with the help of flow sensors & valves.

Now, my question is how do I achieve mixing of both the chemicals to produce a homogeneous mixture? The objective is to do this in-line without use of an additional Tank & Agitator. I have pondered about using a Static Mixer or an Injection Quill, but I am not convinced I'll get a homogeneous mixture from these.

Request somebody with prior experience on similar fields to suggest or guide me towards a solution.

Thanks,
KV

 

[Compositepro]

"Flow-rate of both the chemicals will be controlled with the help of flow sensors & valves."

That method is very expensive and difficult to get right. Use piston or gear pumps to get the ratio you want feeding into a small agitated tank (which may be your machine or washer). Chemical dosing pumps may be your best choice.

 

[Latexman]

Agree with CompositePro, you are making this unnecessarily expensive. 1 liter + 50 liter in a plastic open top drum with a portable mixer is about as simple and inexpensive as it gets. Premix it, then you only have one feed! Or put in a small dedicated plastic or SS tank with mixer if it’s justified. How long does 51 liters last? Is it a 24/7 operation? Can the inventory be replenished on the down shifts/weekends?

Good Luck,
Latexman

 

[kdv1988]

The coolant (or cleaner) will be pumped into my system using a Barrel Mounted Gear Pump. Just that the flow has to be monitored since the actual top-up or refill will be based on what the User inputs into the system.. zB :- If the top-up requires 50 Litres @ 1%, the system automatically calculates how much water & chemical would be required, and this parameter will change a little everyday.

This operation shall be run once in a day, or as per demand.

I simply cannot afford space for a separate mixing tank with an agitator, although I do know it would have been the easiest and cheapest way to do this job.

Please guys, any way I can do this operation inline? I have been researching on this for a while, but haven't really reached anywhere. I understand that this requires extensive trial & error, but I'm looking for some guidance on where to start, preferably from someone who has tackled a similar problem before.

 

[itsmoked]

No tank, then I would still suggest you follow Compositepro's suggestion for using a chemical metering piston pump. Each stroke they inject the amount you dial in.

You then accurately monitor the bulk media (H₂O?) and add the appropriate chemical feed from a piston pump into the water stream. Toss in an appropriately sized "static mixer" and you're done. Two chemicals? Use two metering piston pumps each drawing from the appropriate chem stock barrel. You can control the piston pumps ON/OFF. As they operate each piston stroke injects a specific amount. The strokes are adjustable.

Your system becomes a PLC with a touch screen.
An accurate water meter that is read by the PLC.
Valving to the various machines off the mix mainline.
A couple of outputs that run the valves and the metering pumps.
A user interface that you dial in the amount and the choose the recipe needed.
A GO button.
An E-STOP button.

To deal with the common piping and uncommon mixtures you always Start and End metering in the middle of the flow. Water proceeds and follows the injection process so the main line is only ever left with water standing in it. All the injected chemical has been driven to its destination and followed up with the balance of the water so all the injected chem ends up in the destination machine.

Carry on.





Keith Cress
kcress -

http://www.flaminsystems.com

 

[kdv1988]

Thanks for your reply.

Few questions:-

1. Any particular reason why you suggest a Pulsed metering pump over a continuous flow pump?
2. Do you get Metering pumps that can draw liquid out of a Barrel or a Chemical Drum (200Litre drum)?
3. I didn't quite get your last point. Would mean a lot if you could elaborate on that.

Thanks,
KV

 

[itsmoked]

1. Any particular reason why you suggest a Pulsed metering pump over a continuous flow pump?

I know of no reliable continuous metering pumps. The many fluid dynamic issues associated with continuous methods tend to make EVERYONE use constant volume positive displacement pumps. Especially for anything less than LARGE flows. (Think many inches)

2. Do you get Metering pumps that can draw liquid out of a Barrel or a Chemical Drum (200Litre drum)?

Yes that's how most operate. 5Gal, 10Gal, 15Gal, or 55Gal containers of chemical and the pump sits on a shelf just above the container and draws from them.
Typcial example
Look to chlorinator pumps. Millions sold and they handle problem plagued chlorine. Your app is likely a walk-in-the-park compared to sodium hypochlorite.

3. I didn't quite get your last point. Would mean a lot if you could elaborate on that.

I'm suggesting you essentially surround the chemical you're sending to a machine with just the water part of your deliveries. That leaves the lines out to the machines always filled only with water and all the chemical always makes it into the machine's sump. If you try to mix 100% of each batch in-line to the machines you will have lots of problems because of the mix left in the lines from the last delivery to some other machine.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Latexman]

I’ve used many in-line mixers. Find the vendors blank performance spec on-line and complete it. Just ask yourself do you need 90%, 95%, 99%, or 99.9% homogeneous?

Good Luck,
Latexman

 

[jari001]

Similar situation discussed at thread378-456748