Study Questions

Apply Your Knowledge
20.9
To control three controlled variables you need to adjust the minimum of

Controllability

Engineers must provide sufficient valves in the process design!




1 valve


 

 2 valves
 


 3 valves
 
4 valves

 

 

 

 

 

 

 

 

 

 

 

 

20.10
To control three controlled variables, you can adjust a maximum of

Controllability

 

2 valves

 



3 valves
 



 

4 valves
 
none of the above

 

 

 

 

 

 

 

 

 

 

 

 

 

20.11
For the 2x2 system in Figure 20.8, what is true if no interaction exists?

Interaction

If no interaction exists, the two loops are completely independent.

 

all Gij(s) = 0

 

 G12(s) = G21(s) = 0
 

 G11(s) = G22(s) = 0
 
 none of the above

 

 

 

 

 

 

 

 

 

20.12
For the 2x2 system in Figure 20.8, if all the steady-state gains are non-zero ( Kij <> 0), the system is controllable.

Controllability

TRUE            FALSE

 

 

 

 

 

 

 

 

 

 

 

 

 

20.13
The test for controllability (det(K) = 0) is

Controllability

 

valid for all disturbances

 

 valid for all disturbances of small magnitude 
 

 valid for all set point changes
 
 valid for all set point changes of small magnitude

 

 

 

 

 

 

 

 

 

20.14
For the process boiling water in the figure, how should the pressure and temperature be controlled

Controllability

Process plants use steam for power and heat; steam is important!

 

 

Control P with vA and control T with vB

 

 Control P with vB and control T with vA

 
either of the above will work
 
none of the above

 

 

 

 

 

 

 

 

 

20.15
The following design will control the pressure and flow of a fluid in a pipe.

Controllability

TRUE            FALSE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20.16
The following design will control the two flow rates of a fluid in a pipe.

Controllability

TRUE            FALSE

 

 

 

 

 

 

 

 

 

 

20.17
The following design is adequate for splitting  the two flows

Controllability

TRUE            FALSE

 

 

 

 

 

 

 

 

 

 

20.18
The CSTR in Example 13.12 has the steady-state gain matrix below. Which of the multi-loop control designs will function correctly, i.e., could yield zero-offset, stable control?

Interaction &
Controllability

 

Control T with vC and control Ca with vA

 

 Control T with vA and control Ca with vC
 

 either of the above will work
 
none of the above

 

 

 

 

 

 

 

 

 

 

 

20.19
We want to design controllers for temperature and composition in the non-isothermal CSTR shown below. What is the minimum number of process reaction curve experiments that we must perform?

Modelling

 

One

 

 Two

 
 

 Three

 

 Four

 

 

 

 

 

 

 

 

 

 

 

20.20
The pressure and temperature can be controlled to independent values by the flash drum control system in the figure.

Controllability

TRUE            FALSE