Introduction to Process Safety

8/11/2019 Introduction to Process Safety

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1. INTRODUCTION TO PROCESS SAFETY

CH4101 Chemical, Biological & Plant Safety

Dr. Foo Swee Cheng


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ENGINEERING ETHNICS

1. Defend the truth

2. Expose questionable practice that will lead to unsafe product/ process

Royal Academy of Engineering:http://raeng.org.uk/societygov/engineeringethics/principles.htm

Accuracy and rigour

Honesty and integrity

Respect for life, law and public good

Responsible leadership: listening and informing

Discussion: Nicoll High collapse, 20 April 2004 Singapore Nicoll 40 years: http://www.nce.co.uk/features/nce-40-years/no11-nicoll-highway-collapse/8629881.article

Insurance: http://news.asiaone.com/News/The+Straits+Times/Story/A1Story20080420-60781.html

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http://raeng.org.uk/societygov/engineeringethics/principles.htmhttp://www.nce.co.uk/features/nce-40-years/no11-nicoll-highway-collapse/8629881.articlehttp://news.asiaone.com/News/The+Straits+Times/Story/A1Story20080420-60781.htmlhttp://news.asiaone.com/News/The+Straits+Times/Story/A1Story20080420-60781.htmlhttp://www.nce.co.uk/features/nce-40-years/no11-nicoll-highway-collapse/8629881.articlehttp://raeng.org.uk/societygov/engineeringethics/principles.htm


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SAFETY TERMS: DEFINITIONS

Hazard: Potential source of harm/loss/damage

Risk: Probability of a certain harm/loss/damage

Individual Risk (IR): IR = (Frequency) x (Severity)

Societal Risk (SR): SR = (IR) x (population) = FN

Incident: The result of uncontrolled hazard(s)

Accident: An incident which results in consequent loss

Accident Scenario: A sequence of events which propagatesthe accident

Accident outcome: The consequences of an accident

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SHE (Safety, Health & Environment) HAZARDS

Chemical hazards: Toxicity of artificial/ natural materials

Physical hazards: Flammability of artificial/ natural materials

Fire/ Thermal radiation: Heat

Explosion: Overpressure generated by fire

Biological: Living organisms e.g. bacteria, viruses, fungi

Contaminants: Healthcare/ food/ animal husbandry

Process materials: Vaccine production

Effects: Communicable or non-communicable diseases

Can reproduce itself in host Ergonomic: work load/ tools/ organization on human

Force/ energy/ repetitiveness/ anthropometrics/ time

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SAFETY AND HEALTH

Safety: Accidental/ abnormal release of HAZARDS

Acute/ high level release: large quantity in a short time

High consequence: Acute damage to property/ population/environment

Health: Operational/ Fugitive release of HAZARDS

Chronic/ low level emissions: Small quantity over a long time

Low consequence: Chronic damage to sensitive population/

environment in continuous/ long-term exposure

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PROCESS HAZARDS AND EFFECTS Fire: Thermal effects

Explosion: Over-pressure effects

Toxicity: Toxic/ Health effects

Biological effects: Two unique features; e.g. ebola virus

Communicable (person-person transmission)

Reproduce itself in host (make use of host resources)

AccidentType

Probability ofoccurrence

Potential forFatalities

Potential forEconomic Loss

Fire High Low Intermediate

Explosion Intermediate Intermediate High

Toxic Low High Low

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COMPARING PROCESS AND PERSONAL SAFETY

Equal risk curves: R = C1F1= C2F2

Process Safety

Hazard: Highly hazardous (GHS cat 1 & 2); large quantity

Severity: High; Death/ severe disable

Hazard zone: Large; zone often extends to offsite

Frequency: Low; High reliability system; less no. facilities

WSH personal safety

Hazard: Less hazardous; Wide range; less quantity

Severity: Low; Wide rangeHazard zone: Small; zone confined to location of use

Frequency: High; System less reliable; more no. facilities

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Risk curve

C

F


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PROCESS SAFETY vs PERSONAL SAFETY

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OSH/ WSHManagement

Risk Curve


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PROCESS SAFETY MANAGEMENT (1)Reduce Loss Event Frequency

Inherently safer design: moderate/ simplify Process Reliability: Reliability engineering

Component reliability & System structure

Process Integrity: Maintenance

Prevent system failure: Reliability maintenance/ growth program

Operation reliability

Competency of operators

Technical support for operators

Human factor engineering/ Safety culture

Incident management

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PROCESS SAFETY MANAGEMENT (2)Reduce Loss Event Consequence

Inherently safer design: minimize/ substitute/

Minimize: Reduce the quantity of hazard in loss event

Amount of stock in individual storing units

Amount of material in individual process units

Substitute: Replace a hazardous material with less hazardous one

Direct materials (incorporated into products): Use less hazardousroute

Less hazardous/ amount of intermediates/ by-products/ wastes

Indirect materials not incorporated into products: Use lesshazardous materials

Solvents/ Catalysts/ Energy/ heating media

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PROCESS SAFETY STRATEGY: DEFENSE IN DEPTH

