Practical results of implementing a risk-based protection system design in the offshore industry

摘要

It is now nearly 10 years since the process began to develop the IEC standard 61508, which is intended to define the basis for the specification, design, building, testing and operation of instrumented protection systems (IPS). These are electronic/electrical systems comprising three elements: (a) Sensors to detect unwanted conditions; (b) Logic elements (programmable or hard-wired) which determine appropriate action; (c) Actuating elements which carry out the protective control functions. It is several years since the seven parts were finally issued, and they now have a growing place in the C&I business activities of the process industries. The successful implementation of IEC 61508 (and its junior counterpart ISA S84 or the forthcoming industry version IEC 61511) can still remain elusive - partly because of the structure of the documents and partly through lack of understanding. What should result in a rationalisation and simplification of protection systems can all to easily develop into a snowballing of SILs and over-complication of equipment. This article looks at how Single Buoy Moorings Inc. (SBM) - a designer, supplier and operator of a fleet of floating production, storage and offloading vessels (FPSOs) - is dealing with the introduction of IEC 61508 into its control system design, and identifies both the construction and operational benefits that they will reap from more fit for purpose process protection. It will look at: (1) What is an FPSO and its processes? (2) Traditional design for IPS on FPSOs (API RP14C). (3) Risk-based approach to IPS design. (4) Implementation methodology for IEC 61508 (5) Protection design resulting from IEC 61508, compared with API. (6) Impacts on CAPEX and OPEX.