CALM buoy
General information
Ever since the early days of the offshore industry, the Catenary Anchor Leg Mooring (CALM) buoy has been a succesfull system for importing and exporting of oil. Initially, these buoys were moored in relatively shallow water at near shore locations, often in very harsh wave conditions. In recent years the use of CALM buoys for offloading crude oil from FPSOs in deep water, for example at a number of West of Africa oil fields, is becoming more and more common. Here, the environmental conditions are more mild, but the water depth is a complicating factor.

Services & Activities
The Offshore Department is has been involved in many CALM buoy model tests and numerical simulations, assessing the motions, mooring loads, green water loads, riser behaviour and offloading, both in shallow and deep water. The behaviour of the buoy alone is investigated (e.g. in survival conditions), but also the behaviour of a shuttle tanker moored to the CALM buoy, including possible fishtailing instabilities. Furthermore, detailed investigations of the CALM buoy hydrodynamic properties can be made, through large scale captive and forced oscillation tests.

The Trials & Monitoring Department has been involved in full-scale measurements on several CALM buoys. Buoy motions and mooring line loads are measured and analysed, paying special attention was to mooring line fatigue.

MARIN's nautical simulator centre MSCN can provide training programmes for offloading operations, including the shuttle tanker, CALM buoy, FPSO and assisting tugs in the simulator model.

Facilities & Tools
Calm buoys are tested in the following MARIN facilities :

The behaviour of CALM buoys is simulated with the following tools : (MARIN internal use only)

Software Sales
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.

Experience record
The list below gives a review of deep water CALM buoy model tests carried out at MARIN:

  • CALM buoy large scale model tests, scale 1:20 (Bluewater Energy Services BV, 2004)
  • Erha deepwater CALM buoy large scale model tests, scale 1:28.75 (SBM, 2003)
  • Deep draft export buoy model tests, scale 1:60 (Single Buoy Moorings Inc., 2002)
  • Kizomba SPM model tests, scale 1:60 (Single Buoy Moorings Inc., 2002)
  • CALM buoy large scale model tests, scale 1:20 (Bluewater Energy Services BV, 2001)
  • Bonga SPM model tests, scale 1:60 (Single Buoy Moorings Inc., 2001)
The list below gives a review of shallow water CALM buoy model tests carried out at MARIN :

  • Porto CALM buoy model tests ((Single Buoy Moorings Inc., 2002, 2004)
  • Mooring tests on a shallow water CALM buoy (Bluewater, 1997)
  • Australian North West Shelf CALM (Bluewater, 1996)
Most recent CALM buoy papers presented by MARIN
(complete overview of papers can be found under Publications)

Girassol buoy under tension
Pieter Aalberts, MARIN Report, 2005

New publication on Deepwater CALM Buoy
Hans Cozijn, MARIN Report, 2005

Heave, Roll and Pitch Damping of a Deepwater CALM Buoy with a Skirt
Cozijn, J.L., Uittenbogaard, R. and ter Brake, E., ISOPE Conference, Seoul, 2005

Truncation Methods for Deep Water Mooring Systems for a catenary moored FPSO and a Semi Taut Moored Semi Submersible
Waals, Olaf J. and van Dijk, Radboud R.T., DOT Conference, New Orleans, 2004

Downtime Analysis Techniques for Complex Offshore and Dredging Operations
van der Wal, Remmelt and de Boer, Gerrit, OMAE Conference, Vancouver, 2004

CALM buoy articles written for MARIN Report
(complete overview of articles can be found under Publications)

Girassol buoy under tension
Pieter Aalberts, MARIN Report, 2005

New publication on Deepwater CALM Buoy
Hans Cozijn, MARIN Report, 2005

MARIN helps improve CALM buoy design
Hans Cozijn & Tim Bunnik, MARIN Report, 2002

Contact
For more information on how MARIN can help your organisation with FPSOs, please contact:

For model test and simulation activities: Offshore Department
For full scale measurements: Trials & Monitoring Department
For nautical training :MSCN


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