Category: Case Studies

The CVOW project is a great example of Tekmar Group’s complementary technologies and services working together to support multiple stages of an offshore project.

Tekmar Group companies; Ryder Geotechnical, Agiletek Engineering, Tekmar Energy, and Pipeshield International all contributed to the Coastal Virginia Offshore Wind Project (CVOW) on the East Coast of the US.

The 12 MW CVOW project is the first offshore wind project in US federal waters. This significant project includes the deployment of two 6MW commercial-scale offshore wind turbines that will help to determine the best practices for future offshore wind projects located on the East Coast.

Ryder Geotechnical, who specialises in geotechnical design and analysis, was the first group company to support the project, delivering a Cable Burial Risk Assessment (CBRA) on behalf of Ørsted in 2019. The CBRA was performed during the design stage of the project to quantify the risk to the subsea export and array cables from external sources.

Tekmar Energy, who specialises in subsea protection solutions, has since supplied Seaway 7 with TekLink® cable protection systems and TekDuct cable crossing protection for the construction phase of the project. AgileTek Engineering, who specialise in advanced engineering analysis, performed product design verification analysis on behalf of Tekmar Energy.

CVOW is one of several recent contracts awarded to Tekmar Energy by Seaway 7 and marks a clean sweep for the company in the US offshore wind sector, having previously supplied cable protection systems for Block Island offshore wind farm.

Pipeshield International, who specialises in concrete stabilisation and protection solutions, was also awarded a contract from Seaway 7 to design, manufacture and supply 30 bespoke concrete mattresses and associated lifting equipment for the protection and stabilisation of subsea cables on the wind farm.  Pipeshield’s in-house technical design department has developed a solution incorporating heavy density minerals, a high-quality concrete mix, and their patented N2 edge blocks to provide the industry’s most stable mattress.

AgileTek Engineering

The Problem

Geo-intelligence and asset integrity provider, Fugro, required a large number of simulations of subsea power cable installation operations to be performed to verify procedures, component sizes, and weather windows. Some of the analysis results were required at critical milestone points within the larger project which means server capacity needed to be scalable on-demand to meet these deadlines.

The Solution

To handle this project, we implemented our AELCloud system. This software is an online platform that AgileTek developed in-house, which runs analysis and simulations on both cloud and the client’s own local servers. It drastically reduces the time traditionally needed to run simulations and ensures information amassed is high-quality and traceable.

On this subsea installation project alone, AgileTek ran about 27,000 OrcaFlex simulations, equating to around 57,000 hours or just over six years’ simulation time. Eight terabytes of simulation file binary data were saved and AELCloud processed a total of 1.5 billion data points for critical metrics in the system.

Data at this scale cannot be stored on a laptop or processed with Microsoft Excel, which is why AgileTek have invested in a distributed digital data store with built-in redundancy and a highly efficient query language.

Using AELCloud created a number of benefits:

• Historically, engineering companies have owned their own physical servers, controlled and managed by corporate IT departments. AgileTek does not have an IT department and does not own any physical servers. Instead, we use on-demand server technology in the cloud to provide large machines that are optimised for computationally intensive tasks such as OrcaFlex analysis.
• For the AgileTek engineers, visualising and inspecting the data for these simulations was effortless with the AELCloud web interface. The critical load cases were clearly highlighted and links to graphs showing key metrics were plotted right in the user’s web browser. Summary results sheets were then automatically produced to highlight the weather limits for key operations. These were provided in a format that is easy to use on the vessel, while modeling methodology is documented separately in a concise engineering report.

The true power of AELCloud is that all data transfer, results specification, results from post-processing and reporting are performed automatically on a secure web application. This dramatically reduces the number of manual steps required to report the critical results.

AgileTek’s Managing Director, Steve Rossiter explained the rationale behind developing AELCloud: “I’d seen too many projects over the years where the time to process simulations resulted in delays that impacted project milestones, production slots and vessel availability.

“Constraints on storing and processing data also cause analysts to make assumptions about what data is worth processing and what isn’t. In the age of big data, these delays and limitations should not exist and so we built AELCloud to take advantage of this new wave of technology. After a year of development, it was great to see the system in action on this project with Fugro”

AgileTek Engineering

AgileTek has developed a methodology that takes into account the local stiffness of all cable components and includes a new approach to their non-linear slip/stick behaviour.

The Problem

Power cable projects require a significant number of analysis studies at various phases of development.

These typically include:

• Installation analysis
• Cable fatigue analysis
• Storm response and clashing analysis
• Protection system design and verification
• VIV screening

To obtain solid results, these studies all rely on accurate cable data, specifically bending, axial and torsional stiffness. The most effective way of obtaining these values is to perform testing on the power cable. This testing can be complex and costly to perform and worse, such analysis is often required before a cable sample can even be produced, leading to ever more over-conservative assumptions. Due to cost and time constraints, this has resulted in manufacturers providing values which are merely based on simple analytical formulations and whose basis is not transparent.

These formulations grossly over-simplify the mechanical behaviour of power cable, introducing technical risk and leading to unnecessary project expenditure and delays.

The Solution

AgileTek has developed a methodology which takes into account the local stiffness of all cable components and includes a new approach to their non-linear slip/stick behaviour. In this approach slip regions develop which, after a critical curvature is reached, grow from the cable neutral axis, hence some wires on a cross-section are in the post-critical slip condition while others are not, dependent on the cable curvature. This leads to a transitional region in the moment-curvature relation between the low slip and full slip, residual stiffness regions.

