How Does a Peristaltic Pump Work? Rollers, Tubing, Occlusion?

How does a peristaltic pump work? The motor rotates the rotor. The rotor has rollers. The rollers press against a soft tube. Each press sends the liquid forward. The liquid is just touching the tube.

Innofluid Co., Ltd. produces peristaltic pumps in Lingang New Area, Shanghai. The team has 20 years of R&D expertise. From its spec sheets, one thing is obvious: flow depends on tube size and speed.

Rollers, tubing, the seal, and the flow are important. Innofluid’s pump pages provide genuine figures for each.

A peristaltic pump employs rollers that pinch soft tubing. The rollers rest on a rotating rotor. Each roller pinches off the tube and holds a little of liquid. Then the roller advances the liquid. Behind the roller the tube opens up again, sucking in additional liquid. The liquid just touches the tube.

The Core Idea: Squeeze, Release, Repeat

Your throat uses peristalsis to transport food down. It surges up like a wave. A peristaltic pump accomplishes this also. It employs a motor, a rotor, rollers, and a soft tube.

The rollers squeeze the tube against a curved track. This force is known as tube compression. Liquid flows in front of rollers. Behind it, the tunnel opens up again.

How Does a Peristaltic Pump Work, Step by Step?

A peristaltic pump works in three steps. They repeat: pinch, push and refill.

Step 1. The Roller Pinches the Tube Shut

One roller of the peristaltic pump flattens the tube against the track. At that point the tube is closed.

Step 2. A Pocket of Liquid Moves Forward

Some liquid is trapped between two rollers. The rotor spins. The liquid flows to the outflow.

Step 3. The Tube Opens and Pulls In More

The roller moves on. The tube goes back to its round shape. This pulls in liquid from the inlet. New liquid fills the tube.

Inside the Pump Head: Rotor, Rollers, Track

The pump head holds the rotor, rollers, track and tube.

Main Parts and Their Jobs

Drive: the motor that turns the rotor.

Rotor and rollers: they squeeze the tube.

Track or pressure block: the curved part the tube is pressed on.

Tube clamps: they keep the tube in place.

The Innofluid KD15/KD25 head features a flip cover. Flip the top pressure block open. This allows quick tube changes. You may also run many heads in series.

The EasyPump head has a tube clamp coupling. It makes it easy to load a tube. It has a rubbing wheel adjustment for various-sized tubes. Innofluid also markets stepper, closed-loop stepper, DC, and AC motors.

Why Roller Count Changes Flow and Pulsation

The peristaltic pump rollers determine the smoothness of the flow. How many rollers do you have? Each time, there are fewer rollers, taking a greater pocket. More rollers make smaller pockets and a smoother flow.

Roller Count by Innofluid Pump Head

Take the KD15 with an 18# tube at 600 rpm. The 3-roller variant gets up to 3027.97 mL/min. 2690 mL/min for the 4 roller model. It travels a little slower since its pockets are smaller. Innofluid furthermore provides a fluid pulse damper attachment.

Occlusion: The Gap That Sets Accuracy

What Occlusion Means

Occlusion is how fully a roller closes the tube against the track.

Too Tight or Too Loose?

If the gap is too loose, liquid slips back. If it is too tight, the tube wears out faster.

Fixed or Adjustable Pressure Heads

Innofluid's EasyPump has a tube pressure gap fine-tuning mechanism. It lets you adjust the pressure. This helps the tube last longer. It also makes dispensing more accurate.

Tubing Compression and Why Tube Size Matters

Tube size sets how much liquid each turn moves. The bore sets the volume. The wall thickness sets how the tube bounces back.

EasyPump heads use 1.6 mm and 2.4 mm walls. The UC20 head uses 2.0 mm walls.

Innofluid lists silicone, PharMed BPT, several Tygon grades, Chem-Durance, Versilon F-5500-A and Viton tubing. All of them are in the Peristaltic Pump Tubes category.

Positive Displacement: A Fixed Volume per Turn

A positive displacement pump moves the same volume with every turn. So the flow follows the speed. How does a peristaltic pump work out its flow? It multiplies the volume per turn by the speed.

