Suva Exemplu Metoda-e Brici

Risk of an injury causedby a saw blade withoutany safetymeasures

The Suva methodfor the risk assessment of technical devices and equipment

Risk of an injury causedby a saw blade with safety measures

R1

R2

Working safely

SuvaSwiss national accident insurance fundOccupational safetyP. O. Box, CH-6002 LucerneTelephone 041 419 51 11Fax 041 419 59 17 (for orders)Website: www.suva.ch

The Suva method for the risk assessment of technical devices and equipment

Authors: Mauritius Bollier, Fritz Meyer, Technology section (ALT)

Reproduction stating source permitted.1st issued – July 1990Revised – July 200216th edition – July 2002

Order number: 66037.e

This publication has been issued for use

by the manufacturers and other suppliers of

machinery. It describes a method of risk

analysis and risk assessment for technical

devices and equipment and contains

specific assistance for the compilation of

a technical documentation in accordance

with Machinery Directive 98/37/EC.

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Overview of the procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 How does an incident occur? . . . . . . . . . . . . . . . . . . . . . . . . 7

5 The causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

6 An example based on a circular saw . . . . . . . . . . . . . . . . . . 9

7 Description of the data used in risk assessment and risk reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

8 Determining the limits of a machine . . . . . . . . . . . . . . . . . . . 118.1 Limits of a machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118.2 Listing and describing the life-cycle and operating modes

of a machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118.3 Determining where the machine is to be used . . . . . . . . . 128.4 Identifying the persons involved . . . . . . . . . . . . . . . . . . . . 12

9 Identifying danger situations . . . . . . . . . . . . . . . . . . . . . . . . 169.1 Establishing dangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169.2 Listing danger situations . . . . . . . . . . . . . . . . . . . . . . . . . 189.3 Investigating incidents and their causes . . . . . . . . . . . . . . 18

10 What does «risk» mean? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

11 Risk estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

12 Risk evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2412.1 Formulating safety objectives . . . . . . . . . . . . . . . . . . . . . 2412.2 Determining an accepted risk . . . . . . . . . . . . . . . . . . . . . 2412.3 Risk classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

13 Risk reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2713.1 Choice of safety measures . . . . . . . . . . . . . . . . . . . . . . . 2713.2 Assessment of the safety measures . . . . . . . . . . . . . . . . 29

14 Contents of the technical documentation . . . . . . . . . . . . . . 3014.1 Description of the solutions . . . . . . . . . . . . . . . . . . . . . . . 30

15 Further information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3

Table of contents

In accordance with the Federal Law on the safety of technical devices and equip-ment (STEG), Article 3, the following requirements apply to the manufacturing or introducing of technical devices andequipment:

When used appropriately and with care,such technical devices and equipmentmust not endanger the life and/or health of users and third parties and they must fulfil the essential health and safety require-ments.

If no essential health and safety require-ments have been specified, they must havebeen produced according to recognizedtechnical principles.

For machinery, the essential health andsafety requirements according to Annex I of Machinery Directive 98/37/EC (formerly89/392/EEC) will apply. The third prelimi-nary observation to Annex I of theMachinery Directive states that:

«The manufacturer is under an obligationto assess the hazards in order to identifyall of those which apply to his machine;he must then design and construct it taking account of his assessment.»

The Machinery Directive also requires thatmeasures must be taken to avoid the riskof accidents associated with the machine.

To demonstrate that the technical device or the equipment satisfies all essentialhealth and safety requirements, the person(s) manufacturing or importing the machine must provide a technical documentation.

This documentation must also include a description of the solutions that have beenselected to eliminate or limit the risks in-herent in the use of the machine.

This publication will show you how to carryout the risk assessment systematically. The procedure described is based on theprocedural steps that are given in EN 1050«Safety of machinery – principles for risk assessment».

This is concluded by a description of thedata that can be used for the technicaldocumentation.

The completeness of a risk assessment is decisive for its quality. A result that is ascomplete as possible can only be achievedby means of cooperation between differentexperts who are familiar with the product.For example, cooperation between per-sons from the fields of design, installation,purchasing, sales, occupational safety isdesirable. Users should also be included in the risk assessment.

4

1 Introduction

Fig. 1: Overview of the procedure for risk assessment and risk reduction.

5

2 Overview of the procedure

Ris

k an

alys

is

Ris

k re

du

ctio

nTe

chn

ical

do

cum

enta

tio

nR

isk

asse

ssm

ent

Determining the limits of amachine

Identifying hazardous situations

Risk estimation

Risk evaluation

No further safety measuresnecessary

Select safety measure

Definition of intended use in the operating instructions.Description of the safety measures selected to preventany risks arising from the use of the machine and information on residual risks. A description of residualrisks for which no safety measures are necessary is also recommended.

Is the machine

safe?

