Lecture 8

Question 1

This is a list of items and possible problems in the process that must be checked

Answer 1

Process hazards checklists

Question 2

This can be as simple as an inventory of hazardous materials, or it can be as detailed as the Dow indexes

Answer 2

Hazards surveys

Question 3

are a formal rating system, much like an income tax form, that provide penalties for hazards and credits for safety equipment and procedures

Answer 3

Dow indexes

Question 4

This approach allows the mind to go free in a
controlled environment. Various events are suggested for a specific piece of equipment with
the participants determining whether and how the event could occur and whether the event
creates any form of risk.

Answer 4

Hazards and operability (HAZOP) studies

Question 5

An effective but less formal type of HAZOP study. The results are highly
dependent on the experience and synergism of the group reviewing the process.

Answer 5

Safety review

Question 6

is a formal procedure to identify hazards in a chemical process facility

Answer 6

HAZOP Study

Question 7

when to use HAZOP in new plants

Answer 7

when design is nearly firm and documented

Question 8

when to use HAZOP in existing plant

Answer 8

review current process or a major redesign is planned

Question 9

requirements for HAZOP

Answer 9

Technical data
Technical experts

Question 10

Principles of HAZOP

Answer 10

Concept
Reference/Basis
Method

Question 11

locations (on P&ID or procedures) at which the process parameters are investigated for deviations. these nodes are points where the process parameters have an identified design intent

Answer 11

study nodes

Question 12

defines how the plant is expected to operate in the absence of deviations at the study nodes

Answer 12

intention

Question 13

these are departures from the intention which can be discovered by systematically applying the guide words.

Answer 13

deviations

Question 14

HAZOP MODEL

Answer 14

guide words
|
causes - deviation - consequences

Question 15

guide word: no forward when there should be

Answer 15

NONE

Question 16

guide word: more of any relevant physical property than there should be

Answer 16

MORE OF

Question 17

guide word: less of any relevant physical property than there should be

Answer 17

LESS OF

Question 18

guide word: composition of system different from what it should be

Answer 18

PART OF

Question 19

guide word: more components present in the system that there should be

Answer 19

MORE THAN

Question 20

guide word: what else can happen apart from normal operation

Answer 20

OTHER THAN

Question 21

guide word: flow reverses against intended direction

Answer 21

REVERSE

Question 22

risk is defined mathematically as:

Answer 22

consequences x likelihood
or
severity x frequency

Question 23

the systematic development of numerical estimates of the expected frequency and consequence of potential accidents associated with a facility or operation based on engineering evaluation and mathematical techniques

Answer 23

QRA

Question 24

complexity of QRA depends on

Answer 24

objectives of the study
available information

Question 25

major steps of QRA

Answer 25

1. defining potential event sequences and potential incidents 2. evaluating the incident consequences 3. estimating the potential incident frequencies using event trees and fault trees 4. estimating the incident impacts on people, environment, and property 5. estimating the risk by combining the impacts and frequencies, and recording the risk.

Question 26

a semi-quantitative tool for analyzing and assessing risk

Answer 26

LOPA

Question 27

the protection layers may include

Answer 27

inherently safer concepts basic process control system safety instrumented functions passive devices (dikes/blast walls) active devices (relief valves) human intervention

Question 28

primary purpose of LOPA

Answer 28

determine whether there are sufficient layers of protection against a specific accident scenario

Question 29

protection layers of LOPA are often depicted as an

Answer 29

onion skin

Question 30

the major steps of a LOPA study include

Answer 30

1. identifying a single consequence 2. identifying an accident scenario and cause associated with the consequence 3. identifying the initiating event for the scenario and estimating the initiating event frequency 4. identifying the protection layers available for this particular consequence and estimating the probability of failure on demand for each protection layer 5. combining the initiating event frequency with the probabilities of failure on demand for the independent protection layers to estimate a mitigated consequences frequency for this initiating event 6. plotting the consequence versus the consequence frequency to estimate the risk 7. evaluating the risk for acceptability (if unacceptable, additional layers of protection are required)