Tutorial 3 & Solution

CAB2012: HEALTH, SAFETY AND ENVIRONMENT Tutorial 3 Instructions:

 Answer Answer all all questions questions..  While group discussion is encouraged, this tutorial should be done on an individual basis and will be graded accordingly. MCQ Questions: 1.

Why Why do OSHA OSHA stan standa dard rds s requi require re the the empl employ oyer er to fir first st cons consid ider er engin enginee eerin ring g contro controls ls to corr correc ectt workplace hazards? A. Because Because safety safety is all all about about condition condition,, not behav behaviour iour B. They may completely eliminate the hazard C. They may completely eliminate exposure D. They They may may cost cost mor more e in the the lon long g run run than than enfo enforci rcing ng safe safe wor work k pro proce cedu dure res s

2.

FMEA FMEA is Fail Failur ure e Mode Mode an and Effec Effects ts Anal Analys ysis is,, HAZO HAZOP is Haza Hazard rd and and Oper Operab abil ilit ity y Revie Review w and and HEA is Human Error Analysis. Which of the following is the most complete approach to hazard analysis? A. FMEA FMEA combined combined with HAZO HAZOP P B. HAZOP alone C. FMEA combined with HEA D. HEA alone

3.

Engin Enginee eerin ring g con contr trol ols s sho shoul uld d not not rely rely A. B. C. D.

4.

Whic Which h of the the follo followi win ng is a simil simila arity rity betw betwee een n Hazar Hazard d and Ope Opera rabi bili lity ty Revi Review ew (HAZ (HAZOP OP)) and Failure Mode and Effects Analysis (FMEA)? A. Both are are graph graphical ical methods methods B. Both Both are are qualit qualitat ative ive meth method ods s C. Both Both are are used used to calc calcula ulate te risk risk D. Both Both are are base based d on guide guidewor words ds

5.

on on whic which h of of the the foll follow owin ing g stra strate tegi gies es design design or redes redesign ign removal or substitution barriers or ventilation personal protective equipment

Management Management controls should be used ____________ engineering engineering controls: A. B. C. D.

before before in conjunction with instead of in the absence of

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6.

Event A

Event B

Event C Y 0.3

Y 0.2 Y 0.1 N 0.7 N 0.8

X N 0.9

Consider the above event tree. Given that the initiating event, X has occurred, what is the probability of Event A occurring, followed by Event B but not by Event C? A. 0.08 B. 0.9 C. 0.006 D. 0.014 7.

Methods A to D are hazard control methods. Method A costs RM 100 and has an effectiveness of 40%. Method B costs RM 75 and has an effectiveness of 50%. Method C costs RM 50 and has an effectiveness of 40%. Method D costs RM 50 and has an effectiveness of 30%. Which method gives the most desirable cost-benefit ratio? A. Method A B. Method B C. Method C D. Method C

A. B. C. D. 9.

8. What is the primary function of a fault tree? To identify possible consequences of a given event To identify the most effective method to prevent a given event To identify the events that may lead to a given event To identify the most likely outcome of a given event

What is a major weakness of the walk-around inspection? A. B. C. D.

its takes too much time its only look at the conditions it is not conducted often enough it requires expert


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10. A

C B

D

E

Consider the above fault tree. Which of the fol lowing is TRUE? I. Event A may occur if Events D and E occur simultaneously II. Event A may occur if Event B occurs but not Event E III. Event A will not occur if Events B, D and E do not occur IV. Event A will not occur if Event B occurs but not Event D A. B. C. D.

I, III and IV only I and III only I, II and III only II and IV only

11.

What is the last step in constructing a fault tree? A. Identify the top event B. Identify the initiating event C. Identify the intermediate events D. Identify the basic events

12.

Which of the following is the CORRECT hierarchy for risk control measures? A. Engineering controls, administrative controls, personal protective equipment. B. Administrative controls, personal protective equipment, engineering controls. C. Personal protective equipment, elimination of risks and administrative controls. D. Elimination of risks, administrative controls and engineering controls. 13. Which of the following methods would you use to predict the outcomes of a given event, as well as the risks of those outcomes occurring? I. Fault tree analysis II. Failure mode and effect analysis III. Event tree analysis IV. What if analysis A. B. C. D.

III only I and III only II, III and IV only I, II and IV only


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14. Technique of Operation Review (TOR) and Hazard and Operability Review (HAZOP) are hazard analysis methods. Which of the following is/are TRUE? I. TOR is conducted after the event, HAZOP is conducted before. II. TOR is a quantitative method, HAZOP is a quantitative method. III. TOR uses guidewords, HAZOP does not use guidewords. IV. TOR is a graphical approach, HAZOP is a numerical approach.

16.

A. B. C. D.

III only I only I and IV only II and IV only

A. B. C. D.

15. What is the primary purpose of a hazard analysis? To comply with environmental legislation To identify and control risk and liability To plan and prepare for emergencies To state the company’s commitment to safety

Select the best method of hazard analysis that uses a graphic model to visually display the analysis process. A. Failure mode and effects analysis (FMEA) B. Hazard operability review (HAZOP) C. Risk analysis D. Fault tree analysis (FTA)

17. Which of the following tools is NOT relevant in conducting hazard A. B. C. D.

analysis of a chemical plant? The process flow diagram (PFD) The piping and instrumentation diagram (P&ID) Work permits of all foreign workers (WPF) Material Safety Data Sheet (MSDS)

18. "This hazard analysis technique requires a thorough examination of Process Flow Diagram (PFD) and Piping and Instrumentation Diagram (P&ID) to analyse each process element and deviation of process operating parameter.” The above statement refers to: A. Hazard and Operability Studies (HAZOP). B. Failure Mode and Effect Analysis (FMEA). C. Event Tree Analysis. D. Fault Tree Analysis.

