chpe 5612-1

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by Dr. Omar Houache

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Dr. Omar HouacheIn charge for

Chemical Process Safety

Office: 1008 PCE Dept.

email: omarh@squ.edu.om

Office Hours:

Hours posted on door orBy appointment

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Course Description:The course will provide an overview of Process Safety in theChemical & Process Industry, focusing on the nature of chemical  plant accidents, their causes, and steps to eliminate them, with

emphasis on inherently safe designs. Chemical & Process Industry accidents deal most often with

Flammability and Toxicity issues and these are dealt with inmore detail.

The role of Human Error in accidents is also studied and some

major accidents will be examined to show the relevance intoday's workplace. The course requires active studentparticipation via discussions of system designs, their weaknessand improvements.

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Learning Outcomes: By the end of this course, you should be able to:

1. Understand the risks associated with a process, and the consequences of deviation from normal operation (a, c, e, k);

2. Identify and evaluate hazards associated with a process facility (a, e);3. Understand toxicology & quantitatively analyze release and dispersion

rates of liquids and vapors (a, c, e, k);

4. Understand the technologies to prevent fires and explosions (a, c, e, k);

5. Participate actively as a member of a Process Hazard Analysis team(a, d, e, f, g);

6.  Appreciate the importance of safety, both on-the-job and at home(h, i, j);

7. Recognize the role that ethics plays in process design and operation(f, h).

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Textbook for Safety D. A. Crowl and J. F. Louvar

Chemical Process Safety, Fundamentals with

 Applications Second Edition, 2002

Chapters 1-13

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Topical Outline: 1. Introduction to safety and risk assessment

 A.  Accident process and loss statistics

B. Inherent safety and safety culture

C. Ethics

D. Public perceptions of chemicalindustry/processes

2. Toxicology 

 A. Entry and elimination from humans

B. Dose/response models

C. Threshold limit values

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Topical Outline: 3. Industrial Hygiene

 A. Laws and regulations, MSDS

B. Estimating worker exposure to chemicalsC. Exposure Control/mitigation

4. Source Models

 A. Flow of liquids through holes and pipesB. Flow of vapor through holes and pipes

C. Flashing liquids and liquid pool evaporation

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Topical Outline: 5. Toxic Release and Dispersion

 A. Dispersion modelsB. Pasquill-Gifford model for dispersion coefficient

estimationC. Emergency response planning guidelines

6. Fires and Explosions

 A. Flammability limits

B. Ignition sourcesC. Dust and mist explosions, Vapor cloud explosionsD. Process and equipment designs to prevent fires

and explosions

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Topical Outline: 7. Design to prevent fires and explosions

Relief systems

 A. Relief valves and systemsB. Relief design considerations

8. Hazard Identification and Risk Assessment & Accident Investigations

 A. Evaluation of risk; acceptable risk

B. Hazard surveys

9. Analysis of case studies

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Grading% Date

Midterm 1 15 October 23rd

Midterm 2 15 November 27th

Continuous Assessment

(Quizzes, HWs, Term Project)30

Final Exam 40 January 10th

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Cell / Mobile PhonesIf you have a cell / mobile phone, please

either turn it off or place it in silentmode prior to class.

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Expectations for Students• Attend lectures, pay attention, listen and take

notes;• Work and submit homework;• Homework problems are more open-ended than

previous courses – need to make decisions.Homework is based on real plant problems;

• Homework problems are in both English andmetric units – usually consistent.

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Cell / Mobile Phones

If you have any special problems or

needs:Please see me!

If you cannot hear me or see overheadsor boards:Please see me!

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Purpose of Process Safety

To provide fundamental tools

 which are used to design /manage /

operate a chemical plant safely 

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Definitions Accident: The occurrence of a sequence of eventsthat produce unintended injury, death or property damage.Safety: Strategy of accident prevention.

Loss prevention: Prevention of injury to people, damage toenvironment, loss of equipment, inventory or production.Hazard: A chemical or physical condition that haspotential to cause an accident.

Risk: Probability and consequence of an accident.

Significant Chemical plant hazards: f lammable, explosive, reactive &toxic hazards

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Definitions• Incident: Loss of control of material or energy.• Scenario: A sequence of events which causes the hazard

to result in an accident.• Incident outcome: The physical manifestation of anaccident.

