quote:

Originally posted by RickDaTech:
I don't know where he got his, but here is a similar one:

Eductor

Ouch - $63 for 3/4" CI.

I'm also working on a sketch using your adapter, a 1" cross, 1"-2" reducing coupling, and some type of nozzle (haven't figured that out yet) as a DIY eductor.

BTW, the link to your adapter goes to the burrette nozzle.

Am I correct in assuming you need a pump more powerful than a HF pump to get any results with the reduced pipe size system?

Yes, because the back pressure in the eductor will bog down the HF pump. Been there and done that.

Raften,

quote:

Am I correct in assuming you need a pump more powerful than a HF pump to get any results with the reduced pipe size system?

No, I don't think so.

The HF/NT pumps, setting aside the other issues with them, are designed as high pressure, low volume pumps. So, they actually perform better under some load.

I use an NT with my dual static mixers and get GREAT results. It creates substantial pressure and the pump handles it fine.

I'd recommend the 3/8" eductor for the HF pump. With it you might see 5 psi. With the larger ones, yes you will need a bigger pump to be able to develop any pressure.

The sketch I showed with the pipe nipple nozzle will load up a hf pump. It will bring the amps on the pump up to about 6 amps and like 25psi. Going with a larger nipple size will unload the pump some and it will still work.

I imagine my HF pump is getting a bit long in the tooth because I tried doing the pipe thing last night with no joy. My mixing times have been getting longer so I may switch out pumps soon. Time to build a new reactor with some improvements anyway.

If I were thinking of doing this with a Murphys Machines pump (decreasing the size of the pipe by stepping down from 1" to 3/4 to 1/2, etc. How far would you suggest going down? Murphy had said that it wasn't necessary with his pump, and while I trust his opinion, I would also like to get the "best bang for the buck" when using it...figured this wouldn't hurt.

My initial thought was to go 1" > 3/4" > 1/2 >> 3/4 (with several holes/slots cut in it to create the eductor/venturi effect) > 1/2.

Do you think that would be effective, and if so, would it "slow down" the powerful pump too much? If just running the pump will work, I'm all for that also...just trying to get as much mixing/churning as I can for the tools I'm using.

Thanks,
-Scott

Scott, with Murphy's pump, I'd target midrange for head. In other words, experiment until you find a pressure that you and the pump is comfortable with. I'm sure Murphy has some flow vs pressure curves for it that would give you a target pressure.

Raften,

What do you mean by "no joy"? did it start leaking by the seals? tripping breakers? details please.

Andrew,

While the regenerative turbine design was developed to deliver high head at low flow, these POS pumps are way too loose to develop the 250psi a quality American regenerative turbine pump will routinely develop. At best they will develop 50 psi. So I'd put these particular pumps in the low flow low pressure category.

Sorry, no joy means I did not get any pressure and thus no agitation. I will mess with it more tomorrow.

What size pipe nipple were you using on the end?

Hi Rick,

quote:

While the regenerative turbine design was developed to deliver high head at low flow, these POS pumps are way too loose to develop the 250psi a quality American regenerative turbine pump will routinely develop. At best they will develop 50 psi. So I'd put these particular pumps in the low flow low pressure category.

Yes, I guess it depends on which eductor rated for what PSI. I am not sure where the cutoff is between high pressure and low pressure. I was only pointing to the idea that they can handle some pressure, in the 20-50 PSI range. And that compared to some other types of pumps, that the flow rate will drop less under a given pressure.

So, for one of your homemade pipe reduced type educutors, the NT seems fine, no?

quote:

Murphy had said that it wasn't necessary with his pump, and while I trust his opinion, I would also like to get the "best bang for the buck" when using it...figured this wouldn't hurt.

Necessary and helpful are two different things.

Let us know how it works. If possible, test it both ways, with and without the eductor.

Andrew,

I think Murphy is probably right. If the flow rate can outrun the glycerin drop rate, an eductor is a wasted effort. The little NT pumps can't outrun the glycerin fall rate.

Yes, the pipe eductor will work with an NT pump. All you need is 5-10 psi to keep things stirred up inside the tank. You can go higher, but I'm not sure it would make enough of an improvement to justify the added amp draw on the motor.

Rick, it is a smooth taper from 3/4 to 3/8 over a six inch run.

Ah, ok, you need a smaller nozzle. 3/8" wont develop much pressure and needs a diffuser added to get any mixing action at all. You won't any pressure buildup on these little pumps until you get down to 1/4".

You don't need a smooth taper. If you abruptly change diameters you need about 4-6 diameters of constant bore size to re-establish laminar flow and make a good nozzle.

Raften,

I pulled out the old papers to look at the numbers again. You first start seeing a pressure at 0.300" dia.

Using the plastic eductor:
0.125" dia = 48 psi
0.156" dia = 40 psi
0.188" dia = 30 psi

The 1/8" x 2" pipe nipple at 0.269" dia = 30 psi

I did not try any other sizes of pipe nipples.

The beta testers that drilled out their eductors took them out to .25" with good results.

quote:

I think Murphy is probably right. If the flow rate can outrun the glycerin drop rate, an eductor is a wasted effort.

Could be. Seems to me it would depend on batch size. To be confident, I'd want to see some tests.

Nothing against Murphy. People make all kinds of unsupported claims. Some are true.

That's fine Andrew. It's just that monster pumps in general have been proven to give the same gains as an eductor. The only advantage of an eductor over a monster pump is reduced power draw. Using an eductor on a monster pump would just increase power consumption by loading down the pump.