Ensuring Low-Pulsation Transfer in Liquid Diaphragm Pumps

The oscillating working principle of liquid diaphragm pumps means that there is no constant liquid flow, but rather sequences of fluid output when the outlet valve is open. Since liquids, unlike gases, cannot be compressed and do not absorb energy but rather transfer it through themselves, higher forces on the pump components are created and hydraulic resistance between the diaphragm chamber and the final load occurs. This makes the volume pulses become pressure pulses travelling all the way to the tubing on the outlet.

While typical for all volumetric pumps, high pressure pulsation is a pump performance feature whose impact needs to be reduced to avoid a number of unwelcome effects on the equipment and the process results. Excessive pulsation increases the wear on the pump components and generates strong vibrations that, in turn, produce higher noise levels. On top of this, it may lead to the formation of small bubbles or foam in the pumped liquid and, in some cases, even damage the transferred medium.

Crucially, pressure peaks are undesired in some applications as they prevent achieving consistently high end-product quality. For example, in inkjet printing – a common application for liquid diaphragm pumps – if too high, pulsation can produce an uneven ink flow that negatively affects the quality of the print output, with the increased energy having the potential for damaging sensitive inks. In this demanding industry, reliance on low-pulsation pumps is the key to gaining commercial success.

Reducing Pulsation in Liquid Diaphragm Pumps

There are a number of ways of reducing pulsation when liquid diaphragm pumps are used.

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.

3. Usage of a resonating diaphragm

A resonating diaphragm is used in our modern liquid diaphragm pumps to smoothen the flow of the pump. It acts as an integrated pulsation damper on the inlet side and also has a positive effect on pulsation on the outlet side.

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

Pulsation dampeners designed by Thomas require no adjustment or maintenance and are defined by the same durability and long lifetime as our diaphragm pumps. They feature small dimensions compared to other available dampeners and use G 1/8” tube connection that is compatible with a large number of connectors. Thomas’s pulsation dampeners can also be fitted with an overpressure switch to protect the system. We can customize pulsation dampener technology for the individual pump type and the required application.

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

Thomas’ Low-Pulsation Solutions for Gentle Liquid Transfer

All other components used in the fluid path have an influence on pulsation. For example, the use of a soft tubing material on the discharge side of the pump helps to reduce pulsation; on the other hand, with harder materials such as PTFE, pulses are transferred without any dampening effect. Also, filters and other restrictions including nozzles have an influence on pulsation. Any restriction after the pump will reduce pulsation, but it will also lead to increased system pressure and a decreased flow rate.

Thomas has been using 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 due to the use of an additional resonating diaphragm. Also the usage of optimized elastomeric materials ensures low pulsation.

For applications with a higher requirement on pulsation, Thomas’  6420  Series liquid diaphragm pumps with a capacity of up to 1,800 ml/min and maximum continuous pressure height of up to 10 m H2O stand out through their market-leading smooth transfer of media with minimal pulsation compared to competition.