Process Control Theory (12204-16)

Process control is defined as the application of a control system to a process to provide

the most efficient and reliable operation possible

The operation or operations used in the treatment of materials is known as a

process

Process parameters are subject to change if the energy balance is

upset

A device that operates to regulate the controlled variable directly is a(n)

final control element

The controlled variable in a process is ultimately regulated by the

controller

The three basic types of controllers are mechanical, pneumatic, and

electronic

The two basic categories of control valves are gate valves and

globe valves

The four basic types of process control loops in the instrumentation industry are feedforward control, feedback control, cascade control, and

ratio control

Because some inputs for open-loop control of a process system may not be measured or controlled, the system may require

manual adjustments

The primary performance criterion on any closed-loop control system is

stability

The three criteria for closed-loop control quality are minimum area, minimum disturbance, and

minimum amplitude

How many control loops does a single cascade control system have?

two

Cascade control is a modified form of

feedback control

The type of control that maintains a fixed relationship between two flows, such as a mixture of air and fuel for combustion control is

ratio control

The two basic modes of control that are applied to control loops are On-Off control and

modulating control

The region of overlap in which a controller does not change state is called the

neutral zone

Proportional, integral, and derivative are three basic functioning modes of a

Modulating controller

Proportional control gives an output-to-input signal that is.

linear

Which control mode has no residual offset?

PI

Automatic process control systems that provide rapid responses are typically used for processes in which

high-speed reactions occur

The temperature transmitter in an electronic temperature-control loop converts the temperature-dependent resistance value of an RTD sensor into a(n)

electrical signal proportional to measured temperature

The figure above shows a split-range pneumatic pressure control loop that uses nitrogen to maintain a constant pressure within a closed tank. Why do both the nitrogen supply valve and the vent valve in this type of application typically fail to close?

The component that sends a pneumatic output to the level controller in a pneumatic level-control loop is the

differential pressure transmitter

In the electronic level-control loop shown in the figure above, the level controller produces an electric control

In the pneumatic flow-control loop shown in the figure above, the change in control pressure is produced when a difference exists between the actual flow signal and the desired flow.