Mooring Analysis

Stewart Technology Associates (STA) have designed and analyzed pier project moorings, spread moorings in shallow and deep (up to 3,000 m) water. We use OrcaFlex and other in-house tools for hydrodynamic analysis and dynamic mooring analysis.  We also specialize in SINGLE POINT MOORING analysis and design verification.  

We often take a quick first look at SPMs using our commercially available software, STA SPM.

We analyze and design drag anchors and pile anchors with our commercially available software, STA ANCHOR and STA PILE3.

We use our commercially available software STA CHAIN, to analyze the buried portions of anchor chains to padeyes on pile anchors and to padeyes to buried plate anchors. 

We use or commercially available software, STA PULLOUT to design and analyze driven and suction embedded (SEPLA) plate anchors.


The video above shows an LNG Carrier and an FSRU at a pier mooring in Bangladesh, analysed and mooring system optimized in 2017/18.

Bil Stewart is principal and co-author of two OTC papers comparing offshore industry codes and standards for mooring systems: OTC-26035-Mooring of MRE Structures – Comparison of Codes, Including IEC, 2015, and OTC-27870 Mooring System Considerations for Renewable Energy Standards, 2017.

FPSO Spead Mooring, West Africa

The video below illustrates part of the analysis of an all-chain, 12-leg FPSO mooring off Nigeria.  A squall wind condition is analyzed in the time domain using OrcaFlex.  This particular simulation is run with 2nd-order slow drift forces for just 400 seconds, the full duration of the squall.


Windage and Current Areas

STA has standardized analysis tools for developing the wind and current drag coefficients and areas. An example is shown below, including yaw drag area moments in consistent units for OrcaFlex.


FPSO Plan View Mooring Systen, Excel




We Perform Mooring Analysis
One of the areas of expertise we have at STA is mooring analysis. Marine organizations that need assistance with installing mooring systems have sought out STA. We provide consultation for mooring analysis such as spread moored systems and single point moored systems, which includes turrets, CALMs, SALMs, towers, submerged buoys, and more. We also provide consultation for harbor and jetty moorings, which accommodate large ships, small ships, dolphin interactions and passing ship issues.

We Utilize Technology in Our Analyses
In order to perform our jobs correctly, we have the latest in marine technology at our fingertips. To do jobs such as a mooring analysis, we use Orcina’s OrcaFlex (supplemented with our in-house programs). This is one of the most powerful marine technology software available today. We have used it since we started in 1986. More than 1000 organizations, all over the world, use OrcaFlex for design and analysis work. It is a comprehensive software solution that allows STA to perform a wide range of analyses.

We Have the Experience, Knowledge and Technology
We have earned the reputation as being one of the most trusted marine consultancy agencies in the world because we have the experience, knowledge and technology to do the jobs such as a mooring analysis.