Design for safety

NURUL IKHMAR IBRAHIM SCHOOL OF MANUFACTURING ENGINEERING

UNIMAP

DESIGN FOR SAFETY

Course Outcome

CO 3: Ability to analyze and

evaluate products’ safety

using suitable methods.

Today’s topic

Safety Definition Designing Safe

Products

Safety Problems &

Human Failures

In Malaysia , home is second to road as a place

for injury morbidity and mortality. There were 13,401

home injury cases and of which 44 cases (0.3%) were

fatal.

Products such as floor and flooring surface, stairs,

furniture, toys and baby walkers had been identified

as factors that could contribute to injury.

Source: Hasni, H., Junainah S. and Jamaliah J., 2003, Epidemiology of

Home Injury in Malaysia

SAFETY DEFINITION

WHY? PRODUCTS ARE UNSAFE TO USE

SAFETY DEFINITION

Most product safety problems

arise from improper product use

rather than product defects.

THOMAS A. HUNTER

SAFETY IS FREEDOM FROM

DANGER, INJURY OR DAMAGE

HARM

Physical injury or damage

to the health of people or

damage to property or the

environment.

[ISO/IEC Guide 51:1999, definition 3.3]

SAFETY DEFINITION

HAZARD

Potential source of harm.

[ISO/IEC Guide 51:1999, definition 3.5]

SAFETY DEFINITION

ERGONOMICS HAZARD

In terms of users’ mental &

physical capabilities, which

include:

1. Body dimension.

2. Strength & posture.

3. Frequency, duration &

intensity of task/work.

4. Information processing

(Human error)

5. Environmental factors

SAFETY DEFINITION

RISK

Combination of the

probability of occurrence of

harm and the severity of

that harm.

[ISO/IEC Guide 51:1999, definition 3.2]

SAFETY DEFINITION

DANGER

A combination of risk and

probable hazard

consequences.

SAFETY DEFINITION

Today’s topic

Safety Definition Designing Safe

Products

Safety Problems &

Human Failures

INFLUENCES OF CONSUMER SAFETY m

icro

m

ac

ro

SAFETY INFORMATION

Government Standards Industry

Consumer behaviour Conditions of use

PRODUCT

DESIGN

CONSUMER SAFETY

People can cause or contribute to

accidents – human failures.

THERE ARE 2 CAUSES OF

HUMAN FAILURES

THERE ARE 2 CAUSES OF

HUMAN FAILURES

VIOLATIONS ERRORS + INJURY, DEATH & DAMAGE =

HUMAN ERROR IS THE FAILURE

OF PLANNED ACTIONS TO

ACHIEVED THEIR DESIRED

NEEDS

It is suggest that human error is a

primary cause of 60-90% major

accidents.

There are 2 basic types of

human error:

1.Skill-based error

2.Mistakes

HUMAN ERRORS

Skill-based error

Involve routine tasks in familiar

situations.

May cause by inattention or

over attention.

Two categories – slips and

lapses

HUMAN ERRORS

Slips

Failure of execution of planned

tasks i.e. ‘action-not as-

planned’.

May be due to distraction from

task or preoccupation with other

things.

SKILL-BASED ERROR

Slips – examples

Picking up the wrong

component from a mixed box.

Omitting a step or series of

steps from a task.

Performing the action in the

wrong direction (e.g. turning a

control knob to the right rather

than the left.

SKILL-BASED ERROR

Lapses

Failures to carry out an action

due to forgetfulness (memory

failures).

Can be reduced by minimising

distractions and interruptions to

tasks and by providing effective

reminders.

SKILL-BASED ERROR

Lapses – example

SKILL-BASED ERROR

Mistakes

Do the wrong thing believing it

to be right.

Two types of mistakes – rule-

based and knowledge-based.

HUMAN ERRORS

Rule-based mistakes

Occur when our behaviour is

based on remembered rules or

familiar procedures.

It is called rule-based because

we apply rules of the kind: if

(this situation) then do (these

actions).

MISTAKES

Rule-based mistakes -

example

MISTAKES

Knowledge-based

mistakes

May occur when we have to

think our way through a novel

situation for which we do not

have a procedure or “rule”.

