The EN 50402 for Fixed Gas Detection Systems in Relation to the Generic Standard EN/IEC 61508

• Dieter Wenker

Keywords: Gas detection, Gas sensors, Standardisation, EN 50402, IEC 61508, Type testing, Metrological standards, Functional modules, SIL-capability, Common cause failures, Demand mode

This article is available in:  English. Please login to request translation.

---

Abstract:

The European standard EN 50402 is a product family standard for all gas detection equipment; its subtitle is “Requirements on the functional safety of fixed gas detection systems”. The EN 50402 was transferred as new work item to IEC and will be published as IEC 60079 29 3. An IEC version of the standard will be available at the earliest 2010. The EN 50402 will be used also outside Europe as “state of the art” technical specification. The standard is based on the generic standard EN/IEC 61508 and covers the phase 9 “realisation”.

Gas detection systems differ strongly in structure, complexity and performance. The EN 50402 divides a gas detection system into functional modules to ensure that systems with different structures are handled in a comparable manner. Requirements are specified for each type of simple or complex modules and for different ranges of safe failure fraction (SFF). For each module the SIL-capability is determined. Safety functions are specified by different combinations of modules which may result in different SIL-capabilities.

The EN 50402 includes no requirements for the installation and maintenance of gas detection systems and does not specify the physical positioning of sensors. These items are covered by metrological standards e.g. the EN/IEC 61779 series (in future EN/IEC 60079 29 1) and related guides EN 50073 (in future EN/IEC 60079 29 2).

The calculation of probability of failure on demand (PFD) and the conformity of the software development process are carried out according EN/IEC 61508 without further specification in EN 50402. For the implementation of a gas detection system into an overall safety system the type testing according to EN 50402 will deliver SIL-capability, hardware failure probabilities and diagnostic test intervals for each safety function. © 2008 Inside Publishing. All Rights Reserved.

Volume: 2009   Issue: 1

Readers of this article also bought

Other articles by Dieter Wenker:

Articles by keywords