Tuning a control loop is a skill and although there is some good software to help it isn't that clever in allowing for process conditions.
Increasing or decreasing P (Proportional Band)and I (Integral action) has different effects according to the engineering unit. For example Integral action is scaled in minutes per repeat or repeats per minute (one obviously the reciprical of the other)
In europe controllers normally use minutes per repeat, while older controllers in the usa are typically scaled in repeats per minute.
The classical way to tune a p&I controller waould be to set the integral to maximum time (UK) or Minimum repeats (USA)
Then the P should be reduced until the control becomes unstable and then increased a little.
Next add a set point change to see if the controller will settle to a stable value within your required responce time and without becoming unstable.
If it does but the new value is not at your set point then you should increase the integral action until it removes this new offset in the time required.
These steps will need to be repeated to fine tune your settings, but once done the system should perform many years of service.
It is impossible to answer your magflo setting problem without knowing the manufacturers damping in relation to 0-49. If you have a manual, look for a damping setting equivalent to approx 2 seconds.
Hope this helps
Malvern
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