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Inspection & Construction Petrogas

Inspection & Construction Petrogas

In support of the annual maintenance program, Petrogas requested the services of Bluestream Offshore in order to carry out inspections and construction work at some of their platforms in the North Sea sector. For the purposes of this project the diving support vessel “Deep Helder” was utilised and,carried all the necessary project equipment, materials and project teams (divers, ROV pilots and staff members).

Inspections were carried out on its support structure and the conductor field. Primarily before the inspection work could be undertaken the objects to be inspected (braces, clamps, anodes and joints etc) were cleaned by divers using a high pressure water jet (>1000 bars) and/or grit blaster. A grit blaster uses a combination of compressed air and fine glass particles in order to clean the inspection area from any debris, marine growth and corrosion. After cleaning to the prescribed standards, the inspection work itself consisted of a visual inspection to confirm the objects were still intact and that their operational status (eg mechanical damage, erosion, corrosion etc) was logged and recorded on video. In addition to the visual inspection an MPI (magnetic particle inspection) was also carried out. This method is used to detect any surface cracks in the material at specific joints of the structure. Surface cracks can be caused by the dynamic stresses from waves and wind which have a strong impact on the structure. This type of damage is also known as fatigue.

The platform A12 and the new platform A18 needed to be connected via already installed pipelines on the seabed. The last set of spools therefore had to be manufactured and installed. With a metrology tool, the dimensions of the last spool were measured. The spools were fabricated onshore, collected at the harbour and installed on site. The installation of the spools was completed in cooperation with the A12 and A18 platforms. Spool flanges were connected by hydratight method, a special hydraulic tool procedure to ensure the stud bolts were equally tightened to establish a perfect seal between spool flanges.
Although weather conditions at this time of the year (autumn) can prove to be challenging and often causes delays in the diving and ROV operations, Bluestream was able to keep the number of days on standby to a minimum and the project was successfully completed within the agreed timetable. This was achieved through the efforts of Bluestream’s well-motivated and highly professional team members.

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