Retrofit & Conversion Engineering — Technical Research
Vessel Retrofit Engineering — Aframax Tanker to Plasma Processing Vessel
Converting a second-hand Aframax tanker (80,000-120,000 DWT) into a mobile plasma processing station for ocean plastic. This document covers what gets stripped, what gets built, what gets installed, and what it costs — grounded in real FPSO conversion data and shipyard precedent.
Vessel class: Aframax (LOA ~245m, beam ~44m, depth ~21m) Target conversion: Plasma gasification vessel, 5-10 TPD PRRS, 28-day operating cycles, 1,000nm from Honolulu Analogous industry: FPSO (Floating Production Storage and Offloading) tanker conversions
1. What Gets Stripped
An Aframax crude oil tanker has systems designed for loading, transporting, and discharging crude oil. Most of these are irrelevant or actively harmful to a plasma processing vessel. The conversion strip-out is substantial.
Systems Removed Entirely
| System | Why It Goes |
|---|---|
| Cargo pumping system | Centrifugal/deepwell cargo pumps in each tank, pump room, associated piping. Designed to move crude oil. No crude oil on this vessel. All removed. Estimated 200-400 tonnes of equipment and piping. |
| Crude Oil Washing (COW) system | Fixed/portable tank cleaning machines, COW piping, heaters. Required by MARPOL for crude tankers. Completely irrelevant. Removed. |
| Inert Gas System (IGS) | Flue gas scrubber, IG fans, deck water seal, distribution piping. Keeps cargo tanks inert to prevent explosion. No volatile cargo = no need. Removed. Note: if any tanks are repurposed for syngas buffer storage, a purpose-built inerting system would be installed instead. |
| Cargo heating system | Steam coils in cargo tanks, heating medium (thermal oil or steam) circuits. Keeps heavy crude pumpable. Removed. |
| Cargo tank coatings | Existing tank coatings (epoxy or bare steel) may need blasting and recoating depending on repurposed use. |
| Cargo manifold and loading arms | Midship manifold, reducers, hoses. Replaced with collection system receiving infrastructure. |
| Slop tanks (dedicated) | Two slop tanks typically fitted aft of cargo block. May be repurposed as waste water holding tanks rather than removed. |
| Venting system (cargo) | PV valves, mast risers, vent headers for cargo tanks. Removed and replaced with ventilation appropriate to new tank usage. |
| Ballast treatment system | Modern tankers have ballast water treatment. Retained but may need relocation or upgrade. |
Systems Retained / Modified
| System | Status |
|---|---|
| Main engine and propulsion | Retained. The vessel must transit to/from the GPGP and reposition within it. Aframax tankers typically have a single slow-speed two-stroke diesel (MAN B&W or similar), 12,000-16,000 kW. Adequate for 14-15 knot transit speed. Service/overhaul during conversion. |
| Steering gear | Retained. Serviced and overhauled. |
| Navigation and bridge systems | Retained and upgraded. Radar, ECDIS, AIS, GMDSS — all kept. Add satellite comms upgrade, weather routing. |
| Ballast system | Retained and modified. Ballast tanks, pumps, and piping retained. Ballast plan recalculated for new loading condition (heavy topside equipment vs. distributed cargo weight). |
| Accommodation block | Retained and likely expanded. Aframax tankers typically have accommodation for 25-30 crew. A processing vessel may need 35-50 (operators, maintenance, collection crew). See Section 3. |
| Engine room systems | Retained and modified. Generators, switchboards, air compressors, purifiers, workshop — all retained. Electrical generation likely supplemented with syngas generators. |
| Fire-fighting systems | Retained and significantly upgraded. Existing CO2 and foam systems kept for engine room. New fire protection systems for processing deck (plasma reactor area, syngas handling). |
| Freshwater generator | Retained or replaced. Existing evaporator or RO unit retained if capacity sufficient. Likely supplemented — see Section 3. |
| Deck cranes | Likely removed and replaced. Tanker cranes (if fitted) are provision/stores cranes, typically 5-10 tonne SWL. Processing vessel needs heavier capacity for debris handling. New crane pedestals required. |
Weight Impact of Strip-Out
Removing the cargo handling systems, COW, IGS, and associated piping yields an estimated 500-800 tonnes of removed deadweight. This provides margin for new processing equipment installation but also changes the vessel's lightship weight and stability characteristics — requiring a full inclining experiment and stability recalculation post-conversion.
2. Structural Modifications
This is where the heavy steel work happens. An Aframax tanker deck is designed for distributed liquid cargo loads, not concentrated heavy equipment loads. Every major piece of topside equipment needs a proper foundation, and the entire deck arrangement changes.
