The enhanced reliability and downsizing of electronic equipment in general, together with the increasing power of microprocessors and the use of Industry Standard Protocols, has now opened up more than ever before the opportunity for Subsea Instrumentation Systems, to utilise Standard Instrument and Control equipment


The current exploitation of marginal oil and gas fields has resulted in the use of more cost effective methods of production, such as subsea wellheads. Control and Instrumentation just as in any other oil and gas installation, has a major role to play in the success of such applications. However, what should be a straight forward and simple application of a small DCS/SCADA System IS often complicated and over engineered to compensate for the perceived harsh environment into which the equipment is being placed, especially that which is being located subsea in actual fact, there are many propriety elements of such a DCS/SCADA System available today which, due to the state of current technology and Quality Assurance, are together suitable for such applications without recourse to over specified and therefore excessively expensive solutions. Whilst providing due consideration to the problems of Subsea/Topsides monitoring and control applications the use of PC workstations, PC based process control software packages, dual high security communications and remote intelligent I/0, can provide for a highly featured, secure and cost effective system.

Moreover, the established use of Smart transmitters which communicate digitally has meant that the ‘reading’ of Process values can now be made at the topsides terminal with a much greater degree of accuracy than via a conventional Analogue card Also possible with Smart sensors are enhanced self diagnostics and the ability remotely re-range and recalibrate the transmitters from the topsides terminal. This paper will examine just such a system and provide an overview of what can be achieved simply and effectively


In considering any Subsea Monitoring and Control System, there are three main elements, the Subsea equipment, the Communication equipment and the Topsides Monitoring and Control Sub-system We shall take each of the above In turn and briefly examine proprietary equipment which can be used In the Subsea environment, with little or no changes other than application specification engineering


This category of equipment can be broken down into three sub-headings, Primary Transducer, Electronic Interface and Communications

Taking each of the above in turn we will look at what is currently commercially available, as follows

Primary Transducer - Conventional

There is currently available a multitude of conventional transducers suitable for installation In some extremely harsh environments - far more onerous than can be found in the relatively stable environment of a Subsea Instrument housing Such transducers can be chosen, not only for their particular Interface characteristic se, pressure, temperature, flow, but also chosen for their reliability, quality and construction medium i e stainless steel, flameproof, etc Such transducers provide Industry standard outputs such as 4–20mA, voltage and milli-volt signals which can be "read" by virtually all I/O proprietary input/output equipment

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