NO

YES

Danger:

Danger zone:

Danger situation:

Hazard:

Causes:

Incident:

Origin of an injurious action. Depending on its current effect, the danger can be active or latent.

The zone in which an injurious action will spread.

A situation in which a person is close to a danger. There are three types of danger situations:

A person next to a latent danger

A person in the area of a latent danger

A person next to an active danger

A danger situation in which a person is in the area of a latent danger.

Influences that can change a danger situation and lead to an incident. The causes change the position of the person with regard to the danger zone and/or the activity of the danger.

An incident takes place when a person is exposed to an injurious effect.

6

3 Terminology

Active danger

Danger zone

Latent danger

The co-incidence of an injurious effect and a person is a prerequisite for an incident happening.

The injurious action originates from an active danger.

A danger situation arises when a danger and a person are in close proximity to each other.In these situations, the prerequisite for an incident is incomplete. Causes can change thesesituations in such a manner that a person finds him-/herself in the danger zone of an activedanger. The person is then exposed to an injurious action that results in an incident.

Fig. 2: How an incident occurs.

7

4 How does an incident occur?

Pre-requisite

Dangersituation

Incident

Danger (active or latent)

Person enters thedanger zone

Danger becomes active Person enters the danger zone

Danger becomes

active

Co-incidence Person

or or

Cause Cause

Cause Cause

An injurious action

Prerequisite

affects a person an incident=

Two types of cause can occur:

� A change in the activity of the danger(e.g. a machine can start up unexpec-tedly)

� A change in the position of the person in relation to the danger (e.g. the personenters the danger zone of a rotating sawblade).

Dangers are created when a designer designs a machine. The designer mustmake sure that, with any inherent dangersituations of the machine, the probability of an incident occurring is kept to a mini-mum. Any conceivable residual incidentsmust be prevented by instructing the per-sons who might be involved in a danger situation. All causes that can lead to an incident are therefore dependent on a person's ability, knowledge and intentions.

8

5 The causes

Disposal specialist

Inadequate equipment, . . .

Lack of product information, . . .

Convenience

Disposal

User

Physical size, concentration, reflexes, . . .

Lack of product information, . . .

Ignoring applicationinstructions, absence of a safety culture

Use

Production

Lack of experience in manufacturing and installation, . . .

Lack of material skills, . . .

Cost-cutting, . . .

Manufacture

Design

Over-estimation of one’s abilities, pressureof time . . .

Lack of training, unforeseeable situations, . . .

Cost-cutting, . . .

Development

CausesIncomplete orwrong applicationinstructions

Faulty product properties Careless use of product or non-compliance with instructions

Fig. 3: Overview of causes.

Responsibility

Human qualities:

– inability

– ignorance

– unwillingness

Product life cycle

The following example again demonstratesthese inter-relations.

A machine operator (person) is workingwith a circular cut-off saw (danger: e.g. thekinetic energy and teeth of the saw blade).Whenever the machine operator is close to the saw blade, a danger situation iscreated.

Fig. 4: How an incident arises, an example based on a circular saw.

9

6 An example based on a circular saw

Danger

The saw blade inthe machine

Machine operator

The machineoperator reaches into thedanger zone ofthe saw blade.

The machine opera-tor is in the dangerzone of the non-rotating saw blade.

The saw isstarted.

The machine ope-rator is next to thedanger zone ofthe non-rotatingsaw blade.

The machine ope-rator is next to thedanger zone of therotating saw blade.

The machine operator reachesinto the danger zone of the rotating saw blade.

The saw isstarted.

Person

Cause Cause

The machine operator isin the danger zone of therotating saw blade:The person is injured.

Cause Cause

If the machine operator touches the teethof the rotating saw blade when moving the section to be cut off, an incident willoccur (personal injury). Possible cause: The designer did not provide for an ade-quate guard.

Pre-requisite

Dangersituation

Incident

Co-incidence

or or

The tables on pages 32 and 33 are recom-mended (templates for copying) as they will help you to follow the individual stepsinvolved in risk assessment and risk reduc-tion.

The information collected is then easy tofollow. It may be useful to produce andcomplete the tables on an EDP system.

10

7 Description of the data used in risk assessmentand risk reduction

To enable a risk assessment to be carriedout, all the foreseeable danger situationsmust be identified in connection with the intended use of the product.

8.1 Limits of a machine

Limitations of use

The intended use of the machine is described first. «Intended use» is the usefor which the machine has been built. Any reasonably foreseeable misuse musttherefore also be taken into account.

Attention must be paid to:

– Any foreseeable incorrect action arisingfrom normal inattention

– Any reflexes in the event of a malfunction

– Any unsafe action as users take the«path of least resistance»

– Any use of the machine in a non-profes-sional field (in this case, no technicalskills can be presumed)

Intentional misuse of the machine is nottaken into account.

