Problem: According to many water treatment works managers, tank cleaning and maintenance is one of their big headaches. Many wastewater applications will include one or more tanks for liquid storage and with liquids containing particles, sediment on tank walls is a common problem, particularly if liquids are maintained at fixed levels when filling and emptying the tank. This means there is an increased need for cleaning and the inevitable rising costs of maintenance. How can we cut this problem down to size?
Solution: One answer from ABB is a special level control function built within one of its variable-speed drives’ range. The function prevents sediment build-up on the tank walls by controlling the filling or emptying of wastewater storage tanks by randomly varying the surface level within a range preset by the user.
In addition to taking care of the water level, the level control function reduces operating and maintenance costs associated with sediment tanks. The technique also cuts the need for a control valve, bypass piping and the subsequent energy losses. The level of the water tank can be controlled using proportional and integral (PI) control to maintain smooth but accurate level control with one or several pumps running in parallel.
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