Major Structural Work Items
2.1 Deck Reinforcement for Processing Equipment
The main deck over the cargo tank area becomes the processing deck. Tanker main decks are designed for:
- Distributed cargo pressure from below (hydrostatic)
- Walking/access loads from above (minimal — typically 1.7 kN/m2)
- Pipe stress from cargo piping
- New deck stiffeners (increased scantlings under equipment)
- Pillar supports through to inner bottom or tank top structure
- Stools and grillage foundations for reactor, generators, and syngas train
- Doubler plates in high-stress areas
2.2 Reactor Foundation
The PRRS plasma reactor is the heaviest single item. Based on comparable plasma gasification units at 5-10 TPD scale (see Section 3), the reactor module with refractory lining is estimated at 80-150 tonnes. The foundation must:
- Distribute load to hull primary structure (transverse web frames, longitudinal girders)
- Accommodate thermal expansion (the reactor operates at 1,500-5,000°C internally)
- Include vibration isolation mounts
- Provide for secondary containment (slag/melt escape)
- Route exhaust stack through any overhead structures
2.3 New Bulkheads and Fire/Blast Walls
The processing deck must be subdivided into hazard zones:
- Reactor zone — highest hazard, blast-rated walls on 3 sides
- Syngas handling zone — Zone 1 (explosive atmosphere possible during normal operation)
- Electrical zone — switchgear room, pressurized to prevent gas ingress
- Collection/receiving zone — wet, mechanical hazard
- Accommodation safety zone — protected from all processing hazards
Estimated bulkhead/firewall steelwork: 300-500 tonnes
2.4 Exhaust Stack Routing
The syngas engine exhaust and any reactor off-gas bypass must be routed to a safe discharge point. On an FPSO this is the flare tower — on The Claw it's the exhaust stack system. Requires:
- Structural tower/mast for elevated discharge (30-40m above deck for dispersion)
- Self-supporting or guyed steel structure
- Insulated exhaust ducting from syngas engine and reactor emergency vent
- Foundation stools on main deck with guy wire attachment points
2.5 Crane Pedestals
Processing vessel needs heavy-lift capability for debris collection and equipment maintenance:
- 2x knuckle-boom cranes (25-40 tonne SWL each) for debris handling, port/starboard
- 1x provision crane (5-10 tonne SWL) for stores and personnel transfer
Estimated crane pedestal steelwork: 60-90 tonnes
2.6 Helipad Structure
An offshore-rated helipad per CAP 437 / ICAO Annex 14 standards for medium helicopter (AW139 or S-92 class):
- D-value: ~17m (AW139) to ~20m (S-92)
- Helideck diameter/size: minimum 1.0 x D-value, so 20-22m
- Structure: aluminium or steel deck plate on steel support structure
- Location: forward (bow area, clear of exhaust plume and processing equipment)
- Structural weight: helideck itself ~40-60 tonnes (aluminium deck on steel support)
- Design loads: 12-15 tonne maximum helicopter weight + 2.5x dynamic landing factor
- Additional: helicopter refuelling system, foam fire-fighting, lighting (HAPI, perimeter, flood), windsock, netting
Estimated helipad structure steelwork: 80-120 tonnes (including substructure reinforcement)
2.7 Accommodation Extension
If existing crew accommodation (25-30 persons) is insufficient, a new accommodation module is installed — typically a pre-fabricated multi-deck module lifted onto an extended poop deck or built above the existing accommodation block.
Estimated accommodation module steelwork: 100-200 tonnes (for +20 person extension)
Total New Steelwork Estimate
| Category | Tonnes |
|---|---|
| Deck reinforcement / foundations | 800 - 1,200 |
| Reactor foundation (specific) | 80 - 120 |
| Bulkheads and fire/blast walls | 300 - 500 |
| Exhaust stack structure | 50 - 80 |
| Crane pedestals | 60 - 90 |
| Helipad and substructure | 80 - 120 |
| Accommodation module structure | 100 - 200 |
| Miscellaneous (access ways, ladders, handrails, pipe supports) | 200 - 400 |
| Total | 1,670 - 2,710 |
For context, a typical Aframax-to-FPSO conversion involves 3,000-6,000 tonnes of new steelwork. The Claw's conversion is simpler (no turret, no risers, no subsea interfaces, no gas compression trains at FPSO scale), but still substantial. The FPSO data point of ~5,500 tonnes for a full Aframax conversion (from SPE/OTC papers) serves as an upper bound.
