Consistency Control Chain Evaluation Procedure

Purpose: To identify any equipment or control strategies that would contribute to poor consistency control.


1) Manual Bump Test

  • Place system in manual control
  • Change dilution control valve position by 10 %.
  • Return valve to original position
  • Put system back in automatic control
  1. Note Time to Meter Response =Dead Time.
  2. Note rate of change and time needed to stabilize.
  3. Note time and rate when valve is returned to original position.

2) Set Point Change (Loop is in Automatic Control)

  • Change setpoint by at least 0.2 % consistency
  • Return to original setpoint
  1. Note time to first response = Dead Time
  2. Time of stabilizing period.
  3. Rate of change to stabilize.
  4. Return to original setting.

3) Control Loop Information

  • Average Consistency deviation from setpoint ( 2 min. minimum time frame)
  • Gain and Reset for each loop
  • Dilution Water Header Pressure
  • Dilution Control Valve Type and size
  1. How was size determined
  2. Injection point and style

4) Sampling Procedures

  • How often are samples taken
  • By whom
  • Test Method
  • Sample Valve location & Type of valve
  • How are sample results used