Reverse calculation to determine GPM, PSI? 1

[limey1]

Fluid Mechanics is not my field, but I have been asked to assertain what the correct GPM/PSI would be to effectively "flush" steel tubes out with a diameter of 1" and a length up to 60'. We do have an existing hose system, but I get the impression that it wasnt calculated in the first place. Specs for existing pump are 15 hp at 3450 rpm, pump curve is 84 gpm at 145psi. Seems like overkill to me but ive been wrong before, and hence that is why im here.

 

[zdas04]

What is the goal of this "flushing". Different starting/ending points require different pressures and flow rates.

David

 

[IRstuff]

Velocity is dependent on what you're trying to accomplish, how long you want to do it, and how much damage you're willing to tolerate.

TTFN

FAQ731-376

 

[limey1]

The goal of the flushing is to remove any residaul loose particulate contamination in th i/d of the tube. The tube would be clamped and sealed at one end, with the other, open to atmosphere.

 

[IRstuff]

BUT, what's the nature of the "residual" contamination? Is there grease? Are the particles particularly sticky?

TTFN

FAQ731-376

 

[limey1]

Lime residue. No grease, not sticky...Loose particles.

 

[vpl]

The tube would be clamped and sealed at one end

Where do you expect the water and particles to go?

Instead of sealing it, could I suggest a drain to a sump or other reservoir?

The relationship between gpm and velocity and pressure are pretty easily derived based on the units. Just remember that the psi is pounds-force and the density is pounds-mass and throw in the gravitational constant.

Your 84 gpm in a single 1" tube is around 33 ft/sec velocity. That should sweep out everything, providing its got somewhere to go. Just don't do it too long, or you'll start eroding your pipes.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[IRstuff]

Hmm. The lime in my bathroom is pretty stubborn.

You might need to provide some aeration in the water to move the lime particles along.

TTFN

FAQ731-376

 

[limey1]

VPL, the water and particles go to a sump, and are pumped through a bag filter. This isnt my concern, I think that 84 gpm is overkill. We have a 15hp motor driving this booster pump.(Seems excessive to me, but as I said earlier, Im a newbie at this).

 

[IRstuff]

Sounds like time for an experiment!

Try running some samples at different flows. My guess is that someone determined empirically that the current flow was required to do the job to whatever level of acceptance there is or was. No one would seriously accept 84 gpm loss over any long period of time jsut because they're lazy, since that does represent, literally, money down the drain.

TTFN

FAQ731-376

 

[limey1]

IRstuff, I think you may have hit the nail on the head with your suggestion of aeration. Creating turbulance throughout the i/d would be much more efficient than the current 'blow the hell out of it' approach. I think sometimes a nudge in the right direction can be all we need. Thanks.

 

[Artisi]

What are you trying to establish - is 15 hp sufficient to pump 84 gpm to 145psi or can you pump 84 GPM thru 60'of 1"line or will this flow rate remove the lime particles?

 

[IRstuff]

I think neither. The question, ostensibly, is whether the high flow rate was actually required or justifiable. That's still unclear, since these sorts of processes tend to have nebulous requirements.

Just how free of particulates is it supposed to be?

And while the particulates might not be grossly sticky, they may be Van der Waals sticky, hence the large flow rates.

TTFN

FAQ731-376

 

[unclesyd]

The following website offer variations on the theme of using a brush either propelled by water, air, or water and air to clean tubes. This system eliminates any problems with handling copious amount of water and fluid velocity in a tube.

http://www.projectiletube.com/products.php

http://www.concosystems.com/tubecleaners.php

http://www.johnrrobinsoninc.com/gun_spec.htm

http://www.usaindustries.com/heat_cleaning_equipment.htm

 

[limey1]

I think for clarification I should explain that the aim for flushing out the tubes is to replace contaminated/dirty with water fresh, 'virgin' water as a final step in the process. The Fire-hose system we have today does not effectively flush the tube out through its full length. As IRstuff suggested, aeration may be the answer, which will be my next step. Unclesyd provided a website (projectiletube) that has the necessary equipment for this. I do not want to start 'snaking' cleaning brushes or using projectiles to clean as this would hurt cycle times in production. Im confident that enough turbulant flow will be produced to achieve the required cleanliness with less water. Thanks again everyone