Pumps/Vacuum technology Companies – Innovations – Products Numerous companies in the bottling, manufacturing or packaging industry have to transfer viscous liquids from containers or machines quickly, cleanly and as precisely as possible. In addition to vertical or horizontal eccentric screw pumps, more and more compressed airdriven diaphragm pumps are being used for such applications. For many years, a manufacturing company in the food industry has been using several horizontal eccentric screw pumps of the type JP- 700 HL 50 L, which have an EPDM stator and milk thread connections according to DN40-DIN11851 on the suction and pressure sides. At a speed of 350 rpm, the pumps deliver approx. 40 l/min. The customer used the eccentric screw pumps for all their liquid handling, with very different use cases. In addition to thin to viscous food oils, sugar solutions were also pumped. The principle of the eccentric screw pump has proven itself for many decades in the beverage and food industry as the most frequently used displacement pump for pumping viscous media. With this type of pump, a rotor (a screw conveyor made of stainless steel) rotates in an oscillating manner in a fixed stator, which in the food sector is made of elastomers such as EPDM or NBR or also the solid material PTFE. Due to the precisely matched, coiled geometry of the rotor and stator, the rotation of the rotor between the two components results in equally sized conveying chambers. The chamber volume is always identical and is shifted evenly from the suction side to the pressure side of the pump during the pumping process. Due to the arrangement of the rotor and stator, this pumping principle produces hardly any pulsation and there are also no major shearing forces on the medium to be pumped. The flow rate is proportional to the speed of the motor, whereby the speed cannot be selected at will, but depends on the material used for the stator as well as on the viscosity and abrasiveness of the pumped medium. Initially, the advantages of the eccentric screw pumps were of great importance for the customer’s purchase decision. Consistent, low-pulsation and gentle conveying is particularly advantageous in the food sector. In addition, the compact pumps of the 50L series have achieved a high flow rate of up to 100 l/min (at 900 rpm), which could be regulated at any time via a frequency converter. The pumps of the type JP- 700 HL 50 L were also able to convey solids with a grain size of up to 8 mm due to the free passage and guaranteed a very high dosing accuracy due to the constant chamber volume. It was also very important for the customer that the eccentric screw pumps were a very quiet type of pump and that the energy consumption was also low. In addition, eccentric screw pumps have a high pumping speed and are therefore self-priming even from a depth of 6–9 m. The conveying direction can also be changed very easily in order to empty the pumps at the end. Horizontal eccentric screw pumps were therefore the customer’s preferred type of pump for many years when viscous media had to be pumped around or conveyed to feed the bottling plants. Many years ago, the customer’s processes were very simple and the bottling processes were not very automated. Of course, in addition to numerous advantages, every pumping principle also always has disadvantages by virtue of the nature of the matter. Over time, the customer had to pump more and more media with a temperature of up to 100 °C and also some very abrasive media. It is obvious that the elastomers of the stator in particular expand from a medium temperature of 40–60 °C and that the rotor and stator could become jammed if you did not work with an undersized rotor, but it does again at room temperature of the medium at the expense of dosing accuracy. In addition, dry running had to be avoided when using eccentric screw pumps, since otherwise both the stator and the mechanical seal between the pump and the drive motor would be damaged. In addition, when feeding the filling plant, it had to be ensured that the eccentric screw pumps, which are positive displacement pumps with an outlet pressure of 6 bar, did not pump against the closed gate valve, as otherwise the pump and the filling plant could be damaged or the user could be injured. Even when conveying very abrasive media, increased wear was observed with certain media despite the low pump speed. Due to the fact that the processes in the company became more and more complex over the course of time and that a certain degree of automation also went hand in hand with an expansion of production, the customer tested diaphragm pumps once after a visit to our trade fair stand in order to have a comparison with the previous eccentric screw pumps. Like the screw pumps, the air-operated diaphragm pumps we supply, model JP-810.170 and 400 Food, are capable of being used for several hours at a time, and are also capable of pumping viscous media. Due to their construction, these pumps are self-priming like the eccentric screw pumps. The performance of the pump can be regulated very easily via the compressed air supply. The big advantage for the PROCESS TECHNOLOGY & COMPONENTS 2022 57
