Marine Control System & Instrumentation (Set 1)

1. The controller set point of an automatic control system is 65°C. The valve closes when the output temperature reaches 70°C, and reopens when the temperature falls below 60°C. The type of positioning action in this controller is known as ____________.

one-position single-point

two-position single-point

one-position differential-gap

two-position differential-gap

2. In a pneumatic automation system, a unit producing a signal to govern the position of the controller of the measured variable, relative to the value of the measured variable, is said to have ____________.

reset action

proportional action

two position action

rate action

3. If the loading air pressure for a diaphragm controlled valve drops below the designed operating pressure, the valve will ____________.

fail to stroke open

stroke slowly through its operating range

stroke rapidly closed

fail to stroke through its complete range

4. Every automated machinery plant must have an "engineer's assistance" alarm. Power for this alarm should be taken from the ____________.

main bus

emergency bus

standby generator

general alarm power supply

5. The effect of "reset", when added to a proportional controller is to ____________.

make the controller correction proportional to the rate at which the input change takes place

accelerate the corrective action so as to minimize the possibility of hunting

make the corrective action of the controller proportional to the deviation of the controlled variable from the set point

repeat the proportional action until the controlled variable returns to the set point

6. Which of the following statements expresses the function of proportional-plus-reset action?

The action measures the rate of time of the final control element.

The action gives control without offset under all load conditions.

The action combines proportional-position action and rate action.

The action is very unstable for anything but constant load conditions.

7. One disadvantage of proportional-position action is that ____________.

corrective action is only proportional to offset

exact correction can be made only when there is no change in load

the controlled variable is stabilized

the corrective action is only proportional to the deviation

8. Filters are installed ahead of air line lubricators for the primary purpose of removing ____________.

the heat of compression

air supply pressure pulses

moisture in the air supply

turbulence in the air supply

9. The cylinder unloading mechanism used on low pressure air compressors is an example of which mode of control?

Two position

Derivative

Integral

Single speed floating

10. Which of the listed devices would be installed at a control system air pressure reducing station?

Moisture separator

Vacuum breaker

Lubricator

Nonreturn valve

Marine Control System & Instrumentation (Set 1)

Multiple Choice Questions