Improving umbilical design

Technip’s Maurice Anderson discusses the benefits of using new software for designing umbilicals.

Design software and cross section design. Images from Technip.

The design of a subsea control umbilical is governed by international standards and requires detailed knowledge and experience of the materials, functional component capabilities and umbilical manufacturing processes. Such knowledge ensures successful delivery of a cost-effective and fit-for-purpose solution, which meets client expectations.

Dedicated engineering tools used to design umbilical components have successfully been employed on many clients’ projects over the years, such as TubeCalc Pro and other independently verified third-party tools. These tools perform complex calculations, such as optimizing the wall thickness of a steel tube based upon international standards and client preferences. With a strong supply chain, market challenges to minimize costs and achieve commercially competitive solutions, minimizing tube wall thickness is a critical step in the design process. As the choice between seamless and seam welded tubes has recently expanded, TubeCalc Pro is able to account for differences between the two tube manufacturing techniques and quickly assesses the potential savings, while still ensuring a fit-for-purpose solution.

Although umbilical manufacturers have developed engineering design tools that enable efficient assessment of the functional component’s performance, a key process is positioning the components together into the umbilical cross section design effectively. It is not uncommon for 1500 or more cross sections designs to be created each year. Traditionally, this relied heavily on the umbilical designer’s expert skills and knowledge of material behaviors, umbilical assembly processes and in-service response to the intended environment to achieve a suitable design. The process involved manually drawing a cross section using CAD packages, from which key engineering parameters were extracted and entered into a database. The database provided a backbone from which cross section analysis tools could extract consistent input of data, such as performing tube stress and fatigue calculations.

Recognizing the inefficiencies and potential for human error during the data transfer, a bespoke umbilical cross section design tool has now been created. Rather than manually drawing the cross section by hand, the tool allows the umbilical designer to enter pre-approved functional components into a template driven cross section design. Each template can be easily tailored towards a particular manufacturing process, service application or a particular client preference, allowing the umbilical designer to rapidly create the cross section design. The position of the functional components is then automatically placed and intermediate fillers created where necessary, meaning an umbilical cross section can be created in a fraction of the time. To ensure quality and manufacturability, the tool automatically assesses the design against in-house design rules, so that a risk profile for the design can be mapped against previous experience and any potential engineering concessions can be clearly identified, enabling a more efficient sign-off and approval process.

Once the design has been completed, the key engineering data is automatically extracted into the database. A formal cross section design drawing can be automatically created along with the accompanying cross section datasheet populated with routinely calculated mechanical properties. The tool also synchronize with the existing engineering analysis tools, to repeatedly generate design reports using a standard format. Clients not only benefit from quicker response times to cross section design requests, but the standard reporting format will enable easier review due to the familiar format and confidence in the results given the tool has been verified by an independent third party.

Other than the speed of initial cross section design, inevitable design changes, as the subsea field architecture matures, can be efficiently implemented. For example, if an additional functional component is required, or a tube dimension increases, they can be easily swapped out and positional changes of the remaining components will automatically adjust. All intermediate filler designs, armor packages and outer sheath dimensions are also instantly updated. Design evolution is systematically recorded when the database is updated, ensuring a very clear quality audit trail.

Through the development of this suite of integrated engineering design and analysis software tools, umbilical designs for future projects will be created quicker, more accurately and ensure the most cost effective, fit-for-purpose solution.