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Copyright © Risknowlogy®. All rights reserved. v9
Does it give you the risk reduction you need?
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If you have good data
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From the initial design (assuming you still have the documentation)
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From proof tests (how often did you find dangerous failures - tells you PFD)
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From demands (supports the data from proof tests - how often did it work)
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If you don’t have good data
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You have to open the “black box”
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Get the drawings and go inspect to work out what you have (and how it works)
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Use 3rd party databases or - if all else fails - FMEA
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Be very careful that the numbers you use are relevant and statistically sound
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Don’t forget the other assumptions in the LOPA
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Initiating event frequency
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Other IPL’s
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Demand rate
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