Safety with Machinery

John Ridley, Dick Pearce

• Publisher: Routledge
• Year: 2006
• ISBN:
  9781136367489
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Automation in Engineering
• Index: Technology & Engineering

John Ridley and Dick Pearce, both recognized specialists in machinery safety, guide the reader through the various standards, regulations and best practices relating to the safe design and use of machinery and show which standard is relevant for which type of machine. Safety with Machinery provides a basic grounding in machinery safety and covers safeguarding philosophy and strategy, typical hazards, risk assessment and reduction, guarding techniques, ergonomic considerations, safe use of equipment and plant layout. All types of safeguards are discussed – mechanical, interlocking, electrical / electronic / programmable, hydraulic, pneumatic.The new edition has been updated throughout in line with changes in regulations and standards. The section on electric, electronic and programmable safety systems has been expanded to reflect their increasing importance. The book now focuses on the harmonised standards (e.g. EN ISO 13849, IEC/EN 61131-2) which can be used by manufacturers to self-certify their machines for the European market without the need for third party examination, but also covers other relevant standards (e.g. IEC 62061). Many practical examples set the regulations in context and assist in the interpretation of the various standards. Safety with Machinery is essential reading for all engineers involved in machinery design and maintenance all over the world as every machine sold within or into the EU needs to conform to the harmonised standards. It also provides health and safety professionals, students and employee representatives, as well as certification bodies, health and safety inspectors and safety regulators with a comprehensive overview of machinery safety.

Part I

Safeguarding Philosophy and Strategy

Ever since machinery was first developed to help man with his labours a heavy price in injuries and damage has been paid for the convenience. In the early days of the Industrial Revolution when labour was cheap, little regard was paid to the pain and suffering of injured workers. But the late 18th and the 19th centuries saw great changes in social attitudes and a growing recognition of the value of the people who worked the machines. This resulted in great strides being made in ways and means of providing protection for them. The enormous advances in technology made in more recent years have brought new hazards that have required new techniques to be developed to provide the degree of protection that society now expects employers to provide for their employees.

This part deals with some of the principles involved in providing safeguards, gives basic examples of common hazards and how they can be dealt with. It explains the process of hazard and risk reduction through the carrying out of risk assessments and how the findings can be used to determine safety integrity levels.

Chapter 1

Safeguarding of Work Equipment

1.1 Introduction

As machinery and plant have become more complex, so the techniques for protecting the operators have become more sophisticated. However, there are many of the older, simpler machines still in use, some of which may date from before the days when the safety of the operator was a matter for concern.

This volume is aimed at all who design, manufacture, use, maintain, modify, manage, inspect or advise on machinery, plant and component parts. It is also relevant to those who, while not directly involved with this equipment, have legal and moral responsibilites for ensuring that it is safe when put to use.

It sets out to describe the range of techniques available to the designer, works manager and engineer for guarding a whole range of machinery from the simplest to the most complex. Necessarily it covers a great many techniques and practices but to keep the text as brief as possible, the techniques and practices are described in outline only. Diagrams are provided where pertinent to assist in understanding the methods of operation and to enable the selection of an appropriate type of guard to be made. For further information on techniques and practices reference should be made to international and European standards, many of which are listed in Appendix 1. These standards detail the requirements that need to be met to give conformity with current health and safety legislation and hence ensure a high degree of operator safety. Conformity with a national or international standard is normally recognized as giving compliance with legislative requirements.

The text of this book applies to plant which may be manually or power operated, and extends to include equipment such as robots and pressure vessels that contain stored energy and to process plant in which the substances being processed may themselves be a hazard if they escape. The techniques described are applicable to the wide range of plant and equipment that is currently found in many workplaces and demonstrate many of the different methods by which protection of the operator can be achieved.

Over the years, individual countries have developed machinery safety standards to suit their particular methods of operating and their attitudes towards safety. However, as manufacturing has become more global so there has been, and is increasingly, a move towards international standardization. Where international standards exist, they are used as the basis for the text. Where they do not, the text reflects the best internationally accepted practices.

Ensuring that machines are provided with a suitable level of safeguarding serves two purposes. Firstly, it provides protection for the operator when using the machine. Secondly, conforming with the appropriate official published standard – whether EN, IEC or ISO – ensures that the machine complies with the conditions for importation and sale in the EU. In the latter case a technical file on the machine must be prepared of which an essential element is evidence of conformity with the appropriate standard.