Space limits

Limit the system, establish subsystems:

The scope of the system to be assessed is clearly set out on drawings or in descrip-tions. The limits must be set in such a manner that the machine to be assessed iscovered completely (inc. cable and plug,etc.) and that an assessment is truly practi-cable. Extensive systems must be split upinto clearly separate subsystems to enableeither sub-assemblies, functional units, individual parts or components to be examined.

Indicate any interfaces:

Following this limitation procedure, the interfaces with other systems must beshown and described. Interfaces arise, for

example, with buildings, other technicalsystems, energy providers as well as withthe environment. The interfaces with the adjacent subsystemmust be shown for each subsystem created. As subsystems influence each other, the necessary conclusions must bedrawn.

Time limits

The working life of the entire machine or – if necessary – of parts of the machine(tools, wear-out parts, electrical compo-nents, etc.) is laid down with due regard for intended use.

8.2 Listing and describing the life-cycle and operating modes of a machine

Article 3 of the Federal Law on the safety oftechnical devices and equipment requiresthat the lives and health of users and thirdparties must not be endangered given appropriate and careful use.

All operating modes that are necessary forintended use must be described. Attentionmust be paid to the full life-cycle of the machine from its construction to its finaldisposal. This description of the operatingmodes can also be subsequently used for the formulation of the operating instructions.

Normal operation

Normal operation is theoperating mode in whichthe system fulfils the purpose for which it is intended and for which it has been built (for example, the normal operation of a circular saw: the cutting off of profiles).

11

8 Determining the limits of a machine

Fig. 5: Normal operation of a circular saw.

Special operation

All operating modes required to ensure normal operation are allocated to specialoperation.

For example:

– Installation

– Transport

– Test runs

– Clearing production faults

– Clearing machine faults

– Maintenance

– Dismantling

– Disposal

This list is not conclusive. However, the designer is in a position to lay down precisely the special operating modes of his machine.

8.3 Determining where the machineis to be used

The areas of use (e.g. industry, trade,household) in which the machine is expec-ted to be used must be stated.

8.4 Identifying the persons involved

Persons involved in normal operation

In normal operation, the persons affectedare those who work on the machine when it is being used appropriately. These are the users and the operators.

Persons involved in special operation

In the case of special operation, all thosepersons who ensure that the system canfulfil its intended purpose are affected bythe system. These are the persons who are responsible for the various jobs occur-ring in special operation (e. g. maintenancepersonnel).

Third parties

Third parties are persons who are only indirectly connected with the system. Forexample, they can be other members of the workforce, visitors or persons who arepresent by chance.

The limits of the machine based on a circular saw are described in table 1 onpage 13 and in Fig. 6 on page 14. The individual working steps in the opera-ting modes are described in the secondcolumn of table 2 on page 15.

12

13

Risk assessment: Determining the limits of a machineMachine: circular saw

Intended use, limitations of use:– Sawing of a clamped profile with a rotating saw blade– Resetting, retightening the profile and advancing the saw blade are done manually– Cutting maximum profiles of 80 x 100 mm in mild steels, non-ferrous metals and

synthetic materials

Space limits:Systems as well as the Influences that exceed the system limitations are marked on the drawings SN0.

Time limits:Operating life of the machine: 20 yearsConsumables: Operating life:– Tungsten-carbide saw blade 60 hours (depending on the materials being cut)– HSS saw blade 25 hours (depending on the materials being cut)– Drive belt 5 years

Live-cycle, The persons involvedoperating modes: User* Third Machine Electrician Trasport Disposal

parties operator operative specialist . . . . . . .

Construction X X X

Transport X X X X

Commissioning X X X

Use

Normal operation X X

Production fault X X

Machine fault X X X X

Cleaning X X

Maintenance X X

. . . . . . . . . . . . . . . . . . .

Decommissioning X X

Disposal X X X

. . . . . . . . . . . . . . . . . . .

* Training the user: no training presumed

Area of use: Trade, industry in interior locations with 10 amps power supply and a voltage of 400 volts

Date: 15.02.00 Visto: ay Page: 1 of 1

Tab

le 1

:D

eter

min

ing

th

e lim

its

of

a m

ach

ine

bas

ed o

n a

cir

cula

r sa

w.

14

Designation: Circular sawDrawing number: SN0

Subsystem:«Lighting»

Subsystem:«Cutting head»

Subsystem: «Profile»

Subsystem: «Machine operator»

System: «Machine operator using a circular saw in a workshop»

Subsystem: «Floor»Bearing force

Bearing force

Bearing force

Chips

Clamping moment

Clamping moment

Clamping force

Effort when resetting the profile

Cutting force

Clamping force

Clamping force

Hinge

Release force

Release force

Leve-

rage

Power supply

Chips

Chips

Light Light

Noise

Noise

Vibration

Radiated heat

Gra

vity

Pow

er o

f ad

vanc

e

Bearing force

Subsystem: «Clamping device with stand»

Fig. 6: System and interfaces based on a circular saw.