A. B. C. D.

19. Risk is a possibility of loss in terms of ___________. consequence and hazard incident and likelihood hazard and accident severity and probability

A. B. C. D.

20. Risk management plans response to adverse events before the event occurs. Therefore, risk management is ________________. reactive proactive didactic paranoid


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21.

The following methodologies must be used by the employers when conducting hazard analysis, EXCEPT? A. What-if analysis B. Accident investigation analysis C. Failure mode and effects analysis D. Fault tree analysis.

22.

C.

23. A. B. C.

Which of the following statement is FALSE? A. An "AND" gate is linked to an output event that occurs only if all related input events occur. B. An Event Tree Analysis is to provide information on how a failure can occur and the probability of occurrence. The first step in Fault Tree Analysis, a deductive reasoning process, is to clearly identify the top event. D. An Event Tree Analysis is to identify ways in which hazards can lead to accidents. The best description of hazard is an expression of possible loss in terms of severity and probability. injury and/or major system damage. is an after-the-fact process, triggered by an accident. D. conditions that have the potential to cause harm.

Essay/Short Answer Questions: 1.

Describe TWO (2) differences and TWO (2) similarities between an event tree and a fault t ree. Differences between an event tree and a fault tree are: (i) An event tree is to identify the possible consequences of a given initiating event, while a fault tree is to identify the possible causes of a given unwanted event (top event). (ii) An event tree uses yes-no branches, while a fault tree uses special symbols, some derived from Boolean algebra. (iii) An event tree begins with an initiating event and finishes with a number of end events (consequences), while a fault tree begins with an end event (top event) and finishes with a number of initiating events (causes). Similarities between an event tree and a fault tree are: (i) Both are graphical methods. (ii) Both are used for hazard analysis. (iii) Both are numerical methods used to calculate probability. [6 marks]

2. What is a fundamental weakness common to HAZOP and FMEA? How can this weakness be overcome? The element of human error is missing. Human error is most likely the root cause of a workplace accident. This weakness can be overcome by coupling HAZOP/FMEA with Human Error Analysis (HEA). [2 marks]

3. In a block of home units, 30% of the units have smoke detectors which ring a bell in the unit and also at the fire station. Provided the smoke detector works, the occupant of the unit will wake up and escape 95% of the time without injury. The other 5% of the time, the occupant fails to wake. On 40% of the occasions when the occupant is not woken by t he alarm, the person is rescued. In units which have no smoke detector or the where the smoke detector fails to activate, there is a 40% chance that the fire will be detected by the occupant who will escape without injury. If the


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occupant fails to detect the fire, there is only a 10% chance the person will be rescued. The smoke detector fails to work twice in every 100 occasions. Draw an event tree to describe the situation described above. ii.

What is the probability that a person will perish in a fire?

iii. Referring to the event tree in part (i), suggest TWO (2) methods to reduce the probability of a

person perishing in a fire.

detector

works

noticed/ escape

rescued

Y 0.95 Y 0.98

Y 0.4

outcome

probability

OK

0.2793

OK

0.0059

KO OK

0.0088* 0.0024

OK

0.0004

KO OK

0.0032* 0.28

OK

0.042

KO

0.378*

N 0.05 Y 0.3

N 0.6 Y 0.4 N 0.02

Fire

Y 0.1 N 0.6 N 0.9 Y 0.4

N 0.7

Y 0.1 N 0.6 N 0.9

Probability of a person perishing in a fire = 0.0088 + 0.0032 + 0.378 = 0.39. Methods to reduce this probability are: (i) Increase the % of units with smoke detectors. (ii) Increase the probability of the detector working. (iii) Increase the probability of the person being rescued. 4. i. ii.

What is the most fundamental weakness of both of the following methods? Failure Mode and Effects Analysis (FMEA) Hazard and Operability Review (HAZOP) The weakness of FMEA & HAZOP is that the methods do not consider any human error factor during the analysis. How can the weakness be overcome? Conduct the FMEA & HAZOP with analytical method that consider human error aspect such as Human Error Analysis (HEA) [4 marks]

5.

Describe the FIVE steps for implementing hazard control measures Select method(s) – consider the hierarchy of control to apply the control measures Apply the method(s) - Put the selected method to practical use to test cases as to test and analyse the suitability of the method in a real life situation Monitor/observe - Monitor and observe for any feedback from all parties involved Assess effectiveness – Measure the effectiveness of the methods Adjust as necessary – Modify or change to another method for better effectiveness. [5 marks]

6.

In the Fault Tree Analysis, please define the function of the "AND" and "OR" gate. "AND" gate linked to an output event that occurs only if all related input events occur. "OR" gate linked to an output event that occurs if any input events occur. [2 marks]


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In the fault tree in FIGURE Q1 below, the numbers represent failure probabilities. What is the probability of the sprinkler system failing? 7.

[4 marks]

Sprinkler System Failure R O

No Signal From Controller

No Water

R O

R O

Both Detector Fail

No Supply

Pipes blocked

Controlle r Failure

A N D A N D

Smoke Detector Fail

0.001

0.0005

No Mains

IR Detector Fail

0.001 0.005

0.01

Back-up Water Fail 0.01

FIGURE Q1

(0.005 x 0.01) + (0.001) + (0.001 x 0.01) + (0.0005) = 0.00156


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Tutorial 3 &amp; Solution

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