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Capability · 05 / 09 · Offshore engineering

Mooring System Design

From environmental loads to anchor sizing.

Lead time · 4–8 weeksFixed-fee, fixed-scopePrincipal-ledAuthor · Sérgio Ribeiro e Silva, PhDLast reviewed ·
✦ TL;DR

Mooring system design is the discipline that turns a metocean dataset into a steel bill of materials — spread, taut-leg, single-point, or dynamic-positioning systems for floating renewables, aquaculture, FPSOs, and offshore platforms. KDS Offshore screens configurations in ARIANE-3D, runs dynamic analysis in OrcaFlex or MOSES, and certifies fatigue to DNV-OS-E301 or API RP 2SK.

Overview

What this service is

Mooring is the discipline that turns a metocean dataset into a steel bill of materials. We design spread, single-point, and dynamic-positioning support systems for FPSOs, floating wind, wave-energy converters, aquaculture, and offshore platforms — permanent or temporary.

Quasi-static screening with ARIANE-3D, then dynamic analysis in OrcaFlex or MOSES, then fatigue assessment to the relevant DNV / API rule. The output is a line-tension envelope, an anchor-sizing table, and an installation procedure the operator can hand to the contractor.

We have run this discipline since the GRS Power Platform parametric-rolling assessment with WavEC at Belmullet in 2015. The hard-won lessons live in the assumptions log of every job we run.

See our methods →

Outcomes

Numbers we expect to defend

6 OWCs
analysed in single hybrid platform
GRS Power Platform, WavEC Offshore Renewables, Belmullet (Ireland), 2015
ULS + ALS
design environments per project
operational, survival, and accidental conditions modelled
25 yr
typical fatigue design life
rainflow + S-N to DNV-RP-C203, with margin reported
4–8 wk
lead time on a single-deployment study
screening + dynamic + fatigue + installation procedure
Deliverables

What you get

01
Mooring analysis report (quasi-static & dynamic)
02
Static & dynamic, single-body & multi-body
03
Line tension envelopes
04
Anchor sizing & holding-capacity calculations
05
Fatigue life assessment
06
Installation procedure
07
Operation & inspection manual
Fit

When this is the right call

✓ When to use
  • Floating wind, wave-energy, or solar — coupled controller / mooring problem where uncertainty is in the metocean dataset.
  • FPSO or permanent offshore installation with a multi-decade service life and fatigue-critical lines.
  • Aquaculture or temporary moorings needing a defensible installation procedure for an unfamiliar contractor.
  • Re-analysis of an existing mooring after damage, line replacement, or environmental reassessment.
✗ When not to use
  • Ship-to-ship transfer / tandem mooring operations (use a marine operations consultancy).
  • Pure anchor-design without metocean coupling (use a specialist geotechnical firm).
Methodology

How we run a project

  1. 01 / 04

    Site assessment

    Metocean (current, wind, wave) at the deployment site. Soil characterisation for anchor design.

  2. 02 / 04

    Configuration screening

    Quasi-static analysis in ARIANE-3D across candidate configurations (spread, taut-leg, single-point).

  3. 03 / 04

    Dynamic analysis

    Time-domain simulation in OrcaFlex or MOSES, including line dynamics and hydrodynamic coupling.

  4. 04 / 04

    Fatigue and certification

    Rainflow counting, S-N curves to DNV / API, and a class-society-ready package.

Tools & methods

Software stack we use

  • OrcaFlex
  • MOSES
  • ARIANE-3D
  • KDS Mooring (proprietary)
  • SESAM · DeepC · global response
  • WAMIT
  • Ansys Aqwa
  • Ship@Sea
  • DNV / API rule sets
Regulatory context

Frameworks we help you satisfy

  • DNV-OS-E301Position-mooring — operational, survival, and ALS design rule set.
  • API RP 2SKDesign and analysis of station-keeping systems for floating structures.
  • DNV-RP-C203Fatigue design of offshore steel structures — S-N curves and rainflow methodology.
  • DNV-OS-J103 (floating wind)Design of floating wind turbine structures — mooring and global response.
  • IEC 61400-3Wind-turbine design requirements for offshore (couples with mooring loads).
Vessel types

Where this discipline applies

  • Floating wind sub-structures (semi-sub, spar, TLP)
  • Wave-energy converters (point absorbers, OWCs, attenuators)
  • Floating solar arrays
  • FPSOs and FSOs
  • Offshore aquaculture (fish-farm cages)
  • Temporary moorings (construction, commissioning, decommissioning)
Selected work

Where this discipline was used

·01GRS Power Platform — parametric rolling assessmentWavEC Offshore Renewables2015↗
Common questions

FAQ

Spread vs taut-leg — how do you choose?

Water depth, motion budget, footprint allowed by neighbours, and anchor cost. A taut-leg system gives you a tighter motion envelope but pays for it in anchor pretension. We screen both before recommending one.

Do you cover floating-wind moorings?

Yes. Floating-wind couples mooring, controller, and aerodynamics — we coordinate the mooring side with the wind-side analyst (or run the coupled model in-house) so the controller and the mooring agree on what the rotor is doing.

How do you handle uncertainty in the metocean dataset?

Hindcast plus measured data where available, sensitivity studies on the worst directions, and a documented uncertainty band in every line-tension envelope. We do not hide it inside a "safety factor."

Research

Reference publications

  1. [1]Ribeiro e Silva, S. et al. (2011). Numerical modelling and assessment of the UGEN floating wave energy converter. International Journal of Marine Engineering, Vol. 153.
  2. [2]Ribeiro e Silva, S. et al. (2016). Hydrodynamic optimization of the UGEN wave energy converter. International Journal of Marine Energy, Vol. 15.
  3. [3]Ribeiro e Silva, S. et al. (2021). Model testing of floating wave energy converter with internal U-shaped oscillating water column. Energy Conversion and Management, Vol. 240.
  4. [4]Lourenço, D., Ribeiro e Silva, S., Pinto, L. (2025). Wave Energy Conversion Efficiency of the UGEN along the Western Portuguese Coast. EWTEC 2025, Funchal. ↗
Other capabilities

Eight other disciplines, one office

✦ Brief this service · Mooring

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A 30-minute call with a principal. No deck, no sales engineer. Two engineers, your problem, an honest answer about whether KDS is the right firm.

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