Control System Design & Architecture Flashcards
7 cards from real CCST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Control System Design & Architecture flashcards as text
When performing a hazard and operability study (HAZOP), what do the guide words 'MORE OF' and 'LESS OF' primarily evaluate?
Answer: Deviations in process parameter quantities such as flow, pressure, or temperature
HAZOP guide words like 'MORE OF' and 'LESS OF' prompt the team to consider quantitative deviations in process parameters and their potential hazardous consequences.
What is the function of a 'split-range' control strategy?
Answer: Splitting the controller output signal to operate two or more final control elements across different portions of the output range
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.
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)?
Answer: A circle with a single horizontal line through the middle
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.
In a DCS environment, what is 'controller redundancy' and what is its primary benefit?
Answer: Duplicating the controller hardware so a backup takes over automatically if the primary fails
Controller redundancy provides a hot-standby backup controller that assumes control seamlessly if the primary controller fails, minimizing process downtime.
A process has a very long dead time relative to its time constant. Which control strategy is MOST effective for handling this characteristic?
Answer: Smith predictor or dead-time compensator added to a PID controller
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.
What is the significance of the 'minimum detectable signal' (MDS) specification for an analog input card in a DCS?
Answer: The smallest change in input signal that the card can reliably distinguish from noise
MDS (also called resolution) defines the smallest meaningful input change the card can detect, which determines measurement precision and affects control performance.
In the context of ISA-88 batch control, what is a 'recipe parameter'?
Answer: A variable value (e.g., temperature setpoint or ingredient quantity) that can differ between batch runs
Recipe parameters are configurable values within a master recipe that operators can adjust for each batch run, such as reaction temperature, hold time, or ingredient amounts.