Many pharmaceutical products require particular care when being transported during production. Tony Peters, managing director of AxFlow UK, looks at shear sensitive leak-free pumping with eccentric movement pumps.
Throughout many areas of pharmaceuticals and healthcare products there is a substantial requirement for pumps that are capable of handling shear-sensitive liquids as well as liquids that can have an adverse affect on mechanical seals. Often coupled with this is the need for such pumps to offer leak-free performance.
While many types of pump can accommodate some of these demands, the challenge for plant managers is to find one that ticks all the boxes. The oscillating eccentric piston pump principle, developed by Mouvex, goes a long way to address all these demands. The principle produces the pumping performance of a rotary positive displacement pump. However, its action is far more sensitive, making it ideally suited to applications where shear and potential leakage are major issues.
The direct-drive design of the pump does not require either mechanical seals or magnets, so provides leak-free performance
The Mouvex principle pump differs from other types of positive displacement pumps in that it does not agitate the pumped liquid. Rather, the liquid is pumped by the eccentric movement of the oscillating piston within the pump chamber, this being a very gentle action. The direct-drive design of the pump does not require either mechanical seals or magnets, so it provides leak-free performance.
Gentle action
The oscillating eccentric movement pump consists of a cylinder and a pumping element mounted on an eccentric shaft. As the shaft rotates, the pumping element creates chambers with the cylinder. This has the effect of increasing the size of the intake port and drawing fluid into the pumping chamber.
The fluid is transported to the discharge port where the size of the pumping chamber decreases. The action squeezes the fluid out into the discharge pipework. None of the pumping elements rotates, thereby creating the gentle, low shear forces that many processes require.
Blackmer Mouvex eccentric disc pumps are capable of handling up to 30,000cps (15,000 SSU) liquids, throughputs up to 36m3/h and working pressures of up to 16bar, depending on the model. The speed range is 50 to 1,000rpm, with capacities of 0.6 to 600 litres/min. Rated up to 150ºC, the C-Series and SLC Series have a particle size range of up to 3mm and are effective at handling suspended solids containing mild abrasives.
A constant product flow is produced that is independent of both pressure and viscosity and this, together with the presence of automatic piston/cylinder wear adjustment, ensures full flow efficiency and high levels of product stability at all times. In addition, the design ensures that very high levels of accuracy can be attained for volume metering and dosing.
The Mouvex C and S series pumps, while employing the same operating principle, have sharply contrasting designs. In the case of the C Series, the eccentric shaft is encased within metal bellows constructed from 316 stainless steel (Figure 1). Available in both 316 stainless steel and ductile iron construction, the ATEX compliant C-Series conforms to standard 3A and the hygienic recommendations required by the European Hygienic Engineering & Design Group (EHEDG).
Dry running
Self-priming and capable of dry-running, this type of pump will clear both the intake and discharge lines of any residual liquid. Lubrication of all moving parts is provided by the pumped medium. Cleaning is performed ‘in place’ simply by flushing out the unit without any requirement for disassembly.
Cleaning is performed ‘in place’ simply by flushing out the unit without any requirement for disassembly
The high priming capacity of the pump ensures good decanting regularity and enables the pump to run in a dry condition for several minutes, which is of importance at the end of decanting. The excellent volumetric accuracy of the pump makes it possible at the moment of decanting to simultaneously supply a filtering battery before supplying a storage tank preceding final preparation. Furthermore, the close tolerance characteristics of the pump design provide good priming capability.
In contrast, the S Series pump is a more compact and lightweight unit, having the transmission mechanism protected by a high-resistance elastomer sleeve that is both odourless and taste-free (Figure 2). This enables the pump to meet FDA certification requirements (S4C and S6C).
Figure 2: The S Series is both compact and lightweight
S Series Mouvex pumps have been designed for CIP and SIP cleaning. The slow movement of the oscillating piston provides accurate volumetric metering and enables precise dosing and mixing for viscous or fluid products.
A number of factors are fuelling growth in demand for this technology. First is their seal-less construction, which helps to eliminate high value product loss. Of even greater importance to users is the pump’s true CIP capability, recognised as a significant economic advantage over pumps that require time-consuming disassembly between batches for them to be properly cleaned.
Mouvex C and SLC Series pumps can be completely drained, flushed and cleaned in place without the need for disassembly. Nor is there any need to remove piping or pump housings, so maintenance time and costs can be reduced.
