How Can You Minimize Pulsation in a Liquid Diaphragm Pump?

Is the inconsistent flow from your liquid pump ruining your results? This pulsation can destroy the precision of your chemical dosing or medical analysis, making your expensive device unreliable.

To minimize pulsation, you can integrate a pulsation dampener, use a pump with multiple heads working out of phase, or optimize your system with rigid, short, wide-bore tubing. These methods smooth out the pressure spikes inherent in diaphragm pump operation.

I'll never forget a frantic call I got from a client developing a new medical diagnostic tool. Their machine needed to dispense a tiny, precise volume of reagent, but the results were all over the place. Their entire project was at risk. When they showed me the fluid line, I could literally see the tubing vibrating with each pump stroke. The pulsation was so severe it was throwing off their optical sensors. We solved it by implementing a dual-head pump and changing their tubing. Seeing the flow smooth out and their results become repeatable was a huge win. It reinforced a core lesson: controlling pulsation isn't just a minor refinement; it's fundamental to achieving precision.

What Actually Causes Pulsation in a Diaphragm Pump?

You see the pulsing flow, but you're not sure why it's happening. Without understanding the root cause, any fix you attempt is just guesswork, wasting time and money on ineffective solutions.

Pulsation is a natural result of a diaphragm pump's mechanical design. The diaphragm's reciprocating (back-and-forth) motion creates distinct phases of fluid intake and discharge, resulting in a pulsing, rather than a steady, stream.

Think of the pump's action like a single piston in an engine. As the motor turns an eccentric cam, it pulls the diaphragm back, sucking liquid into the pump head through an inlet valve.

In this intake phase, there's no output flow. Then, the cam pushes the diaphragm forward, forcing the liquid out through an outlet valve. This creates a surge of pressure and flow. Because this cycle repeats continuously, you get a "push-pause-push-pause" effect, which is the pulsation¹ you see. This is why single-head diaphragm pumps, by their very nature, do not produce a perfectly smooth flow. The problem becomes critical in applications like high-performance liquid chromatography (HPLC)² or medical infusion, where any flow variation can compromise the entire process.

The Push-and-Pull Cycle

At the heart of the pump is this simple mechanical cycle. The diaphragm moves in and out, and check valves direct the flow. This design is reliable and robust, but the stop-start nature of the flow is its primary drawback.

Why Pulsation is a Problem

• Inaccuracy: In dosing or metering applications, pulsation means the volume delivered per second is not constant.
• Vibration: The pressure waves can cause tubing and other components to vibrate, leading to noise and mechanical stress.
• System Interference: In analytical instruments, pressure fluctuations can interfere with sensitive sensor readings.

Is Adding a Pulsation Dampener the Best Solution?

Your system is vibrating and your flow is unstable. You need a reliable fix without a complete redesign. Is adding another component the right way to solve the problem?

A pulsation dampener is often the simplest and most effective external solution. It acts like a shock absorber for your fluid line, absorbing pressure spikes and releasing liquid during pressure troughs to even out the flow.

I often recommend a dampener as the first thing to try, especially on an existing system. Think of it as a small chamber or accumulator installed in the tubing right after the pump. Inside this chamber is a compressible gas³ (often air or nitrogen), separated from the process liquid by a flexible membrane. When the pump discharges its pulse of liquid, the pressure spike compresses the gas, storing some of the energy. Then, as the pump goes into its intake stroke and the pressure drops, the compressed gas expands, pushing the stored liquid out into the system. This action effectively fills in the "gaps" between pump strokes, transforming a choppy stream into a much smoother, more continuous flow. It's a highly effective and relatively low-cost way to dramatically improve system performance.

How Dampeners Work

The key is the compressible element inside the dampener. It absorbs the peak energy of the pulse and then releases it during the trough, smoothing the average flow and pressure downstream.

Placement is Key

For maximum effectiveness, the dampener should be installed as close to the pump's discharge outlet as possible. This intercepts the pressure wave⁴ before it has a chance to travel down the tubing and cause vibration.

How Do Multiple Pump Heads Smooth the Flow?

You need the absolute smoothest flow possible for a high-precision application. Is there a more integrated solution than adding external components like dampeners to your system?

Using a pump with two or more heads is a highly effective way to intrinsically reduce pulsation. By offsetting the cycles of each head, one head discharges while the other is in its intake phase, creating a far more continuous and stable flow.

This is one of the most elegant engineering solutions to the pulsation problem. I worked with an OEM building an ink-jet printing system for medical diagnostics, where even microscopic flow variations could ruin a sample. A dampener helped, but it wasn't perfect. I recommended they switch to one of our dual-head diaphragm pumps⁵.

In a dual-head pump, two diaphragms are driven by the same motor, but their cams are offset by 180 degrees. This means that as Head A is finishing its push stroke, Head B is just beginning its push stroke. Their power strokes overlap. The result is that the deep "valley" of zero flow between pulses is almost completely filled in. While you still have small ripples where the flows combine, the major pulsation is gone. This creates a much smoother flow without any extra parts.

The Power of Overlapping Cycles

The core concept is to use one pump head to compensate for the other's downtime. The more heads you add (e.g., three heads offset by 120 degrees), the smoother the resulting flow becomes.