Interaction between armour wires and the surrounding material is based on test data with zero applied tension. The non-linear moment-curvature response for two example cables is presented below along with the linear bend stiffness values from the supplied cable datasheets.

This provides the user with a realistic non-linear relationship between the bending moment and the curvature rather than simply a linear estimation.

The Results 

By using the non-linear curve rather than the linear curve, AgileTek have been able to calculate power cable fatigue lives of at least an order of magnitude larger than the conventional method. This methodology has been reviewed by DNV and validated through physical bend testing of a cable to an industry-recognised standard at an industry-leading cable manufacturer facility.

In addition, the use of non-linear stiffness curves in analysis models allows the hysteresis exhibited by cables in bending to be properly implemented. This can reduce unrealistic results in power cable simulations under the vessel and environmental loading.

Ryder Geotechnical

The Arabian Gulf remains at the forefront of oil and gas extraction with many fields still being developed and exploited. Jack-up vessels are in high demand and there are numerous hazards and constraints to their operation which include hang up and punch through; deep leg penetration and scour induced instability.

Expert advice when considering operations often with limited data can mean the success or failure of a project. Ryder supports their clients in the region to ensure that jack up operations are achieved safely, by carrying out full risk appraisals for jack-up sites and predicting the behavior of jack-up legs during installation.

Ryder Geotechnical

Wave energy is a hugely undervalued resource, and Ryder is very proud to be involved in the sector, using their knowledge of the behaviour of piles subject to complex loading conditions to further the development of foundation solutions.

Ryder supported their clients on a challenging project, in challenging conditions, off the western coast of Australia, and delivered a foundation study that aims to ensure that client needs are met, whilst design efficiency is satisfied.

Ryder Geotechnical

FPU Mooring Pile Design – East Java 

Sitting near the boundary between the Sunda Plate and the Indo-Australian Plate, East Java presents numerous design challenges when considering permanent moorings, with complex soil patterns in a seismically active region.

Using our proprietary inhouse mooring foundation design tool, we were able to fully appreciate the risk each variable posed to the mooring foundations, to ensure that our clients received an efficiently designed and cost-effective mooring pile, that satisfied API design requirements.

FPSO Mooring Pile Design – Sarawak

Ryder Geotechnical

Offshore wind in Taiwan is a booming sector, and Ryder is delighted to be involved. We recently completed a complex Burial Assessment Study (BAS) for our client for export and array cables associated with future developments.

This involved a full review of the bathymetrical, morphological, and geotechnical conditions, and identified potential risks and constraints to cable routing and cable design, along with recommendations on installation tools and performance requirements.

Pipeshield International

In 2019 Pipeshield supplied a number of shallow and deep water turning bollards for the Shah Deniz II project in Azerbaijan.

Contracted to Saipem Netherlands (Azerbaijan Office) the complex project involved the design, manufacture & supply.  The solution needed to perform at 250m & 500m depths but on bottom conditions were critical so extensive technical evaluation was required before the final design could be established. The design criteria had to conform to strict dimensional and weight parameters to ensure the solution was successful.

Pipeshield’s technical solution consisted of bespoke made bollards based upon a multi-drop bag concept filled with a specialist lightweight aggregate chosen specifically to meet the weight and density criteria calculations.

The turning bollards were designed to be installed in situ for up to two years, activated at the point of installation, and at the point of decommissioning recovered depositing the contents onto the seabed and the bollards themselves recovered to the surface.

Extensive factory acceptance trials were carried out on both bollard types, including the decommissioning system. All trials were carried out at Pipeshield’s new quayside manufacturing facility within the Port of Blyth.

Upon technical acceptance, Pipeshield proceeded to manufacture the 42no. deep water and 29no shallow water turning bollards in record time.

For installation and decommissioning, Pipeshield designed and manufactured two project-specific quick-release frames.

Case Study: Agiletek Engineering

The Problem

Cable protection systems (CPS) are a requirement on the vast majority of offshore windfarms. They are designed to protect the power cable between the hang-off deck and the transition into burial. It is important that the manufacturers, installers and buyers of these systems have confidence that they perform as designed and give the required protection throughout the design life. However, these systems exhibit complex structural behaviour and if this is not properly quantified then the results of any analysis will be invalid.

The Solution

AgileTek have developed detailed analysis models for each element of the CPS:

Hang-Off

Cable hang-off is modelled from the point at which the armour wires are fixed in translation and rotation. The part of the cable inside the monopile is shielded from environmental loading but is allowed to be influenced by CPS movement at the monopile interface.

Latch

Some Cable Protection Systems require a latched interface. But when this is required, the latch body must be smaller than the hole within the monopile in order to allow installation, which introduces a complex boundary condition at the interface whereby the latch is allowed to rotate in vertical and horizontal planes by differing amounts. Modelling this condition is achieved in our global models with interconnected rotational constraints.

This allows us to determine the precise combination of shear force, axial force and bend moment at each point in the latch assembly, and we can then put models into local structural FEA which exhibit hyperelastic material behaviour. This way the extreme loads in every single latch component can be verified against design limits.

Bend Limiting

The bend limiting components will exhibit complex non-linear behaviour. Using an arbitrary relationship here can result in under or overestimation of loads at various points in the system. We use local FEA models to determine the exact relationship between curvature and restoring moments which we then can use in our global models.

The Result

AgileTek analysis has been performed on numerous projects at various phases of the project life-cycle. This has allowed AgileTek to offer advice on CPS design optimisations and provide all stakeholders with confidence in the system’s suitability for use throughout the design life.