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Spec Conflicts Solved With Creative Solutions
December 27, 2007
December 27th by Stan Prutz
This week we are completing the central SCADA tie in to the newly installed RTU at Pump Station 3.
In the past two weeks we solved the conflicting requirements on the alternation issue with a unique scheme. The algorithm determines alternation order of pumps based upon least run time and sets this order once per day. This is combined with a user settable maximum run time per pump. This scheme favors the least run pumps, but still requires all pumps to run each day, helping to prevent the accumulation of sediment within the pumps.
The conflict between PID control and speed control based upon level was resolved with an algorithm that changed the PID setpoint to the midpoint of the start/stop range of the last pump switched on, giving 4 PID setpoints. This has the effect of causing the VFD-driven pumps presently called to attempt to search for a speed at which they can match the incoming flow, rather than operating at 100% speed to force the wetwell down to one setpoint.
Posted by on December 27, 2007 | Comments (0)