Table of contents
- Introduction
- When You Need a Custom Cabin (vs Standard Enclosure)
- Environmental Conditions Offshore Cabins Must Handle
- Standard Cabin Configurations
- Critical Design Features
- Compliance Standards You'll Encounter
- Project Workflow: From RFQ to Commissioning
- Typical Offshore Cabin Projects
- Custom Offshore Cabin FAQ
- Ready to spec your custom offshore generator cabin?
Introduction
Offshore generator installations face conditions no land-based or recreational marine power plant has to deal with: 24/7 salt spray, 30+ degree wave-induced vibration, explosive atmospheres on oil and gas platforms, and the lurking risk that a generator failure 100 miles from shore can shut down a $10 million-per-day operation. Custom offshore generator cabins are how engineers solve these challenges— purpose-built enclosures that go far beyond standard sound shields. This guide walks through when you need a custom cabin, what design features matter, which compliance standards apply, and how a typical offshore cabin project unfolds.
When You Need a Custom Cabin (vs Standard Enclosure)
Standard sound-attenuated enclosures work fine for protected installations: yachts, workboats, coastal applications. You need a custom offshore generator cabin when one or more of these apply:
- Continuous offshore exposure (oil platforms, FPSOs, offshore wind support vessels)
- Hazardous zone classification (Zone 1 or 2 — IECEx, ATEX compliance required)
- Extreme temperature ranges (-40°C arctic operations, +55°C Persian Gulf)
- Non-standard footprint (vessel deck constraints, retrofit between existing equipment)
- Integrated fire and gas detection required by client or class society
- Special vibration isolation for sensitive equipment co-located in the cabin
- Medium voltage output (3.3 kV or 6.6 kV) requiring transformer integration
If any two of the above apply, a custom cabin is almost always more cost-effective than trying to modify a standard enclosure to fit.
Environmental Conditions Offshore Cabins Must Handle
Salt Spray Protection (ISO 12944 C5-M)
Offshore corrosion protection follows ISO 12944, with C5-M as the standard for marine atmospheres. This dictates a minimum 280-320 microns total dry film thickness across primer, intermediate, and topcoat layers. Specifications typically include zinc-rich epoxy primer (60-80 μm), high-build epoxy intermediate (140-180 μm), and polyurethane topcoat (60-80 μm). Bolt heads and fasteners are stainless steel (316L minimum) or hot-dip galvanized. Salt spray testing (ASTM B117) of 1,000-3,000 hours is typically required for type approval.
Vibration and Shock Loads
Cabins on floating platforms or vessels must withstand continuous vibration (engine and wave-induced) plus impact loads from heavy weather. Design typically uses double-isolation: vibration-damped engine mounts inside, isolation pads between cabin and deck outside. Structural framing is reinforced beyond standard ISO container specs — usually 5-8 mm corner posts with welded reinforcement at lifting points.
Temperature Extremes
Arctic operations (-40°C) require fuel and coolant pre-heaters, glycol coolant systems, and battery heating. Desert installations (+55°C) demand oversized radiators, cabin air conditioning to keep electronics under 40°C, and engine room ventilation rates 2-3x standard. Both extremes need insulated cabin walls — typically 50-100mm mineral wool with vapor barriers.
Explosive Atmospheres (IECEx / ATEX)
For hazardous zone installations (oil and gas platforms, fuel handling areas), the cabin and all internal equipment must comply with IECEx (international) or ATEX (European Union) standards. This includes Ex-rated lighting, junction boxes, motors, and intake/exhaust spark arrestors. Zone 1 (likely explosive atmosphere present in normal operation) and Zone 2 (only present abnormally) have different equipment requirements — Zone 1 is more restrictive and expensive.
Standard Cabin Configurations
Skid-Mounted Units
The simplest custom option: generator mounted on a structural steel skid with weather-protective coverings, lifting eyes, and integrated fuel day tank. Best for fixed offshore installations where the unit can be lifted into a sheltered area or housed under permanent structure. Footprint-efficient, lower cost than fully enclosed cabins.
