Essentially, gear pumps are simple devices which transport plastic melts and other media, along with the empty volume of gear toothing in the pump shaft, in the extrusion process or in the process to manufacture plastics in the chemical industry. They comprise a small number of key components, such as housings, shafts, bearings, and shaft packing. On closer inspection, the simple system is seen to be much more complex. Since MAAG gear pumps usually process polymer melts, the behavior of these long-chain molecules must be understood and taken into account when subjected to the relevant stresses. Reaction to high temperatures and shear rates is of great importance here. The dwell time and the distribution of the dwell time in the melt pump must also be taken into account.
The plastics manufacturing industry needs maximum efficiency in production processes, and demands the lowest possible temperature rise in the bearings and in the polymer melt being processed. Less play between the components quickly improves efficiency. However, this can have a negative effect on product quality and affect the function of the gear pump in the extrusion process. There is a risk that shafts and bearings will seize up.
The research, development and manufacture of gear pumps for extrusion and other fields of application in the production and processing of plastics are part of MAAG’s corporate history. It has built up great knowledge over many decades of cooperation with customers worldwide, which is fully reflected in the x6 class melt pump. Gear pumps for extrusion and plastics production in the chemical industry are used today to pump a wide variety of polymer classes. New knowledge is continually flowing into the development and enhancement of melt pumps.
Good volumetric efficiency enables pumping at slower speed, reduced shear rate, lower temperature, and tight dwell time distribution. Improving these attributes results in better pumping rate, higher polymer quality, greater reliability, and longer service life. At the same time, energy consumption is significantly reduced. MAAG melt pumps and extrusion pumps adhere to that principle.
In the plastics manufacturing chemical industry, the pump geometry has a considerable influence on the degassing stage, where minimal filling levels in the tank directly connected to the gear pump lead to a shorter dwell time. This is especially interesting for manufacturers of easily degradable polymers because it means volatile compounds can be minimized. The x6 class gear pump in particular achieves an extremely low NPSHr (net positive suction head required) pressure value, and so can process polymer melts of up to 200,000 Pas (0 shear viscosity), depending on pump size.
The operating pressure of the gear pump has a major influence on product quality in extrusion. The higher the pressure, the finer the filters and screen changers that can be used downstream of the pump. High volumetric efficiency and low pulsation ensure consistent polymer quality and uniform output of the end product.
The smaller the pump the better for the customer’s plant planning. MAAG pumps are optimized to use the given installation space to attain maximum plant capacity.
Energy, energy cost and energy consumption are crucial aspects of plant planning. MAAG gear pumps optimize energy consumption.
MAAG pumps can be used for a wide range of polymers. There is a wide variation between high-viscosity and low-viscosity products. The pumping pressure can be increased when processing low-viscosity polymers.
MAAG extrusion pumps and melt pumps offer long service life. Even lower bearing temperatures of the x6 class melt pump generation – thanks to the high efficiency of the pump – extend it even further, and provide for an even more stable lubricating film between the shaft and bearing. That makes the pumps extremely reliable.
The optimal solution for discharge from reactors is an important aspect in polymer production. The key in this is the difference between extraction from containers in production processes entailing standard requirements for the NPSH value (such as PET) and other processes where the required filling level in the connected container must be minimized. MAAG offers different housing designs for extraction melt pumps to meet the different requirements, so as always to be able to realize an economical and technically optimal solution.
The increased torque load capacity of MAAG gear pumps (melt pumps) boosts safety during start-up and operation, and aids general safety in production.