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BS EN 50402:2017

BS EN 50402:2017

$215.11

Electrical apparatus for the detection and measurement of combustible or toxic gases or vapours or of oxygen. Requirements on the functional safety of gas detection systems

Published By Publication Date Number of Pages
BSI 2017 102
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This European Standard is applicable to detection and measurement apparatus and systems for flammable or toxic gases or vapours or oxygen. It covers apparatus intended to measure reliably, gas concentration and to provide an output signal (alarm and/or measurement signal), the purpose of which is to give a warning of a potential hazard.

This European Standard is a product standard which is based on EN 61508 (all parts) and for gas detection systems covers both low and high demand mode at SIL capabilities of 1, 2 or 3 only. Gas detection apparatus and gas detection systems are developed as generic products. This European Standard covers part of the phase 10 ā€œrealizationā€ of the overall safety lifecycle defined in EN 61508-1:2010, Figure 2. Configuration and integration into specific applications is not covered by this European Standard.

In the event of conflict between the requirements of this European Standard and those of EN 61508, EN 50402 will take precedence.

NOTE 1 Applications requiring a SIL capability of 4 for a gas detection system are not practicable.

This European Standard is dedicated mainly to fixed apparatus and systems. However, it can also be applied to transportable gas detectors which are intended to be used as temporary replacements for fixed apparatus.

This European Standard supplements the requirements of the European Standards for electrical apparatus for the detection and measurement of flammable gases, vapours (e.g. EN 60079-29-1 or EN 60079-29-4), toxic gases (e.g. EN 45544) or oxygen (e.g. EN 50104).

NOTE 2 These European Standards are called in the text ā€œmetrological standardsā€.

The examples above show the state of the standardization for industrial applications at the time of publishing this European Standard. There may be other metrological standards covering other application fields, for which this European Standard is also applicable.

EN 50271 specifies minimum requirements for apparatus using software and/or digital components. It also defines additional optional requirements for compliance with SIL 1 in low demand mode operation. EN 50402 includes all requirements of EN 50271.

EN 50402 is also dedicated to apparatus and gas detection systems and/or components and should be used instead of EN 50271 in the following cases:

  • at SIL 1 when the system contains components not covered by EN 50271;

  • at SIL 1 high demand mode operation;

  • at SIL 2 and SIL 3;

  • at all SILs when non-digital based apparatus is used.

Applying the above-mentioned metrological standards will ensure the performance is adequate in normal operation of a gas detection system. Additionally, the requirements of this European Standard address the functional safety of gas detection systems and encompass criteria for reliability, fault tolerance and avoidance of systematic failures. The avoidance and control of systematic failures will be covered by the requirements for the development processes and techniques and diagnostic measures chosen in the design. This European Standard will lead to the characterization of the gas detection system by a SIL-capability and related hardware failure rate representing a hierarchical order of safety levels. This will allow the user to incorporate the gas detection system into an overall safety system according to the safety integrity levels of EN 61508 (all parts).

This European Standard is applicable for gas detection systems, which may consist of the following functional units:

  • gas-sampling;

  • sensor;

  • signal transmission;

  • input to control unit;

  • signal processing in control unit;

  • output from control unit.

This European Standard does not specify requirements for the installation and maintenance of gas detection systems. It also does not specify the physical positioning of measuring points / locations.

This European Standard does not specify which SIL-capability is sufficient for which application.

NOTE 3 The SIL-capability required for an application will be specified by the user (see Clause 9 and Annex A).

