Chapter 24    Process Control Design: Definition and Decisions

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Check Your Reading             Study Questions             Thought Questions

In this chapter, there were three main concepts.   The questions will be categorized according to the most significant concept.

Control Design Objectives Operability
Instrumentation Loop Pairing

 

 

 

 

 

 

 

 

 

 

 

Check Your Reading

Solidify the Concepts
24.1
Controllability determines

Operability

the region in which control is possible.


 

 all possible loop pairings.
 


 the possibility of achieving control for specified controlled and manipulated variables regardless of control type.
 
the possibility of achieving control for specified controlled and manipulated variables using feedback control.

 

 

 

 

 

 

 

 

 

 

 

 

24.2
When the steady-state operating window has been defined, the process always remains within the window

OPERABILITY

TRUE            FALSE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

24.3
Sensor accuracy is




the difference between several measured values at the same process conditions.


 

 the difference between the sensor value and the true process variable under specified conditions.
 


 the difference between the sensor value and the true process variable regardless of conditions.

 


is not meaningful to

practicing engineers.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

24.4
The Control Design Form is 

Control Design Objectives


used to define the PID control strategy for later programming.

restricted to safety issues, which must be documented for later audit.

 

used to define the control problem (opportunity) before we begin to evaluate technology

can be completed based on information in the process flow diagram.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

24.5
 Which of the following statements most closely defines CONTROLLABILITY 

Operability

 

Independently selected values for every set point can be achieved by adjusting the manipulated variables.

Every manipulated variable affects only one controlled variable.

 

 The number of manipulated and controlled variables are equal.

The system is stable without control.

 

 

 

 

 

 

 

 

 

 

 

 

 

24.6  Which of the following are goals for improving dynamic performance via process modifications?

Operability

Can you think of other goals not on the list?   

 

Speed feedback dynamics.

Increase disturbance time constants

 
 Reduce disturbances near the feedback critical frequency.

Decrease the magnitude of disturbances.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

24.7
General guidelines for feedback loop pairing include

Loop Pairing

Can you think of other goals not on the list? 

 

always control unstable variables.

Pair MVj - CVi that has a causal relationship

 
 Pair MVj - CVi that has a large gain

Pair MVj - CVi that a small range for the MVj