Chemical and Risk Analysis, Management,

and Safety

Some Major Accidents in the CPI and their Costs

No. Location Date Substance involved

Event Loss Plant unit involvedKilled Injured Financial loss [$]

1 Texas City, TX, USA 4/16/97 Ammonium nitrate F, Ex 552 ~3000 - Two ships

2 Feyzin, France 1/4/66 Propane Bleve 18 81 87 M Storage vessel

3 Pernis, Netherlands 1/21/68 Oil slops Vcex 2 85 123.6 M Slop tanks

4 Flixborough, UK 6/1/74 Cyclohexane Vcex 28 104 521.3 M, 635.9 M Caprolactam plant

5 Beek, Holland 11/7/75 Propylene F 14 - 114.7 M, 72.8 M Petrochemical plant

6 Caracas, Venezuela 12/19/82 Oil froth Vcf, Bleve

150 >500 74.5 M Storage tank

7 San Juan Ixuatepec, Mexico

11/19/84 LPG Tox 650, 550

6400, 7000

28.5 M, 31.3 M Terminal

8 Bhopal, India 12/3/84 Methyl isocyanate Ex, F ~4000 - - Storage tank

9 Alpha Pier, North Sea 7/6/88 Gas, oil Ex, F 167 - 1.86 B, 1.38 B, 8.85 B

Compression unit, drilling platform

10 Pasadena, TX, USA 10/23/89 Isobutane Vcex 23 ~103 >623.5 M, 994.2 M, 1.77 B

Polyethylene plant

11 Munich, Germany 5/23/93 Peroxide F, Ex 2 - 3.6 B Cleaning of peroxide installatioin

Introduction to Introduction to Chemical Risk Chemical Risk ManagementManagement

“Managing risks” identification and assessmentWhere possible risks are preventedRisks must always be managed to the point of being reduced to “acceptable” levels.

What is RISK What is RISK MANAGEMENT?MANAGEMENT?

The systematicsystematic application of management policies , procedures, and practices to the tasks of analyzing, assessing, and controlling riskrisk in order to protect employees, the general public, and the environment as well as company assets while avoiding business interruptions

What is RISK?What is RISK?A measure of potential economic loss, environmental damage, or human injury in terms of both the probability of the loss, damage or injury occurring and the magnitude of the loss, damage, or injury if it does occur

In short, it relates to the occurrence of undesired events (e.g., explosion), which lead to undesired effects (e.g., damage from explosion), and the probability that these events and effects occur.

RISKRISK RISK = (mathematical) function of

{(seriousness of undesired effects), {(seriousness of undesired effects), (probabilities of effects occurring)}(probabilities of effects occurring)}

RISK ASSOCIATED WITH RISK ASSOCIATED WITH CHEMICAL PROCESSES AND CHEMICAL PROCESSES AND

CHEMICAL PRODUCTSCHEMICAL PRODUCTS1) Toxicological risks to humans

and the environment2) Fire and explosion risks of

chemical products and chemical installations

3) Noise risks4) Ionizing radiation risks

What is a HAZARD?What is a HAZARD?- An inherent chemical or physical characteristic (e.g., toxicity, flammability and explosiveness) that has the potential for causing damage to people, property, or the environment- Typically a combination of a hazardous material, an operating environment, and certain unplanned events that could result in an accident

What is a HAZARD/RISK What is a HAZARD/RISK ANALYSIS?ANALYSIS?

Refers to methods for systematically identifying, estimating, and assessing Safety, Safety, Health, and EnvironmentalHealth, and Environmental hazard/risks

What is EXPOSURE?What is EXPOSURE?GENERAL:confrontation of people, plants or animals with an unwanted agent (substance or energy)Expressed: intensity factor + time duration

What is EXPOSURE?What is EXPOSURE?• INTENSITY FACTOR:

toxic substance: concentration fire: heat flux (W/m2) explosion: pressure sound: decibel

• TIME FACTOR – the amount of time to which a ‘target’ is exposed to some given intensity of a hazardous agent

Intensity, Time Intensity, Time duration, & Riskduration, & Risk

What are SAFETY What are SAFETY RISKS?RISKS?

