UK +44(0)7826 521741 | South Korea +82 (0)108752 1741 | info@broadreachmarine.com
UK +44(0)7826 521741 | South Korea +82 (0)108752 1741 | info@broadreachmarine.com
A ship owner (A National Oil Company) had several MOSS-type LNGC vessels that were each approaching 15 years old. Broadreach Marine mobilized several specialists, experienced surveyors, to attend onboard five sister vessels and carry out Life Extension Surveys over a period of about 12 months.
Our scope of work was to provide the Owner with reports for each vessel that would enable them to make informed decisions about the continued operation of the vessels and to quantify and qualify the extent of investment needed to repair and upgrade various aspects of the vessel’s hull and machinery to keep them in service for a further 10 years.
Image of generic MOSS-type LNGC
Among the concerns from the Owners was that each vessel had recurring hull stress cracking at the same location, due to the hogging and sagging and poor initial fatigue design at these specific locations within the hull structure.
Having established that each vessel had similar, recurring fatigue cracking, that was repeatedly ‘repaired’ at Special Survey, we needed to reverse engineer old information from the shipbuilder. Unfortunately, we did not have the original construction drawings. These are proprietary information and are not normally available to Owners.
We took the General Arrangement and the Shell Expansion Drawings with basic information about the hull structure and scantlings and with our expert design partners we prepared a 3D Finite Element Method (FEM) Model.
Image of a MOSS LNGC hull structural drawing
Image of a MOSS LNGC hull structural drawing in the region of the inner hull and cargo tanks
Using the fine mesh computational process, we prepared the 3D model of the ship:
Image of a 3D fine mesh model of a MOSS LNGC
Then by applying dynamic loads (Von Mises) to the model to replicate the different ship laden conditions, we were able to recreate the stresses in the hull structure that were causing the repeated problems.
Image to show fine mesh analysis in the affected areas of the 3D model.
We reduced the mesh size to focus on the affected areas, so that we could get more accurate results and then apply cyclic load analysis.
Image to show higher areas of stress in hull structure in the 3D model.
By sectioning the structure, we were able to focus on the exact points with the highest stresses.
Image to show higher areas of stress across the hull structure in the 3D model.
Once these high-stress areas were identified in the 3D model we were able to reverse engineer the structure to design out the stress.
Image to show the high-stress areas have been designed out of the hull structure in the 3D model.
Having produced this data and an extensive report for the Owners we were able to assist them in preparing a detailed refit plan for the replacement of structural steel within the hull to engineer out the recurring problems. This 3D modeling and analysis formed part of the overall life extension study for the five vessels. Our experience and report recommendations has enabled the Owner to continue to operate their ships safely and cost-effectively for many more years.
For more information about our services please contact us at:
info@broadreachmarine.com
If you would like to speak to a member of our team about any of the services that we provide, please contact us today.
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Broadreach Marine supports global clients with expertise spanning ship construction, refits, and advanced marine technologies.
+44(0)7826 521741
info@broadreachmarine.com
5 Brayford Square
London
E1 0SG
+82 (0)10 8752 1741
info@broadreachmarine.com
54, Okpodaecheop-ro 2-gil, Geoje-si, Gyeongsangnam-do,
Republic of Korea, 53233
경남 거제시 옥포대첩로2길 54, 53233.