The Design Trade-Off

The main trade-off is size and cost. A dual-head pump is inherently larger, more complex, and more expensive than its single-head counterpart. However, for applications where flow stability⁶ is non-negotiable, the superior performance justifies the investment.

Can Your Tubing Be Making Pulsation Worse?

You've optimized the pump but you still have vibration and unstable flow. Could the simple tubing you chose be the real culprit, undermining your entire system's design and performance?

Yes, your tubing plays a huge role. Flexible, long, or narrow-bore tubing can absorb energy and then release it out of sync with the pump, amplifying pulsation. Using short, rigid, wide-bore tubing minimizes this effect and maintains a smoother flow.

I consider the tubing to be an active part of the fluidic system, not just a passive connector. A client was once having terrible trouble with pressure spikes⁷ in a dispensing system. They had already implemented a dual-head pump. I asked them to send me a video of the machine running. I immediately noticed they were using very long, soft silicone tubing. With every pump stroke, the tubing was visibly expanding and contracting like a balloon. It was absorbing the pressure pulse and then releasing it with a delay, creating its own set of waves in the system. We had them switch to short lengths of rigid PTFE tubing⁸. The problem vanished overnight. The rigid walls of the PTFE tubing didn't expand, so the flow from the pump was transmitted directly and smoothly.

Key Tubing Characteristics

1. Material: Rigid materials (PTFE, PEEK) prevent expansion and dampen pulsation. Flexible materials (Silicone, PVC) can worsen it.
2. Length: Shorter tubing provides less opportunity for pressure waves to develop. Keep it as short as possible.
3. Bore Size: A wider internal diameter can help reduce pressure drop and smooth flow, assuming the flow rate is appropriate.

Does Controlling the Pump's Speed Reduce Pulsation?

You're running your pump at full speed to meet flow requirements, but it's shaking the device apart. Is simply running it at 100% the only option, or is there a smarter way to operate it for a smoother output?

Yes, controlling the pump speed can absolutely help. Operating a pump at a lower, consistent speed often produces less violent pulsation than running it at maximum RPM. Using Pulse Width Modulation (PWM) control to find an operational "sweet spot" can significantly reduce vibration.

One of the most interesting challenges I encountered was with a water quality analysis device. At certain speeds, the entire machine would start to hum and vibrate loudly. The client thought the pump was defective. After some investigation, we realized the pump's operating frequency (its speed) was hitting the natural resonant frequency of the machine's chassis. Just like a singer can shatter a glass by hitting the right note, the pump was "exciting" the system and amplifying the vibration.

The solution wasn't a different pump, but better control. By using a simple PWM signal to adjust the motor speed down by just 15%, we moved it away from that resonant frequency. The loud humming stopped completely, and the entire system ran much more smoothly. This shows that intelligent control is just as important as mechanical design.

Finding the Sweet Spot

• Avoid Resonance⁹: Every physical system has natural frequencies. If your pump's pulse frequency matches one, vibration will be amplified. Changing the speed moves it out of this zone.
• Lower Speed, Lower Energy: A slower pump stroke creates a less energetic pressure wave, which is inherently smoother.
• PWM Control¹⁰: Most modern DC pumps, especially brushless models, allow for precise speed control using a PWM signal, making it easy to tune the pump's performance within your system.

When Should You Consider a Different Pump Technology?

You've tried dampeners, multi-head pumps, and optimized tubing, but the flow isn't smooth enough for your ultra-sensitive application. Are you forcing the wrong technology to do a job it was never meant for?

For applications requiring a near-pulseless flow, you might need to consider other technologies. Gear pumps and centrifugal pumps provide a genuinely continuous flow, while multi-roller peristaltic pumps can also offer improvements over diaphragm pumps.

My job is to find the best solution for the client, even if it means acknowledging the limits of our own primary technology. I recently consulted for an OEM developing a medical infusion system that needed to deliver medication with incredible stability. Even our best dual-head diaphragm pump had micro-ripples in the flow that were unacceptable for their needs. In this case, a diaphragm pump was simply not the right tool for the job.

I explained that for their level of required precision, a high-end peristaltic pump with multiple rollers or a micro gear pump would be a better choice. While diaphragm pumps are fantastic for their reliability, efficiency, and pressure capabilities, technologies that produce a truly rotary, non-reciprocating flow will always be inherently less pulsatile. Being honest about this builds trust and helps the client succeed.

A Quick Comparison of Low-Pulsation Pumps

• Gear Pumps¹¹: Provide a very smooth, continuous, high-pressure flow. Best for non-abrasive, viscous fluids.
• Peristaltic Pumps¹²: Low pulsation, especially with multiple rollers. Excellent for sterile applications as the fluid never touches the pump.
• Centrifugal Pumps: Pulseless flow, but generally for higher flow, lower pressure applications.

Conclusion

To control pulsation, use dampeners for a quick fix, multi-head pumps for an integrated solution, and always optimize tubing. This ensures the stable, precise flow your application demands.

👉 At BODENFLO, we specialize in custom micro diaphragm pumps and precision flow solutions for OEM applications. If you are developing medical devices, analytical instruments, or dosing systems, our team can help you achieve smoother, more reliable performance.

📧 Contact us: info@bodenpump.com