Usually refer to exposure situations of human beings in which the intensity level is high, the time of exposure short, and the type of effects

e.g., explosion or thermal radiation from an intense fire

What are What are ENVIRONMENTAL ENVIRONMENTAL

RISKS?RISKS?Usually refer to exposure situations (all forms of life & physical surrounding) in which the levels of intensity are low, the duration times (very) long and the effects long term

e.g., exposure for decades to low levels of sulfur dioxide and other atmospheric pollutants eventually causing extensive forest destruction

What are HEALTH What are HEALTH RISKS?RISKS?

Lie in between safety and environmental risks

e.g., those occurring in occupational situations

SAFETY, HEALTH, SAFETY, HEALTH, ENVIRONMENT & ENVIRONMENT & SUSTAINABILITYSUSTAINABILITY

Hierarchical Approach to Hierarchical Approach to Reducing Safety RisksReducing Safety Risks

METHODOLOGIES AND METHODOLOGIES AND MODELSMODELS

FORANALYZING SAFETY, HEALTH,

ENVIRONMENTAL AND SUSTAINABILITY HAZARDS

AND RISKS

Basic Factors Determining Basic Factors Determining Magnitude of Chemical Hazards and Magnitude of Chemical Hazards and

Risks of Chemical Processes Risks of Chemical Processes 1) Amounts of materials in process and

storage – scale of operations (e.g., mg or tons)

2) Physical and chemical properties of materials (e.g., fire explosion, toxicity properties, volatility, and solubility)

3) Types of chemical operations (e.g. simple neutralization or nitration of hydrocarbons)

Basic Factors Determining Basic Factors Determining Magnitude of Chemical Hazards and Magnitude of Chemical Hazards and

Risks of Chemical ProcessesRisks of Chemical Processes4) Process conditions (e.g., high

pressure, high temperature)5) Complexity of operations (e.g.,

complicated process consisting of many highly integrated sub processes)

6) Age of the plant (e.g., old plant require much maintenance)

7) Spatial location of process equipment and their distances of separation (plant layout)

Basic Factors Determining Basic Factors Determining Magnitude of Chemical Hazards and Magnitude of Chemical Hazards and

Risks of Chemical ProcessesRisks of Chemical Processes8) Spatial location of plant relative to

population centers and distances of separation (plant siting)

9) Vulnerability of surroundings (e.g., office buildings/people concentrations)

10)Preventive and protective measures taken (e.g., control and safety systems)

Basic Factors Determining Basic Factors Determining Magnitude of Chemical Hazards and Magnitude of Chemical Hazards and

Risks of Chemical ProcessesRisks of Chemical Processes11)Design and operation relative to

legal standards and codes12)Special factors (e.g., special

geological conditions, political stability, etc.)

13)Risks of human error14)Use of safety and environmental

management systems in mitigating risk

Fishbone (Ishikawa) Fishbone (Ishikawa) DiagramDiagram

The Layers of Protection The Layers of Protection ModelModel

The General Risk ModelThe General Risk Model

DEFINITION OF TERMS IN DEFINITION OF TERMS IN THE GENERAL RISK THE GENERAL RISK

MODELMODEL• EMISSIONS – can be hazardous forms

of energy (e.g., intense radiation from a huge fire) or hazardous substances (e.g., highly toxic substances, like phosgene or dioxins)

• TRANSMISSION – the process by which a hazardous emission travels from a source to a ‘target’

DEFINITION OF TERMS IN DEFINITION OF TERMS IN THE GENERAL RISK THE GENERAL RISK

MODELMODEL• RISK ASSESSMENT – the process

of determining the magnitude of risk; scientific

• RISK EVALUATION – the process by which it is decided whether a risk is “acceptable” or not; more than scientific - value judgment

Safety, Health, and Safety, Health, and Environment (SHE) Environment (SHE)

AnalysisAnalysis

The Generic Exposure-The Generic Exposure-Risk RelationRisk Relation

The Accident SituationThe Accident Situation

HAZARD IDENTIFICATION and

ANALYSIS METHODS

(1) Checklists Methods based on lists of questions

and points related to safety and environment

Goal: “to achieve an optimum standard of safety in the design, construction, operation, and maintenance of new processing plants, likewise modification in existing plants”

