What Are the Key Considerations in Designing a Peristaltic Pump?

[a.mlw.walker]

Hi Guys,
Been researching peristaltic pumps, but can't find an industry standard in designing them.
Wiki (http://en.wikipedia.org/wiki/Peristaltic_pump) has a little bit of maths on the occlusion, and a basic idea on calculating the flow rate
and this article explains a little of the theory
http://www.coleparmer.com/TechLibraryArticle/579
but there doesn't seem to be much in the way of a set of rules in designing one.
I came up with a little bit of methodology and wondered whether you guys could comment - or had a better way of dealing with it:

So if I put a tube on the table a metre long, and put one end in a bucket of water (assuming no height changes anywhere for now), then squeezed it in the middle (@ 0.5m) and dragged your fingers down towards the other end (not in bucket) what would be occurring:
I.e assuming a perfect squeeze (completely sealed) and I know the inner/outer diameters, young's modulus, and density of fluid (water), distance of drag is 0.5m I need to know my flow rate and "effort" required to pull some water up the pipe
flow rate is (pi*ID^2/4)*[speed I drag at) (iD is inner diameter)
work is force required * 0.5m,
Force required is...? The effort to "suck" water up the pipe? Thats going to be this equation: resulting in the change in pressure inside the pipe, which can be converted into a force by multiplying by the cross sectional area of the pipe:
$\Delta P=f.\frac{L}{D}.\frac{\rho V^{2}}{2}$

?
If L is 0.5m D is inner diameter (at non squeezed point) and f comes from a moody diagram
Then as my fingers that are squeezing the pipe reach the free end, my other hand squeezes at 0.5m and does the same thing, I keep repeating this technique and I have peristaltic motion.

So now thinking of a peristaltic pump, i.e

the distance moved is half the circumference, the torque on the motor is the force required to "suck" * distance to pivot
The available speed is from Power = T* rotational velocity
therefore I now know the speed at which I can move that amount of fluid, so I have a flow rate?

If I increase the number of squeeze points to 4 (like the picture) then my force required increases by 4?
However the distance that I am sucking is now the distance between squeeze points

And what happens if I don't have "perfect squeeze"? I am thinking the force required (and flow rate) may fall away with a 1/r^2 rule? what do you think?
Perfect squeeze can only be considered depending on the tubing used - to stiff and creating a perfect squeeze may crack (damage) the tube, so maybe I would just want a 50% squeeze...

Anyone agree/disagree or have a good reference - would love the comments, thanks

 

[Tabrez.Mahamad]

Hi Guys,
Been researching peristaltic pumps, but can't find an industry standard in designing them.
Wiki (http://en.wikipedia.org/wiki/Peristaltic_pump) has a little bit of maths on the occlusion, and a basic idea on calculating the flow rate
and this article explains a little of the theory
http://www.coleparmer.com/TechLibraryArticle/579
but there doesn't seem to be much in the way of a set of rules in designing one.
I came up with a little bit of methodology and wondered whether you guys could comment - or had a better way of dealing with it:
Anyone agree/disagree or have a good reference - would love the comments, thanks

Hey, it looks like you were on the right track back in 2012. I'm surprised that in the span of 2 years or so, there's not been a single response to your post. I'd be happy to know what you found out later and what your experience was with building a peristaltic pump. I'm trying to design one myself. Please let me know if you can help.

 

[Baluncore]

Tabrez.Mahamad, welcome to PF.

A peristaltic pump moves the fluid volume in the tube along the tube. Since the tube can lie around almost 360° there is only a need for two pinch rollers, so one is always pinching the tube at anyone time.

Fluid flow rate is proportional to the cross section of the tube multiplied by the linear rate that the pinch moves along the tube. The flow is reduced by the volume of the pinch rollers.

The energy needed to drive the pump will be the change in potential energy of the fluid being pumped, plus the net energy loss in pinching and releasing the elastic tube. Less pinch rollers will require less energy to pinch the tube, so use as few rollers as is geometrically possible while avoiding a loss of pinch. The change in fluid potential energy is quite independent of the number of pinch rollers used.

You can expect variation of a few percent in fluid flow rate depending on tube distortion effects at the pinch roller. That will change with time, temperature and the tube batch properties.