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Category: Instrumentation and Control

Troubles, Investigation of causes and Counter-measures – PID Controllers

Troubles, Investigation of causes and Counter-measures – PID Controllers

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Troubles Causes Counter-measures

[PID CONTROLLERS]

Output air pressure of pid controllers do not increase or decrease in spite of the change of detection input.

 When it does not increase.

  1. Supply air pressure is abnormal.
  2. Orifice of pilot relay is clogged.
  3. Leakage at the air piping at output side (due to cracking), or leakage at soldered joint or damage of diaphragm of control valve.
  4. Inferior connection or disconnection of link systems inside the controller.
  5. Leakage of various piping or tubes inside the controller.
  6. Damage of element at measuring part.
  1. Adjust it into normal conditions.
  2. Press the cleaning push button.
  3. Adjust it into normal conditions.
  4. Adjust it into normal conditions.
  5. Replace the tube
  6. Replace the element.

 
When it does not decrease.

  1. Nozzle at the flapper is clogged.
  2. Clogging of piping from pilot relay to piping from down of tube
  3. Loosening of pilot relay orifice
  4. Inferior connection or disconnection of link mechanism inside the controller.
  5. Leakage of various piping or tubes inside the controller.
  1. Clean it with a wire of less than 0.4mm
  2. Adjust it into normal conditions.
  3. Retighten it
  4. Adjust it into normal conditions.
  5. Replace the tube

[CONTROL VALVE]

Control valve life does not change due to the increase or decrease of output pressure of controller.

 Sticking of valve guide and valve stem.

  1. When positioner is provided sticking of positioner pilot.
  2. Disconnection of diaphragm stem and positioner.
 Inspection by disassembly.When foreign matters are caught into the parts, remove them and repair any possible damage.

  1. Repair the damage caused by sticking using fine mesh grinding paper or file.
  2. Adjust it into normal conditions.

[FILTER REGULATOR]

Pressure does not increase even when setting knob is turned to increase pressure. Or pressure increase is abnormal or pressure does not go down.

 When pressure does not increase.

  1. Damage of diaphragm.
  2. Damage of setting spring.
  3. Sticking of pilot valve.
  4. Leakage at air piping at secondary side.
  1. Replace the parts.
  2. Replace the parts.
  3. Repair the damage caused by sticking using fine mesh grinding paper or file.
  4. Adjust it into normal conditions.
When pressure does not come down.

  1. Sticking of pilot valve.
  2. Clogging of exhaust hole of the cover.
  1. Repair the damage caused by sticking using fine mesh grinding paper or file.
  2. Clean it.
    HP P