Centre for Chronic Disease Control (CCDC) Interview Questions and Answers

A Distributed Control System (DCS) is a computerized control system used to control and monitor industrial processes.

• Consists of multiple control elements distributed throughout a system

• Allows for centralized control and monitoring of processes

• Used in industries such as oil and gas, power generation, and manufacturing

• Examples include Honeywell Experion PKS, Emerson DeltaV, and Siemens PCS 7

Cascade loops are a series of control loops where the output of one loop is used as the setpoint for the next loop.

• Cascade loops improve control performance by reducing the effect of disturbances.

• They are commonly used in industrial processes where multiple variables need to be controlled.

• An example is a cascade control system in a chemical plant where the flow rate of a reactant is controlled based on the level in a tank.

A distillation column is a piece of equipment used in chemical processes to separate mixtures into their individual components.

• Distillation columns use the principle of vapor-liquid equilibrium to separate components based on their boiling points.

• They consist of a vertical column with multiple trays or packing material to facilitate the separation process.

• The feed mixture is introduced at the bottom of the column, and as it rises, the components with lower boiling points vapo...read more

Open Loop is a control system where the output is not fed back to the input for correction or adjustment.

• Open Loop control does not use feedback to make adjustments

• It relies solely on the input and predefined control actions

• Examples include automatic doors, traffic lights, and irrigation systems

Reaction is the response or behavior triggered by a stimulus or event.

• Reaction is a response to a stimulus or event.

• It can be physical, emotional, or cognitive.

• Reactions can vary in intensity and duration.

• Examples include flinching when touched by something hot, feeling happy after receiving good news, or thinking critically when faced with a problem.

Heat exchangers are devices used to transfer heat between two or more fluids.

• Shell and tube heat exchanger

• Plate heat exchanger

• Double pipe heat exchanger

• Finned tube heat exchanger

• Regenerative heat exchanger

Control valves are used to regulate the flow of fluids in a process system by varying the size of the flow passage.

• Globe valves: used for throttling and control of flow

• Butterfly valves: used for on/off control of flow

• Ball valves: used for quick shut-off

• Diaphragm valves: used for precise control of flow

Types of reactors include batch reactors, continuous stirred tank reactors, plug flow reactors, and fluidized bed reactors.

• Batch reactors operate in a closed system with a fixed amount of reactants.

• Continuous stirred tank reactors have continuous flow of reactants and products.

• Plug flow reactors have a continuous flow with no mixing of reactants along the length of the reactor.

• Fluidized bed reactors use a fluid to suspend solid particles, allowing for better mixing and heat t...read more