15

Risk assessment Machine: circular saw

Operating mode: Normal operation Subsystem: . . . . . . . . . . . . . . . . . . .

Severity of harm (S) Probability (P)I Death A frequentII Severe, permanent injury to health B occasionalIII Slight, permanent injury to health C infrequentIV Curable injury with incapacity to work D improbableV Curable injury without incapacity to work E almost impossible

Page 1 of .........Signature: ayDate: 15.02.00

No.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

No. No. Cause IncidentRisk

S P

Residualrisk

S P

Safetyobjective No. Measures Information

Descriptionof operatingmode

Placing theprofiles in the vice

Positioning theprofile

Clamping theprofile

Starting the saw

Lowering the sawblade

Making the cut

Raising the sawblade

Switching of the saw

Removing thesawn-off piece

Releasingthe profile

Removing the pro-file from the vice

Cleaning the vice

Danger situation

Danger Person in/danger zone

Table 2: Description of normal operation based on a circular saw.

9.1 Establishing dangers

All the danger that can occur in connectionwith the intended use of the machine withinthe individual subsystems and on the inter-faces between the systems must be iden-tified and documented. In addition, thedangers that can appear owing to a fore-seeable, anticipated use of the machinebased on reasonable considerations mustalso be identified.

Particular attention must be paid to the following points when looking for dangers:

� Each danger can have an injurious effect.

� The injurious effect spreads in the dangerzone.

� The injurious effect can either be per-manent or temporary, e.g. unexpectedstart-up.

The following list contains a selection ofpossible dangers. It must be supplementedaccording to the product. Further infor-mation regarding dangers can be found inEN 1050, Annex A.

Example of dangers in connectionwith machinery

1. Danger caused by the machine

– Crushing

– Shearing

– Cutting, severing

– Entangling

– Drawing in, trapping

– Impact

– Stabbing, puncture

– Friction, abrasion

– High pressure fluid injection or ejection

2. Danger caused by electricity

– Contact of persons with live parts

– Contact of persons with parts which have become live under faulty condi-

tions

– Approach to live parts under high voltage

– Electrostatic phenomena

– Effects from short circuits

3. Danger caused by thermal energy

– Touching extremely cold or hot solid materials, fluids or gases

– Fire, explosions, radiation from heat sources

– Cold or hot working environment

4. Danger caused by noise

– Effect on the hearing and balance, awareness

– Effect on speech communication, perception of acoustic signals

5. Danger caused by vibrations– Effects on nerves and vessels (in the case of hand-held tools)

16

9 Identifying danger situations

– Effects on the whole body (vibration felt by the whole body, particularly when combined with poor postures)

6. Danger caused by radiation

– Radiation with low frequency, radio frequency, microwaves

– Infrared, visible and ultraviolet light

– X-rays and gamma rays

– Alpha rays, beta rays, electron or ion beams, neutrons

– Lasers

7. Danger caused by materials and substances

– Contact with harmful fluids

– Inhalation of harmful gases, mists, fumes and dusts

– Fire and explosions

– Contact with biological or microbio-logical materials (viral or bacterial)

8. Danger caused by the neglect of ergonomic principles in machinery design

– Unhealthy postures, excessive efforts

– Inadequate consideration of human anatomy

– Neglected use of personal protection equipment

– Inadequate local lighting

– Mental overload and underload, stress

– Human error, human behaviour

– Inadequate design, location or identi-fication of manual controls

– Inadequate design or location of visual display units

9. Danger caused by a combination of different dangers

10. Danger caused by unexpected start-up

11. Danger caused by the impossibility of stopping the machine under the best-possible condition

12. Danger caused by changes in the rotational speed of tools

13. Danger caused by a power failure

14. Danger caused by control circuit failures

15. Danger caused by faulty fitting

16. Danger caused by break-up during operation

17. Danger caused by falling or ejected objects or fluids

18. Danger caused by a loss of stability/overturning

19. Danger caused by slipping, tripping, falling

20. Dangers in connection with special types of machinery

9.2 Listing danger situations

The possible danger situations are identi-fied by investigating whether an existingdanger can possibly have a negative effecton a person. Danger and person are entered under a number in the table.

17

9.3 Investigating incidents and theircauses

The causes can be determined by investi-gating how a danger situation must changeso that a person enters the danger zone of an active danger. The incidents can beestimated together with the causes found.These approaches must be followed for allsystems and their interfaces in all operatingmodes.

The following listing shows some examplesof causes.

18

Danger of cuts resultingfrom a rotating sawblade

Danger of cuts resultingfrom the teeth of the sawblade

Danger caused by stabbing by the sawblade during operationfollowing break-up

Danger caused by thesaw head falling

Danger caused by crushing at the hinge

Danger caused by vibrations

Danger caused by electricity

. . . . . . . .

Fig. 7: "Sawing head" subsystem in normal operation: risks during normal operation (selection).

