Methodology for functional safety assessment of protective systems for potentially explosive atmospheres

This European Standard provides guidance on the procedure and information required to allow functional safety assessment to be carried out for the design of protective systems. The purpose of this European Standard is to assist technical standardization committees responsible for specific families of protective systems in preparing safety standards. Such standards should be as homogenous as possible and should have the basic structure of functional safety assessment as it is stated in this standard. If there are no specific standards for a particular protective system, the manufacturer should use this standard for functional safety assessment of this protective system. In this procedure the following information is to be taken into account to ensure a sufficient level of functional safety: a) intended use, b) possible operating faults, c) reliability of protective systems, d) misuse which can reasonably be anticipated. A sufficient level of functional safety is characterized by the following objectives: 1) System can stop an explosion at a very early stage or reduce the impact of an explosion to an acceptable level. 2) In the event of faults, failures and/or interference1) the capacity to function remains effective by use e.g. of fail safe techniques or redundancy. This European Standard does not cover identification of possible ignition sources. This European Standard only deals with the functional behaviour of the protective system i.e. hazards caused by malfunctions, e.g. false activations are excluded. This European Standard specifies neither specific methods to analyse fault conditions, nor specific requirements for a given type of protective system (see EN 1127-1). It specifies the methodology of functional safety assessment. This European Standard provides advice for decisions to be made for all types of protective systems referred to in EU Directive 94/9/EC, but does not provide means to prove the conformity of a given type of protective systems.