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S-A-F-E-T-YS - Management Systems A – AttitudeF – FundamentalsE – Experience

T – Time Y - YouSafety cannot be prioritized - it is a condition of employment!

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Statistics-1OSHA Occupational Safety & Health

 Administrationincidence rate per 100 worker years = 200,000 hours

exposure 100 years x 2000 hours/year

FAR  Fatal Accident Ratefatalities per 1000 employees and entire life = 108 hoursexposure 50 years x 2000 hours/year x 1000 employees

FR  Fatality Rateper person per year (exposure poorly defined)

For all of these indicators, smaller is better!

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What is an Accident?

 An "accident" is an unplanned, undesired event whichmay or may not result in injury or property damage, that interferes with the completion of an

assigned task.

 A "near miss" is a form of an accident that does notresult in injury or property damage.

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Why do Accidents Occur?

 We choose to handle dangerous process materials andenergies

To make a living

To provide society with desirable products

 As long as we choose to handle them, a potential forloss events exists

Things can be done to reduce their likelihood and severity to negligible or tolerable levels

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Background

Many people believe that "accidents happen". They believe that the occurrence of an accident is inevitableand cannot be avoided. Some say "it was just bad luck"

or "they were in the wrong place at the wrong time". All of these excuses fail to identify the true causes of accidents. One researcher found that for every seriousor disabling injury, there are:

10 minor injuries 30 property damage incidents

600 near-miss accidents

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How Do Accidents Occur?

The causes of accidents can be broken down into 2 basiccomponents, unsafe conditions and unsafe acts.

Unsafe conditions are hazardous conditions orcircumstances that could lead directly to an accident.

 An unsafe act occurs when a worker ignores or is not

aware of a standard operating procedure or safe workpractice designed to protect the worker and preventaccidents.

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How Do Accidents Occur?Unsafe Acts Unsafe Conditions

Operating equipment or

machinery without permission

Lack of guarding on machinery

Defeating safety devices Defective tools or equipment

Using defective equipment Crowding workers into one areaUsing the wrong tool for the job Inadequate alarm systems

Not using personal protective

equipment

Fires & explosions

Incorrect lifting techniques Poor housekeepingWorking while intoxicated Hazardous atmospheres

Horseplay Excessive noise

Inadequate lighting

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How Do Accidents Occur?Personal Factors Job Factors

Lack of knowledge or skills due

to inadequate training

Non-existent or poorly

developed work standards

Improper motivation Substandard equipment design

Physical limitations of the

worker

Poor equipment maintenance

Distractions which interfer withthe worker’s ability to

concentrate on their job

Purchase of substandardequipment, tools, and materials

Unusual increases in equipment

usage

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How Do Accidents Occur? The personal factors described in previous Table

generally lead to unsafe acts and the job factors arelikely to contribute to the unsafe conditions. If you can

identify the personal and job factors which may contribute to an accident in your work area, you havetaken the first step toward the prevention of accidents.

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Chemical Plant Accidents

Consequences

Probability Hazard Fatalities Hazard EconomicLoss

Fire High Low Intermediate

Explosion Intermediate Intermediate HighToxic Releases Low High Low

31

30

36

3

Types of loss for large hydrocarbon-chemical plant accidents

Fires

Explosions

 Vapor Cloud

Others

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What must we do to keep them from happening?

Design of process

Management of process

Operation of Process

Regulations

 You will learn about these things in this course!

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Inherently Safer Design

Inherently safer designs permanently andinseparably reduce or eliminate process hazardsthat must be contained and controlled to

avoid accidents.

“The essence of the inherently safer approach to plant design is theavoidance of hazards rather than their control by added-on

 protective equipment.”

T. A. Kletz, Plant Design for Safety: A User-Friendly Approach(NY: Hemisphere, 1991)

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Inherently Safer Design StrategiesMINIMIZE = Reduce hazardous material/energy quantity 

• Reduces energy • Reduces potential accident severity 

SUBSTITUTE = Replace with a less hazardous material• Reduces/eliminates available chemical energy • Reduces/eliminates potential accident severity 

MODERATE = Use under less hazardous conditions• Available energy may be the same, but• Passively reduces potential loss event impacts• For chemical processes, this usually means lowertemperatures, pressures, concentrations, etc.

SIMPLIFY = Reduce unnecessary complexity • Reduces likelihood of an accident

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When?

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When?