Nautec completed the strengthening of a three legged MOPU platform located in East Java, Indonesia. Nautec was commissioned for the grouting of X-Brace clamps as part of a structural strengthening program. The X-Braces are connected horizontally and diagonally to the circular legs in order to improve the fatigue life of the platform. In consultation with the Client, Nautec proposed a full engineering and technical solution that comprised offshore grouting using UHPC (Ultra High Performance Cementitious) grout.
PT Radiant Utama Interinsco.
The scope of work included the cleaning and removal of existing OPC grout, sealing of the leaks in the clamps and filling of the annulus with UHPC grout. The X-Braces are connected horizontally and diagonally to the circular legs in order to improve the fatigue life of the platform.
One of the challenges of this project was to ensure that the identified leakages would be properly sealed. Grouting of the X-brace clamps was previously attempted by other contractors using OPC materials. Because of leakages the process could not be completed.
Water depth is 58m.
The offshore grouting was carried out following a thorough visual inspection using a high definition boroscope camera. The inward parts of the clamps’ annulus and tubular legs were inspected providing crucial information to plug the various leakages. During the offshore operations, comprehensive grouting monitoring and recording was carried out following specific QA/ QC procedures. The grouting operations were successfully completed within schedule.
Typical OPC grouts, because of their inherent physical properties, are not suitable to seal leaks. However, using UHPC grouts, mixed with gravel aggregate, makes the self-sealing of leakages possible. UHPC grouts also offer the advantage of developing the designed strength quickly thereby reducing the total number of offshore days and allowing other offshore activities to commence.
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