Controls - Part A Flashcards
(T/F) A controlled system is made up of all the equipment in which the controlled variable exists. This includes all of the automatic control equipment.
False
(T/F) An example of a direct means of measurement is using a pressure gauge to calculate the height of liquid in a vessel.
False
(T/F) An example of a primary element is the float in a low water cut-off that senses the height of the boiler water in a steam boiler.
True
(T/F) A closed loop system gives feedback on the isolated controlled area back to the controller.
True
(T/F) In a cascade system, there is generally a (major) inner loop and a (minor) outer loop.
False
What is a pneumatic operator?
A pressure actuated device
What are two (2) types of pneumatic operators?
A) dampers
B) valves
Normally open = Failsafe _______
Open
Normally closed = Failsafe _______
Closed
In a parallel operation, the spring ranges for the final operators are the same. This means that more than one operator will open and close _________.
Together
On a direct acting controller, when the temperature increases, the pressure on the outpost signal _________.
Increases
On a reverse acting controller, when the temperature decreases, the pressure on the outpost signal __________.
Increases
The type of controller that can continually exhaust branch-line control air is a ________ ________.
Bleed type
When moving a dial on a thermostat to 21°C (70°F), you are adjusting the ______ _______.
Set point
(T/F) An auxiliary device is usually found between the controller and the final element.
True
(T/F) An electric to pneumatic relay converts a pneumatic signal to an electric signal.
False
(T/F) A bias start relay is used to sequence overlapping spring ranges on the final elements.
True
(T/F) A positive-positioner is used in a control valve operator to increase the stroking speed.
False
One of the primary importance of instrumentation is:
Pressure
A device that will give a direct measurement is a:
Gauge glass
An example of a type of indicator is a:
Bimetal strip
Using a direct acting controller and a normally closed valve; as the temperature rises, the NC valve will:
Open
The maximum pressure setting on an instrument air main is:
25psi
The type of controller that exhausts from the branch-line only while reducing the branch-line pressure is:
Non-bleed type
Two position controllers are also called:
Positive-acting
A volume booster is used on a:
Final element
In cold freezing conditions that are affecting a heating coil, the primary function of a freeze-stat is to:
Shut down fans
The type of element that is normally used as a freeze-stat is:
Averaging sensor
