Name & Registered Office:
CATHODIC PROTECTION NETWORK INTERNATIONAL LIMITED
Development of dynamic computerisation of corrosion control
Automatically controlling corrosion reactions on networks of pipelines<7/FONT>
The program is being developed while "in use" and, at present, is limited to disclosing cathodic protection defects which could have been detected by any competant engineer.
However, historical data, from old records, has been subject to this program which has already revealed the causes of leaks that have actually occurred.
It is realised that human hindsight can normally perform this function but, by highlighting all the CP system defects as soon as the data is gathered, this tool would allow the
engineer to decide his priorities more clearly, and in many instances, would have prevented the leaks.
It is clear that the real cause of some of these particular leaks, was the huge amount of infomation presented to the engineer, which could not be examined and analysed manually.
WHAT IS MANUAL ANALYSIS?
It is normal practice to examine survey results page by page, looking for individual readings which are below a particular criterion. The next step is to examine related readings which are on the same page, and then to turn from one page to another, examining related readings. The weight of information relating to the leak area, obviously, clouded the issue before the application of the computer analysis.
CP is so complex that it is difficult to follow any line of logic and even more difficult to visualise the knock-on effects of all the readings that are available.
HOW DOES THE COMPUTER HELP?
The program under development has a display which highlights the electrical nodes where the current readings do not, apparently, balance according to the laws of DC electricity (Kirchov). It is clear that this condition cannot exist, and that the measurements must be inaccurate or the circuit diagram incorrect.
A sub-routine is being developed to explore the possibility that polarities have not been noted correctly. This can cope with any node with up to six connected conductors, at the
present stage of development. This will define the arrangement of polarities that will give a balanced result and could identify any pipeline that is discharging current from the system.
The computer analysis of pipe-to-soil potential readings is being approached on a statistical basis, as there is no international agreement with respect to a definative criterion, at present.
The computer is programmed to display certain conditions graphically, where they suggest that the electrical pressures might cause current to leave the pipelines. Once more, no
contentious theories are being utilised, but the massive number of voltage readings that are already available, are being displayed on a simple graphical format which allows more of the relevant data to be examined at one instance.
TESTING A HYPOTHESIS
One notion, that has been applied to historical data, has proved to be accurate. This uses potential shifts, calculated from voltage readings between unconnected steel
and other steel which is connected to the negative side of the CP system. Both measurements are normally made, in practice, with reference to an electrode in the same position at each location.
It has been noticed that there is a tendency for corroded pipelines to have fallen into an identifiable group, which is being used as an indicator to identify pipelines which
require special attention.
In this case, the supporting theory is too vague to report to this conference, but the results so far, look very promising. The computer is being used to perform boring, repetitive
calculations that would be time consuming and may not be of consequence. However, now that this routine is in place, the computer can test the theory against a limitless amount of data at no extra cost.
It is easy to compare the theoretical current flow, deduced from the voltage readings, with the actual current readings, taken in the field, as these are on the same spread sheet. The program simply brings these together in graphical display, on the same screen.
Future development of this project is to design and implement the integration of all the oil fields and trunk line cathodic protection systems so that one gigantic spread-sheet can
handle every voltage and current reading taken in the region.
This will be a relatively simple achievement, as spreadsheets can now handle enormous amounts of data.
The more difficult task will be to make it possible to compare data historically, by linking all the spreadsheets containing every reading ever taken so that every reading can be related to every other reading, both topographically and chronologically.
A feasibility study has been carried out in the UK, confirming that it is possible to construct a computern software product which will display a complete map of all pipelines etc. in the whole of an operation region. It will be possible to zoom in on any detail and view this in three dimensions. The computer will be capable of displaying the calculated amount of CP current and direction of flow at any node of the whole circuit.
This display would provide user friendly access to a data base containing tabular or graphical information, relating to the location selected on the map. This data-base could
contain all data relating to the asset depicted on the display. When this stage of the development has been reached as a cathodic protection tool, then it would seem opportune
to extend the data base to all other information.
USER FRIENDLY GRAPHICS
It is visualised that potentials will be represented by shading and colours and current flow by arrows such as are used on television weather reports. This would allow for product flow and pressure to be represented in the same way and it would enable this type of computer handling to be integrated with a total condition monitoring and operation control system.
Such a program would take time and expertise to construct, but would be a model on which all future development could be based. It could even contain all the drawings etc. (in CAD) which are presently held in drawing office archives.
The feasibility of such a program may seem far fetched, but there is already a transport planning program in the UK that is based on a similar concept. It consists of a map of most of the roads in the UK through which the user can access a wealth of information relating to any location.