Triton Naval Architects

services / mooring analysis

Dynamic Mooring Analysis

Non-linear dynamic (time domain) mooring analysis were performed on a number of Oil Rigs and FPSO's as listed below.

1.1 F.P.S.O. Glas Dowr (2003) Alongside Dynamic Mooring
1.2 Semi Sub - South Seas Driller (Pride South Seas) Alongside Dynamic Mooring
1.3 Semi Sub - Gavea Lifter / Sedco 709 Alongside Dynamic Mooring
1.4 F.P.S.O Dalia Alongside Dynamic Mooring
1.5 Semi Sub Orca Alongside Dynamic Mooring
1.6 Semi Sub - Atlantic Venture Alongside Dynamic Mooring
1.7 Semi Sub - Transocean Richardson Alongside Dynamic Mooring
1.8 Semi Sub Scarabeo Alongside Dynamic Mooring
1.9 FPSO - Glas Dowr Alongside Dynamic Mooring (2009)
1.10 Semi Sub - Sedex 701 Alongside Dynamic Mooring (2009)
1.11 Jack Up - Hercules 185 Alongside Dynamic Mooring (2009)
1.12 Semi Sub - Transocean Celtic Sea Alongside Dynamic Mooring Saldanha Bay (2011)
1.13 CALM Buoy 8 Point Offshore Dynamic Catenary Mooring PetroSA (2012)
1.14 Semi Sub ORCA Alongside Dynamic Mooring (Coega) (2013)
1.15 Scarabeo 7 (A Berth Cape Town) (2013)
1.16 Semi Sub Ensco E3001 - Alongside Dynamic Mooring Cape Town (2014)
1.17 Dhirubhai Deepwater KG1 Drillship Alongside Dynamic Mooring (2014)
1.18 Qurban Abasov 8 Point Catenary Mooring Caspian Sea standing off and gangway connected to a BP Platform (2014)
1.19 Transocean Marianas Alongside Dynamic Mooring Coega (2015)
1.20 Maersk Deliverer Alongside Dynamic Mooring Coega (2015)
1.21 Semi Sub ORCA Offshore Dynamic 9 Point Catenary Mooring at Mossel Bay (2015)
1.22 Semi Sub CBC Newbuild Offshore Dynamic 8 Point Catenary Mooring in Caspian Sea (2016)

These were all analyzed for moorings for extended periods of stay in Cape Town, Walvis Bay, Saldanha Bay, Mossel Bay and lastly Caspian Sea and assumed 10yr, 25yr, 50yr and 100yr return wind and gust speeds, as applicable, or other applicable client supplied data. Most requiring foreign third party approval. The CALM Buoy is a permanent mooring off the coast of Mossel Bay / Agulhas. These were all TIME DOMAIN dynamic analysis, which would then predict peak line tensions, dynamic bollard reactions, dynamic fender reactions and displacements off and along the quay. Single line failure analysis would also be performed, as required by the various approval authorities.

The offshore moorings cases would be analyzed for compliance against compliant with DNV os-e301_2010-10 and API RP 2SK and analyzed for both Diffraction Analysis (motions) and in the Time Domain (for dynamic prediction of mooring line responses and vessel offsets). ULS (Intact), ALS (Single Line Failure) and Transient Analysis (dynamic response prediction during line failure) is performed. Statistical Analysis of time series results are performed according to the requirements of DNV os-e301_2010-10.


QURBAN ABASOV - Dynamic Mooring in the Caspian Sea (2014)

This catamaran shaped accommodation and supply vessel, chartered by BP, to offer crew accommodation and support for their Central Azari Oil Platform, off Baku in the Caspian Sea, required stringent dynamic mooring analysis, to ensure compliance for both Alongside the Platform, for servicing an articulated motion compensated gangway for crew changes, or whilst standing off, for severe weather scenarios, each with their own set of minimum requirements. The analysis being performed to DNV-OS-E301 and API Rp 2SK requirements, and approved by the BP Houston office.

The 8 point mooring catenary spread made more complex by the very long, multi section mooring lines, comprising of chain, wire rope and dyneema fibre arranged in such a way as not to infringe or make contact with various subsea assets including gas and oil pipe lines, coupled to severe metocean conditions including 9m Significant Wave Height conditions (in certain directions). The analysis was performed as a Hydrodynamic Diffraction Analysis followed by Time Domain Analysis, using the ANSYS AQWA software suite.



Triton has also designed numerous fender barges and docking frames, customised to the specific quay, so as to maintain the required fendered distance off the quay. Many of these frames are semi submersed to allow the semi submerged hull of the rig to bear directly against the frame which in turn, bears directly against the quay wall, at that same level.


Triton Naval Architects
No. 8 Foregate Square, Harbour Rd
Foreshore, Cape Town, SOUTH AFRICA
Tel: +27 21 418 2090 | Fax: +27 21 425 2722 | Email:

By Triton Naval Architects


photos & images


Gavea Lifter carrying the Sedco 709 on her Back


FPSO DALIA - 300m in length, 60m in beam, moored in Cape Town for about 4 months, through the winter storms.


3 Legged Semi Sub, ORCA during her 1yr refit in Cape Town.


3 Legged Jack Up Rig, Hercules 185 in Walvis Bay - Triton involvement included Mooring Analysis and Deadweight Survey for Stability purposes.


Typical Custom Designed Fender Pontoons with submerged Docking Frame