CCST Control System Design & Architecture 4

Question 1

When performing a hazard and operability study (HAZOP), what do the guide words 'MORE OF' and 'LESS OF' primarily evaluate?

Accepted Answer

Deviations in process parameter quantities such as flow, pressure, or temperature

Answer

HAZOP guide words like 'MORE OF' and 'LESS OF' prompt the team to consider quantitative deviations in process parameters and their potential hazardous consequences.

Question 2

What is the function of a 'split-range' control strategy?

Accepted Answer

Splitting the controller output signal to operate two or more final control elements across different portions of the output range

Answer

Split-range control sends portions of a single controller output to multiple actuators (e.g., 0–50% opens a cooling valve; 50–100% opens a heating valve) to cover the full control range.

Question 3

According to ISA-5.1, what shape symbol represents a controller function that is located in the primary instrument panel (board-mounted, accessible to the operator)?

Accepted Answer

A circle with a single horizontal line through the middle

Answer

ISA-5.1 uses a circle with a single horizontal line to denote instruments mounted in the main control panel (accessible to the operator), while a dashed line indicates a DCS/shared display function.

Question 4

In a DCS environment, what is 'controller redundancy' and what is its primary benefit?

Accepted Answer

Duplicating the controller hardware so a backup takes over automatically if the primary fails

Answer

Controller redundancy provides a hot-standby backup controller that assumes control seamlessly if the primary controller fails, minimizing process downtime.

Question 5

A process has a very long dead time relative to its time constant. Which control strategy is MOST effective for handling this characteristic?

Accepted Answer

Smith predictor or dead-time compensator added to a PID controller

Answer

The Smith predictor uses a process model to compensate for dead time, effectively allowing the controller to act on predicted future process output rather than delayed feedback.

(CCST) Certified Control Systems Technician Practice Test

(CCST) Certified Control Systems Technician Practice Test

CCST Control System Design & Architecture 4