engineering

Safety life cycle

Safety life cycle is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Safety life cycle rather than just read about it. In short: The safety life cycle is the series of phases from initiation and specifications of safety requirements, covering design and development of safety features in a safety-critical system, and ending in decommissioning of that system. This article uses software as the context but the safety life cycle applies to other areas such as construction of buildings, for example.

Key takeaways

Safety life cycle belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Safety life cycle to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Safety life cycle from memory before moving on to harder problems.

Reference excerpt

The safety life cycle is the series of phases from initiation and specifications of safety requirements, covering design and development of safety features in a safety-critical system, and ending in decommissioning of that system. This article uses software as the context but the safety life cycle applies to other areas such as construction of buildings, for example. In software development, a process is used (software life cycle) and this process consists of a few phases, typically covering initiation, analysis, design, programming, testing and implementation. The focus is to build the software. Some software have safety concerns while others do not. For example, a Leave Application System does not have safety requirements. But we are concerned about safety if a software that is used to control the components in a plane fails. So for the latter, the question is how safety, being so important, should be managed within the software life cycle.

What is the Safety Life Cycle? The basic concept in building software safety, i.e. safety features in software, is that safety characteristics and behaviour of the software and system must be specified and designed into the system. The problem for any systems designer lies in reducing the risk to an acceptable level and of course, the risk tolerated will vary between applications. When a software application is to be used in a safety-related system, then this must be borne in mind at all stages in the software life cycle. The process of safety specification and assurance throughout the development and operational phases is sometimes called the ‘safety life cycle’.

Phases in the Safety Life Cycle The first stages of the life cycle involve assessing the potential system hazards and estimating the risk they pose. One such method is fault tree analysis. This is followed by a safety requirements specification which is concerned with identifying safety-critical functions (functional requirements specification) and the safety integrity level for each of these functions. The specification may either describe how the software should behave to minimize the risk or might require that the hazard should never arise. A ‘normal’ process model is then followed with particular attention paid to the validation (inspection, testing etc.) of the system. Part of that validation should be an explicit safety validation activity.

See also Safety engineering Safety engineer System safety

References

External links Safety Life Cycle - Implementation Benefits and Impact on Field Devices (PDF), ISA.org, archived from the original (PDF) on 31 March 2012

Worked examples

Example 1 — a first encounter with Safety life cycle

Start with the simplest possible case. Write down what Safety life cycle claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Safety life cycle before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Safety life cycle ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Safety life cycle

In research: Safety life cycle appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Safety life cycle in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Safety life cycle is common in secondary-school and first-year university syllabi. It links to neighbouring topics Safety engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Safety life cycle outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Safety life cycle in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Safety life cycle means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Safety life cycle out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Safety life cycle in simple terms?

Why does Safety life cycle matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Safety life cycle?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Safety life cycle.