Essentials of Machine Safety

Standards in Perspective

Why Safety?

Legal Framework

AS 4360 Risk Management

A Type

AS 4024 Safety of Machinery AS 61508 Functional Safety

EN954-1EN954-1EN418EN418EN294EN294

IEC 61508IEC 61508

B Type

AS60621

Safety of Machiner

y

AS61511

Process Safety

AS61513

Oil & Gas

AS1755

Conveyors

AS1219

Power Presses

AS2939

Robot Cells

CType

Australian Standards

Occupation Safety and Health Act

supported by

The General DutiesResolution of IssuesSafety and Health RepresentativesSafety and Health CommitteesEnforcement of Act and Regulations

Occupation Safety and

Health Regulations

and

Set minimum requirements for specific hazards and work practices

Reference to National Standards developed by NOSHAustralian Standards developed by Standards AustraliaNational Standard of Plant

Guidance Material

Codes of Practice Advisory Standards National Codes of Practice and National Standards developed

by the NOHSC Australian Standards developed by Standards Australia

Legal Framework

Safety - Acceptable Risk Level

• Risk 0 does not exist but it must be reduced up to an acceptable level

• Safety is the absence of risks which could cause injury or damage the health of persons.

• It’s one of the machine designer job to reduce all risks to a value lower than the acceptable risk.

“It is the control of the design and design-associated activity that leads to a

responsibility as an obligation bearer, not their classification as a manufacturer,

supplier, etc.”

National Occupational Health and Safety Commision -

Safe Design Project Report 2000

Safe Design

Hierarchy of Control

Making it safe

Basic concepts

• According to the requirements of standard EN/ISO 12100-1, the machine designer’s job is to reduce all risks to a value lower than the acceptable risk

• It gives guidelines for the selection and installation of devices which

can be used to protect persons and identifies those measures that are implemented by the machine designer and those dependent on its user

●This standard recognises two sources of hazardous phenomena:● moving parts of machines● moving tools and/or workpieces

Reasonably Practicable How WorkSafe applies the law in relation to Reasonably Practicable

WORKSAFE POSITION

A GUIDELINE MADE UNDER SECTION 12 OF THE OCCUPATIONAL HEALTH AND SAFETY ACT 2004 (November 2007)

In applying the concept of reasonably practicable, careful consideration must be given to each of the matters set out in section 20(2) of the Act. No one matter determines ‘what is (or was at a particular time) reasonably practicable in relation to ensuring health and safety’. The test involves a careful weighing up of each of the matters in the context of the circumstances and facts of the particular case with a clear presumption in favour of safety. Weighing up each of the matters in section 20(2) should be done in light of the following:

a) Likelihood

b) Degree of Harm

c) What the person knows about the risk and ways of eliminating that risk

d) Availability and suitability of ways to eliminate or reduce the risk

e) Cost of eliminating or reducing the risk

• NOTE: A risk assessment must never been a bill of materials or allow the controls selection to be driven by what the vendor has to offer.

Risk Assessment

• Machines are sources of potential risk and the Machinery Directive requires a risk assessment to ensure that any potential risk is reduced to less than the acceptable risk

• Risk assessment consists of a series of logic steps which make it possible to systematically analyse and evaluate machinery-related risks

• Risk assessment steps:– Identification of the potential hazard– Risk estimation– Risk evaluation

• EN/ISO 13849-1 => Performance Level (PL)

• EN/IEC 62061 => Safety Integrity Level (SIL)

– Risk reduction

Risk Assessment Principles

Risk Evaluation

• On the basis of the risk assessment, the designer has to define the safety related control system. To achieve that, the designer will chose one of the two standards appropriate to the application:

– either standard EN/ISO 13849-1, which defines performance levels (PL)

– or standard EN/IEC 62061, which defines safety integrity levels (SIL)

• The table below gives relations between these two definitions

• To select the applicable standard, a common table in both standards gives indications:

-

(1) For designated architectures only

d

• Reliability - the ability of a system or component to perform its required functions under stated conditions for a specified period of time.[1] It is often reported as a probability.

• Probability is the likelihood or chance that something is the case or will happen.

Change of Standards

• The qualitative approach of the EN 954-1 is no longer sufficient for modern controls based on new technologies (Electronic and Programmable Electronic systems):

– insufficient requirements for programmable products,– The reliability of the components is not taken into account,– too deterministic orientation (designated architectures).

• Standard EN ISO 13849-1 will totally replace the EN 954-1 in November 2009, and will upgrade the qualitative approach by the new quantitative (probabilistic) approach and is consistent with safety standards in general.

– At the moment both standards EN 954-1 and EN/ISO 13849-1 are valid

• For complex machines using programmable systems for safety-related control, the sector specific standard EN/IEC 62061 has to be considered

– EN/IEC 62061 based on EN/IEC 61508

Standard EN/IEC 62061

• Specific to the machine sector within the framework of EN/IEC 61508:– gives rules for the integration of safety-related electrical, electronic and

electronic programmable control systems (SRECS)– does not specify the operating requirements of non-electrical control components

in machine (ex.: hydraulic, pneumatic)

• The probability of failure associated to the required SIL (Safety Integrity Level) depends on the frequency of usage of the safety function to be performed

Safety of Machineryapplication

EN/IEC 62061

Standard EN/ISO 13849-1

• The Standard gives safety requirements for the design and integration of safety-related parts of control systems, including software design.

• The Risk Graph helps to determine the required PL (Performance Level) of each safety function– S - Severity of injury

> S1 Slight injury> S2 Serious or permanent injury or death

– F - Frequency and / or exposure to a hazard> F1 Seldom to less often and / or short time> F2 Frequent to continuous and / or long time

– P - Possibility of avoiding the hazard or limiting the harm> P1 Possible under specific conditions> P2 Scarcely possible

Relationship Between Different Criteria

• Relationship between Categories, DCavg, MTTFd and PL

*In several application the realisation

of performance level c by category 1

may not be sufficient. In this case a

higher category e.g. 2 or 3 should

be chosen.