1

1

2

3

4

5

6

7

8

4

6

23

5

7

Designation: Saw head subsystem

Drawing number: SN1

Dangers in normal operation:

Inability:

� Physical size

� Handicap

� Design faults

� Unfavourable ergonomics

� Pressure of time

� Over-estimation of one's abilities

� Lack of understanding

Ignorance:

� Poor information

� Lack of experience

� Incomplete operating instructions

Unwillingness:

� Convenience, path of least resistance

� Lack of reason

� Economy

An example of how to identify a possible incident with the relevant cause is given in table 3.

19




Page 1 of .........Signature: abDate: 15.02.00

No.

1.

No.

1.1

No.

1.1.1

1.1.2

Cause

Unexpected start-up after a power failure andoperator’s clothing istrapped by the saw blade

Unexpected start-up after a power failure whenmachine operator iscorrecting the position of the profile

Incident

Hand-and/orarm injury

Hand-and/orarm injury

Risk

S P

Residualrisk

S P

Safetyobjective No. Measures

Infor-mation

Description ofthe operatingmode

Place profileon support

Danger situation

Danger Person indanger zone

Cutting Hand orwith the arm ofrotating the operatorsaw in the areablade of the saw

blade

Table 3: Establishing incidents based on a circular saw.

Procedure for finding causes

If, in a given danger situation, the incident is known or if an incident can be presumed,a «fault tree» is a possible procedure to follow when investigating the individualchanges in the danger situation step bystep until the origin, the actual cause, has been found.

The use of the fault tree is shown in detail in Suva brochure 66025.e «Sample risk assessment for technical devices andequipment».

20

Injury caused by a rotatingsaw blade

Unexpectedstart-up

After a power failure

The saw is beingstarted

Being started by a second personwho has nooverview of thedanger zone from the point ofstarting

Machine opera-tor’s clothing is entangled by thesaw blade

Cut piece jamsbetween the pro-file and the stop

and

or

or or

Saw bladerotates

Fig. 8: Fault tree for the incident "User is injured by a rotating saw blade".

�

�

�

�

� �

�

Machine operators in thedanger zone ofthe saw blade

After the sawblade hasjammed in theprofile

Machine operatorintends to removethe cut piece

Machine operatoris correcting theposition of theprofile

21

10 What does «risk» mean?

An incident can arise from any specific danger situation with a certain degree ofprobability.

The

risk of a dangerous situation

is dependent on

the severity of the possible harmcaused by the incident

and by the

probability of occurrence

The probability of occurrence is deter-mined by the following factors:– The frequency and duration of the

danger situation that precedes the incident

– The probability of the incident occurringif the danger situation is present

– The possibilities for avoiding or limitingthe harm

The

risk when working with the saw blade

is dependent on

the severity of an injury by the sawblade

and on the

probability of occurrence, i.e. the probability of an injury

The probability of it occurring is deter-mined by the following factors:

– Exposure time, i.e. how frequently andhow long the machine operator workswith the saw each time

– The probability that the machine operator is injured by the saw bladewhile working with the saw

– The possibility of limiting the harm, e. g. by withdrawing a hand quickly

For example: a circular saw

Risk of a danger situation: a machine operator and a rotating saw blade

Fig. 9: A person operatinga circular saw.

The maximum harm possible and the probability of this harm are estimated foreach risk situation.

The following diagram can be used to depict the risk:

Matrix representation of a risk

Severity of harm

Based on the injury or the effect on per-sonal health of the persons concerned, the severity of harm can, for example, beallocated to the following categories:

I Death

II Serious, permanent injury, fails to healcompletely (irreversible), quality of lifesubstantially reduced

III Slight, permanent injury to health, fails to heal completely (irreversible), qualityof life is only slightly reduced

IV Curable injury with incapacity to work (reversible)

V Slight injury without incapacity to work(reversible)

Probability of occurrence

The probability of occurrence is dependenton the specific risk situation. Existing acci-dent data based on statistics can only beused if the risk situation preceding the acci-dent is always the same. For this reason,the probability of occurrence is usually eva-luated qualitatively. For example, its proba-bility can be recorded in the following cate-gories:

A frequent

B occasional

C infrequent

D improbable

E almost impossible

22

11 Risk estimation

Never

Risk X

Most serious injury

No injury Severity ofharm X

Severity ofharm

At any time

Probabilityof occur-rence X


Incr

easin

g risk

Fig. 10: Matrix representation of a risk.

If the probability of occurrence is still unclearduring the drafting phase of a product, a fairly high degree of probability should beset. The values can be corrected on receiptof subsequent, more precise information.

For example: Working with a circularsaw

The risk of an injury to the machine operatorcaused by the saw blade.

� Maximum severity of harm: Slight, perma-nent injury to health (injury to finger(s) orhand)

� Probability of occurrence: Based on thecauses, (machine operator inserts his/her hand in the danger zone of the sawblade, saw blade starts up), the probabi-lity of occurrence is assessed as being«occasional».