3. Equipment Installation
3.1 PRRS Plasma Reactor Unit
Supplier: PyroGenesis (Montreal, Canada) System: PRRS (Plasma Resource Recovery System) — 5-10 TPD capacity Technology: Two-step plasma gasification with syngas recovery
| Parameter | Estimate | Basis |
|---|---|---|
| Capacity | 5-10 TPD (start at 5, design for 10) | PyroGenesis PRRS product range (1-100 TPD modules) |
| Footprint | 150-250 m2 (including gas cleanup) | Scaled from PAWDS 65 m2 at ~5 TPD, plus cleanup train |
| Weight | 80-150 tonnes (reactor + refractory) | Estimated from comparable plasma gasification systems — 10 TPD unit at NCKU Taiwan, InEnTec PEM systems |
| Form factor | Modular, ISO container-skid mounted | PyroGenesis PRRS is designed as containerized/transportable system (confirmed: 10.5 TPD Hurlburt Field system was ISO-container-skid-mounted) |
| Power draw | 0.8-1.1 MWh/tonne of feedstock | Per energy-balance.md research: 0.817 MWh/ton at 10 TPD scale |
| Operating temp | 1,500-5,000°C in plasma zone | PyroGenesis standard plasma torch range |
| Output | Syngas (H2 + CO) + vitrified slag | Standard PRRS output |
Procurement note: PyroGenesis has delivered 4 PAWDS systems to the US Navy (Ford-class carriers) and designed the 10.5 TPD PRRS for Hurlburt Field USAF base. They are the only qualified supplier with proven marine plasma experience. Budget estimate for the PRRS unit: $8-15M (estimated from PAWDS pricing of ~$5.5M per unit for the smaller naval system, scaled up).
3.2 Syngas Cleanup Train
Raw syngas from plasma gasification contains particulates, tars, acid gases (HCl, H2S from chlorinated/sulfur-containing plastics), and trace metals. Must be cleaned before engine use.
| Component | Purpose | Est. Weight | Est. Footprint |
|---|---|---|---|
| Cyclone separator | Remove coarse particulates | 5-10 t | 15 m2 |
| Quench tower | Cool syngas from 800-1000°C to 200°C | 15-25 t | 20 m2 |
| Wet scrubber | Remove acid gases (HCl, H2S, SOx) | 10-20 t | 25 m2 |
| Baghouse / fabric filter | Remove fine particulates | 8-15 t | 20 m2 |
| Activated carbon bed | Remove trace metals, dioxins | 5-10 t | 10 m2 |
| Syngas cooler | Final cooling to engine inlet temp (~40°C) | 5-10 t | 10 m2 |
| Condensate separator | Remove water from cooled syngas | 3-5 t | 5 m2 |
| Syngas blower/compressor | Deliver syngas at engine inlet pressure | 3-8 t | 10 m2 |
| Total cleanup train | 54-103 t | ~115 m2 |
3.3 Syngas Engine / Generator
Purpose: Convert cleaned syngas to electricity for station self-sufficiency.
Primary candidate: INNIO Jenbacher Type 6 (J612/J616/J620)
- Jenbacher engines are proven on syngas, landfill gas, and low-calorific gases
- Type 6 range: 1.8-4.5 MWe
- Jenbacher J620 GS (syngas variant): ~3.3 MWe electrical output
| Parameter | Specification |
|---|---|
| Model | Jenbacher J620 GS (syngas rated) or equivalent |
| Electrical output | 2-3 MW (matches station demand — see energy-balance.md) |
| Weight | ~85-100 tonnes (engine + generator + baseframe) |
| Footprint | ~120 m2 (including service clearances) |
| Foundation | Vibration-isolated grillage on deck, double-elastic mounting |
| Exhaust | Routed to stack, catalytic converter for CO/NOx |
| Fuel | Cleaned syngas from cleanup train |
| Backup fuel | Marine diesel (dual-fuel capability for startup/emergency) |
| Cooling | Seawater-cooled heat exchangers (standard marine arrangement) |
Alternative candidates: Caterpillar CG260 series (syngas capable, 2-4 MW range), MAN gas engines. Jenbacher has the strongest track record on non-standard gas compositions.
3.4 Electrical Distribution and Switchgear
The existing tanker electrical system is designed for ~3-5 MW of generation capacity (diesel generators powering cargo pumps, accommodation, and engine room). The conversion must:
- Add new main switchboard section for syngas generator connection
- Install bus-tie breakers between existing diesel generators and syngas generator for seamless power transfer
- New motor control centers (MCCs) for processing equipment (reactor, conveyors, cranes, shredders)
- Emergency generator — existing tanker emergency generator retained, but may need uprating
- Power management system (PMS) — new PMS to manage load sharing between syngas and diesel generators
- Variable frequency drives (VFDs) for major motor loads (pumps, conveyors, shredders)
- Transformer and distribution for accommodation and low-voltage systems
- Hazardous area electrical equipment — all equipment in syngas zones must be Ex-rated (ATEX/IECEx Zone 1/2)
3.5 Collection Equipment
The vessel needs to collect plastic debris from the ocean surface. This is an area where The Claw differs most from an FPSO (which receives product from subsea).
