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Track 2 Session 2
10:20 to 11:30 a.m. Wednesday
April 11, 2007
Estimating Reliability Parameters
and Demand Availability for Well Emergency Shut-Down Systems on
Offshore Platforms
The valves activated by the
Emergency Shut-Down (ESD) system on an offshore platform act to
shut off the flow of oil or gas from the wells in the event of a
breach of the topsides process equipment, downstream of the flow
wing valve. Reliability-wise, each well forms a 3-component parallel
system with the platform reliability being given by up to 40 wells
comprising a series system. The ESD system is a Safety Instrumented
System (SIS) to which the general requirements of IEC 61508 may be
applied. This presentation analyses the ESD test data from a large
platform consisting of 35 wells showing the issues around the
estimation of the component failure rates, specifically the valves.
Failure rates from well test histories are calculated using
parametric, non-parametric and Bayesian methods and the results are
compared with failure rates published in industry databases. The
test interval and the next test date, given the valve failure rates
and the ESD availability at the platform level to meet Safety
Integrity Level (SIL) 3, are predicted using spreadsheet functions.
A spreadsheet simulation of the combined well ESD testing is used to
validate the ESD availability calculations for the platform.
Key Words: Production Process, ESD, Safety Integrity Level
(SIL), Reliability, Availability, (Non-) Parametric, PFD,
Simulation, Safety Instrumented Systems
Geoffrey F.
Hampden-Smith
Process Physics Limited - Quest Technology Group
United Kingdom |
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