Most of the positive displacement pumps or volumetric pump, move the fluid handled in an enclosed volume. However, syringe pumps are also positive displacement pump with the difference of handle a fixed volume. Here the differences between the classical volumetric pumps and syringe pumps are discussed to help readers to distinguish and select a pump for your application.
Most of the volumetric pumps work by two general mechanisms: a reciprocating or rotary mechanism. Engineers use positive displacement pumps for systems requiring pressurized fluids, especially in the chemical industry. However, you can find these volumetric pump types in small plants and factories. The injection systems for engines is another classic positive displacement pumps. Positive pumps under this modality are a conventional piston or plunger pumps.
Reciprocating Volumetric Pumps
In the Reciprocating pumps, the displacement bodies as a piston container gradually and periodically increase and decrease the working volume as the pumping takes places, in this way, a volume is transported from the inlet to the outlet. It is essential for this process that working volumes remain isolated through separated elements as check valves; the intrinsic pressure differences control these elements during pumping the case of rotatory mechanics the rotational speed controls the valves. The main advantage of the isolated devices called valves is that the prevention of fluid flowing back to the suction or discharge line; this feature keeps the positive displacement. The most commonly known positive displacement pumps are piston pumps/plunger pumps. Their displacement body, e.g., a plunger, describes a linear motion.
Reciprocating Volumetric Pumps
Regarding the variable volume displacement, these pumps are the rotating principle; the conventional rotatory pumps are the gear pump, screw pump or peristaltic pumps. In general terms this pumps moved finite elements, gear pumps do the process driving the liquid between gear teeth, peristaltic pumps does the same process between the rotatory element there is a hose. The mode of displacement varies slightly as the rotatory element moves through different positions, displacement per shaft revolution may not be accurate after hundreds of operational hours. However, for the case of peristaltic pumps; microfluidic characterization with these pumps is not recommended1.
Syringe pumps are positive displacement pumps with a fixed volume and usually are not part of the previous classification (please check What a syringe pump is?). As it is discussed in the Chemyx website, syringe pumps feature several advantages over standard volumetric pumps: working with minimal rates as one microliter/min, picoliter control, high viscosity and high pressure with flow control. Chemyx syringe pumps allow the most accurate and reliable operation in a wide range of rates.
In general terms, all these pumps allow fluid motion. However, the most important features to distinguish is the precision and the rates they can provide. In-plane terms, syringe pumps are more useful pumps for microfluidic applications, high-tech development, and research applications. From the previous description, the pumps that allow a similar control is a peristaltic pump which also provides free contamination because the elements never touch the fluid. Nevertheless, the hose should be clean or sterilize depending on the application. Although the flow fluctuation may be problematic in low flow rate condition (~uL/hr), the syringe pump is very intuitive a reliable.
Chemyx syringe pumps offer the higher standard with the Fusion 200 and 4000; these pumps used micro-step motors, and they can be customized for high pressure and high viscosity application. Therefore, Chemyx syringe pumps allow the development of microfluidics for the most exciting fields as biochemistry, biotechnology, material synthesis and chemical synthesis among others.
- O’Connor, R.P., Fisher, J.D., Gopalratnam, P.C., Towler, G., Smith, S., Agrawal, P.D., Fegan, S.D., Hasbronck, J.F., Knnesh, J.G., McHarg, R.E., Pezone, A.L., Starkweather, R., Yohe, T.H., 2010. Positive Displacement Pumps: A Guide to Performance Evaluation, Positive Displacement Pumps: A Guide to Performance Evaluation. https://doi.org/10.1002/9780470924754