20ft / 40ft Containerized
The most popular custom format. Standard ISO container dimensions (20ft = 6.06m, 40ft = 12.19m) allow shipment via any standard logistics network. Inside, the generator is fully enclosed with attenuators, integrated control panel, fuel tank, fire suppression, lighting, and maintenance walkways. Containerized cabins can be stacked or relocated between
Custom Footprint
For installations where standard containers don't fit — between existing deck equipment, in a vessel engine room conversion, or designed to match an existing aesthetic — fully custom dimensions are designed. Common drivers: low headroom decks (less than 2.4m), unusual footprint shapes, or matched paint scheme requirements.
Critical Design Features
Fire Suppression Systems
Offshore cabins almost always include automatic fire suppression — most commonly FM-200 (HFC-227ea) or Novec 1230 clean agents. These extinguish fires without damaging electrical equipment or requiring extensive cleanup. The system includes detection (smoke + heat sensors), control panel, agent storage cylinders, and discharge nozzles. Designed to suppress fire within 10 seconds of detection.
Acoustic Insulation
Target noise levels depend on application. Crew quarters proximity typically demands 70 dBA at 1 meter or less. Heavy-duty industrial settings may accept 80 dBA. Achieving these targets requires lined cabin walls (mineral wool + perforated steel), inlet and exhaust attenuators (silencer banks), vibration isolation under the generator, and sealed cable penetrations.
Ventilation and Combustion Air
An offshore diesel generator needs roughly 4-6 m³ of combustion air per kWh of fuel burned. Total ventilation rates are higher to handle heat rejection — often 10-15x combustion air flow. Inlet and exhaust louvers must include weatherproofing (rain hoods, sand traps in desert use, mist eliminators for marine spray) and Ex-rated fans if in hazardous zones.
Integrated Fuel Day Tank
Day tanks of 4-12 hour capacity are typically inside the cabin, with bulk fuel transfer from external storage. Tanks include level sensors, vent lines to a safe location, overflow protection, leak detection in a bunded base, and shut-off valves accessible from outside the cabin.
Lighting and Maintenance Access
Internal lighting is Ex-rated LED, with both normal and emergency battery-backed circuits. Maintenance walkways are minimum 600mm wide on service-access sides. External lighting illuminates control panels and access doors. Service access typically requires double doors on the alternator end, hatch panels above the engine for component removal.
Compliance Standards You'll Encounter
- ABS (American Bureau of Shipping) — Type approval for floating offshore installations
- DNV (Det Norske Veritas) — Norwegian Continental Shelf, North Sea standard
- Lloyd's Register — Common UK and Commonwealth requirements
- IECEx — International hazardous area certification
- ATEX 2014/34/EU — EU directive on equipment for explosive atmospheres
- API 7B-11C — American Petroleum Institute standard for engines on oil and gas operations
- SOLAS Chapter II-2 — IMO fire safety requirements for marine installations
- NORSOK S-001 — Norwegian petroleum standards for technical safety
For a deeper breakdown of marine certification requirements, see our Understanding Marine Generator Certifications guide.
Project Workflow: From RFQ to Commissioning
A custom offshore generator cabin project typically follows this sequence:
- Specification Phase (2-4 weeks): Client provides RFQ with power requirements, operating conditions, compliance needs, and site constraints. Engineering team produces a budget proposal with preliminary general arrangement drawings.
- Detailed Design (4-8 weeks): Approved purchase order triggers detailed mechanical, electrical, and structural design. Generates fabrication drawings, P&IDs, electrical schematics, and stress calculations. Class society pre-review if required.
- Fabrication (10-16 weeks): Cabin steelwork manufactured. Generator and major components procured in parallel. Painting per ISO 12944 specification. All sub-assemblies prepared.
- Assembly and Internal Testing (3-4 weeks): Generator installed in cabin. Fuel, electrical, control, and safety systems integrated. Factory acceptance test (FAT) includes load bank testing, noise measurement, vibration analysis, and safety function checks.
- Witness Test and Shipping (1-2 weeks): Client and class society representatives witness FAT. Punch list addressed. Cabin packed for ocean shipment, lifting arrangement verified.
- Site Installation and Commissioning (1-3 weeks): Cabin lifted onto vessel or platform, connected to vessel systems (fuel, electrical, water). Site acceptance test (SAT) with full load and operating conditions. Final commissioning and operator training.
