Engineers View of Human Error - Kletz

8/3/2019 Engineers View of Human Error - Kletz

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AN ENGINEERS VIEW OFHUMAN ERROR

Trevor Kletz

Loughborough University


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ALL ERROR IS HUMAN ERRORAS:

People have to decide what to do.

People have to decide how to do it.

People have to do it.


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The concept of human error

is unhelpful as it lumps

together different typeswhich need different

actions.


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TYPES OF HUMAN ERROR1 MISTAKES

Does not know what to do -

Poor training or instructions.

Intention wrong.

,


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TYPES OF HUMAN ERROR

2 VIOLATIONS

Does not want to do it -

Poor motivation


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TYPES OF HUMAN ERROR

3 MISMATCHES

Is not able to do it -

Beyond ability


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TYPES OF HUMAN ERROR:

4 SLIPS OR LAPSES OF

ATTENTION.Inevitable from time to time.


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THIS CLASSIFICATIONHELPS US SEE THE

BEST METHODS OFPREVENTION FOR EACH

TYPE OF ERROR.


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PREVENTING MISTAKES

Teach flexibilityProvide training and instructions

Make task easierAvoid contradictory instructions

(What you dont say is asimportant as what you do say.)


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Human Error

Are your instructions written

to help the readers or protectthe writer?


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PREVENTING VIOLATIONS

Explain need

Make task easier

Checks and audits

Dont turn a blind eye


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BEFORE BLAMING SOMEONE ASK:

Were the rules known & understood?Was it possible to follow them?

Were the reasons for them known?

Were previous violations overlooked?

Did the rules cover the problem?

Was he/she trying to help?


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Human Error

AN IRREGULAR VERB

I SHOW INITIATIVE

YOU BREAK THE RULES

HE IS TRYING TO WRECK THE JOB


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If instructions are wrong (dueto ignorance or slips)violations can preventaccidents

Human Error


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A good method of

persuasion is to discussaccidents and let those

present say what they think

should be done.


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Impossible tasks

Overload

Underload

Habit breaking

Mind-sets

REASONS FOR MISMATCHES


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PREVENTING MISMATCHES

Change Work Situation

ie, design or methods ofworking


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PREVENTING SLIPS ANDLAPSES OF ATTENTION

(Intention correct but notfulfilled)

Change work situation


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SLIPS & LAPSES OFATTENTION OCCUR ONLY

WHEN PEOPLE ARE WELL-

TRAINED.


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MANAGERS & DESIGNERS

ERRORS:are rarely slips as there is

usually time to check.

Sometimes violations.Usually mistakes.


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CHAOSSLIPS & LAPSES OFATTENTION

CHAOSMISMATCHES

Unable to do it

Persuasion/CHAOSVIOLATIONS Decides not to do it

Better training &instructions/CHAOS

MISTAKES Does notknow what to do

ACTIONERROR TYPE

CHAOS = ChangeHardware And/Or Software


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Early chloroform dispenser

From air

bulb

To face

mask


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Typical Piping

Settling Leg arrangement


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Phillips 66 IncidentOctober 23, 1989

23 lives lost

More than 130 people injured $750 million in property damages

Explosive Force = 2.4 tons of TNT


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DURING ROUGH WEATHER

WATER ENTERED SHIPS

ENGINE ROOM THROUGH

VENTILATION INTAKE AS

LOUVRES WEREINSTALLED INCORRECTLY.


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Wrong Right


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WATER FELL ON

SWITCHBOARD.

ALL POWER LOST.SHIP TOWED TO PORT.


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RECOMMENDATION:

INSPECT LOUVRES.

NO MENTION OF DESIGN


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PROBABILITY OF SUCCESS -

TOTAL

0.9999 x 0.9995 x 0.9998 x 0.9985 x 0.9998 x 0.9996

= 0.9971

ie, three or four errors canbe expected in every 1000operations.


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Figure 5

Temperature recordercontroller

& high temperaturetrip

Temperature recordercontroller

& high temperaturetrip

Furnace A Furnace B

Auto Hand control Auto Hand control


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ACTIONS IN ORDER OF

CHOICE1 Avoid hazards by IS design

2 Passive protection

3 Active protection

4 Procedures

5 Behavioural science


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OPERATORS ARE THELAST LINE OF DEFENCE.

STRONG OUTERDEFENCES REDUCE THE

DEMANDS ON THEM.


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CAN THE TECHNIQUES OF

BEHAVIOURALSCIENCE BEEXTENDED TO INCLUDEE

DESIGNERS ANDMANAGERS?


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DONT ASK FOR CAUSES.ASK WHAT WE SHOULD DO

DIFFERENTLY.

DONT SAY AN ACCIDENT WAS DUE TO

POOR DESIGN, MAINTENANCE,

OPERATION etc.

SAY IT COULD BE PREVENTED BY

BETTER DESIGN, MAINTENANCE,

OPERATION etc.


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Blaming human error

diverts attention from

what can be done by

better engineering.


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ERRORS BY DESIGNERS

TURN OPERATORS

SLIPS INTO ACCIDENTS.


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We cannot change the human

condition but we can change the

conditions in which humans work.

- James Reason


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Man was a creature made at the

end of a weeks work. when

God was tired. - Mark Twain

Engineers View of Human Error - Kletz

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