THEMA:

I have been designing a piston ballast tank and have also considered building a peristaltic pump with a tank.I really like the simplicity of the peristaltic pump and ballast tank system but it is about 3 times slower.This could change when using a higher torque brushless motor and an eccentric roller design pump.

360 Degree eccentric design

A unique approach to peristaltic hose pump design employs a single oversized roller on an eccentric shaft that compresses an engineered, low friction hose through 360 degrees of rotation. The benefits of this design include more flow per revolution and only one compression and expansion per cycle. At equal performance points this pump runs more slowly, with consequent longer hose lifetime, than pumps with multiple shoes or rollers.

Many older hose pumps use shoes to compress the hose. When the shoe slides over the outside of the hose, it creates friction and heat, which shortens hose life. A single roller pump uses a large diameter lubricated roller on an eccentric shaft that rolls over the hose. This means that it produces less friction, and therefore less heat, than a pump with shoes.

In addition to less heat, an eccentric shaft hose pump functions with only a single compression of the hose per revolution. For every one rotation, the pump has one compression of the hose, while pumps with multiple shoes or rollers have at least two compressions per revolution, and in some cases three or four. Since the hose is the heart of a peristaltic hose pump, and hose life is inversely proportional to the number of squeezes, this design will outperform a pump with shoes at the same speed.

The hose in this type of pump takes up the full 360 degrees of the pump housing. This is important, because at an equal size, this design will produce 55% more flow at the same speed. This means that one can get more flow at the same pump speed, or run the pump more slowly to generate the same flow.

Advantages
Because the only part of the pump in contact with the fluid being pumped is the interior of the tube, it is easy to sterilize and clean the inside surfaces of the pump. Furthermore, since there are no moving parts in contact with the fluid, peristaltic pumps are inexpensive to manufacture. Their lack of valves, seals and glands makes them comparatively inexpensive to maintain, and the use of a hose or tube makes for a relatively low-cost maintenance item compared to other pump types. Peristaltic pumps also minimize shear forces experienced by the fluid, which may help to keep colloids and slurry fluids from separating.

Hello sunworksco,

I can fully agree with your considerations about the advantages of your "monoroll" 360 degree design, supposed that that single roll will also block the water transition when passing the top position and pressing both sections of the hose.
The considerations about my triple roller (120 degree) design was to smoothen the load torque (you can see that just one roll starts to press on the tube when the next (trailing) is leaving it, so the torque ripple is rather low. And there is always at least one roll that blocks the water transition through the hose. Of course friction is higher (although all the rolls have ball bearings) and the water volume pumped by one revolution is less due to the additional pressed hose sections.