Certain words that have specific health and safety meanings keep recurring throughout the book. Definitions of the meanings of those words are gathered together in a glossary in Appendix 2. Similarly, acknowledged abbreviations are used – the first time in parentheses after the full title – and these have been gathered together in Appendix 4.

Throughout the book, a variety of different methods of providing protection against machinery hazards are shown. However, these are not necessarily the only way in which the desired protection can be achieved. If a ‘non-standard’ method of providing protection is used the manufacturer and user may be called upon to justify their reason for using it.

It is incumbent upon the designer and engineer to select one, or a combination of more than one, method of safeguarding to suit a particular machine, method of working and safety culture. Those concerned must ensure that the method or means selected provides the level of protection that the international community is coming to expect for the people employed to operate the machines and equipment.

1.2 Design Considerations

When designing machinery not only must the designer consider the efficiency of performance, achieving desired output and the economies of manufacture but he must also ensure that the finished machine will be safe in use and will not present risks of injury or damage at any stage of the machines life ‘from the cradle to the grave’.

1.3 Life Cycle

The three most common phrases in use that refer to the safety of machinery throughout its design and operating life to final disposal are design life cycle, safety life cycle and the cradle to the grave concept. While these all broadly cover the design, operating and disposal of machines, they each approach from different backgrounds. Design life cycle looks at the designer’s role, safety life cycle is more administrative and puts emphasis on recording actions taken for safety and why, whereas ‘the cradle to the grave’ concerns itself with safe functioning of machines from the operator’s and user’s points of view.

Each of these aspects should cover every stage of the life of the equipment including:

1. design
2. manufacture
3. transport
4. installation and erection
5. testing
6. commissioning and preparation for production
7. operation from start-up to shut-down
8. setting, adjusting and process change
9. cleaning
10. maintenance, repair and overhaul
11. removing from service and dismantling
12. disposal of parts especially if contaminated by hazardous materials.

For each of these stages, consideration should be given to how the work is to be carried out and what safety features are required, remembering that it is the safety of others as well as the operator that needs to be considered.

The particular procedure followed will depend on the approach adopted but should encompass one or more of those shown diagrammatically in:

Figure 2 of EN ISO 12100-1:2003 to identify hazards and reduce risks to a minimum.

Figure 1 of EN 954-1 in respect of the design of safety related components of control systems whether electrical, electronic, pneumatic or hydraulic (this standard is being updated and will be issued as EN ISO 13849–1 when approved).

Figure 1 of EN 1050 for an iterative process to achieve safety (this standard is being updated and will be issued as EN ISO 14121 when approved).

Figure 2 of IEC 62061 for safety related electrical control systems design and development.

Where conflict arises between two or more safety considerations, the aim must always be to reduce the overall risk as far as possible, giving greatest consideration to the aspect that poses the greatest risk.

1.4 Designer’s Responsibility

In the early design stages, particular aspects the designer should consider include:

1. Carrying out a preliminary design risk assessment to identify potential hazards that changes to the design could avoid. This is particularly important where new plant or equipment is to be installed in an existing work area with other plant and people movement.
2. Incorporating ‘state-of-the-art’ safety arrangements.
3. Utilizing feedback from other users of similar equipment to identify and eliminate hazards and improve ergonomic features.
4. Complying with legislative requirements in both the manufacturing and customer countries and ensuring that the design satisfies both these requirements.
5. Designing with the end user in mind – whether to a specific order or speculatively to offer on the open market.
6. Ensuring components, particularly those that are bought in, are compatible with the materials and other equipment with which they are likely to have contact and provide a matching degree of reliability.
7. Where control equipment is to be linked to other controls, ensuring compatibility of signals and responses.
8. Ensuring that when put into operation, the equipment does not interfere with the functioning of adjacent equipment – physically, electrically or electromagnetically.
9. The safety implications of possible changes in use and of the misuse of the equipment.

As the design progresses, other factors may arise that the designer will need to resolve.

Particular attention should be paid where access is necessary to automated or remotely controlled plant. This is especially important with robots since they retain stored energy whose release can initiate machine movement...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright
• Contents
• Preface to the second edition
• Preface to the first edition
• Part I: Safeguarding philosophy and strategy
• Part II: Guarding techniques
• Part III: Safeguarding systems
• Part IV: Other safety related arrangements
• Part V: Appendices
• Index