MOSS | Mechanical On Site Services

Ring Type Joint Machining

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Moss were approached by a Aberdeen fabrication company with regard to the machining of a subsea tie in spool that had been sent onshore for refurbishment.


The spool had been stored open to the elements and when it was required for installation it was not fit for purpose due to the heavy corrosion on the flange sealing faces . Both 7.1/6 5K BX156 seal grooves required machining to remove the corrosion and pitting and return the dimensional sizes back to tolerance.


The seal grooves had to be machined with the minimum amount of metal removed to remove the corrosion and to be within the stated dimensional tolerances. The spool had to refurbished within a tight timeframe as subsea installation was only days away.


Competent Moss technicians and an external mount flange facing machine was used to machine the faces and angles of the sealing groove. The corrosion was removed and the dimensions were measured using ball trammels to ensure the necessary tolerances of +/- 0.05mm (0.002) were achieved.

Dimensional report s were produced for each flange, detailing both pre and post machining sizes satisfying the project quality plan. The spool was returned to the fabricator where it was successfully hydrotested ready for installation load out within the required timeframe.