NORMAL OPERATIONALCONTROL SYSTEM

ALARM SYSTEM

SAFETY INTERLOCK/

EMERGENCY SHUTDOWNSYSTEM

RELIEF SYSTEM

Seriousness

of event

Divert material safely

Stop the operation or part of

operation

Bring unusual situation to theattention of a plant operator

Closed-loop control to

maintain process withinacceptable operating region F

ourindependentprotection

layers(IPL

)

CHEMICAL PLANT PROCESS

Protection

Systems

ControlSyste

ms

BPCS

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WSH MANAGEMENT

Workplace pollution prevention

Prevention system reliability

Protection system reliability

Operator reliability

Workers exposure control/ monitor

Manage exposure dose: level x time

Biological/ medical control/ monitor

Early detection excessive absorption

Manage sensitive workers

Hierarchy of Control

Elimination

Substitution

Engineering control

Administrative control

Administrative control

Personal protection

Early detection/ treatment

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RISK ACCEPTANCE CONCEPTS

Except in extraordinarycircumstances

Risk reduction impracticalor cost disproportionateto gain

Cost of reduction exceedthe improvement

To ensure r isk remainsat this level

Unacceptable region

No exposure allowed

ALARP region

Risk is tolerated only

if a benefit is desired

ALARP required

Broadly acceptable region

ALARP not required

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EXAMPLE: AN RISK ACCEPTANCE CRITERIA

Public Risk Criteria Occupational Risk

Unacceptable Risk

10-3Unacceptable Risk

Tolerable if emergencyprocedures and protectiveequipment are in place

10-4Acceptable for manufacturing,warehouses, open spaces,parkland, golf courses, etc.

Tolerable if emergencyprocedures are in place

10-5Acceptable for commercialoffices, low density residential

Negligible risk

10-6Negligible risk - No land userestrictions

IR/yr

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http://ch4101_1%20qra%20nea_guidelines%20_pcd_2013.pdf/


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ACCIDENT STATISTICS

Singapore, MOM: Accident frequency Rate (AFR)

AFR: Accidents per 1,000,000 man-hrs worked

Singapore, MOM: Accident Severity Rate (ASR)

ASR: Man-days lost per 1,000,000 man-hrs worked

Fatal Accident Rate (FAR)

British: Fatalities per 100,000,000 man-hrs worked

MOM: fatalities per 100,000 workers per year

Fatality Rate (FR): Deaths per person per year

Individual Risk (IR): The chance of death per person per year

Relationship between (FAR) and (FR)

British: (FAR)(man-hrs worked/person-year)/(108) = (FR)

MOM: (FAR)/(100,000) = (FR)

Read: Textbook 1 3 Accident and Loss Statistics, page 4 12

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EXAMPLE: Accident Rates

Factory A (100 workers): #man-hours worked per year:

100 x 50 x 5 x 8 = 200,000 man-hrs No. of accidents: 5 per year

AFR (MOM): 5 x 1,000,000 / 200,000 = 25

Total number of MC-days: 10 days per year

ASR (MOM): 10 x 1,000,000 / 200,000 = 50

No. of Fatalities: 1 per year

FAR (British): 1 x 100,000,000 / 200,000 = 500

FAR (MOM): 1 x 100000/100 = 1000

Fatality Rate (FR): 1/100 = 1 x 10

-2

per person per year British: man-hr worked per person = (FR)/(FAR)

(1/100)/(500/100,000,000) = 2000 man-hrs per person-year

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SAFETY TARGETS: FAR OR FR

For planning or design To meet national or company requirements

e.g.Singapore 2018 target: FR = < 1.8 by 2018

Plant risk:

Mult iple/ Overall risk: (FAR) < 2

Single/ Each risk: FAR < 0.4


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ACCIDENT PROCESSES

Initiation:

Event that starts the accident

Propagation:

Event/ events that maintain/ expand the accident

Termination:

Event/ events that stop the accident/ diminish it in size

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ACCIDENT MITIGATION PRINCIPLES

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Initiation Diminish

(Prevent/ removethe potential ofaccident causing

events)

Grounding and bonding

InertingExplosion proof electricalGuardrails and guardsMaintenance proceduresHot work permitsHuman factors designProcess design

Awareness of dangerous properties of chemicals

Propagation Diminish

(Reduce potentialfor accident to

continue escalation)

Emergency material transferReduce inventories of flammable materialsEquipment spacing and layoutNonflammable construction materialsInstallation of check and emergency shutoff valves

Termination Increase

(Increase capacityto terminate the

accident)

Fire-fighting equipment and proceduresRelief systemsSprinkler systemsInstallation of check and emergency shutoff valves


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JOHORE TANK FIRE

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Initiation: Lightning?

Propagation: Spread to another tank

1/3 of content in 2ndtank transferredbefore catching fire

Termination: Fire put out in 67 hours


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LEARNING OBJECTIVES

Understand the basis concepts/ definitions of safety, health &

environmental terminology/ principles in

Hazards

Risk: Frequency & Consequence

Risk management principles

Accident processes

Safety performance indicators: Accident statistics

The differences between

Safety and health

Process safety and WSH/ personal safety

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END

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Documents

Introduction to Process Safety