Hi all,
I have a chlorine contact chamber (ccc) at a water plant that I have been trying to control the level of chlorine in for a few months now with an SLC 5/05. The flow is typically 600-1200 gpm.
Albeit, the customers setup in definately not optimal, but it's what I have to work with. The problem is that the injection point is at the influent end of the CCC and the CL2 instrument is at the effluent end - with a lag time of about 30-40 minutes.
I had the customer add an analyzer 10 feet after the injection point (only spot avail) to get a quicker reading of the CL2 level, but there is still a lagtime of about 8-10 minutes including the fact that the analyzer (CL17) only reports back sample data every 3 minutes.
I eventually went to a stepper type function in the PLC to control the CL2 pumps since I couldn't regulate the PID loop because of the extreme lag time. Even with the stepper function (look-up table) type code, I CANNOT stop the pumps from hunting. I even added 4 ranges (0-500gpm/501-750gpm/751-1000gpm/1001-3000gpm) for flow with different setting & timer values for function. Nothing seems to be working!!
I've successfully set up extreme lag time heating controls in the steel industry, but this one almost has me ready to go postal!
Has anyone found a solution that has worked with the type of extreme lag time with chemical pump control.
Thanks for any assistance with this,
Steve
p.s. I did read the post at: http://www.plctalk.net/qanda/showthread.php?t=19563&highlight=pump+control which is somewhat similar to my challenge. The flow through the sample line is very good back to the analyzer. There is just an inherent long lag time I'm trying to overcome.
I have a chlorine contact chamber (ccc) at a water plant that I have been trying to control the level of chlorine in for a few months now with an SLC 5/05. The flow is typically 600-1200 gpm.
Albeit, the customers setup in definately not optimal, but it's what I have to work with. The problem is that the injection point is at the influent end of the CCC and the CL2 instrument is at the effluent end - with a lag time of about 30-40 minutes.
I had the customer add an analyzer 10 feet after the injection point (only spot avail) to get a quicker reading of the CL2 level, but there is still a lagtime of about 8-10 minutes including the fact that the analyzer (CL17) only reports back sample data every 3 minutes.
I eventually went to a stepper type function in the PLC to control the CL2 pumps since I couldn't regulate the PID loop because of the extreme lag time. Even with the stepper function (look-up table) type code, I CANNOT stop the pumps from hunting. I even added 4 ranges (0-500gpm/501-750gpm/751-1000gpm/1001-3000gpm) for flow with different setting & timer values for function. Nothing seems to be working!!
I've successfully set up extreme lag time heating controls in the steel industry, but this one almost has me ready to go postal!
Has anyone found a solution that has worked with the type of extreme lag time with chemical pump control.
Thanks for any assistance with this,
Steve
p.s. I did read the post at: http://www.plctalk.net/qanda/showthread.php?t=19563&highlight=pump+control which is somewhat similar to my challenge. The flow through the sample line is very good back to the analyzer. There is just an inherent long lag time I'm trying to overcome.
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