The Simple Flow Formula

Flow (mL/min) = mL per turn × rpm.

Take the LabV3. Its 18# tube moves 4.3 mL per turn. Its top speed is 350 rpm. So 4.3 × 350 = 1505 mL/min. That matches the top flow listed for the LabV3.

LabV3 Tube Size and Flow at 350 rpm

Self-Priming, Backflow, and Clean Stops

Self-Priming

A self-priming pump pulls in liquid on its own. The tube bounces back. This makes suction.

No Backflow

At least one roller always pinches the tube. So the pump works as its own valve.

Anti-Drip at the End of a Dose

The LabV3 has a back suction angle setting of 0-360°. Back suction pulls a little liquid back when a dose ends.

For safety, the KD15/KD25 head has an optional lid-open stop.

Fluid Isolation: Only the Tube Touches Liquid

Fluid isolation means the liquid touches only the tube. No seals, valves or gears touch the liquid.

An EasyPump head can hold two tubes at once. That gives two channels on one head. Labs, factories and device makers use this feature. Innofluid's article What Is a Peristaltic Pump Used For? lists the jobs.

Pressure Limits, Pulsation, and Tube Wear

Larger tube bores handle less pressure.

Tube Pressure Ratings on the LabV3

13#, 14#, 19# and 16# tubes: 0.27 MPa intermittent, 0.17 MPa continuous

18# tube: 0.10 MPa intermittent, 0.07 MPa continuous

The tube is the part that wears out. Tubing compression and speed both affect how long it lasts.

The LabV3 has flow accuracy under ±0.5%. It also has intelligent calibration. You can fine-tune the flow while the pump runs.

Who Builds These Pumps? About Innofluid

Innofluid Co., Ltd. focuses on peristaltic pumps. It does design, R&D, production and sales. It is based in Lingang New Area, Shanghai.

The company has 20 years of R&D experience and 119 patents. It serves 110 countries. R&D staff make up 26% of the team. Dosing accuracy is ±0.5%. It adds 3-5 new product series a year. All products are CE certified.

Innofluid supplies complete pumps, pump heads and OEM pumps. It also offers ODM service and full fluid solutions.

Foire aux questions

What is the working principle of a peristaltic pump?

The working principle of a peristaltic pump is simple: rollers squeeze a soft tube. Each roller shuts the tube and pushes a pocket of liquid ahead. Then the tube opens again and pulls in more liquid from the inlet.

Does a peristaltic pump need valves?

No, a peristaltic pump does not need valves. At least one roller always pinches the tube. So the liquid cannot flow back. Fluid isolation keeps the liquid inside the tube, so no valve touches it.

How many rollers does a peristaltic pump have?

Innofluid pump heads have 2, 3 or 4 rollers. The UD15 has 2. The SN15 has 3. The KD15/KD25 has 3 or 4. The EasyPump has 4. More rollers give a smoother flow.

What does occlusion mean in a peristaltic pump?

Occlusion is how fully the roller shuts the tube against the track. If the gap is loose, liquid slips back. If it is tight, the tube wears out faster. Some heads let you adjust the gap.

Is a peristaltic pump a positive displacement pump?

Yes, a peristaltic pump is a positive displacement pump. Each turn moves the same amount of liquid. On the LabV3, 4.3 mL per turn at 350 rpm gives 1505 mL/min.

Can one pump head run two tubes at once?

Yes, the EasyPump V and VI heads hold two tubes. That gives two channels on one pump head. Both use 1.6 mm wall tubing.

Conclusion

So, how does a peristaltic pump work? It squeezes, seals, moves and refills. Peristaltic pump rollers pinch the tube. Occlusion keeps the seal. Each turn moves the same amount of liquid.

Innofluid Co., Ltd. is a good place to start. Its pages list tube sizes, flow ranges and pressure ratings for each head. It also offers OEM and ODM options. Need help to match a pump head and tube to your liquid? https://www.innofluid.com/contactus.html.