| Component | Specification | Est. Weight | Est. Cost |
|---|---|---|---|
| 2x Knuckle-boom cranes | 25-40t SWL, offshore-rated (Liebherr, Palfinger, NOV) | 30-50t each | $2-4M each |
| Conveyor system | Receiving hopper → shredder → dewatering → reactor feed. ~100m total belt/screw conveyor. Enclosed, corrosion-resistant. | 40-60t | $1-2M |
| Shredder/grinder | Industrial dual-shaft shredder for mixed ocean debris including fishing nets. 5-10 TPH capacity (well above reactor feed rate, to allow batch collection). | 20-30t | $0.5-1M |
| Dewatering system | Screw press or centrifuge to remove saltwater. Waste heat from reactor exhaust used for secondary drying. | 10-20t | $0.3-0.5M |
| Debris collection nets/booms | Deployable boom system or net trawl arrangement. Stored on deck, deployed by cranes. | 10-20t | $0.5-1M |
| Workboat/RIB | 1-2 rigid inflatable boats for collection support and boom deployment. Davit-launched. | 3-5t each | $0.1-0.2M each |
| Davits | 2x gravity/pivot davits for workboat launch/recovery | 5-10t each | $0.2-0.3M each |
| Receiving hopper | Deck-level receiving hopper with drainage, feeding conveyor intake | 10-15t | $0.1-0.2M |
| Total collection systems | ~170-260t | $6-12M |
3.6 Helipad and Aviation Systems
| Component | Specification |
|---|---|
| Helideck | 22m diameter aluminium deck on steel substructure, CAP 437 compliant |
| Design helicopter | AW139 or S-92 (medium category, typical offshore crew change helicopter) |
| HAPI lighting | Helicopter Approach Path Indicator |
| Perimeter lighting | Flush-mounted green perimeter lights |
| Floodlights | For night operations |
| Status lights | Red (deck not available) / Green (clear to land) |
| Windsock | Illuminated, visible from approach path |
| Fire suppression | Foam monitors (minimum 2), agent capacity per CAP 437 (typically AFFF) |
| Fuel system | AVGAS/JET-A1 storage and dispensing (if helicopter refuelling provided) |
| Deck netting | Safety netting around helideck perimeter |
| Motion monitoring | Helideck monitoring system (HMS) for vessel motion limits |
3.7 Accommodation Module
Existing Aframax accommodation typically provides for 25-30 persons. The processing vessel likely needs 35-50 persons:
- 10-15 vessel crew (navigation, engine room, deck)
- 8-12 processing plant operators (24/7 shift work, 3 shifts)
- 4-6 maintenance/electrical technicians
- 2-4 collection system operators
- 2-3 HSE / medic / admin
- 2-4 spare berths (visitors, class surveyors, supernumeraries)
| Parameter | Specification |
|---|---|
| Additional capacity | +20-25 persons |
| Decks | 2-3 storey module |
| Facilities | Single/double cabins, galley/mess, recreation, laundry, offices, hospital |
| Weight | 200-400 tonnes (fully outfitted) |
| Footprint | 20m x 15m per deck (approximate) |
| Standard | SOLAS compliant, classed to same notation as vessel |
| Budget | $5-10M |
3.8 Water Maker and Utility Systems
| System | Purpose | Est. Cost |
|---|---|---|
| Reverse osmosis water maker | 20-40 m3/day freshwater production (replace or supplement existing) | $0.3-0.5M |
| Sewage treatment plant | For expanded crew (50-person IMO-compliant) | $0.2-0.4M |
| HVAC upgrade | Additional cooling/ventilation for processing areas and expanded accommodation | $0.5-1M |
| Compressed air system | Instrument air and utility air for processing equipment | $0.2-0.3M |
| Potable water treatment | UV/chlorination for domestic water | $0.05-0.1M |
| Satellite communications | VSAT for operational data, crew welfare, remote monitoring | $0.3-0.5M |
| Waste water treatment | For process water from dewatering (salt water + plastic residue), cannot discharge untreated | $0.3-0.5M |
4. FPSO Conversion Precedents
The Claw's conversion is not an FPSO, but the FPSO industry is the closest analogue — both involve taking a trading tanker and converting it into a stationary processing platform. The FPSO industry has converted hundreds of tankers since the 1970s. Key examples:
4.1 Notable Conversion Projects
FPSO Cidade de Itaguai (MODEC, 2015)
- Donor vessel: VLCC Alga
- Conversion yard: MODEC/Sofec consortium, hull work in Asia, topsides integration in Brazil
- Field: Iracema Norte (Lula), Santos Basin, Brazil
- Capacity: 150,000 bbl/day oil, 280 MMscf/day gas
- Water depth: 2,240m
- Timeline: Achieved first oil July 2015, 5 months ahead of schedule
- Key lesson: Modular topsides approach enabled parallel fabrication and faster integration
FPSO Prosperity (SBM Offshore / Keppel, 2022-2024)
- Hull: New-build Fast4Ward hull (not a conversion, but relevant for yard work)
- Conversion yard: Keppel Shipyard, Singapore
- Field: Payara, offshore Guyana (ExxonMobil)
- Capacity: 220,000 bbl/day
- Hull arrived Keppel: August 2021, entered drydock October 2021
- Delivery: Less than 4 years from engineering start
- Key lesson: Keppel Singapore is a proven FPSO integration yard
FPSO Liza Unity (SBM Offshore, 2021-2022)
- Hull: First Fast4Ward hull
- Field: Liza Phase 2, offshore Guyana
- Capacity: 220,000 bbl/day oil, 400 MMscf/day gas, 2 million bbl storage
- Purchase price (ExxonMobil buyout): ~$1.26 billion
- Key lesson: Standardized hull + modular topsides reduces delivery time. The purchase price includes all topsides and years of embedded engineering — not comparable to a stripped tanker conversion.
