Schwing Bioset Inc. announced its positive displacement pump with optional continuous flow for a pulsation-free system. Based on the same technology used to pump concrete, the wear resistant positive displacement mining pumps have been used in both cemented and uncemented tailing applications.
Traditional piston pumps have a momentary pause in material flow through the pipeline while the discharge valve system switches in either a single or twin hydraulic circuit arrangement. In certain situations, this momentary pause in material flow can induce an undesirable water-hammer effect in the pipeline. Achieving continuous flow from the piston pump eliminates the water-hammer created by these momentary pauses in material flow.
Continuous flow is attained by operating each hydraulic cylinder of the piston pump independently. While one cylinder is discharging, the opposite cylinder retracts at a faster rate to fill its material cylinder, then begins to move forward to pre-compress the product in the cylinder, such that it matches the system pressure. As the pumping cylinder nears the end of its stroke it begins to ramp down to zero speed.
The opposite cylinder during this period likewise ramps up its speed such that the total volume being discharged into the pipeline remains constant. Once the first cylinder arrives at a zero speed, it then retracts at an accelerated rate to charge and pre-compress its cylinder, to begin its pumping stroke again once the opposing cylinder begins to decelerate. This achieves a virtually constant flow rate, only limited by the electronic proportional control.
With this new development, each working cylinder gets a control block to support the required oil flow, independent from the other cylinder. The independently operating hydraulic cylinders are equipped with position transducers which allows their direction, position, and speed to be controlled continuously through a PLC.