Cleaning a Flange to Bare Steel Without a Diver or an ROV
A bend stiffener clamp needed bare steel to land on, at the bottom of an I-tube under an STL buoy. Everything had to be run from the deck of the FPSO, and everything had to be Zone II.
- Client
- Jadestone Energy
- Location
- Montara FPSO, Timor Sea
- Delivery
- Two shifts on site, 2019
- Sector
- Subsea & Offshore
- 2 shifts Tool install and all cleaning operations
- Zone II Rating on all supplied equipment
- 360° UHP jetting rotation at the target
- None Diver or ROV intervention required
The problem
Jadestone had a requirement to install a new umbilical in a previously unoccupied I-tube at the base of the STL buoy. As part of that scope a bend stiffener clamp had to be clamped onto the flange at the bottom of the I-tube. For the clamp to be effective, the flange had to be cleaned back to bare steel.
That meant removing all marine growth and coatings from the internal surface of the I-tube, from the base, side and top of the flange, and from the external surface of the I-tube up to 100 mm above the flange face. Two constraints shaped the tool: the cleaning had to be operated remotely from on board the FPSO, and all equipment supplied had to be Zone II rated.
What we built
The I-tube cleaning tool uses an ultra-high pressure water jetting nozzle to provide the required level of cleaning. It is installed into the I-tube with the assistance of a winch, through the I-tube opening on top of the STL buoy. Because of the build-up of marine growth in the bore, the tool had to clean a path ahead of itself as it descended. Once at the target location, the jetting nozzle extends up to the surface to be cleaned and a 360-degree rotation is completed.
A suspension system provides a solid foundation for the tool during all cleaning activities and accommodates variation in the bore of the tube. In this instance the tool also had to traverse a constriction in the diameter as it was lowered. The design can be tailored to different sizes of pipework without redesign.
Outcome
Once the UHP equipment was set up, installation of the cleaning tool and all cleaning operations were completed over two shifts. The tooling provides a remote, Zone II method of cleaning I-tubes and J-tubes with all operations completed from on board the FPSO or platform, removing the requirement for diver or ROV intervention entirely.
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