Make wrong judgement due to

insufficient knowledge or

experience (lack of expertise).

MISTAKES

Knowledge-based

mistakes - example

MISTAKES

VIOLATIONS ARE ANY

DELIBERATE DEVIATIONS FROM

RULES, PROCEDURES,

INSTRUCTIONS & REGULATIONS

There are 3 categories of

violations:

1.Routine

2.Situational

3.Exceptional

HUMAN ERRORS

Routine

Breaking the rule or procedure

has become a normal way of

working within the work group.

VIOLATIONS

Routine - example

VIOLATIONS

Situational

Breaking the rule is due to

pressures from the job such as

being under time pressure, the

right equipment not being

available, or even extreme

weather conditions.

VIOLATIONS

Situational – design features which increase

violation

VIOLATIONS

Situational - example

VIOLATIONS

Exceptional

Rarely happen and only then

when something has gone

wrong.

VIOLATIONS

Exceptional - example

VIOLATIONS

Today’s topic

Safety Definition Designing Safe

Products

Safety Problems &

Human Failures

SAFE PRODUCT DESIGN CAN BE

ACHIEVED VIA 3 COMBINED

APPROACHES

Intrinsic Safety

Focused on immediate/initial

use.

Minimizes direct injury from

device (e.g. sharps, burns)

DESIGNING FOR SAFETY

Ergonomic Safety

Focused on repetitive and/or

long-term use.

Minimizes fatigue and

cumulative injury effects (e.g.

carpal tunnel)

DESIGNING FOR SAFETY

Usable Safety

Focused on full life-space of

product use.

Minimizes opportunities for

incorrect use (e.g. overdose)

DESIGNING FOR SAFETY

SAFE PRODUCTS CAN BE

DESIGNED THROUGH ERGONOMICS

EVALUATION METHOD

What should you

evaluate?

The features of the product.

DESIGNING FOR SAFETY

#1

What should you

evaluate?

The physical and psychological

characteristics of the user.

DESIGNING FOR SAFETY

#2

What should you

evaluate?

How the product will be used,

associated with tasks and

activities.

DESIGNING FOR SAFETY

#3

What should you

evaluate?

Environmental factors.

DESIGNING FOR SAFETY

#4

The evaluation must consider

all stages of product’s

lifecycle.

A

FRAMEWORK

FOR

PRODUCT

EVALUATION

PROCESS

Some useful guidelines:

Designer must avoid any design which expects

or requires individual/users to:

Exceed their physical strength.

Perform too many functions simultaneously.

Detect and process more information than is possible.

Perform meticulous task under difficult environmental

conditions.

Work at peak performance for long periods.

Work with tools in cramped spaces, etc.

EXAMPLES OF EVERYDAY

PRODUCTS

Figure 1 : Labelling around the

programme control is difficult to

read

Figure 2 : Protruding dials are

easy to grip and the labelling

easy to see

A B C

Figure 3 : Interface design of microwave ovens. Design A combines

simplicity and functionality. Design B and C leads to confusion and

many user errors

Figure 4 : Switches which are identical in shape and arranged in one-

dimensional row make it more possible to commit error. There are two

solutions: place a visual display with the switches (A) or arrange the

switches to match the room layout (B)

A B

Figure 5 : Which control goes to

which burner?

Figure 6 : Full natural mapping of controls and burners

Figure 7 : A typical power

plant control room

Figure 8 : Make the controls look and

feel different. The control-room

operators in a nuclear power plant tried to

over come the problem similar-looking

knobs by placing beer-keg handles over

them

Make sure that the user can

figure out what to do!

Make sure that the user can tell

what is going on!

References

Ergonomics and Safety in Consumer Product Design, B.

Norris and J.R. Wilson in Human Factors in Product

Design: Current Practice and Future Trends. (2001)

Patrick W. Jordan and William S. Green

Rapid Alert System for non-food products posing a

serious risk (RAPEX).

http://ec.europa.eu/consumers/ipm/risk_assesment_guid

elines_non_food.pdf

Designing safety into products, Beverley Norris and John

R. Wilson

http://person.hst.aau.dk/pm/ab/DSP.pdf

References

MS ISO 12100:2012 Safety of machinery - General

principles for design - Risk assessment and risk

reduction