CCST Control System Design & Architecture 5

Question 1

When designing a control system for a high-vibration environment, which signal transmission method is LEAST susceptible to mechanical vibration-induced errors?

Accepted Answer

4–20 mA current loop

Answer

4–20 mA current loops are immune to resistive voltage drops from long cable runs and are far less affected by vibration-induced connector resistance changes than low-level voltage or millivolt signals.

Question 2

A control engineer is designing a gas compressor surge control system. What is the primary purpose of surge control?

Accepted Answer

Preventing flow reversal through the compressor that causes damaging oscillations

Answer

Surge control keeps compressor operation to the right of the surge line by recycling flow when needed, preventing destructive flow reversal and mechanical damage.

Question 3

In IEC 61511 (functional safety for the process industry), what is a 'protection layer' in the context of a Layer of Protection Analysis (LOPA)?

Accepted Answer

An independent safeguard that can prevent a hazardous event without relying on other protection layers

Answer

A protection layer (or independent protection layer, IPL) in LOPA is an independent safeguard — such as a BPCS, SIS, or relief valve — that reduces risk without depending on the failure of other layers.

Question 4

What design practice helps prevent 'alarm flood' during a process upset in an advanced alarm management system?

Accepted Answer

Implementing alarm suppression, shelving, and state-based alarming to present only actionable alarms

Answer

Techniques such as alarm suppression, shelving, and state-based alarming rationalize alarm presentation so operators receive only relevant, actionable alerts during upsets, in compliance with EEMUA 191 / ISA-18.2.

Question 5

A control valve is specified with an equal-percentage inherent flow characteristic. What does this characteristic describe?

Accepted Answer

Equal increments of valve travel produce equal percentage changes in flow

Answer

Equal-percentage valves produce the same percentage change in Cv (flow coefficient) for each equal increment of stem travel, providing better rangeability for applications with variable pressure drop.

(CCST) Certified Control Systems Technician Practice Test

(CCST) Certified Control Systems Technician Practice Test

CCST Control System Design & Architecture 5