SISTEMA Cookbook 4 - When the designated architectures don’t match

Sep 18, 2026

Upload by Asher

SISTEMA Cookbook 4 (Version 1.0 EN) explains how to determine dangerous failure probability under EN ISO 13849-1 when the implemented control architecture does not match the designated Category architectures. It introduces practical modeling workarounds, including minor conceptual changes that still allow analysis in SISTEMA. The cookbook covers single-fault tolerance in single-channel structures, encapsulated subsystems with parallel functional channels, systems with more than two functional channels, and Category 2 test-rate cases, providing SISTEMA input guidance and remarks.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages17

Reading Time43 min

AccessFree to download

Introduction

Single-fault tolerance in single-channel structures

Encapsulated subsystem with parallel functional channel

More than two functional channels

Test rate in Category 2

The SISTEMA Cookbook 4 When the designated architectures don’t match Version 1.0 (EN) Authors: Michael Hauke, Ralf Apfeld Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA) Alte Heerstraße 111 53757 Sankt Augustin, Germany Tel.: +49 2241 231-02 Fax: +49 2241 231-2234 [Internet: www.dguv.de/ifa](Internet: www.dguv.de/ifa) Published by: Deutsche Gesetzliche Unfallversicherung e. V. (DGUV) Mittelstraße 51 10117 Berlin – March 2012 – Contents Introduction ..........................................................................................................................4 1 Single-fault tolerance in single-channel structures .............................................5 1.1 Description................................................................................................................. 5 1.2 Input in SISTEMA ...................................................................................................... 5 1.3 Remarks .................................................................................................................... 6 2 Encapsulated subsystem with parallel functional channel .................................7 2.1 Description................................................................................................................. 7 2.2 Input in SISTEMA ...................................................................................................... 7 2.3 Tip.............................................................................................................................. 8 2.4 Remarks .................................................................................................................... 8 3 More than two functional channels...................................................................... 10 3.1 Description............................................................................................................... 10 3.2 Input in SISTEMA .................................................................................................... 10 3.3 First step.................................................................................................................. 11 3.4 Second step............................................................................................................. 12 3.5 Tip............................................................................................................................ 13 3.6 Remarks .................................................................................................................. 13 4 Test rate in Category 2 .......................................................................................... 15 4.1 Description............................................................................................................... 15 4.2 Case 1: The ratio of the test rate to the demand rate upon the safety function is lower than 100 but at least 25................................................................................. 16 4.3 Remarks .................................................................................................................. 16 4.4 Case 2: Fault detection and fault response are triggered by the demand upon the safety function and occur more quickly than incidence of the hazard situation .......17 4.5 Remarks .................................................................................................................. 17 Introduction A condition for determining of the probability of a dangerous failure per hour in accordance with the simplified method described in EN ISO 13849-1 is that the control system that is implemented must correspond to one of the designated architectures for the Categories. If this is not the case, the simplified method cannot be used and a more involved method, such as Markov modelling, is generally required. On occasions h

FAQs

Why can the simplified method in EN ISO 13849-1 fail to apply in SISTEMA?

It requires the implemented control system to correspond to one of the designated architectures for the Categories. If it does not, the simplified method cannot be used and a more involved method such as Markov modelling is generally required.

How can analysis still be performed when architectures deviate from the designated Categories?

In some cases a minor conceptual change is sufficient so the architecture can be modelled to a designated architecture, and four special cases are described for deviations that can nevertheless be analysed by SISTEMA.

What does the cookbook cover under “Test rate in Category 2”?

It discusses Description, then two cases explaining how the ratio of test rate to demand rate affects the outcome, and how fault detection and fault response timing relate to the demand upon the safety function.

Sep 18, 2026

Upload by Asher