The paper describes a distributed-processor system for centralized monitoring, alarming, and control of the machinery plant of the MSV Tharos, a new multiservice vessel operating in the North Sea. The system architecture is unique in vessel control applications in that it uses multiple microprocessors located throughout the vessel and interconnected by a serial data link. This arrangement offers significant advantages in design, installation, operation, maintenance, and flexibility for change. The system configuration is described, with close attention given to the aspects affecting the above-mentioned areas. The benefits realized and problems encountered during vessel construction, system installation, and initial operations are discussed. It is concluded that the system has been successful in achieving its design goals and in realizing the benefits offered by its distributed architecture. This type of system is applicable to any vessel or platform which employs complex systems at diverse locations. These include drillships, production platforms, pipe-lay barges, etc. Judging from the experiences on the MSV Tharos and the trends established in shoreside process control, control systems using this architecture will be observed in more and more offshore applications in the future.
In January of this year the MSV Tharos ended its maiden voyage from Japan to the North Sea. Its mission is to provide support services, primarily diving, heavy lift, and on-site repair, for vessels and platforms in the British sector. At the same time it stands ready for fire fighting and emergency well control. A dynamically positioned semisubmersible, the vessel is impressive in appearance as well as in capabilities. But a close look at the engineer's control room (ECR) will reveal features that are truly unique on a vessel.
For instance, the entire machinery plant of the MSV Tharos can be monitored and controlled in the ECR from a single 30-inch-wide console. A second identical console immediately adjacent augments the first, at the same time serving as a backup. The engineers and other personnel who use these consoles perform their duties effectively and with confidence.
As a second example, the ECR exhibits surprisingly little cabling. In fact, the cable trays in the entire vessel are missing thousands of meters of signal cable normally found in a vessel of this complexity.
These are the two most striking features of the MSV Tharos which result from its information and control system, called the data management system (DMS). The DMS on the MSV Tharos is a newer version of systems of the same name on the dynamically positioned drillships SEDCO 472, SEDCO/BP 471, and the dynamically positioned drill semisubmersible SEDCO 709. (Reference 1.) But two important differences exist between the two versions. First, while the earlier systems relied on a centralized minicomputer to perform their processing, the latest DMS makes use of a process control technique known as distributed processing. Second, the system scope has broadened to include all commands, rather than just engine/generator start/stop commands. The effects of these differences are substantial.
