IEC TS 61508-3-1:2016

Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 3-1: Software requirements - Reuse of pre-existing software elements to implement all or part of a safety function

IEC TS 61508-3-1:2016(E) presents requirements by the application of which pre-existing software elements may be claimed to be proven-in-use for all or a part of safety function(s) of SIL1 or SIL2.

General Information

• Status: Published
• Publication Date: 12-Jul-2016
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.240.50 - IT applications in industry
• Technical Committee: SC 65A - System aspects
• Current Stage: PPUB - Publication issued
• Start Date: 13-Jul-2016
• Completion Date: 30-Sep-2016

Overview

IEC TS 61508-3-1:2016 is a technical specification developed by the International Electrotechnical Commission (IEC) that establishes requirements for the reuse of pre-existing software elements in electrical, electronic, or programmable electronic (E/E/PE) safety-related systems. This standard addresses the implementation of all or part of a safety function using pre-existing software for systems targeting Safety Integrity Levels (SIL) 1 or 2. IEC TS 61508-3-1:2016 supplements the IEC 61508 series, particularly with regard to claiming proven-in-use for software elements as part of functional safety applications.

The standard is especially relevant to engineers, integrators, and safety professionals who are responsible for certifying or developing E/E/PE safety systems. By following its guidelines, organizations can optimize the development lifecycle by leveraging existing software while maintaining compliance with international safety benchmarks.

Key Topics

• Proven-in-Use Justification: Defines criteria for claiming that pre-existing software is sufficiently reliable based on its prior operational experience.
• Documentation and Evidence: Stipulates detailed requirements for documenting prior use, configuration, operational profiles, and analysis of previous operation.
• Scope Limitation: Applies only to safety functions up to SIL 2, reflecting current limitations in proven-in-use methods for higher integrity levels.
• Failure Detection and Reporting: Requires comprehensive evidence that all failures during prior use were reliably detected and properly reported.
• Compatibility and Configuration: Necessitates assessment of hardware, software, libraries, compilers, and operational conditions to ensure consistency with previous use.
• Restriction After Modification: Establishes that any modification to proven-in-use software invalidates its status, requiring compliance with new software development standards before reuse.

Applications

IEC TS 61508-3-1:2016 is vital for the industrial automation and process control sectors, particularly where functional safety and regulatory compliance are paramount. Typical applications include:

• Industrial Process Control Systems: Enables reuse of certified software components within programmable logic controllers (PLCs) and distributed control systems (DCS) for safety functions.
• Machine Safety: Facilitates integration of previously validated safety software in machinery, simplifying certification for SIL 1 and SIL 2 functions.
• Safety Instrumented Systems (SIS): Supports claims of functional safety compliance within chemical, petrochemical, and energy industries by allowing reuse of software in safety-critical applications.
• Embedded Safety Devices: Allows manufacturers to incorporate trusted software elements into new products while demonstrating ongoing conformity to international safety standards.

By ensuring that proven-in-use software elements are thoroughly assessed and documented, organizations can reduce development costs, leverage existing expertise, and maintain robust safety integrity in critical systems.

Related Standards

For comprehensive functional safety and software reuse strategies, IEC TS 61508-3-1:2016 should be employed alongside the following standards:

• IEC 61508-3:2010 - Functional safety of E/E/PE safety-related systems - Part 3: Software requirements
• IEC 61508-2:2010 - Functional safety of E/E/PE safety-related systems - Part 2: Requirements for E/E/PE safety-related systems
• IEC 61508-4:2010 - Functional safety of E/E/PE safety-related systems - Part 4: Definitions and abbreviations

These related standards provide the foundational terminology, system requirements, and procedural guidance necessary for implementing robust safety-related software reuse within the IEC 61508 framework.

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Keywords: IEC TS 61508-3-1, functional safety, proven-in-use, pre-existing software, safety function, SIL 1, SIL 2, E/E/PE systems, software reuse, IEC standards, documentation, failure detection, safety integrity.

Standards Content (Sample)

IEC TS 61508-3-1 ®
Edition 1.0 2016-07
TECHNICAL
SPECIFICATION
Functional safety of electrical/electronic/programmable electronic safety-related
systems –
Part 3-1: Software requirements – Reuse of pre-existing software elements to
implement all or part of a safety function
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IEC TS 61508-3-1 ®
Edition 1.0 2016-07
TECHNICAL
SPECIFICATION
Functional safety of electrical/electronic/programmable electronic safety-related

systems –
Part 3-1: Software requirements – Reuse of pre-existing software elements to

implement all or part of a safety function

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.240.50 ISBN 978-2-8322-3516-4

– 2 – IEC TS 61508-3-1:2016 © IEC 2016
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative References . 6
3 Terms and definitions . 6
4 Requirements . 6
Bibliography . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/PROGRAMMABLE
ELECTRONIC SAFETY-RELATED SYSTEMS –

Part 3-1: Software requirements –
Reuse of pre-existing software elements
to implement all or part of a safety function

FOREWORD
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Technical specifications are subject to review within three years of publication to decide
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– 4 – IEC TS 61508-3-1:2016 © IEC 2016
IEC TS 61508-3-1, which is a technical specification, has been prepared by subcommittee
65A: System aspects, of IEC technical committee 65: Industrial-process measurement, control
and automation.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
65A/780/DTS 65A/802/RVC
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61508 series, published under the general title Functional safety
of electrical/electronic/programmable electronic safety-related systems, can be found on the
IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

INTRODUCTION
The requirements set out in this technical specification deal with the reuse of software
elements when they are intended to form part of a safety function.
In many fields of automation, software elements are used today in support of safety functions.
Such applications will certainly be further developed and extended. Software engineers,
however, do not always wish to write the software for these applications from scratch, but will
in many cases use already existing software and integrate it with the new application which
might be slightly different from the one for which the software was originally specified.
In IEC 61508-3:2010, a requirement is given in 7.4.2.12. It offers three routes to the
achievement of the necessary integrity for the pre-existing software element. The
requirements to compl
...