3.1 ‘Failure mode, effect and criticality analysis’ (FMECA) is used to systematically determine and record the safety information. The standard FMECA as defined by the HSC Code has been expanded and manipulated to fit Rescue Boat requirements more accurately.
3.2 The functional analysis provides a systematic structure for investigating possible failures. A methodical brainstorm involving relevant design and operational personnel can then be used to generate the information required by the FMECA.
3.3 Each item specified in the functional analysis should be studied in turn, with the initial aim of identifying all possible failure modes that could occur. A failure mode is a way in which an item can fail, and each failure mode should be given a separate row in the FMECA table. For each failure mode, immediate causes should be generated. The effects of each failure mode
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should also be determined. The aim is to determine the overall effect of the failure at the highest level: these final effects are named ‘end events’ and should be determined at the outset of the FMECA. A qualitative measure of the severity of each event should also be determined at the outset. As such
‘local’ effects can be described as all the effects that occur as a result of the failure that are prior to the end event. The appropriate end events can then be simply chosen from the list.
3.4 By looking at causes and effects associated with each identified failure mode, possible failure paths (‘a combination of basic events which occur together to produce an end event’) are being determined. The failure path leading to a specified end event is also known as a ‘hazard’. In order to facilitate the identification of hazards, key words can be used during the brainstorm to
‘trigger’ thought processes. A list of key words that normally form the basis of a standard HAZOP (HAZard and OPerability) assessment can be used.
3.5 The probability of each identified failure path occurring can be judged using accepted qualitative criteria. The probability is the likelihood that the failure mode will occur and lead to the end event i.e. the probability of the path, and not just the failure mode in isolation. Risk is a combination of the likelihood of a failure path occurring and the severity of consequence of the associated end event. Using a risk matrix, a measure of risk (or criticality) can be associated to each identified failure path.
3.6 A failure mitigation process should be carried out whereby risks considered unacceptable by the FMECA can be mitigated to a level of at least ‘as low as reasonably practicable’.
3.7 This guide details definitions for HAZOP identifiers, failure probabilities, consequence severities and risks. A spreadsheet should be created to store the FMECA information, see Para 8 of this Appendix.
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4. HAZOP keywords
Key Word Parameter
Operation - No action Intended action did not occur; action not possible
Operation - More action More than intended occurs; Other actions affecting this action occur – Rescue Boat Organisation assumes that he is intended to conduct additional actions
Operation - Less action Action does less than intended – equipment does not perform as required – insufficient time to complete action.
Operation - Extra action Extra actions carried out other than what was intended – Rescue Boat Organisation assumes that he is intended to conduct several actions.
Operation - Incorrect action
Operator conducts wrong action – misses out a step in action process etc.
Environment – Wind What is the effect of wind – what is the limiting speed?
Environment – Waves What is the effect of waves – what is the limiting size?
Environment – Surf What is the effect of surf – what are the limiting factors?
Environment – Night What effect does night time have?
Environment – Day Are we limited to day time only?
Environment – Visibility Is visibility a limiting factor?
Environment – Temperature
Does heat/cold have an effect – what are the limits?
Effect – Stability Will anything have an effect on boat stability?
Effect – Structure Will anything have an effect on boat structure / fittings?
Effect – Fire Will anything induce a fire?
Effect – Safety Will anything require personal protective eqp’t, etc.
Effect – Training Requirements for specific training?
5. Probability definitions
FMECA Code
PROBABILITY Definition
F Frequent Likely to occur often during the operational life of a particular craft.
RP Reasonably probable
Unlikely to occur often but may occur several times during the total operational life of a particular craft.
R Remote Unlikely to occur to every craft but may occur to a few craft of a type over the total operational life of a number of craft of the same type.
ER Extremely remote
Unlikely to occur when considering the total operational life of a number of craft of the type, but nevertheless should be considered as being possible.
EI Extremely improbable
An event that is so extremely remote that it should not be considered as possible to occur.
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