SIST EN 15233:2007

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Methodology for functional safety assessment of protective systems for potentially explosive atmospheresRWHQFLDOQRMéthodologie relative a l'évaluation de la sécurité fonctionnelle des systemes de protection pour atmospheres explosiblesMethodik zur Bewertung der funktionalen Sicherheit von Schutzsystemen für explosionsgefährdete BereicheTa slovenski standard je istoveten z:EN 15233:2007SIST EN 15233:2007en,fr,de13.230Varstvo pred eksplozijoExplosion protectionICS:SLOVENSKI
STANDARDSIST EN 15233:200701-oktober-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 15233August 2007ICS 13.230 English VersionMethodology for functional safety assessment of protectivesystems for potentially explosive atmospheresMéthodologie relative à l'évaluation de la sécuritéfonctionnelle des systèmes de protection pour atmosphèresexplosiblesMethodik zur Bewertung der funktionalen Sicherheit vonSchutzsystemen für explosionsgefährdete BereicheThis European Standard was approved by CEN on 13 July 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 15233:2007: E

Example of a functional safety assessment.15 Annex B (informative)
Methods for failure identification and functional safety assessment.20 Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC.23 Bibliography.24

For relationship with EU Directive 94/9/EC, see informative Annex ZA, which is an integral part of this document. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.

1) Interference is everything in normal operation that can disturb the normal operation of the system e.g. electromagnetic waves, heat, flames and pressure waves.

NOTE 1 Functional safety covers all aspects where safety depends on the correct functioning of the protective system and other technology safety-related systems.
NOTE 2 This definition deviates from the definition in EN 61508-4 to reflect differences in explosion safety terminology. 3.3 protective system device other than components of the equipment, which is intended to halt incipient explosions immediately and/or to limit the effective range of an explosion and which is placed separately on the market as autonomous system [EN 13237:2003, A.5] 3.4 functional safety estimation determination of the probability of occurrence of the failures violating the functional safety of the protective system 3.5 functional safety evaluation procedure to determine whether the functional safety of the protective system meets the predefined acceptance criteria 4 General requirements 4.1 Basic concept Functional safety assessment is a series of logical steps (see Figure 1) that enable designers and safety engineers to examine in a systematic way, the function of a protective system or a part of it. The objective shall be to achieve an adequate level of functionality and reliability according to the state of the art and technical and economic requirements at the time of construction.

a) description of the protective system (5.2); b) identification of failures (5.3); c) functional safety estimation (5.4); 1) functionality; 2) reliability; d) functional safety evaluation (5.5). These four steps are the basis for the decision whether the intended level of functional safety necessary for the intended use is achieved. The result of the assessment shall be detailed in the technical documentation (see Clause 6). If the required function and level of reliability is not achieved, it shall be necessary to improve the protective system or to define an appropriate intended use.
NOTE The choice of the suitable measures is not part of the standard. If the assessment is done by the manufacturer the result of the assessment shall be detailed in the technical documentation (see Clause 6). Decisions in functional safety assessment shall be supported by qualitative methods complemented, where appropriate, by quantitative methods. 4.2 Extent of functional safety assessment The protective system shall be assessed on the basis of the information specified in 4.3.
The functional safety assessment shall be limited to the intended use and the misuse, which can reasonably be anticipated for a particular protective system. NOTE Misuse which can reasonably be anticipated means an incorrect use and/or operation of the protective system by the operator due to negligence or misunderstanding. Misuse is not part of the normal operation. Intent is not included in foreseeable misuse. 4.3 Information needed The information needed to perform the functional safety assessment shall include the following where appropriate: a) intended use; b) safety characteristics used for the design of protective systems;
c) requirements for maintenance; d) actual and foreseeable surrounding area conditions; e) relevant design drawings; f) results of design calculations made, examinations carried out; if available:

NOTE The data is used to define foreseeable operation requirements related to reliability, serviceability, durability, disposability, benign failure and failsafe characteristics and labelling, warnings, identification, traceability requirements and instructions. Data based on the consensus of expert opinion derived indirectly from experience as opposed to measured data, may be used to supplement qualitative assessment. 5 Functional safety assessment procedure 5.1 Principle The principal steps for the functional safety assessment procedure are shown in Figure 1. It is comprised of four steps taking into consideration the information in the oval blocks. Maintenance requirements shall also be considered in the assessment. The manufacturer shall consider all necessary maintenance requirements in the instruction manual and shall also consider lack of maintenance relevant for the intended use.