Total project timeline: 20-32 weeks for standard custom cabins, longer for highly specialized projects.
Typical Offshore Cabin Projects
500 kVA Crew Boat Genset Cabin
40ft containerized format, ABS type approved, located on aft deck. Twin 250 kVA units in parallel for redundancy. Sea water cooled, integrated fuel day tank (12-hour capacity), FM-200 fire suppression. Target noise: 75 dBA at 1m.
800 kVA Offshore Wind Farm Support Vessel Cabin
Custom footprint (5.4m × 2.4m to fit between deck cranes), IECEx Zone 2 rated. Variable speed alternator for fuel optimization at partial loads. North Sea-rated paint (3,000-hour salt spray). Integrated with vessel's J1939 monitoring system.
1,200 kVA Drilling Rig Emergency Genset
20ft containerized cabin, API 7B-11C compliant. Black start capability for power restoration. Ex-rated electrical components throughout. 24-hour day tank, gas detection integrated with rig safety system. Acoustic target: 80 dBA at 1m.
Custom Offshore Cabin FAQ
How much does a custom offshore generator cabin cost?
- Custom cabins typically run $80,000-$400,000 above the cost of the bare generator, depending on size, complexity, and compliance requirements. A standard 20ft containerized cabin around a 500 kVA genset usually falls in the $120,000-$200,000 range. ATEX/IECEx Zone 1 hazardous area cabins can add 30-50%.
How long does a custom cabin project take?
- 20-32 weeks from approved purchase order to delivered cabin is typical. Standard containerized cabins are toward the shorter end; highly custom or class-witnessed projects toward the longer end. Add 4-8 weeks for site commissioning.
Can a custom cabin be relocated between projects?
- Yes — containerized cabins (20ft or 40ft) ship via standard logistics and are commonly redeployed. Custom footprint cabins are usually project-specific but can be relocated with engineering review. Skid-mounted units are the most portable.
Do I need ABS or DNV certification for my cabin?
- It depends on the operating location and class of the installation. Vessels classed by ABS, DNV, Lloyd's, or other societies require equipment that complies with the same standard. Oil and gas platforms typically require certification by the local regulator (BSEE in the US Gulf, NOROG in Norway) plus the IOC's internal standards.
What's the difference between Zone 1 and Zone 2 hazardous areas?
- Zone 1 areas have explosive atmospheres present during normal operations (e.g., near wellheads, tank vents). Zone 2 areas only have explosive atmospheres under abnormal conditions (e.g., adjacent to Zone 1 areas, downwind of vent stacks). Zone 1 requires more restrictive Ex-rated equipment (Ex d flameproof, Ex i intrinsically safe), making it 20-40% more expensive than Zone 2.
Can the generator be replaced inside an existing cabin?
- Yes, in most cases. Cabin design typically includes removable roof or end panels for component removal. We've replaced engines, alternators, and major auxiliary equipment inside cabins ranging from 5 to 20 years old. Verify lifting points are still rated for the new equipment weight.
What spare parts should I stock for an offshore cabin?
- Recommended onboard spares: fuel filters (3-6 months supply), oil filters, air filters, full set of belts, water pump impellers, primary fuel injectors, and one complete control module. For remote locations, also stock starter motors, alternator brushes, and engine sensors. Total spare parts kit typically $5,000-$15,000.
How much warning does the fire suppression give before discharging?
- Most systems have a 10-30 second pre-discharge alarm with strobes and horn. Personnel inside the cabin (rare during normal operation) have time to exit before agent discharge. The system can be inhibited from the control panel during maintenance work.
Contact
Ready to spec your custom offshore generator cabin?
Need a generator cabin that passes ABS/DNV witness testing, survives Zone 1/2 hazardous environments, and ships on schedule? Contact us. We support oil & gas operators, offshore wind contractors, and shipyards end-to-end—from RFQ specification and detailed design through fabrication, FAT witnessing, and on-site commissioning—focusing on the issues that derail most projects: class society alignment, harsh-environment durability (ISO 12944 C5-M salt spray), and seamless integration with existing vessel or platform systems.
Send us your project specs (power rating, operating location, compliance requirements, deck constraints), and we'll come back with a budget proposal, preliminary GA drawing, realistic delivery timeline, and a clear next-step checklist.
