At the beginning of 2007 British Energy approached Mike Lloyd Technical Services Ltd to develop a new measuring system for a specific in boiler pipe section replacement. The pipe section to be replaced was not easily accessible.
This view shows a typical section to be replaced; the boiler casing has been removed to show the internal location. To give an idea of scale, the height difference on the replacement pipe is 350mm.
The initial problem was access and visibility, also the system had to deliver real-time accuracy confirmation and be capable of measuring nine pipe ends for position and attitude, in a two hour time period.
The options reviewed were laser scanning, Photogrammertry, total station auto target observation, CMM arm measurement and a bent wire. All were rejected due to the cramped conditions and lack of visibility or accuracy.
The system chosen was developed in Norway by Metronor. The Metronor Solo had the advantage of fast, accurate hidden point measurement. The Solo system with operator guidance software developed by Mike Lloyd Technical Services Ltd fulfilled all of the British Energy requirements; 'accuracy and the saving of time in the vessel are very important to British Energy. Time saved = dose hence the speed of the Metronor system compared to the old system or any alternatives were an important part of the selection criteria'.
Doosan Babcock; British Energy's vessel entry contract partner played a vital role in the implementation of the system, creating procedures and training documentation to complete the task of surveying in a very confined and hostile environment.
The Metronor Solo system www.metronor.com which uses a camera and carbon light pen, enable accurate (+/-0.2mm) hidden point observations.
This system uses a single camera and a small array of LEDS on the light pen.
To allow the light pen probe to contact the pipe end a special drilled pipe plug was developed. This had two advantages; the operator could not always see the probe to know if it was in the correct position on the pipe before initiating a measurement and if the array of drilled holes are on a known circle then accuracy confirmation can be achieved.
The application developed to confirm accuracy during measurement and simplify the overall task played an important part in the overall success of the project. Any task undertaken in a nuclear power station boiler requires meticulous planning and a high degree of automation. The work face operators benefited from a simplified method for this difficult measurement task.
The final solution was to transmit the observation via an umbilical to the controller outside the vessel. The controller can review the application input and accuracy confirmation and give instructions to the work face operator.
The final report can be produced immediately as part of the confirmation process.
Together with this report a design file is produced for the manufacture of the new insert.
The manufacture of the new insert has been established for a number of years and the control of the dimensional accuracy of this is achieved using our pipe spool measuring system automet®.