Key a Conformity is not part of functional safety assessment. NOTE Dotted lines are not part of this standard. Figure 1 — Functional safety assessment for design of protective systems 5.2 Description of the protective system The step-approach (by following flow-chart in Figure 1) shall be carried out with an understanding of the function of the protective system and of the types of explosions.
Intended use shall consider, for example, the following items: a) life cycles of the protective system;
b) limits in terms of use, time, space; c) accurate definition of the function; d) selection of materials for construction;
e) performance, lifetime and configuration; f) description of the type of explosions;

5.3.1 General Generally, a protective system shall be assessed by potential sources of failure of the protective system. A functional and state analysis for the intended use shall be undertaken for this purpose. Protective systems are distinguished in the following way: a) passive systems (e.g. flame arrester, venting system), b) active systems (e.g. suppression system). An illustrative example of such an approach is given in Annex A. The possible failures shall be assessed through a functional and systematic analysis and shall be considered separately with regard to whole lifecycle: NOTE The listed possible failures are examples. Additional failures may occur. 5.3.2 Assessment 5.3.2.1 Design and manufacturing In the phase of planning and design the following shall be considered: a) that the compliance of the intended use shall be achieved. Examples are: 1) sufficient heat conduction of flame arresters, 2) effective pressure release of venting devices, 3) sufficient suppression efficacy of suppression systems. b) mechanical dimensioning of the protective system is adequate. Failures can occur due to e.g.: 1) insufficient pressure resistance, 2) insufficient temperature resistance, 3) insufficient resistance against vibration and shock, 4) insufficient resistance against ageing or corrosion. c) incorrect installation location, an incorrect installation position or an installation method with regard to the nature of the explosion shall be avoided. d) correct mode with regard to the process, the ambient temperature, the ambient pressure shall be taken into account as well as the correct operating threshold or sensitivity. e) use of non appropriate software and controlling equipment (hardware). f) resistance of the hardware against electromagnetic disturbance.

To be able to provide proper information on the installation the manufacturer shall consider the following possible failures: a) lacking or deficient consideration of effects due to the intended function (e.g. vacuum breakers, danger areas in front of pressure-relief devices, recoil forces, risk of injuries); b) insufficient sealing or possible circumvention; c) insufficient electric conditions (e.g. short circuit, open circuit, overload and earth faults); d) insufficient energy supply and/or back-up power supply for controlling and indicating equipment (CIE). 5.3.2.3 Operational and maintenance requirements The possible failures that can occur during the use and maintenance of the protective system, shall be considered. The manufacturer shall advise the user how to prevent them. Possible failures, which may arise during the use and maintenance, are: a) Contamination; b) incorrect or insufficient intervention by persons (faulty operation, faulty mounting, incorrect maintenance, unintended interventions); c) indication of fault messages and lack of emergency stop procedures. Such lacking or deficient situations and the possible failures that may occur shall be described clearly in the instructions for use. 5.3.2.4 Modification Any safety related modification of a protective system shall be considered a new system which shall require a reassessment. 5.4 Functional safety estimation 5.4.1 General After the failure identification the functional safety of the protective system has to be estimated by determining the probability of failure occurrence. The functional safety estimation can be done qualitatively, semi-quantitative or quantitative depending on the criticality of the protective system in reducing the probability of failure and/or the complexity of the system and the safety related devices. The required performance of the protective system shall be considered in terms of its: a) function, i.e. the ability to perform the functions required by the intended use of the system (e.g. halt an incipient explosion, reduce explosion pressure), and b) integrity, i.e. the reliability in performing those functions (on demand or in time).
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