## Typical Controller Settings

If you design processes or control loops, you might have to come up with reasonable controller settings before you have the chance of doing any tuning. If you are faced with this situation, you could use the table of typical controller settings below to give you more appropriate starting values for a controller.

The table can also be used to validate tuning settings on problem control loops. Sometimes one setting is so far off that simple trial-and-error tuning seems to make no difference. If you compare your controller settings to those in this table, you might find the culprit setting.

Important:

Settings in this table are for information only. Process characteristics can vary widely from the “typical” process, requiring greatly different controller settings. You should always tune a controller according to the actual process dynamics (by doing step tests and applying the appropriate tuning rules) before anyone places it in automatic control mode.

The controller settings are for controllers with the noninteractive algorithm, using controller gain for proportional and minutes for integral and derivative. If your controller has a different algorithm or uses different engineering units, you have to do the appropriate conversions.

If you have any questions or suggestions about the settings, please contact me.

Stay tuned!

Jacques Smuts – Author of the book Process Control for Practitioners

Controller Setting | Likely Minimum | Likely Maximum | Typical Value | Unit of Settings |

Flow and Liquid Pressure |
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Gain | 0.2 | 1.5 | 0.5 | gain |

Integral | 0.05 | 0.5 | 0.2 | minutes |

Derivative | 0 | 0 | 0 | minutes |

Filter | 0 | 0.2 | 0.02 | minutes |

Sampling | 0.5 | 2 | 1 | seconds |

Inline Temperature |
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Gain | 0.5 | 4 | 1 | gain |

Integral | 0.2 | 1 | 0.5 | minutes |

Derivative | 0 | 0.25 | 0.1 | minutes |

Filter | 0 | 0.1 | 0 | minutes |

Sampling | 1 | 5 | 2 | seconds |

Column or Reactor Temperature, Gas Pressure |
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Gain | 2 | 10 | 5 | gain |

Integral | 2 | 20 | 5 | minutes |

Derivative | 0 | 5 | 1 | minutes |

Filter | 0 | 0.2 | 0 | minutes |

Sampling | 1 | 15 | 10 | seconds |

Tight Level Control |
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Gain | 1 | 10 | 5 | gain |

Integral | 2 | 30 | 10 | minutes |

Derivative | 0 | 2 | 1 | minutes |

Filter | 0 | 0.5 | 0.2 | minutes |

Sampling | 1 | 5 | 2 | seconds |

Surge Tank Level |
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Gain | 1 | 4 | 2 | gain |

Integral | 10 | None | 60 | minutes |

Derivative | 0 | 0 | 0 | minutes |

Filter | 0 | 1 | 0 | minutes |

Sampling | 5 | 30 | 10 | seconds |

Composition |
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Gain | 0.1 | 1 | 0.5 | gain |

Integral | 10 | 30 | 20 | minutes |

Derivative | 2 | 5 | 3 | minutes |

Filter | 0 | 0.5 | 0 | minutes |

Sampling | 10 | 30 | 20 | seconds |

I have absorbed that when steam temperature is below the set point (Set point: 560C, Process value: 545C), the temperature control valve (spray valve) remain close but when process value start to increase (By tilting up the burner or any other way) at that time temperature control PID start to open the spray valve which affect the temperature raising.

I have asked this point with one of DCS engineer; he said that, “PID follow the trends of process value if it is in increasing trends then the temperature control PID will take action and generates the out put”.

Why this is happing, while we need to increase the temperature up to desire level. If the temperature goes more than set point then only PID should take action.

This is happening not only in temperature loop even some other loop also like pressure control.

Can you please explain me about these phenomena?

Ravi,

What you describe is likely to happen on lag-dominant processes such as temperature and gas pressure.

Since the error is getting smaller, the proportional control action decreases. This can make your controller output seemingly move in the wrong direction. If your controller is properly tuned, the process variable should continue to increase up to the setpoint.

Think of it this way: When you want to quickly accelerate your car (also a lag dominant process) to a speed of 60, you initially step down hard on the gas pedal, but as your speed approaches 60 you decrease your gas pedal to the final position – even before 60 is reached.