Typical Aframax FPSO Conversions (Various)
- Cost range: $150M-$400M for conversion work (excluding topsides equipment procurement)
- Steelwork: 3,000-6,000 tonnes of new steel (includes turret, flare tower, piping supports, module foundations, helideck, accommodation)
- Duration: 18-30 months yard time for hull conversion; 24-36 months total with topsides integration
- Man-hours: 3-4 million man-hours for hull conversion alone
4.2 Key Lessons from FPSO Conversions
1. Donor vessel condition is paramount. Steel renewal (replacing corroded plates) can consume 30-50% of hull conversion cost if the tanker is old or poorly maintained. Target a tanker <15 years old with recent special survey.
2. Stability recalculation is non-trivial. Removing distributed liquid cargo weight and adding concentrated topside equipment weight fundamentally changes the vessel's stability characteristics. Full intact and damage stability analysis required.
3. Fatigue life reassessment required. Trading tankers accumulate fatigue damage from wave loading during voyages. The classification society will require a fatigue life assessment for the new operational profile (permanently moored/stationed vs. trading). A 15-year-old tanker with 15 years of trading service may have 50% of its fatigue life consumed.
4. Parallel fabrication is critical for schedule. While the hull is being converted in dry dock, topsides modules (reactor skid, syngas train, switchgear room, etc.) should be fabricated elsewhere and shipped to the yard for integration.
5. Tank inspection and steel renewal. Every cargo tank must be entered, inspected, cleaned, and assessed. Corroded structure is renewed. For The Claw, most cargo tanks will be repurposed (feedstock buffer storage, slag storage, ballast, etc.) — each repurposed tank needs appropriate coating and structural assessment.
5. Shipyard Selection
5.1 Capable Yards — Global Overview
| Shipyard / Group | Location | FPSO Track Record | Strengths | Weaknesses | Labour Rate (approx.) |
|---|---|---|---|---|---|
| Seatrium (formerly Keppel + Sembcorp Marine) | Singapore | ~15% market share. Multiple FPSO conversions including Prosperity integration. | World-class quality, deep FPSO experience, strong project management, proximity to classification society offices | Highest cost in Asia, capacity constraints from order backlog | $25-35/hr |
| COSCO Shipping Heavy Industry | Dalian, Qidong, China | ~20% market share. Built/converted FPSOs for Modec, SBM, others. | Lowest cost, massive capacity, experience with large structures | Quality control variability, communication challenges, IP concerns for novel technology | $10-15/hr |
| CIMC Raffles | Yantai, China | Semi-submersibles and FPSO hulls. Growing FPSO capability. | Large deepwater dock, competitive pricing | Less FPSO conversion-specific experience than COSCO | $10-15/hr |
| Drydocks World | Dubai, UAE | ~8% market share 2020-2030. Decade+ of FPSO/FSO conversion experience. | Strategic location (between Asia and Europe), competitive pricing, strong conversion track record, handles complex refurbishment projects | Smaller than Chinese yards, limited heavy-lift crane capacity | $15-20/hr |
| Samsung Heavy Industries | Geoje, South Korea | Major FPSO builder (primarily new-build). | Extremely high quality, advanced automation, strong LNG experience | Very expensive, focused on new-build, conversion work is lower priority | $30-40/hr |
| Hyundai Heavy Industries | Ulsan, South Korea | FPSO new-build capability. | Same quality/cost profile as Samsung | Same — oriented toward new-build, not conversion | $30-40/hr |
| Damen Verolme | Rotterdam, Netherlands | Occasional FPSO/FSO work. | European quality, close to classification societies, good for small/medium conversions | Very expensive (European labor rates), limited capacity | $50-70/hr |
5.2 Recommended Shortlist for The Claw
Tier 1 (Best fit): 1. Drydocks World, Dubai — Best balance of cost, quality, and conversion experience. Strong track record with FPSO refurbishment and conversion. Strategic location. Labor rates are moderate. Has handled novel/non-standard projects. 2. Seatrium, Singapore — Highest quality and deepest FPSO experience. More expensive but lower risk. If budget allows, this is the safest choice.
