Engineers' Data Book

Foreword

This book is an essential tool to help you as you embark on your career in mechanical engineering, providing a wide range of useful information you will need during your studies, and later as a professional engineer.

The Institution of Mechanical Engineers (IMechE) is your dedicated partner throughout your career and we are committed to supporting you through your studies to graduation and beyond. Home to 98,000 engineering professionals working in the heart of the country's most important and dynamic industries, we will ensure that you have the skills, knowledge, support and development advice you need at every stage of your career.

Because we set the standard for professional excellence in mechanical engineering our members are recognised for their professional competence and enjoy enhanced career opportunities as a result. To achieve this recognition of your skills and to manage your career development, it is important that you maintain your membership of IMechE and take advantage of the opportunities available to help you fulfil your potential.

As an Affiliate member, during your studies you will benefit from career advice and support as well as regular information about engineering and how to get involved in your local IMechE community. By becoming a member, you also have access to Career Developer, our suite of online reporting tools, enabling you to record your professional experience as soon as you start your industrial placement.

Upon graduation you can apply to become an Associate Member of IMechE and begin the journey towards professional registration. With appropriate work experience and support from IMechE to develop your skills and knowledge, you can apply for registration as an Incorporated or Chartered Engineer. Your membership of IMechE will bring ongoing support for your continued professional development, through a range of member resources, events and activities. Engineers need to continue their professional development to keep their skills fresh and progressive, so we will help you stay up to date, broaden your knowledge and deepen your understanding of your chosen industry.

We hope that your relationship with IMechE will be a lifelong one that supports you throughout your career. As you join this exciting and essential profession, we wish you luck and look forward to helping you stay ahead in an increasingly varied, dynamic and rewarding industry.

Preface

This significantly updated 2012 edition of the Engineers'Data Book replaces the three successful previous editions published in 1998, 2000 and 2004. Since the data book's inception, feedback from engineers and students has indicated that, despite the proliferation of technical information in published and electronic format, there is still a need for a source of core mechanical engineering information in a readily available form. The 2012 data book has increased in content by approximately 60 percent compared to the first edition. As well as an increase in the coverage of basic units, data, and engineering rules, the content has gradually been extended to cover vital aspects of structural integrity and reliability of engineering components: these are important current issues in the engineering business.

Finally, it is important that the content of this data book continues to reflect the information that is needed and used by student and experienced engineers. If you have any suggestions for future content (or indeed observations or comment on the existing content) please let me know on: [email protected]

Clifford Matthews

Introduction

The Role of Technical Standards

What role do published technical standards play in mechanical engineering? Standards have been part of the engineering scene since the early days of the industrial revolution when they were introduced to try to solve the problem of sub-standard products. In these early days they were influential in increasing the availability (and reducing the price) of basic iron and steel products.

What has happened since then? Standards bodies have proliferated, working more or less independently, but all subject to the same engineering laws and practical constraints. They have developed slightly different ways of looking at technical problems, which is not such a bad thing – the engineering world would be less of an interesting place if everyone saw things in precisely the same way. Varied though they may be, published standards represent good practice. Their ideas are tried and tested, rather than being loose – and they operate across the spectrum of engineering practice, from design and manufacture to testing and operation.

The current trend in Europe is towards harmonization of national standards into the Euronorm (EN) family. Whether you see this as rationalization or simply amalgamation is not important – the harmonized standards will have significance for the mutual acceptability of engineering goods between companies and countries. Some recent ‘standards’, such as the Machinery Directive and Pressure Vessel Directive have real statutory significance, and are starting to change the way that mechanical engineers do things. They may be written by committees, but they are not without teeth.

Since the first edition of the Data Book, the number of EN harmonized engineering standards has increased significantly. However, their influence is still to be felt in many areas. Engineering companies that have been used to working to existing British and US standards can be reluctant to change, with the result that many companies still prefer to work to superseded standards. In some disciplines (pressure equipmentis a good example) the amount of equipment being manufactured to the new EN standards is quite small. Things are changing, but slowly.

Technical standards continue to be an important model for technical conformity in all fields. They affect just about every mechanical engineering product from pipelines to paperclips. From the practical viewpoint it is worth considering that, without standards, the design and manufacture of even the most basic engineering design would have to be started from scratch.

Section 1

Engineering Careers

1.1 Introduction: What is an Engineer?

You can hear, and read, long opinionated, but largely inconclusive, arguments as to what the title ‘engineer’ actually means. For every view that the title should be limited to those with a certain level of qualifications, or have attained a prescribed level of Institution membership, there is a contrary view that says it should relate equally to those who can prove a level of practical or craft skill, or demonstrate so many years of vocational experience.

Unlike some countries, where the designation is better defined, the situation in the UK remains liberal and self-regulated. In many industries the titles ‘engineer’ and ‘technician’ are used freely and interchangeably, without causing too much chaos. Older, more traditional industries often have more a definitive intenal understanding of what the titles mean to them. This owes as much, or more, to their own hierarchical structure and heritage, however, as to any technical interpretation they really ascribe to the terms. This older view of the world, whether you are called ‘technician’ or ‘engineer’, paints to them a picture of whether or not you sit in an office or get your hands dirty, what you wear, and how much you get paid.

Looking back in time to the start of it all, it becomes clear that job titles and delineations are much more artificial than they appear. The earliest engineers conceived the ideas, designed their innovative steam engines, bridges and ships, raised the funds, and did many of the jobs themselves. This was born of necessity, because there were no ready-trained technicians waiting to take on the engineers' concepts and turn them into reality. Once under way, however, industry matured quite quickly and separate job roles soon started to crystallize out, driven by people's preference to concentrate on things that they naturally did best.

