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Hybrid applications of IEC61511 – Laurie Blackmore
Disadvantages include:
§
SIS is as big or even bigger than the non-61511 (API) design leading to increased
complexity of operation, maintenance. This increases the risk of systematic faults - the
primary cause of major incidents
§
Testing frequency is still based on API RP14C (3 months transmitters, 1 year SDV‘s)
rather than (longer) IEC61511 intervals. This reduces ability to focus on the high-risk
functions.
§
The engineering cost and potential schedule increase associated with IEC61511 is
incurred without the benefit of equipment rationalisation or reduced testing costs
Lifecycle/contract issues:
§
Make sure it is clear in the contract if IEC61511 applies to only safety or includes asset
etc
§
Only apply 61511 lifecycle requirements for stages after SIL assessment for safety
SIF‘s at SIL 1 or above? (Clarify in the contract since it has an impact on engineering
hours and potentially equipment)
11
Full lifecycle implementation but with retention of all API protection