PDF Catalog

PDF Pages PDF Title
12 1 Scope
13 2 Normative references
14 3 Terms and definitions
19 4 General requirements
4.1 Specification of safety functions
25 4.2 Determination of safety function
26 4.3 Functional safety characteristics of modules
27 5 Functional modules and elements ā€” Characterization and requirements
5.1 General
5.1.1 Structure of functional modules
31 5.1.2 General requirements
32 5.2 Gas sampling
5.2.1 Gas aspiration
5.2.2 Conditioning of measured gas
33 5.2.3 Gas multiplexer
5.2.4 Gas sampling by diffusion mode
5.2.5 Automatic calibration and adjustment
34 5.3 Sensor
35 5.4 Signal-transmission
5.4.1 General requirements
5.4.2 Signal-transmission between spatially separated modules
37 5.4.3 Signal-transmission between modules not spatially separated
38 5.5 Input to signal processing
5.5.1 General
5.5.2 Interface for measured signal
5.5.3 Input system communication
5.5.4 User interface
39 5.5.5 Input from periphery
5.5.6 Power supply
5.5.6.1 External power connection
5.5.6.2 Internal regulated power supply
5.6 Signal processing
5.6.1 General
41 5.6.2 Calculation of measured values
5.6.3 Special state
42 5.6.4 Signal assessment
43 5.6.5 Diagnostic means within a control unit
45 5.6.6 Reduced mode of operation
46 5.6.7 Aspiration control
5.6.8 Gas multiplexer control
5.6.9 Control of automatic calibration
47 5.6.10 Control of automatic adjustment
5.7 Output of the control
5.7.1 Visual indication
48 5.7.2 Switching output
49 5.7.3 Output system communication
50 5.7.4 Output to periphery
5.7.5 Data archives
51 6 Software
6.1 General requirements
6.2 Context of the Software Standard
6.3 Requirements from ENĀ 615083
52 6.4 List of replaced or not relevant clauses in ENĀ 615083:2010
53 6.5 List of changes to clauses in ENĀ 615083
56 6.6 ENĀ 50402 Levels of rigour
57 6.7 Tables of techniques and measures from ENĀ 615083:2010, AnnexĀ A
6.7.1 Explanation of terms
6.7.2 Writing conventions in the tables of techniques and measures
6.7.3 Software requirements specification
6.7.3.1 ENĀ 50402 software requirements specification
59 6.7.3.2 Semi-formal and formal methods
6.7.3.3 Verification of the requirements specification
6.7.3.4 Verification of completeness and correctness
60 6.7.3.5 Understandability
6.7.3.6 Freedom from adverse interference by non-safety functions
6.7.3.7 Capability of providing a basis for validation
6.7.4 Software architecture design
6.7.4.1 ENĀ 50402 software architecture design
63 6.7.4.2 Verification of the software architecture
64 6.7.5 Software design and development ā€“ Support tools and programming language
6.7.6 Software detailed design
6.7.6.1 ENĀ 50402 software detailed design
66 6.7.6.2 Semi-formal methods
67 6.7.7 Software module testing and integration
69 6.7.8 PE integration (hardware + software)
70 6.7.9 Software validation
71 6.7.10 Modification
72 6.7.11 Software Verification
74 7 Combining Functional Modules to Safety Functions
7.1 SIL-capability
75 7.2 Determination of SIL-capabilities for a safety function
7.2.1 General
76 7.2.2 Summarizing of single chains
7.2.3 Summarizing of parallel chains
77 8 Determination of hardware failure rates for each safety function
78 9 Gas detection as part of an overall safety function
79 10 Information requirements
80 11 Validation
81 12 Functional safety management
13 Functional safety assessment
14 Documentation
82 AnnexĀ A (normative)Transformation of the SIL-capabilities of gas detection systems
A.1 Introduction
A.2 Transformation of the SIL-capabilities of gas detection systems to the safety integrity levels of ENĀ 61508 (all parts)
83 AnnexĀ B (normative)Transformation from generic standard requirements to modules
B.1 General
B.2 SIL-capability 1
B.3 SIL-capability 2
84 B.4 SIL-capabilityĀ 3
85 AnnexĀ C (informative)Determination of SIL-capability of a safety functionof the gas detection system
C.1 General
C.2 Procedure of determination of SIL-capability
91 C.3 Example: Determination of SIL-capability for a gas detection system
C.3.1 General
C.3.2 Example: Characterization of relay outputs of control units A and B
93 C.3.3 Example: Characterization of relay output of common alarm
95 AnnexĀ D (informative)Failure modes for specific measuring principles
D.1 Introduction
D.2 Failure modes relevant to most or all types of measuring principles and types of sensing elements
D.2.1 Generic failure modes
D.2.2 Failure modes identified in the metrological standards
96 D.3 Catalytic sensing elements
D.4 Thermal conductivity sensing elements
D.5 Infrared sensing elements
D.5.1 Point detectors
97 D.5.2 Open path detectors
D.5.3 TDLAS (e.g. for oxygen)
D.6 Semiconductor sensing elements
D.7 Electrochemical sensing elements
D.7.1 Galvanic ā€” Lead based oxygen
98 D.7.2 Amperometric with organic or aqueous electrolyte
D.8 FID sensing elements
D.9 FTA sensing elements
99 D.10 Paramagnetic sensing elements
D.10.1 General
D.10.2 Principle using a dumbbell
D.10.3 Microflow Measuring Principle
100 D.10.4 Measurement of magnetic susceptibility
D.10.5 Paramagnetic thermal effect
D.11 PID sensing elements

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BS EN 50402:2017
$215.11