Tier 2 (Cost-optimized): 3. COSCO Dalian or Qidong — Lowest cost option (potentially 40-50% cheaper than Singapore). Requires strong owner's team supervision and quality assurance presence. Best if budget is the primary constraint.
Not recommended:
- Korean yards — too expensive for a conversion project, focused on new-build
- European yards — prohibitively expensive for this scale of work
- Smaller Asian yards without FPSO track record — too risky for a novel vessel type
5.3 Cost Impact by Yard Location
Using Singapore as the baseline (index 100):
| Location | Relative Cost Index | Estimated Total Conversion Cost |
|---|---|---|
| Singapore | 100 | $55-80M |
| Dubai | 75-85 | $42-68M |
| China | 55-65 | $30-52M |
| South Korea | 110-130 | $60-104M |
| Europe | 150-200 | $82-160M |
6. Classification & Certification
6.1 Why Classification Matters
A converted vessel operating 1,000nm offshore needs classification society approval for:
- Insurance (P&I and hull & machinery)
- Flag state registration
- Port state control acceptance
- Regulatory compliance (SOLAS, MARPOL, flag state regulations)
- Financing/investor confidence
6.2 Class Notation
There is no existing class notation for "plasma processing vessel." The classification society will need to develop a bespoke classification approach, likely building on existing notations:
Likely class notation components:
- +1A1 (or equivalent) — Hull structural notation for unrestricted service
- SHIP — Self-propelled vessel
- EO — Unattended machinery space (if applicable)
- DYNPOS or POSMOOR — Positioning system notation (if DP or spread mooring fitted)
- PROD or equivalent — Production/processing notation (adapted from FPSO notation)
- HELIDECK — Helicopter landing facility
- CLEAN — Environmental compliance notation
- Additional qualifiers — Likely a special feature notation for the plasma processing function
6.3 Classification Society Comparison
| Society | FPSO Experience | Novel Vessel Types | Design Approval Timeline | Recommendation |
|---|---|---|---|---|
| DNV (Norway) | 30+ years FPSO classification, market leader in offshore | Strong — has classed novel offshore units, floating LNG, etc. "Alternative Design" framework for novel concepts | 6-12 months for design approval (AIP), 12-18 months for full approval in parallel with construction | Best choice. Deepest FPSO experience, most flexible framework for novel vessel types, strongest presence in environmental/clean tech maritime. |
| Lloyd's Register (UK) | Extensive FPSO portfolio, especially in West Africa and North Sea | Good — classed naval PAWDS systems (relevant precedent — they certified the PyroGenesis plasma system for US Navy) | Similar to DNV | Strong second choice. The fact that they certified PAWDS for marine use is directly relevant. |
| ABS (USA) | Strong in Gulf of Mexico FPSOs, dominant in US-flagged vessels | Good for US regulatory framework, close to USCG | Typically fast for US-flagged projects | Worth considering if US-flagged. Less relevant if foreign-flagged. |
| Bureau Veritas (France) | Strong in West Africa FPSOs | Adequate | Similar | Lower priority for this project. |
6.4 Design Approval Process
1. Concept review (2-3 months) — Present concept to class society, identify applicable rules and any gaps requiring special consideration 2. Approval in Principle (AIP) (4-6 months) — Submit basic engineering package, class reviews and issues AIP confirming the concept is feasible within their rules framework 3. Detailed design review (8-12 months, concurrent with detail engineering) — Submit detailed drawings, calculations, specifications. Class reviews and approves each discipline (structural, mechanical, electrical, fire safety, stability, etc.) 4. Plan approval (rolling, concurrent with construction) — Final approved-for-construction drawings 5. Survey during construction — Class surveyor attends key milestones (steel cutting, block erection, equipment installation, commissioning) 6. Inclining experiment and sea trials — Class witnesses final stability verification and operational testing 7. Certificate issuance — Class issues certificate of classification
Total timeline for class approval: 12-18 months from first submission to full plan approval. Runs in parallel with engineering and construction — not a serial addition to the schedule.
Estimated classification fees: $1.5-3M (design review, plan approval, construction surveys, certificates). Higher end if significant "novel technology" review is required for the plasma reactor installation.
