Networks For Offshore Instrumentation Available to Purchase

The implementation of current instrumentation schemes on offshore structures requires a careful analysis of system interconnections, not only between instruments but also between data acquisition systems and operator interfaces. Offshore structures place constraints, principally of distance, local interference, power and environment upon networks and their components. In addition, particularly in the case of safety systems, minimum response times must be maintained despite multiple alarms and power failures. Network topologies are examined, available standards reviewed and suggestions made as to suitable criteria for the various components, both hardware and software, for offshore instrumentation networks. Particular attention is paid to the materials used, interconnection methods, failure modes and fall back systems. Conventional cable, coax and fibre optic systems are examined with attention paid to the specific requirements of offshore cables and installation practices. Data transmission standards are examined with respect to robustness, peak load capacity, error detection/correction and redundancy. Particular attention is paid to the points at which analogue to digital conversion takes place, multiplexing and intermediate data storage. Finally the issues of data presentation, archiving and distribution to other networks are examined. Included is a review of methods of remote access to the data and system maintenance. It must be kept in mind that offshore instrumentation systems typically work as standalone systems without dedicated staff or maintenance. There are economies possible by the shared use of instrumentation between the structural instrumentation and the process/operations instrumentation which can be obtained by good system design and interconnection networks. The paper is based upon instrumentation for past Arctic and North Sea structures as well as current practices proposed for the latest structures under design. Emphasis is placed upon the multiple use of instrumentation and systems to overcome the limited space and maintenance resources in the offshore. Reliability and ease of use are highlighted.