Bowtie Analysis – An

Bowtie

Analysis – An

Effective Risk Management

Hindustan Petroleum Corporation Limited

Corporate HSE Department

By

Murthy V

S

S

Malyala

Manager –HSE

Contents

Risk analysis –background

Incidents in Oil Industry

Bowtie

– a visual risk evaluation

tool

Terminology

Development

of Bowtie

Case study – Gas fired Pipe heater explosion modelling

Barriers for controlling incidents

Barrier Effectiveness

End users of Bowtie

Better than other Hazard

identification Techniques

Risk Analysis

3

Risk = Probability X Consequence

Vapor cloud explosion ( Explosion during start up)

4

Mexico (1984)

Flixborough

(1974

)

Piper Alpha 1988

LPG Leakage –

Sampling/ water draining

18 fatalities and 81 injured

Feyzin

, France - 1966

28 fatalities and 36 injured

500 fatalities and terminal destroyed

Rupture of 8 inch LPG pipeline

Leakage from pump discharge relief valve

167 fatalities and platform destroyed.

Bhopal Gas Incident- 1984

Operating

Procedure

Management Of Change

Assert Integrity

Emergency Preparedness

MOC

Staffing

Multiple Failures

Work permit system

Hazard communication

3000 fatalities

MIC Release

Decades of learning from disasters

Years of learning

Loss – Human & Property

5

Pasadena

1989

Esso

Longford

(1998)

BP Texas (2005)

Buncefield

(2005

)

Jaipur

Terminal

(2009)

overfilling of a large storage tank

Over filling of column

.

Fatalities 15. Over 170 injured

Leakage occurred during maint. work on valve

.

Fatalities 23. Over 130 injured2 fatalities and 8 injured

Catastrophic failure of heat exchangers

Maintenance practices

Assert Integrity

Operating Discipline

Contractor Safety

Hazard Analysis

Years of learning

Loss – Human & Property

Operating Discipline

Decades of learning from disasters

The

Bow-tie Diagram is a user-friendly, graphical illustration of how hazards are

controlled.

Bowtie …. A simplified fusion of

Fault Tree Analysis and Even Tree Analysis

FTA + ETA = BowtieEffective risk management is only possible if people are assigned responsibilities for controls via HSE-Critical Tasks

Visible

links are made to

HSE-critical systems

and competenciesBowtie methodology demonstrates not only

what controls are in place today and their effectivenessUsed in Oil & gas , Aerospace, Railways6

Bowtie Analysis

Bowtie analysis for high risk Activities

ALARP

Bowtie Analysis

8

Bowtie Analysis

9

Terminology

Top event

-

no catastrophe yet but the first event in a chain of unwanted events.

Threats - The top event can be caused by

(

sufficient or necessary causes).

Consequences

- The top event has the potential to lead to unwanted consequences. Barriers -

Preventive or mitigate measures taken to prevent threats from resulting into the top event. Escalation factor - a condition that defeats or reduces

the effectiveness of a barrier. 10

Bowtie analysis – Development

Describe unwanted event for the Bowtie Knot

Determine scope of analysis – operational

boundries

Identify threats that could cause the event

Identify possible

consequence

of the event

Select the optimum set of control to manage the causes and consequence of the eventIdentify failure mode

for important controlDetermine items for control assurance management

Case Study - Simple Pipe still Heater

12

Case Study – Gas fired Pipe Heater Explosion

13

Threats

Consequence

14

Threats Preventive Barriers Unwanted Event

15

Threats Preventive Barriers Unwanted Event

16

Threats

Preventive

Barriers

Unwanted Event

17

Threats Preventive

B

arriers Unwanted Event

18

Top event Mitigation barriers Consequence

Complete Bowtie Diagram

19

Swiss

cheese

model –Hazard -Barriers– Incident

Barriers in accident prevention

The

Hierarchy of

Hazard Control Methodology

Barrier system

Increased reliability

1. Accountability

2. Detect

– Decide - Act

3. Safety

Critical Task

4. Safety

Critical

Equipment

Simple application - Bowtie

- Car Incident

Why incidents happen

.

Swiss cheese model

Organisations manage risk using ‘barriers’

Barriers – use of equipment, design of plant (redundancy, overflows, etc.), following rules, procedures, standards …… usually barriers are people doing a job

Barriers are ‘functions’

Why do barriers fail? & Weakness in Incident causation path

An organisation

Error / violation promoting conditions

That influences the person

Creates

To take action or inaction

That causes barriers to fail

That result in

Accidents, incidents and business upsets

SMS

Leadership

Culture

Performance influencing factors (PIFs)

Competence

Fatigue

Environment

Supervision

Task

Etc.

Human action or inaction

slips, lapses, mistakes, violations

Underlying causes

Immediate causes

Preconditions

1. Detect – Decide - Act

2. Safety

Critical Equipment 

3. Safety

Critical

Task

4. Accountability

Types of Barrier in Bowtie

End users of Bowtie Analysis

Bow tie is Visual risk depiction tool for a failure mode situation

Technician

– Look for Hardware controls –active & passive

Supervisor

– Look for administrative controls - Health of

controls

Manager

- Identify weak links in controls & monitor Sustained Operational discipline &

timely maintenance & Skill development.

Thanks

29

Questions?

30

31

HAZARD IDENTIFICATION Techniques

Commonly used :

HAZOP

- Identifies

“process plant” type

incidents(time consuming)

What

If

Analysis

- Possible outcomes of change(high dependency of skills) FMEA/FMECA

-Equipment failure causes (Extremely time consuming)Task Analysis-(JSA ) Maintenance etc, incidents (Does not address process deviations

Fault Tree Analysis-Combinations of failures(identified the incident first& difficult to update )

Checklists-questions to assist in hazard identification(no new

hazard types are identified)HAZAN -Risk ranking tools are used Dow index OR MOND index