23

Curable injury with-out incapa-city to work(reversible)

Curableinjury withincapacity to work (reversible)

Slight, permanentinjury tohealth (irreversible)

Severe, permanentinjury tohealth (irreversible)

Death

frequent

occasional

infrequent

improbable

almost impossible

A

B

C

D

E


Fig. 11: Representation of risk based on a circular saw.

Risk of a dan-ger situation:«machine ope-rator and rota-ting saw blade»

V IV III II I

The Machinery Directive basically requiresthat the essential health and safety require-ments formulated in Annex I be fulfilled.These requirements are formulated partly as safety objectives and partly as specificdemands.

12.1 Formulating safety objectives

If the requirements cannot be met owing tothe given state-of-the-art technology, themachine must be designed and built in linewith the basic safety and health require-ments as far as possible.

A safety objective must be established foreach result obtained.

Formulating safety objectives describes the conditions that the solutions must fulfilin order to prevent any occurrence of thepossible incidents.

A neutral formulation of safety objectivesthat is wide in scope permits a larger selec-tion of solutions.

For the «circular saw» example given in thisbrochure, one of the safety objectives mightbe worded as follows:

Manual access to the danger zone of the rotating saw blade must not bepossible.

A more generally worded formulation mightread as follows:

It must not be possible for anyone tobe injured by the saw blade.

The difference between the two formula-tions becomes clear when solutions are required.

The safety objective first noted can be ful-filled if the saw is switched off when accessto the danger zone is necessary. In thecase of the second safety objective formu-lation, access by the user to the saw bladecannot be possible even when the machinehas been stopped, which necessitates asafety guard over the saw blade.

It often makes sense to prevent several incidents with one safety objective.

When the safety objectives have been for-mulated for all incidents, safety objectiveswith the same statement can be summa-rized. However, nothing important shouldbe omitted when doing so. This is particu-larly important for safety objectives relatingto special operation.

When the solutions are being formulated, it can be seen whether several safety objectives can be fulfilled by one solution.

12.2 Determining an accepted risk

Each machine will represent a certain riskor residual risk even after the best-possiblesolution at the time has been taken into account. It is the task of the designerto confine the residual risk to an acceptabledegree.

For this reason, it is important to reflect on the acceptable risk. The judgment onwhether a risk is acceptable or not is in-fluenced by numerous factors (see Fig 12).

24

12 Risk evaluation

25

Accepted risk Accepted risk

Accepted riskAccepted risk

Accepted risk

Accepted risk

Accepted risk

Accepted risk

Degree of self-determination Working environment Degree of voluntariness Cause

Minor degree ofself-determination:

Railway users areunwilling to acceptinjuries resultingfrom mistakesmade by the rail-way company.

Influenceson accep-table risks

Risk accep

tance

Major

Minor

Major degree ofself-determination:

Hang-glider pilotsaccept that theycan crash owing toerrors they make.

Clerical profes-sions:

Clerical workersare unwilling to ac-cept almost any in-juries resultingfrom their profes-sional activities.

Construction in-dustry:

Workers in the con-struction industryaccept minor, re-versible injuriesthat occur despitetheir adhering tosafety measures.

At work:

Persons generallyhave to work andare in a situation ofdependence whilethey work. Theywould thereforelike to carry outtheir activitieswithout their per-sonal health beingaffected.

At leisure:

In the case of voluntary activities,substantial risksare accepted tosome degree.

Cause independentof the user (faultyproduct proper-ties):

Lift users will notaccept any injuries,e.g. owing to a ca-ble breaking.

Cause dependenton the user:

A blow on the fin-ger is acceptedwhen hammering ina nail.

Fig. 12: Risk factors.

A se

lectio

n o

f facto

rs that in

fluen

ce th

e a

ccep

tan

ce o

f risks

In the field of machinery, the following influential factors can be of particular importance:

� Degree of voluntariness:

The persons who work with a machinemust earn their living and are in a situa-tion of dependence while at work. Theytherefore expect to be able to carry outtheir professional activities without anyprofessional injury to their health.

� Cause:

An injury resulting from a faulty product is neither accepted by law (Federal lawon the safety of technical devices andequipment, the Machinery Directive,product liability law) nor is it accepted by society.

The following matrix can be used to deter-mine the limits between an «acceptable»and an «unacceptable» risk with the help of the influential factors mentioned above.

12.3 Risk classification

In the example described in Fig. 14, occa-sional, insignificant injuries are tolerated. A fatal injury is, however, totally unaccep-table.

26

Fig. 13: Risk limitation.

