CHEE2020

Question 1

Design specifications?

Answer 1

• Equipment technology
• Equipment sizing and configuration
• Material of construction
• Control and safety features
• Sustainability features

Question 2

Operating parameters

Answer 2

• Operating mode (batch, continuous)
• Process stream operating conditions (flow, temperature, pressure, composition)
• Equipment operating conditions (vessel pressure, liquid levels, equipment temp)

Question 3

SIS trip system

Answer 3

takes action automatically to avert an unwanted event (eg shutting off pumping, closing valve…)

Question 4

Interlock system

Answer 4

a group of devices that senses an off-limit condition or an improper sequence of events and acts to shutdown the process equipment.

Question 5

Controlled variable guidelines

Answer 5

CV1. Not self-regulatory
CV2. Equipment/process constraints
CV3. Interactions with other loops (minimise)

Question 6

Measured variable guidelines

Answer 6

MV1. Controlled variable
MV2. Easily measured
MV3. Sensitivity
MV4. Speed of response (minimise lag/ delay)

Question 7

Manipulated variable guildelines

Answer 7

MPV1. Direct action
MPV2. Sensitivity (large gain)
MPV3. Speed of response (minimise lag/delay)
MPV4. Interactions with other loops (minimise)

Question 8

Personal safety

Answer 8

may result in injuries to one or a few workers at a point in time
typically occur over a short timeframe and can occur frequently
falling on stairs

Question 9

process safety

Answer 9

can result in severe damage to people, environment, assets, production,
an organisation’s reputation
are less common events that result from design flaws and/or a drift into
failure that occurs over longer timeframes

Question 10

good personal safety

Answer 10

Taking responsibility for safe working
➢ Wearing necessary personal protective equipment
(PPE)
➢ Not working under influence of alcohol, drugs or
tiredness
➢ Being aware of hazards and risks
➢ Completing required workplace training
➢ Abiding by company procedure and rules
➢ Abiding by government regulations

Question 11

Hazard

Answer 11

a source or a situation with the potential to cause harm to people, property, and
environment.
Hazards are generally associated with sources of energy e.g. chemical, thermal, kinetic,
potential energy

Question 11

good process safety

Answer 11

Inherently safe design of plant
➢ Strong commitment to safety from senior
management
➢ Strong safety policies, procedures and
communication
➢ Well maintained equipment and plant
➢ Well trained staff
➢ Continuous learning about process safety

Question 12

Risks

Answer 12

‘Risk is uncertainty that matters because it can positively or negatively affect the achievement of objectives
Risk is usually associated with uncertainty, unknown information, incomplete knowledge.
are the effects of the hazards

Question 13

controlled variable

Answer 13

operating variable that needs to be controlled e.g. reactor
temperature, tank level, feed flowrate

Question 14

set point

Answer 14

• target value for the controlled variable.

Question 15

Measured variable

Answer 15

operating variable/s that is measured to determine how the unit/
equipment is performing e.g. reactor temperature, tank level, feed flowrate

Question 16

Manipulated variable

Answer 16

operating variable that is changed to affect the controlled
variable e.g. tank outflow, steam flowrate

Question 17

disturbance variable

Answer 17

operating variable that can disturb the process control loop
e.g. change in feed composition, feed flow, ambient conditions

Question 18

Feedback control

Answer 18

➢ Compensates for disturbances after the
disturbance has affected the process
➢ Compensates for all disturbances (has no
intelligence on disturbance)
➢ Controlled and measured variables are the
same
➢ Very common in process industries

Question 19

Feedforward control

Answer 19

➢ Compensates for a disturbance before it hits
the process
➢ Sensor is located on the fluctuating stream
➢ Relies on good understanding of the
dynamics of the process
➢ Uncommon to have straight FF in process
industries

Question 20

Cascade control

Answer 20

➢ Two control loops working together –
master and slave loops.
➢ The output signal of the master loop
output acts as the setpoint for the
slave control loop.
➢ Slave loop typically adjusts for shortterm variations e.g. steam flow.
Master loop adjusts for longer-term
variations.
➢ May lead to better control for some
processes.

Question 21

Ratio control

Answer 21

➢ Controls the proportion or ratio of two
variables
➢ Can be used to maintain two flows at a
constant ratio e.g. reagent flow/ process
feed flow to a reactor