The use of minimal intervention operations and keep it simple designs lead to successful distributed control systems on well buoy type applications To make minimal intervention successful a balance of the following characteristics must be used
Extremely high availability
Minimum complexity and size
High levels of remote live diagnostics drawings both of the control system and the production facilities
High level of system integration and low system diversity
Obviously the first three characteristics are a must on small remote installations, as equipment space is minimal and accessibility is not good Therefore high availability systems guarantee operability for extended periods At the simplest level it can be achieved by a minimum of components, but this is not often the case as most applications need to be designed so that they continue to function even when a fault occurs This generally leads to the use of some form of redundancy The fourth item is in the man an important characteristic As experience has shown us, remote diagnostics as a requirement by operations personnel, is essential to providing maximum production, with minimum support costs Using live diagnostic drawing it is possible to pinpoint faults, and ensure dispatch of the right person together with the right spares, keeping unnecessary visits and down time to a minimum.
The last characteristic is where there is a need for simple design, and getting away from the box on top of a box syndrome, which is most evidently used in many system designs The concept of box on top of a box inherently makes the system very complicated As every box, or part of a system which interfaces to another third party type of box, is laden with complexity and bugs waiting to emerge Also the component count increases dramatically which in general proportionally impairs the overall reliability of the system
To overcome these pitfalls the use of a simple single box which comprises all of the above criteria is needed. In doing so, it will remove the knit one purl one mess of interconnects between boxes keeping component count down and helping to keep reliability high and overall cost down.
This type of design will also help operations personnel to understand the mass of real time information which is rapidly changing in then system By unification of different systems like ESD, F & G and Fiscal Metering under the same information technology umbrella, operations personnel can view their facilities through the same unambiguous window, from the production base right down to the field terminals(Diagram 1 and 2 are available in full paper)
Diagram 2 shows a single box comprising all the integration to various Fieldbus technologies, with fully open system connectivity and the capability of bringing in conventional I/O wiring, simplifying systems design completely. On top of this add the ability to bring back to the operator a real time diagnostic drawing which shows all process changes as they happen, you have a unique and very powerful system. The units can also be networked together to form larger systems using standard LAN type technology like Ethernet and open system type TCP/I/P protocols The LAN acts as the flexible backbone for the system and it allows for straight forward expansion if the need arises.