Peristaltic pump pressure calculation

[AHartman]

If I know that I need 1.5 L/min max flow rate and cannot exceed 50 psi, how do I size the tubing/roller(s)/motor for a peristaltic pump? I'm designing a disposable, handheld medical pump and want to see if a peristaltic approach can work.

Any suggestions of places to look for calculations, or resources for learning more? I'm a mechanical engineer, but not a pump designer by any stretch of the imagination, so I may be a bit dense and overlooking something obvious.

Thanks in advance for any help or suggestions the forum may have!

-Adam Hartman

 

[BigInch]

The squeezable portion of the tubing must have a volume such that the number of times it is squeezed each minute = 1 liter.
Speed your motor, and/or gear ratio, for the number of times it needs to be squeezed.
It doesn't sound like more than 15 Watts, if I did my conversions right.

What would you be doing, if you knew that you could not fail?

 

[AHartman]

Thanks, BigInch. If I need a 30 psi output pressure, how do I know what size tube to pick? Also, how do I know the torque on the motor so as to size the motor correctly?

 

[BigInch]

You have to look at the diameter and length of tube on which you can get the roller action functioning.

25 ml/sec
squeezed volume of tube must be 25 cm3 each second
10 mm inside diameter tube has area of 0.785 cm2
if the tube is 1 cm long, that's 0.785 cm3
25 cm3/sec / 0.785 cm3 = 31.8 squeezes / second
32 x 60 = 1920 rpm, if you get 1 squeeze/revolution. If you can get two rollers on the tube, then cut the motor rpm in half, etc. etc.

Play with the diameter and length of tube squeeze until you get some commercial motor characteristics.
Power = density * volume/unit time * height/efficiency
I used water before, if not water, change the density.
No idea what efficiency might be, I estimated 50% before.

Never done that before, so ... I don't claim any expertise in sizing these things, but the method should work reasonably well.

What would you be doing, if you knew that you could not fail?

 

[MikeHalloran]

You won't get anywhere near 30 squeezes/second, because the tube has to open itself up after being squeezed, and hysteresis in the rubber (and flow resistance in the suction) limits how fast that can happen.

In order for the tube to open itself, the OD has to be at least twice the ID, probably more.

Unfilled, unreinforced rubber will give best life, but won't like 30 psi at all.

If you really need 30 psi, I wouldn't go near a peri pump. ... but I've had a lot of bad experiences with them, so I wouldn't go near them at all, given any choice.

If you must use a peri pump, and you are compelled to build your own, you need to start building and breakng them as soon as possible.


Mike Halloran
Pembroke Pines, FL, USA

 

[BigInch]

Mike, thanks for clearing that up.

What would you be doing, if you knew that you could not fail?