Copyright © 2011 Underwriters Laboratories Inc. ® All rights reserved HAZARD ANALYSIS: Hazard Based Safety Engineering & Fault Tree Analysis Tom Lanzisero,

Copyright © 2011 Underwriters Laboratories Inc. ® All rights reserved

HAZARD ANALYSIS:Hazard Based Safety Engineering

&Fault Tree Analysis

Tom Lanzisero, UL

Slide 2

What do we mean by Safety, Risk, Harm and Hazard?

What is Hazard Based Safety Engineering (HBSE)?

What is Fault Tree Analysis? How do these Hazard Analysis

tools help us meet our Safety Objectives?

Slide 2

Hazard Analysis

Slide 3

Keep it Simple, but…

“Everything should be made as simple as possible, but not one bit simpler.”

Albert Einstein

Slide 4

SAFETY - freedom from unacceptable risk RISK - combination of the probability of

occurrence of harm and the severity of that harm HARM - physical injury or damage to the health of

people, or damage to property or the environment HAZARD - potential source of harm

Example Definitions (International Safety Community):

ISO/IEC Guide 51, Safety aspects – Guidelines for their inclusion in standards

ISO – International Organization for Standardization; IEC – International Electrotechnical Commission

Slide 4

Safety Terms

Slide 5

Expressing Relative Risk

Pro

ba

bili

ty o

f Ha

rm (

P)

Severity of Harm (S)

P x S = constant P x S = constant

Higher

Risk

Higher

Risk

Lower

Risk

Lower

Risk

Slide 6

Hazard Analysis

Hazard Analysis - Determine what harm can occur and how– What: Harm types, degrees, potential sources (hazards)– How: Harm mechanisms, conditions and causes

Hazard Based Safety Engineering (HBSE)– Systematic process - design / evaluate– Addresses conditions and mechanisms: harm protection– Analysis tools include 3-Block Model and FTA Model

Fault Tree Analysis (FTA)– Graphical representation of causes of a fault (undesirable event)– Covers conditions, events, root causes and logical relationships– Analyzes harm and protective measures, strategies and priorities

Slide 7

Surroundings Transfer Susceptible Entity

General Model for Harm

HARM: due to improper transfer between a susceptible entity and its surroundings

Harm to:PersonsProperty

Environment

Too much / too fast(Hazardous)

Too little / too slow(Needed)

Energy /Material

Slide 8

Model for Harm from a Hazard

HazardousEnergy,MaterialSource

TransferSusceptible

PersonProperty

Environment

HAZARD(Potential source of Harm)

HARM(Injury / damage)

Slide 9

HBSE 3-Block Model for Injury

Mechanical (kinetic) energy(e.g., moving part)

Electrical energy(e.g., live part)

Thermal energy (heat)(e.g., hot surface)

Contact

Contact(current thru

body impedance)

Contact(conductive heat flow)

Laceration to hand(minor to severe)

Ventricular fibrillation(lethal)

Skin burn(1st, 2nd, 3rd degree)

HazardousEnergySource

TransferMechanism

Susceptible Body / Part

E.g.,

Slide 10

Protection Strategies

HazardousSource

Transfer SusceptibleEntity

Eliminate (inherently safe), limit, or control

the hazard

Eliminate, limit or control the

transfer (exposure)

Decrease the susceptibility of

the entity to harm(as applicable)

Slide 11

ENERGY TRANSFERHAZARDOUS

ENERGY

INJURY

BODILYEXPOSURE

AND

Fault Tree Analysis (FTA)

HBSE Fault Tree for InjuryTop Level Model

Slide 12

ENERGY TRANSFERHAZARDOUS

ENERGY

INJURY

BODILYEXPOSURE

AND

Hazardous

Energy

Source

Transfer

MechanismBody

Susceptibility

Fault Tree with 3-Block Model

Slide 13

Expanding the Fault Tree Model

Top Event(System Fault)

Minimum,concurrent,

necessary & sufficient

conditions

Primary Events(Root Cause)

From generalto incrementallymore specific

categories

ENERGY TRANSFERHAZARDOUS

ENERGY

INJURY

BODILYEXPOSURE

AND

OROR

Hazard DueTo Fault

~~~~AND

….

ANDAND

….

~~~~AND

….

ANDAND

….

Root cause failures of Protective Measuresintended to eliminate, limit or control

Energy / Material Transfer

Root cause failures of Protective Measuresintended to eliminate, limit or control

Hazards

IntermediateConditions / Situations /

Events

Individualor In

combination

Hazard in Normal Condition

Hazard in Normal Condition

Slide 14

HBSE Fault Tree Model for Injury

ENERGY TRANSFER

INJURY

AND

INADEQUATEPERSONAL

SAFEGUARD

PERSONALSAFEGUARD

FAILURE

NOPERSONAL

SAFEGUARD

OR

INADEQUATEPERSONALAVOIDANCE

AVOIDANCENOT

POSSIBLE

AVOIDANCENOT

ATTEMPTED

OR

BODILYEXPOSURE

AND

INADEQUATEEQUIPMENTSAFEGUARD

EQUIPMENTSAFEGUARD

FAILURE

NOEQUIPMENTSAFEGUARD

OR

INADEQUATEEQUIPMENTSAFEGUARD

EQUIPMENTSAFEGUARD

FAILURE

NOEQUIPMENTSAFEGUARD

OR

HAZARDOUSENERGY

AND

(EVENT)

OR

(EVENT)

OR

Slide 15

ENERGY TRANSFER

INJURY

AND

INADEQUATEPERSONAL

SAFEGUARD

PERSONALSAFEGUARD

FAILURE

NOPERSONAL

SAFEGUARD

OR

INADEQUATEPERSONALAVOIDANCE

AVOIDANCENOT

POSSIBLE

AVOIDANCENOT

ATTEMPTED

OR

BODILYEXPOSURE

AND

INADEQUATEEQUIPMENTSAFEGUARD

EQUIPMENTSAFEGUARD

FAILURE

NOEQUIPMENTSAFEGUARD

OR

INADEQUATEEQUIPMENTSAFEGUARD

EQUIPMENTSAFEGUARD

FAILURE

NOEQUIPMENTSAFEGUARD

OR

HAZARDOUSENERGY

AND

(EVENT)

OR

(EVENT)

OR

Fault Tree Protection Strategies

ELIMINATETHE

HAZARD

1

GUARDAGAINST THE HAZARD

(Energy / Exposure)

2

WARNOF

HAZARD

3

Slide 16

Thanks! Questions?

Thomas Lanzisero, P.E.Sr. Research Engineer

[email protected]+631-546-2464

For more, please see Applied Safety Science and Engineering Techniques (ASSETTM)Paper published and presented at 2010 IEEE Symposium on Product Compliance

Engineering, sponsored by IEEE Product Safety Engineering Society:

http://www.uluniversity.us/common/ncsresponse.aspx?rendertext=thoughtleadership#research_development

Underwriters Laboratories (UL)1285 Walt Whitman Rd

Melville, NY 11747-3081 USAwww.ul.com