7. Retrofit Timeline
Phase Breakdown
| Phase | Duration | Months (Cumulative) | Key Activities |
|---|---|---|---|
| 1. Concept & FEED | 6-8 months | 0-8 | Vessel selection, concept engineering, class AIP, initial cost estimate, shipyard pre-qualification |
| 2. Basic Engineering | 6-8 months | 6-16 | Naval architecture (stability, structural), process engineering (PRRS integration), P&IDs, equipment specifications, procurement specifications. Overlaps with end of Phase 1. |
| 3. Detail Engineering | 8-12 months | 12-24 | Production drawings (structural, piping, electrical, instrumentation), vendor drawing review, construction work packs. Starts while basic engineering is ~60% complete. |
| 4. Long-Lead Procurement | 6-12 months | 8-20 | PRRS reactor (longest lead — 12+ months), syngas engine, cranes, switchgear, helideck. Ordered during basic engineering, delivered to yard during construction. |
| 5. Vessel Purchase & Delivery | 2-4 months | 10-14 | Identify and purchase donor Aframax tanker, pre-purchase condition survey, deliver to conversion yard. Can happen in parallel with engineering. |
| 6. Yard Mobilization & Strip-Out | 2-3 months | 14-19 | Drydock vessel, gas-free and clean cargo tanks, strip out cargo systems, initial steel surveys, begin steel renewal |
| 7. Hull Conversion (Structural) | 8-12 months | 16-28 | Steel renewal, new foundations, bulkheads, deck reinforcement, crane pedestals, helipad structure, accommodation module. The main construction phase. |
| 8. Topsides Installation | 4-6 months | 24-34 | Install PRRS reactor module, syngas cleanup train, syngas engine/generator, switchgear, piping, instrumentation. Overlaps with late hull conversion. |
| 9. Integration & Hook-Up | 3-4 months | 28-36 | Connect all systems, cable pulling, piping tie-ins, instrument calibration, control system programming, fire and safety system integration |
| 10. Commissioning | 3-4 months | 30-38 | System-by-system testing, loop checks, cold commissioning, hot commissioning, reactor first fire, syngas engine first run, safety system testing |
| 11. Sea Trials | 1-2 months | 34-40 | Vessel performance (speed, manoeuvrability), stability verification, equipment operation under sea conditions, class survey completion, flag state inspection |
| 12. Crew Training & Handover | 1-2 months | 36-42 | Operator training on PRRS system, emergency procedures, helicopter operations training |
Critical Path
The critical path runs through: Basic Engineering → PRRS Procurement (12+ month lead) → Topsides Installation → Commissioning.
Hull conversion work is substantial but typically not on the critical path because it proceeds in parallel with PRRS fabrication.
Timeline Summary
| Scenario | Total Duration | Notes |
|---|---|---|
| Aggressive | 30-34 months | Everything goes right, experienced yard, pre-qualified vessel, minimal steel renewal, good weather |
| Realistic | 36-42 months | Normal delays, some steel renewal beyond estimate, equipment delivery slippage, commissioning issues |
| Conservative | 42-48 months | First-of-its-kind delays, class approval challenges for novel reactor installation, supply chain issues |
This aligns with FPSO conversion industry data: 18-30 months of yard time, plus 12-18 months of pre-yard engineering and procurement. The Claw's topsides are simpler than an FPSO (no gas compression, no water injection, no subsea interface), but the PRRS is novel technology requiring more commissioning time.
8. Retrofit Cost Breakdown
8.1 Cost Estimate — Bottom-Up
Based on real FPSO conversion cost data, adjusted for The Claw's simpler topsides but novel processing technology.
| Category | Low Estimate | High Estimate | Notes |
|---|---|---|---|
| Design & Engineering | $5M | $10M | FEED + basic + detail engineering. Novel technology adds cost vs. standard FPSO conversion. |
| Vessel Purchase | $15M | $30M | Second-hand Aframax, 10-20 years old. Price highly dependent on market conditions (tanker market was elevated 2022-2024, softening into 2026). |
| Steelwork & Structural | $8M | $16M | ~2,000t new steel at $4,000-8,000/t fabricated and installed (varies by yard location). |
| Steel Renewal (hull repair) | $3M | $8M | Depends entirely on vessel condition. Budget 200-500t of renewal plate. |
| PRRS Reactor System | $8M | $15M | Plasma reactor, torches, refractory, controls. Largest single equipment item. |
| Syngas Cleanup Train | $3M | $5M | Cyclone, scrubber, filters, coolers, blower — all industrial standard equipment. |
| Syngas Engine/Generator | $2M | $4M | Jenbacher or equivalent, dual-fuel capable. |
| Electrical & Instrumentation | $4M | $8M | Switchgear, MCCs, cable, VFDs, control system, Ex-rated equipment. |
| Collection Equipment | $6M | $12M | Cranes (2x), conveyors, shredder, dewatering, booms, workboats, davits. |
| Helipad | $2M | $4M | Structure, lighting, fire systems, monitoring. |
| Accommodation Module | $3M | $8M | Pre-fabricated LQ for additional 20-25 persons (only if needed). |
