Variable speed waste water pumps
KSB Pumps and Valves recently introduced the PumpDrive variable speed system for effective and controlled pumping of waste water. The variable speed system has been especially designed to overcome problems experienced when pumping waste water.
Three innovative functions have been seamlessly incorporated into the system to allow the most effective operation of pumps in the field. These include establishing a complete water column almost immediately during start-up. This is done through a system which allows the pump to be taken to maximum speed within four seconds and maintained for three minutes so that an appropriate flow passes through all piping elements before the system starts its controlled, demand-driven operation. This ensures that the discharge line and pump casing are completely primed with the fluid to be handled.
Another unique feature of the variable speed system is the so-called flushing function. This can be activated either automatically or manually by operators using a control panel. The PID controller increases the speed up to a maximum value, which triggers the required flushing effect. The current control task is temporarily put on hold for this process. After the defined flushing period, the flushing function stops, and the system returns to its previous, controlled operation.
Flow velocity monitoring is another new feature that is designed to improve operating reliability of pumps in the field. It ensures that the minimum flow velocities specified at the time of selection are met in order to keep the pipes free from deposits. If the flow velocity falls below the programmed minimum, PumpDrive can either transmit a fault message to the control station or start the flushing function to remove any deposits from the piping. The flow velocity is computed by the variable speed system based on measured electric values of the drive. No external sensors are required.
Up to six PumpDrives can be combined into a controlling unit via plug-in bus lines, which allows the user to operate six pumps in parallel. This unit starts and stops the pump sets in line with demand while ensuring that the operating load is distributed evenly. It compensates the failure of individual components without interrupting the operation. All PumpDrives are designed for motors with ratings of up to 55 kW with a harmonised design.