No injuries Severe injuries

Severity of harm

Severityof harm

At any time

Never


Area of unacceptedrisk

Area of accepted risk = residual risk

Fig. 14: Risk limitation based on a circular saw

Curableinjurywithoutincapacityto work(rever-sible)

Curableinjury with incapacityto work(rever-sible)

Slight,perma-nent injury tohealth (irrever-sible)

Severe,perma-nent injury tohealth (irrever-sible)

Death

frequent

occasional

infrequent

improbable

almostimpossible

A

B

C

D

E


Risk acceptance limit

V IV III II I

Risk of an in-jury caused bya rotating sawblade withoutany safetymeasures

Area of unaccepted

risk

Area of accepted risk

Limit between «acceptable» and «unacceptable» risks

For all risks encountered in the area of un-accepted risks, solutions have to be foundand applied that reduce the risk originatingfrom the machine to an acceptable degree,i.e. the residual risks.

13.1 Choice of safety measures

When choosing an appropriate solution, amanufacturer must adhere to the followingprinciples in the order given (cf. MachineryDirective, Annex I):

1. Elimination or reduction of the risks(integration of the safety concept in thedevelopment and construction of themachine)

2. Inclusion of safety measures requiredto combat risks that cannot be elimi-nated

3. Informing users about the residualrisks due to shortcomings of the safetymeasures adopted; information on special training or personal protectionequipment that may be required

Fig. 15: Risk reduction.

27

13 Risk reduction

Safety measure:third priority:

Informing usersabout residualrisks and the correct behaviour

Safety measure:second priority:

Technical safetymeasures tocombat risksthat cannot beeliminated

Safety measure:first priority:

Elimination or reduction of the risk

1 2 3

An injurious action affects a person

an incident=

An example based on a circular saw:

Choice of safety measures:

1. Avoiding the risk, i.e. eliminating the rotating saw blade, is impossible in thiscase as the machine would otherwise no longer be able to fulfil its purpose.

2. The harmful effect of the rotating sawblade can be limited by a safety meas-ure, in this case by a pivoting safetyguard that encloses the saw blade as far as possible.

Fig. 16: Pivoting safety guard.

3. Owing to the incomplete effect of thesafety guard, users of the saw must beinformed about the residual risks. Amongother things, the following information isalso given in the operating instructions:

� When the saw blade is lowered, coverage is incomplete. Warning: It is forbidden to touch the rotating saw blade.

� Prior to cleaning, maintenance or repairs being carried out, the machine must be switched off at the main switch and secured with a personal padlock.

� The safety guard must be checked regularly for correct operation. If the safety guard is faulty, it must be repaired before the machine is started up again.

� In order to avoid eye injuries, all persons working in the area of the saw must wear safety goggles.

Hints on the search for solutions:

� The essential health and safety require-ments relating to the design and con-struction of machinery in Annex I of theMachinery Directive are binding.

� General design principles can be found inEuropean standard EN 292, parts 1 and2 (see Bibliography, page 34).

� Solutions are listed in the European safety standards. When implementingharmonized standard solutions, it is assumed that the essential health andsafety requirements are fulfilled. However, the following questions mustalways be clarified precisely:

– Is the standard still up to date?

– Is the risk situation on the machine to be built actually identical to the risk situation for which the standard solu-tion is intended?

– Does the standard not contradict essential health and safety require-ments?

� The examination of measures that havebeen implemented on other machineswith comparable risk situations helps tofind solutions with an acceptable risk.

28

Informing usersabout residualrisks:

Operating instructions

Warnings on themachine

Safety measuresto combat a risk that cannotbe eliminated:

Pivoting safetyguard

Elimination or reduction of the risk:

Impossible

1 2 3

Fig. 17: Risk reduction based on a circular saw.

An injurious action affects a person

an incident=

13.2 Assessment of the safety measures

The assessment of safety measures is carried out on the basis of the risk assess-ment described in the procedure in Fig. 1,page 5.

This ensures that the safety measure fulfilsits purpose and does not create any newrisk situations.

29

Severity of harmCurable

injury with-out incapa-city to work(reversible)

Curable injury withincapacity to work (reversible)

Slight, permanentinjury tohealth (irreversible)

Severe, permanentinjury tohealth (irreversible)

Death

frequent

occasional

infrequent

improbable

almostimpossible

A

B

C

D

E


Area of accepted risk

Area of unaccepted

riskRisk of an in-jury caused by a rotatingsaw blade with-out any safetymeasures

V IV III II I

Fig. 18: Assessment of safety measures based on a circular saw.

Risk of an injury causedby a rotatingsaw blade with safetymeasures

Where machinery is concerned, the require-ments for the technical documentation(technical file) are described in Annex 3 ofthe ordinance on the safety of technical devices and equipment (STEV). This de-scription in the STEV largely corresponds to the description of the technical docu-mentation given in Annex V of MachineryDirective 98/37/EC (formerly 89/392/EEC).