| Piping | $3M | $6M | Process piping, utility piping, fire-fighting piping. |
| Marine Systems Upgrades | $2M | $4M | Navigation upgrade, VSAT, safety equipment, LSA/FFA upgrades. |
| Coatings & Insulation | $1M | $3M | Tank recoating, thermal insulation on hot piping, deck coatings. |
| Commissioning & Sea Trials | $2M | $4M | Includes fuel, harbour dues, tug assist, class surveyor attendance. |
| Classification Fees | $1.5M | $3M | Design review, plan approval, construction surveys, certificates. |
| Project Management | $3M | $5M | Owner's team, marine warranty surveyor, third-party inspectors. |
| Contingency (15-20%) | $10M | $25M | Standard for first-of-a-kind vessel conversion. |
| TOTAL | $82M | $170M |
8.2 Working Budget Estimate
$100-130M total conversion cost (mid-range estimate, assuming):
- Vessel purchased for $20-25M (decent condition, <15 years old)
- Conversion at Drydocks World Dubai or equivalent mid-cost yard
- ~2,000 tonnes new steelwork, ~300 tonnes steel renewal
- PRRS system at $10-12M
- 15% contingency
- DNV classification
8.3 Cost Context — FPSO Industry Benchmarks
| Benchmark | Cost | Source |
|---|---|---|
| Simple FPSO hull conversion (no topsides) | $50-100M | Industry average |
| Full FPSO conversion with topsides | $150-700M | Industry range (complexity dependent) |
| New-build FPSO | $1-3B | Large projects (Guyana, Brazil) |
| Single-hull conversion (simplest) | ~10% of new-build cost | SPE/OTC papers |
- No turret/swivel (FPSO-specific, $30-80M alone)
- No subsea interface or risers
- No gas compression train (FPSOs process reservoir gas at high pressure)
- No oil offloading system
- Simpler topsides than oil/gas processing
- Novel plasma reactor (first marine installation at this scale)
- Collection systems (no FPSO equivalent)
- Higher contingency for first-of-a-kind risk
8.4 Cost Breakdown by Percentage
| Category | % of Total |
|---|---|
| Vessel purchase | 18-20% |
| Structural / steelwork | 12-15% |
| Processing equipment (PRRS + cleanup + genset) | 18-22% |
| Collection systems | 7-9% |
| Electrical & instrumentation | 5-7% |
| Piping, marine, coatings | 5-8% |
| Accommodation & helipad | 5-8% |
| Engineering & management | 8-10% |
| Commissioning, class, trials | 3-5% |
| Contingency | 12-18% |
Key Risks and Mitigations
| Risk | Impact | Mitigation |
|---|---|---|
| Vessel condition worse than surveyed | +$5-15M steel renewal, +3-6 months | Thorough pre-purchase survey by independent marine surveyor, include class surveyor in inspection |
| PRRS delivery delay | Delays entire topsides installation (critical path) | Early engagement with PyroGenesis, consider pre-ordering during FEED phase |
| Class approval delays for novel reactor | +3-6 months | Early AIP engagement with DNV, provide comprehensive risk assessment documentation |
| Syngas quality insufficient for engine | Reactor doesn't produce consistent syngas quality → engine trips | Over-design cleanup train, dual-fuel engine capability (fall back to diesel) |
| Yard schedule slip | Typical for first-of-a-kind, +10-20% schedule | Choose experienced yard, strong owner's team on-site, milestone-linked payment schedule |
| Scope creep | Additional systems/features added during engineering | Freeze scope at end of FEED, change order process with cost/schedule impact assessment |
| Regulatory uncertainty | No precedent for ocean-going plasma processing vessel in flag state regulations | Flag state engagement during FEED, choose pragmatic flag (Marshall Islands, Bahamas, Panama — experienced with offshore units) |
Sources and Data Quality
Real data from industry:
- FPSO conversion costs ($150-700M range), steelwork tonnages (3,000-6,000t for full Aframax FPSO), labour rates by region, timeline ranges (18-30 months yard time) — from SPE, OTC papers, and industry publications
- PyroGenesis PRRS containerized at 10.5 TPD (confirmed from Hurlburt Field project), PAWDS at 65 m2 footprint for naval system
- Jenbacher Type 6 syngas engine range (1.8-4.5 MWe)
- Specific FPSO projects: Cidade de Itaguai (MODEC), Prosperity and Liza Unity (SBM/Keppel), with real costs and timelines
- Shipyard market shares and capabilities from offshore industry databases
- PRRS weight (80-150t) — estimated from comparable 10 TPD plasma gasification plants, not from PyroGenesis specification sheet
- PRRS cost ($8-15M) — extrapolated from PAWDS $5.5M pricing, scaled up
- Total conversion cost ($100-130M working estimate) — derived from FPSO conversion benchmarks adjusted for simpler topsides but novel technology
- Individual equipment weights and costs — engineering estimates based on comparable offshore equipment
- Exact PRRS 5-10 TPD weight, dimensions, and foundation loads — must come from PyroGenesis
- Syngas composition from ocean plastic feedstock — determines cleanup train design and engine suitability
- Specific yard quotes — requires formal RFQ process during FEED
- Classification fee and timeline — requires formal engagement with DNV or Lloyd's Register