Chapter 86

Question 0

When controller output is proportional to the amount of deviation, the controller is:
A) derivative only
B) integral
C) two position
D) proportional plus reset plus rate
E) proportional

Answer 0

E) proportional

Question 1

The pneumatic transmitter nozzle receives a constant air supply pressure of approximately _____kPa.

Answer 1

140

Question 2

When an operator uses CRT or LCD displays, the computer control display:
A) can stretch or compress time periods
B) will be equipped with graph limiters
C) will not have printout capabilities
D) has only single trend display
E) will not be connected to the transmitter signal

Answer 2

A) can stretch or compress time periods

Question 3

A valve that seals on the downstroke is:
A) reverse acting
B) single sealed
C) direct acting
D) double sealed
E) uni directional

Answer 3

C) direct acting

Question 4

As used in instrumentation, state the difference between an indicator and a recorder.

Answer 4

An indicator only shows the current value

A recorder shows the current value and previous values to allow the operation of the process to be analyzed over time

Question 5

Explain why double seated throttle valves are better suited to throttling action than single seated.

Answer 5

Less force is required to position the control valve because the pressure of the fluid acts on the top of one seat, and the bottom of the other. This nearly cancels out the force due to this pressure that tends to hold a single seated valve open or closed

Question 6

Explain the meaning of direct acting and reverse acting valve bodies on pneumatic control valves.

Answer 6

With a direct acting valve body, the valve is closed as the spindle and disk move down away from the diaphragm. With reverse acting, the valve closes as the disk and spindle move up toward the diaphragm.