4 Procedure of the risk analysis A written risk analysis shall be performed on an FBES to ensure that:
a) all reasonably foreseeable hazards and hazardous events, including reasonably foreseeable misuse throughout the anticipated lifetime, have been identified; b) the risk for each of these hazards has been estimated from the combination of its probability of occurrence and of its foreseeable severity; c) the two factors which determine each one of the estimated risks (probability and severity) have been eliminated or reduced to a level not exceeding the acceptable risk level as far as reasonably possible according to the following principles in the order given:
– eliminate hazards or reduce risks by inherent design measures,
– take necessary protective measures in relation to risks that cannot be reduced by inherent design measures,
– inform intended users and where appropriate other persons of the residual risks, indicate whether any particular training is required and specify any need to use personal protective equipment. For example, failure mode and effects analysis (FMEA), fault tree analysis (FTA) methods, hazard and operability study (HAZOP), and/or the following International Standards shall be used as guidance:
• IEC 6081 2;
• IEC 61 025.
5 Safety requirements and protective measures
5.1 General Each secondary battery has a different structure and therefore only the features critical or specific to the flow battery shall be taken into consideration. The flow battery energy system as shown in Figure 1 differs from other secondary batteries, in that a system for circulating the electrolyte is present. The fluid circulating system consists of tanks, pumps, piping, sensors and some safety-relevant devices. From a chemical safety point of view, since fluid is contained in tanks, pipes and stacks, the sealing is an important factor. There is also the possibility of hazardous gases being present, requiring that appropriate countermeasures be implemented. Clause 5 specifies the safety requirements and protective measures in consideration of the above-mentioned aspects.
5.2 Risk information The manufacturer shall provide the user with risk information based on the risk analysis to describe hazards and the appropriate measures taken or to be taken for mitigation purposes. The information shall include a safety data sheet (SDS). The information can be provided in the form of a user manual. See the recommended structure for user manual in Annex A.
5.3 Electrical hazards 5.3.1 Electrical shock The FBS is an electrical energy storage device and contains hazardous live parts of DC and/or AC voltage which can cause a risk of electrical shock. Electrolyte is to be considered as carrying dangerous voltages. Batteries are sources of dangerous voltages and en
ergy (current flow) also when they are not connected to an external power circuit. In flow batteries the amount of residual energy is, when no electrolyte circulates, limited to the charge stored in the electrolyte remaining in the stack itself. In all cases protective measures according to IEC 60364-4-41 shall be implemented.
5.3.2 Short-circuits The electrical energy stored in an FBS can be released in an inadvertent and uncontrolled manner due to short-circuiting the terminals. Because of its considerable level of energy and subsequent high current, the heat generated can melt metal, produce sparks, cause explosion, or vaporize fluid. To avoid short-circuits, protective devices such as insulation shrouds, fuses and circuit breakers shall be installed in a way that a short-circuit does not occur under any foreseeable conditions.
For the type of conductor arrangement of unprotected sections, IEC 60364-4-43 shall be taken into consideration. For protective measures, the FBS shall mitigate a short-circuit fault which occurs outside stacks by:
– stopping the supply of energy and fluids to the flow battery cells;
– stopping PCS and opening circuit breaker(s); and,
– interrupting the short-circuit current path by using fuses between stacks.IEC 62932-2-2 pdf download.