Low-Pulsation Transfer in Liquid Diaphragm Pumps

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Liquid diaphragm pumps are appreciated for their many benefits. They handle various fluids, offer strong suction, high efficiency, and durability. Their easy setup and simple maintenance make them one of the most popular pump technologies.

However, the inheremt nature of diaphragm technology is also causing unwelcome pressure peaks, affecting the pump efficiency and lower the product quality. To address this, Thomas has incorporated modern design features in its pumps, to significantly minimizing these issues.

What is Pulsation?

Just like other positive displacement pump types, including peristaltic and piston pumps, liquid diaphragm pumps have their flow rate generated by periodic volume changes inside the pump. By the rotation of an eccentric, a flexible diaphragm is moving up and down, drawing the medium into the pump chamber on the down stroke and expelling it on the upstroke. Internal valves located within the pump head controlling the direction of flow.

The oscillating working principle of liquid diaphragm pumps means the liquid flow isn't constant but occurs in sequences when the outlet valve opens. Unlike gases, liquids can't be compressed and transfer energy through themselves, creating higher forces on pump components and hydraulic resistance between the diaphragm chamber and the final load. This turns volume pulses into pressure pulses that travel to the outlet tubing.

High pressure pulsation, typical for all volumetric pumps, needs to be reduced to avoid negative effects on equipment and process results. Excessive pulsation increases wear on pump components, generates strong vibrations, and produces higher noise levels. It can also create bubbles or foam in the pumped liquid and potentially damage the transferred medium.

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Pressure peaks are undesirable in some applications as they prevent consistently high end-product quality. For example, in inkjet printing, high pulsation can cause uneven ink flow, affecting print quality and potentially damaging sensitive inks. In this industry, low-pulsation pumps are crucial for commercial success.

Reducing Pulsation in Liquid Diaphragm Pumps

There are several ways to reduce pulsation when using liquid diaphragm pumps.

1. Reduction of the diaphragm stroke

In order to minimize the pulsation amplitude, the diaphragm stroke can be reduced. This means that a smaller eccentric is used, which will reduce the flow rate as well. To counter the flow rate reduction while maintaining the lower pulsation amplitude, a faster motor turning speed can be applied.

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2. The correct diaphragm material

Liquid diaphragm pumps can be equipped with different materials depending on the use case. The choice typically depends on the medium to be transferred. For chemically aggressive media, diaphragms with an elastomeric base layer and a PTFE coating are often required. The rigid PTFE layer increases the diaphragm's overall hardness, leading to higher pulsation. Softer materials like EPDM can help decrease pulsation.

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3. Usage of a resonating diaphragm

Our modern liquid diaphragm pumps use a resonating diaphragm to smooth the flow. It acts as an integrated pulsation damper on the inlet side and positively affects pulsation on the outlet side.

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4. Usage of a double-head liquid diaphragm pump

A very common and effective way of reducing pulsation is using liquid diaphragm pumps with two heads. In this option, the two individual heads are mounted in parallel and alternate in pushing out liquid, thus creating overlapping pressure curves.

white-papers_reducing-pulsation_single and double head — Single head diaphragm pump (6410) Twin head diaphragm pump (6420)

In comparison to a single head diaphragm pump, a similarly constructed double head pump can reduce pulsation by over 70%.

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5. Usage of an external pulsation dampener

Such devices are installed on the discharge side of the pump and are designed to absorb the pressure peaks present in the pumped medium with the help of a flexible diaphragm, ensuring significantly smoother fluid flow. The reduction of pulsation can be more than 90% compared to pump operation without a pulsation dampener. If necessary, pulsation can be reduced by up to 99% by using additional flow restriction and optimized tubing.

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Thomas's pulsation dampeners require no adjustment or maintenance and offer the same durability and long lifespan as our diaphragm pumps. They are compact compared to other dampeners and use a G 1/8” tube connection compatible with many connectors. Additionally, Thomas's pulsation dampeners can be fitted with an overpressure switch to protect the system.

Contact us, if you are interested in a customized solution.

Thomas’ Low-Pulsation Solutions for Gentle Liquid Transfer

All components in the fluid path influence pulsation. For example, soft tubing on the discharge side of the pump helps reduce pulsation, while harder materials like PTFE transfer pulses without dampening. Filters and other restrictions, including nozzles, also affect pulsation. Any restriction after the pump reduces pulsation but increases system pressure and decreases flow rate.

Thomas uses pulsation-reducing solutions in its liquid diaphragm pumps to ensure even fluid flow in pulsation-sensitive applications. Our single-head 1210, 6311 and 6410 Series pumps are optimized for limited pulsation with an additional resonating diaphragm and optimized elastomeric materials.

For applications with higher pulsation requirements, Thomas's 6420 Series liquid diaphragm pumps, offer market-leading smooth media transfer with minimal pulsation.

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Learn More | Additional Resources

Discover more insights on reducing pulsation and achieving extremely consistent flow rates with Thomas's liquid diaphragm pumps. Learn how our technology can help you overcome pulsation challenges in your fluid-handling applications.

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Ensuring Low-Pulsation Transfer in Liquid Diaphragm Pumps