Hi All,
I have been asked to modify our contact tank pumping station controls. Currently pump speeds are manually entered (as %) by operators. There are 4 pumps. 2 large ones and 2 small ones. The operators start/stop pumps or up/down the speeds to maintain a level in the Contact tank.
I understand how i would do this using PID if all 4 pumps were of the same size, but not sure how to go about it using different sized pumps. Im think Large group Duty/Assist and small group duty/assist. Take the output from a PID loop (looking at the level meter compared to a setpoint) and divide that between the ratio of pump sizes (ive not yet got together all the details of the pumps yet). But when to start the assist pump? If 1 big and small pump isnt enough to make up the level, do we stop the small pump and run the assist big pump?
I know the pumps arent efficient or really pump anything below 60%. The usual running is two big pumps at 80%, but when were doing high flows, a smaller pump is started aprox 80% with the large ones up to 90%.
Ive done projects with PID's with the same sized pumps, its all this large and small pumps.
All pumps are on VSD controlled by the PLC (manual entered speed) with feedback already into the PLC. As is the level instrument.
EDIT: Its a PLC5 control system.
I have been asked to modify our contact tank pumping station controls. Currently pump speeds are manually entered (as %) by operators. There are 4 pumps. 2 large ones and 2 small ones. The operators start/stop pumps or up/down the speeds to maintain a level in the Contact tank.
I understand how i would do this using PID if all 4 pumps were of the same size, but not sure how to go about it using different sized pumps. Im think Large group Duty/Assist and small group duty/assist. Take the output from a PID loop (looking at the level meter compared to a setpoint) and divide that between the ratio of pump sizes (ive not yet got together all the details of the pumps yet). But when to start the assist pump? If 1 big and small pump isnt enough to make up the level, do we stop the small pump and run the assist big pump?
I know the pumps arent efficient or really pump anything below 60%. The usual running is two big pumps at 80%, but when were doing high flows, a smaller pump is started aprox 80% with the large ones up to 90%.
Ive done projects with PID's with the same sized pumps, its all this large and small pumps.
All pumps are on VSD controlled by the PLC (manual entered speed) with feedback already into the PLC. As is the level instrument.
EDIT: Its a PLC5 control system.
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