More specific information is also given inthe Suva publication «Type-ExaminationCertificate Process for Machinery accordingto EC Machinery Directive 98/37/EC [formerly 89/392/EEC] (Annex V/VI)», ordernumber CE93-15.e. The description of the solutions selected to prevent the risksoriginating from the machine represent an important part of the technical docu-mentation.

14.1 Description of the solutions

It is recommended that the results of therisk assessment and risk reduction be en-tered up in the same table that has beenused for the risk analysis. It is important togive a reason for each solution that is finallychosen in the column «Information».For the description of the solutions thathave been selected to prevent the risksoriginating from the machine, the columns«Measures» and «Information» can be used.

«Measures» columnThe solution chosen for the fulfilment of the corresponding safety objective must be described and reasons given for its selection. In this way, the choice of solutionis comprehensible.

«Information» column

References must be included whereversupplementary documents are required forthe assessment of the solution chosen.

Supplementary documents can consist of:

– Layout drawings, prospectuses, descrip-tion

– Design drawing

– List of parts

– Operating instructions

– Strength calculations

– Stability calculations

– Impact trials, fall trials of guards

– Functional schedule of safety devices

– Circuit diagrams for the channels relevantfor safety

– Component list for the channels relevantfor safety

– Hydraulic diagram

– Pneumatic diagram

– Failure effect analysis for the chosen solution

– Examination of corrosion issues

– List of materials used

– Test report

– Measurement report

– Component test

– Laboratory analysis

– Certificates

– Declarations by the manufacturer of purchased components

– Declarations of conformity for purchasedcomponents

– ...

30

14 Contents of the technical documentation

31




Page 1 of . . . .Signature: ayDate: 15.02.00

No.

1.

No.

1.1

No.

1.1.1

1.1.2

Cause

Unexpected start-upafter a power failureand operator’s clothingis trapped by the sawblade

Unexpected start-upafter a power failurewhen machine operatoris correcting the positionof the profile

Incident

Hand- and/or arm injury

Hand- and/or arm injury

Risk

S P

III B

III B

Residualrisk

S P

IV D

IV D

Safetyobjective

Nobody must be injured by a rotating saw blade

Nobody must be injured by a rotating saw blade

No. Measures

Pivoting saw bladeguard, warning on the machine, information in the operating instructions.

Pivoting saw bladeguard, warning on the machine, information in the operating instructions.

Infor-mation

*

*

Descriptionof theoperating mode

Place profileon support

Danger situation


Cutting Hand or armwith the of therotating operatorsaw in the areablade of the saw

blade

If the saw blade is in the upper end position, the blade is completely encapsulated. During sawing operations, some areas of the saw blade are open.User information in the operating manual and a warning on the machine warn against this residual risk.Assembly drawing no. . . . Saw unit with pivoting guard.

*

Table 4: Basis for a risk assessment and risk reduction based on a circular saw.

Risk assessment: Determining the limits of a machine

Machine: . . . . . . . . . . . . . . . . . . . . . . . . . . .

Intended use, limitations of use:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Space limits:Systems and influences that penetrate the system limits are marked on drawing SN0

Time limits:Operating life of the machine: . . . . . years

Wear-out parts: Operating life:

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Life-cycle, operatingThe persons involved

modes: Users* Thirdparties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Construction

Transport

Commissioning

Use

Normal operation

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

Decommissioning

Disposal

. . . . . . . . . . . . . . . . . . .

* User training: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Area of use: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Date: . . . . . . . .. . . . . . Signature:. . . . . . . . . . . . . . . . . . . . Page: . . . . of . . . .

32

Tab

le 5

:Ta

ble

fo

r d

eter

min

ing

th

e lim

its

of

a m

ach

ine.

Can

be

cop

ied

33

Risk assessment Machine: circular saw: . . . . . . . . . . . .

Operating mode: Normal operation Subsystem: . . . . . . . . . . . . . . . . . . . .


Page ..... of .....Signature: ...............Date: ...............

No. No. No. Cause IncidentRisk

S P

Residualrisk

S P

Safetyobjective No. Measures

Infor-mation

Descriptionof theoperating mode

Danger situation


Table 6: Table for the entry of data on risk assessment and risk reduction. Can be copied

34

Federal law on the safety of technical devices and equipment (STEG), SR 819.1,Ordinance on the safety of technical devices and equipment (STEV), SR 819.11,Ordinance on the procedure for the conformity evaluation of technical devicesand equipment (VKonf), SR 819.115

� Federal law on product liability, SR 221.112.944

� Machinery Directive 98/37/EC (formerly89/392/EEC and its amendments)

� EN 292-1:1991Safety of machinery – Basic concepts, general principles for design –Part 1: Basic terminology, methodology

� EN 292-2:1991/A1:1995Safety of machinery – Basic terms, general principles for design – Part 2: Technical principles and specifi-cations

� EN 1050:1996Safety of machinery – Principles for riskassessment

15 Further information

Order number: 66037.e

Documents

Suva Exemplu Metoda-e Brici