Over the last 100 years or so, with increased maturity of the industrial society, the division of labour has continued, each engineering specialism soon fragmenting into several subspecialisms of its own, and so on. This is why the argument as to what exactly delineates an engineer from a technician has no real answer, and probably never will have. It is simply too difficult to draw a line in the sand, within such a large and varied continuum of skills, on which everyone will agree.

Assuming that you have no wish to spend the next forty or so years worrying about a question to which you know there is no answer, here is another way to look at it. Think of engineers and technicians as all being part of the wide spectrum of engineering. A spectrum has no gaps between its colours, each one leads seamlessly on to the next. Now think what it would look like viewed in black and white rather than colour – they are now all the same colour (grey) differentiated from each other only by the depth of their shade of grey.

What if the shades of grey represented technical difficulty? The light grey shades would represent job roles that are easier to learn, with the dark ones being progressively more difficult. Difficulty might also be associated not only with the technical depth of the subject or role but also with the time it would take to learn to do it well. At no point in this continuum from white (easy) to black (difficult) could we draw a definitive line dividing ‘light’ from ‘dark’, all we can say is that the spectrum consists of varying degrees of lightness and darkness and that every shade forms part of the complete picture. So this is our conclusion:

Generic job titles such as ‘engineer’ and ‘technician’ cannot, realistically, be accurately defined – they are simply parts of the continuous spectrum of job roles in the engineering industry. However . . .

One way to view the difference in roles is to consider how difficult each one is, and how long it would take to master it (properly!).

1.2 A Rough Guide to Industry Breakdown

There are many hundreds of different industry types, roles, job descriptions and specialisms in the world of mechanical engineering, all of which are spread over a multitude of different industry sectors. There are various systems that attempt to categorize these into standard industry classifications (SICs) using code numbers or letters, but they are complicated and do not always fit well with each other.

Simplistically, you can think of the engineering industry, and the job roles within it, as a matrix. To keep this matrix to any sort of manageable size means that it needs to be generalized – providing an overall picture rather than a detailed or comprehensive analysis.

Figure 1.1 shows the matrix. The more basic industries lie near the bottom, rising to the increasingly complex and technologically advanced ones towards the top. Although pure science elements exist at all these levels they become more prevalent (and are used in greater detail) in those industries near the top of the matrix. There is no implication of value or worth to industry in the position of any entry in the vertical scale, it is just a crude grading based on the overall complexity and resultant difficulty of the subject. The horizontal axis of the matrix is different. This shows the basic allocation of job roles which is equally applicable to all the industry sectors in the vertical scale. There may be a few differences, but the basic breakdown is much the same for all. The horizontal axis is based on a chronological (time) scale, running left to right. Unlike the vertical axis, the differences in complexity and difficulty are less well spread across the horizontal axis. Product conception and design fit naturally together as a discrete skill-set, but the others are fairly well separated out, representing discrete and identifiable job roles.

Figure 1.1

The left-hand end – conception and design – suits those people with high levels of innovation and conceptual skills. They can spot an idea, visualizing its final function and form, but lack a full set of skills suited to turning it into hard engineering reality. At the right-hand end, plant operators and technicians have the business and practical skills to operate a plant or a range of products on a commercial basis, but lack the skills to conceive, design and build a plant or product range from scratch. They need others to provide those skills.

You can use this rough matrix to plot your current position in the industrial landscape, or to plan where you might like to be in the future. It is neither complete nor exhaustive (there would need to be 40+ vertical categories to accomplish that), but as a broad career route map it is not a bad place to start.

1.3 Training and Professional Development

Whatever you do, don't confuse these two. It is best to think of training as your initial academic qualification: craft training or whatever – an activity whose prime purpose is to get you into your first engineering job. It also provides essential (and useful) technical background to get you onto the doorstep of your subject, but does not yet provide you with any of the full skill sets you need to move forward. This training is a benchmark, slotted into the system to differentiate between those who have it and those who do not.

Professional development is the next step. This is any training activity that has a specific job-related objective or purpose. It is often mistakenly seen as comprising mid-career courses in generalized disciplines such as marketing, finance, QA, project management skills and similar. Such-temptingly-named courses are really not what it is about. Whilst they may look and sound good, they lack cutting edge in differentiating those people with real ability in the core skills of the industry from those who do not. They are too general, too short, and woefully lacking in core skills, technical content and bite.

Productive professional development must be centred on the core skills of your particular industry. To possess the quality of being able to differentiate between its participants, productive professional development has to be structured to have a pass or fail criteria, with a pass mark high enough (and overall pass rate low enough) to buy it credibility and give it some teeth.

The best time to start productive professional development is as soon as possible after your initial training is complete. For best effect try to run it in parallel with a role that gains you practical hands-on experience of the discipline in which you are employed. This will force the productive and professional elements to complement each other, multiplying the effect of them both. Coupled with sound initial training and a bit of hands-on experience, the way in which you choose to pursue professional development activities in the early career years seems to be one of the clear factors in determining those who progress quickly up the technical jobs hierarchy and those who do not.

1.4 Degrees of (Engineering) Excellence

You have probably decided that getting a degree is a good idea – or why would you be reading this book? The reason why any high-level qualification is required is always a good talking point. Opinions differ about why it is necessary, and what is the point of it all.

The time-honoured explanation you will be given is that it is all about training