Significant cost savings achieved at BP
19/04/2010
BP and Oceaneering engineering personnel working together at BP Wytch Farm in Dorset (UK) have achieved significant cost benefits by the application of advanced NDT technology. The ability to carry out the inspections whilst the plant remained in production are estimated to have generated cost benefits in the region of £12 million.
The scheduled 2009 inspection programme on statutory equipment at Wytch Farm, under the Pressure Systems Safety Regulations Written Scheme of Examination, stipulates a requirement for intrusive inspection which would have required a costly process shutdown. Pressure vessels and pressure systems are required to undergo periodic statutory invasive inspection and other NDT to ensure continued safe and reliable operation. This requires vessels to be inspected for possible internal degradation and this is frequently achieved by means of an internal visual inspection coupled with surface flaw detection methods. However, there can be a very high cost associated with shutting down a vessel (loss of production), isolating it and preparing it for entry. Furthermore, the mechanical disturbances involved in the preparation and reinstatement of the vessel for internal access may adversely affect its future performance. Finally, and by no means least, man access is always potentially hazardous.
The assembled team of BP and Oceaneering engineers, using the guidelines detailed in 'Recommended Practice DNV-RP-G103 Non-Intrusive Inspection', were able to justify the use of advanced corrosion mapping technology to be deployed by Oceaneering technicians, alleviating the need for costly vessel entry, the subsequent disposal of Naturally Occurring Radioactive Material (NORM) polonium-210 deposits and ultimately and most significantly no requirement for a 14-day process shutdown.
Preferential Weld Corrosion (PWC) was identified in wellsite flow line welds by conventional radiography during a planned wellhead shutdown. An inspection campaign was initiated on pipe diameters and fittings ranging from 4" to 16" with wall thicknesses from 12.7 mm to 33 mm, to identify the full extent of the problem. Geometry and wall thickness coupled with a requirement to inspect whilst the process was online made conventional radiography impractical. Following onsite trials on a known defect, advanced computed radiography technology was identified as a suitable technique to reliably identify the welds affected by PWC. Approximately 1100 welds were radiographed by Oceaneering personnel; the radiographic images identified 200 welds with flaws, of which 50 welds with significant defects were replaced.
During the inspection campaign, Oceaneering radiography technicians were HSE audited by BP on three separate occasions. On each occasion a 100% score was achieved; the technicians were congratulated on the work ethic, safety culture and safety record with no recordable accidents or incidents.
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