Service

OSV & Vessel Conversion Engineering

Conversion engineering for offshore support and work vessels: OSV to well-stimulation vessel, barge to pipe-lay barge, tanker to FSO/FPSO and LNG carrier to FSRU. We deliver the feasibility study, the structural, stability and systems engineering and the class approval package, as on a 200-tonne-steel OSV-to-WSV conversion completed in Norway in 2024.

What you receive

Conversion feasibility study: weight and stability budget, deck-strength survey, class-notation route and cost/schedule drivers
Structural design for deck strengthening, new foundations, tank modifications and accommodation additions
Intact and damage stability, longitudinal strength and lightship re-assessment after conversion
Mooring, station-keeping and DP capability inputs where the mission changes
Systems integration engineering: piping, HVAC, electrical loads and process skids interfaces
Class approval drawings and calculations, plus owner’s-engineer review of yard proposals

Why conversions need their own engineering approach

A conversion is constrained by a hull that already exists. Lightship and centre of gravity have moved, deck structures were designed for another load pattern, and the class notation the owner wants may require rules the vessel was never built to. The engineering therefore starts with a survey and a weight budget, not with a design: what can the hull carry, where, and what does the stability margin allow before the new mission equipment is even chosen.

From that budget we develop the structural modifications, re-run intact and damage stability for the new loading conditions, and map the class and flag requirements for the new notation so the yard scope is complete before steel is cut.

Conversion types we have engineered

OSV / PSV to well-stimulation vessel (WSV): deck strengthening for stimulation skids and tanks, 200 tonnes of steel added on a Norwegian project, DNV class
Barge to pipe-lay barge (PLB): owner’s advisory and design review for the conversion scope
Tanker to FSO / FPSO: hull requalification, topside integration structure and class compliance (see the FPSO guide in our insights)
LNG carrier to FSRU: regasification interfaces, mooring and cryogenic piping stress (see the FSRU service page)
Pre-purchase surveys and condition assessments before a conversion is committed

Working with owners, yards and class

We work either as the owner’s engineer reviewing the yard’s engineering, or as the design house delivering the package to the yard. In both cases the class society is engaged early with a notation and drawing-list plan, which is where most conversion schedules are won or lost. Founder experience as a class surveyor and ten class societies’ rules in daily use keep that path short.

Vessel types

OSV / PSV / AHTSWSVPipe-lay bargeFSO / FPSOFSRUAccommodation vesselsJack-ups

Class societies

ABSDNVLRBVIRSNKKRBKIRINACCS

Software

MaxsurfNAPAGHSShipConstructorRhinoSACSOrcaFlexAVEVA E3D

← Class approval drawings

Third-party design review →

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Projects that prove it

OSV to WSV conversion — Norway, 200 MT steelDetailed engineering for OSV to Well Stimulation Vessel conversion — deckhouse structure, nesting plans, fabrication drawings, 200 MT+ steel engineered.Owner's advisory — vessel selection & PLB conversionStrategic advisory for purchase and conversion of a vessel to Pipe Lay Barge — vessel purchased at a reasonable negotiated price.Vessel pre-purchase survey & inspectionFull vessel condition assessment, thickness gauging, and engineering recommendations — vessel purchased at a 20% discount on asking price.Pipelay vessel upgrade — piggyback pipeline installationTwo-phase engineering to modify an operating pipelay vessel for piggyback pipeline installation — from technical feasibility and modification concept to detailed engineering.

Related services

Class Approval Drawings & Statutory DocumentationClass approval drawings, calculations and statutory documents for newbuilds, conversions and modifications, prepared to the rules of ABS, DNV, LR, BV, IRS, NK, KR, BKI, RINA and CCS and taken through plan approval on the owner’s or yard’s behalf. Founder experience as an IRS surveyor means the package is written the way the reviewer reads it.FSRU & LNG Terminal Engineering with Cryogenic PipingEngineering for FSRU conversions and LNG import terminals: regasification and hull interface structure, jetty berthing and mooring analysis, cryogenic piping design and stress analysis to ASME B31.3, and class and IGC Code compliance. Cryogenic piping is a capability few boutique consultancies hold, and it lets us take an FSRU or terminal scope from marine structure to the regas manifold.Stability Booklets, Loading Manuals & Inclining ExperimentsIntact and damage stability booklets, loading manuals and inclining experiment procedures and reports for offshore support vessels, barges, jack-ups and converted units, prepared to the IMO Intact Stability Code, SOLAS and the class rules and taken through class and flag approval. Required for every newbuild and after every conversion that moves lightship.Third-Party Verification & Independent Design ReviewIndependent verification of offshore structural, naval architecture and pipeline engineering: design reviews, re-analysis with our own models, structural integrity assessments and owner’s-engineer review of contractor deliverables. Our team has reviewed five jackets and topsides for an operator and assessed 39 ONGC jacket structures, and supports jack-up site assessments in ONGC, ADNOC and Aramco fields.

Regions we serve for this

Naval Architecture & Vessel Conversion Engineering for Norway and the North SeaRemote engineering support for vessel owners, conversion yards and offshore contractors in Norway, the UK and the wider North Sea: OSV and PSV conversions, deck strengthening and class approval under DNV, stability and mooring analysis, and third-party design review. In 2024 our team engineered an OSV-to-well-stimulation-vessel conversion in Norway that added 200 tonnes of steel under DNV class.Offshore Engineering Support for the Gulf: UAE, Saudi Arabia, Qatar, Oman, KuwaitEngineering support for EPC, T&I and fabrication contractors and jack-up operators working in the Arabian Gulf: jacket and topside engineering, sea-fastening and load-out packages, lifting engineering, jack-up site-specific assessment support and third-party design review, delivered from Mumbai in the same working day. Saudi Aramco and Lamprell are among our clients.Offshore, Marine & Pipeline Engineering in IndiaKannamwar Engineering is headquartered in Mumbai and delivers offshore structural, naval architecture and pipeline engineering to operators, EPC contractors and yards across India: ONGC’s western offshore fields, HPCL’s marine terminals, west-coast LNG infrastructure and the east-coast basins. 39 ONGC jacket structures assessed, riser and conductor installation campaigns engineered, and 120+ days of offshore site supervision at Mumbai High.Offshore & Marine Engineering Support for Nigeria and West AfricaEngineering support for vessel owners, installation contractors and terminal developers in Nigeria, Ghana, Angola and the wider Gulf of Guinea: vessel upgrades and deck-equipment installation, pipe-lay and installation engineering, class approval packages and design review. Our team has delivered a pipe-lay vessel piggyback pipeline upgrade and a four-davit installation on vessels operating in Nigeria.

Sectors

Marine, Vessels & Conversions LNG, FSRU & Cryogenic Infrastructure Offshore Oil & Gas

Disciplines

Naval Architecture Offshore Structural Engineering

Frequently asked questions

How long does an OSV-to-WSV conversion feasibility study take?

Typically three to six weeks from receipt of the vessel drawings and the intended mission equipment list, covering weight and stability budget, deck-strength survey, class-notation route and the main cost and schedule drivers.

Can you act as owner’s engineer while the yard does the design?

Yes. We review the yard’s engineering against the specification and class rules, attend key surveys and resolve comments, as we did on a barge-to-pipe-lay-barge conversion.

Which class societies have you converted vessels under?

Conversion and modification packages have been approved under DNV, IRS, BV and ABS among the ten societies we work with; the Norwegian OSV-to-WSV project was under DNV.