Checklist structure of processing plants: AREAS of attention for

safe design1) The selection, location and layout of a site2) Process substances3) Reactions, process conditions, design and testing4) Equipment (including piping and appliances)5) Trip systems and self-actuating safety devices6) Civil engineering constructions7) The storage and loading of hazardous wastes8) Treatment and disposal of hazardous wastes9) Division of areas into hazard (or danger) zones10) Organizational facilities11) Emergency contingency planning12) Literature dealing with aspects of safety in the processing

industry

(2) Hazard Ranking (or Index) Methods

Methods based on amounts (inventories) of substances, material properties of those substances, process conditions, and preventive and protective measures

Characteristics of Hazard Ranking or Index Method

Gives a number or class to a hazardous situation – hazards are ranked according to their potential for causing them

Gives an indication of the type of hazard which exists

Fast – can be done in some hours for a single installation and will take only some days for a large plant

Readily accessible and easily applicable

Classification of Hazard Indices

Class 1 – purely based on the properties of materials used, e.g., toxicity, flammability and reactivity

Class 2 – takes into account the quantities of hazardous materials used

Class 3 – includes penalties for hazardous operating conditions

Class 4 – takes into account certain preventive and protective measures which have been taken in order to increase plant safety

National Fire Protection Agency (NFPA) Rating System for Flammability (Nf) and

Health (Nh)Flammability

(f) NFPA rating (Nf)

Reactivity (r ) NFPA rating (Nr)

Health (h) NFPA (Nh)

Non-combustible

0 Non-reactive, even under fire

0 No hazard beyond that of

ordinary combustibles

0

Flash point>100oC

1 Mildly reactive, upon heating and

pressure

1 Only minor injury likely

1

40o<flash point<100oC

2 Significantly reactive without

heating

2 Medical attention required to avoid

temporary or residual injury

2

20o<flash point<40oC

3 Detonation possible with confinement

3 Materials causing serious injury

3

Flash point<20oC

4 Detonation possible without

confinement

4 Short exposure causes death or

serious injury

4

DOW Fire and Explosion Index

Introduced in 1964Most widely used hazard indexBasically provides weighing (or penalty)

factors for (many of) the pointsBuilt around two factors: material

(reactivity and flammability) and process hazard (process type and conditions) factors

In order to use DOW Index the following information are required:

• An accurate plot plan of the plant• A flow sheet of the plant• A process description• A summary of process conditions• A listing of the substances used

within the plant, the quantities employed , and the conditions at which the substances are used

(3) Hazard and Operability studies (HAZOP)

• A qualitative procedure in which a small team examines a proposed design by generating questions about it in a systematic manner

• “GUIDEWORDS” are handy• COLECTIVE EXPERTISE should also include

essential process, chemical and managerial knowledge relating to the hazards concerned

• Brainstorming is essential

HAZOP Guidewords

(3) Hazard and Operability studies (HAZOP)

• The team may find it helpful to compare the proposed design with relevant engineering standards

• The need for action is decided semi-quantitatively based on the team’s experience and judgment of the seriousness of the consequences, together with the expected probability (frequency) of the occurrence

(3) Hazard and Operability studies (HAZOP)

• Identification are not carried out vigorously

• MAIN PURPOSE: to identify the main hazards and operability problems and to establish their causes

Example of HAZOP

(4) Incident Data Banks and Other Means of IdentificationFAILURE MODE AND EFFECT

ANALYSIS (FMEA) , What-If and Cause-Consequence

Basically a qualitative methodBy preference a team activity to

combine the knowledge and experience of various experts

Organized mistrust – others shall be asked to comment on the first result of an analysis

(4) Incident Data Banks and Other Means of IdentificationFault tree – tracing an undesirable

event backwards to its root causesEvent tree – tracing a primary event

forwards in order to define its consequences

Sample table for Failure Mode and Criticality Analysis (FMECA)

Component Failure or error mode

Causes Effects Criticality Detection method

Remarks

Other components

System Hazard severity

Frequency

The Event Tree

END