1. Preliminary Design Review (Pre-Approval Stage)
Before construction begins, DNV conducts a concept and preliminary design review to ensure compliance with applicable rules (e.g., SOLAS, MARPOL, DNV Class Rules). Key activities include:
Hull structural analysis using Finite Element Analysis (FEA) to verify strength under various loads.
Stability and safety assessments, including damage stability calculations and escape route planning.
Emission compliance checks for engines, scrubbers, and fuel systems under IMO Tier III or EEDI regulations.
Risk assessments for novel designs (e.g., alternative fuels like LNG or hydrogen).
DNV issues Approval in Principle (AiP) if the design meets preliminary criteria, allowing the shipyard to proceed.
2. Detailed Plan Approval (Drawing & Technical Documentation Review)
Once the preliminary design is accepted, DNV conducts a detailed drawing review covering:
Structural drawings (welding plans, scantlings, and framing arrangements).
Machinery and electrical schematics (engine layouts, piping systems, and automation).
Fire safety plans, including compartmentation and fire suppression system details.
Fuel and ballast system designs to prevent pollution risks.
DNV engineers cross-check all submitted documents against class rules and statutory regulations. Any deviations require resubmission before construction begins.
3. Material & Component Certification (Supplier & Manufacturing Oversight)
DNV mandates strict material traceability and quality control for critical components:
Steel plates and welds must undergo ultrasonic testing (UT) and chemical composition checks.
Propellers, shafts, and bearings require material certificates (e.g., DNV GL Type Approval).
Piping and pressure vessels must comply with DNV standards for thickness and corrosion resistance.
Electrical equipment (e.g., switchboards, cables) must meet IEC and DNV fire safety standards.
DNV conducts factory audits at supplier facilities to verify manufacturing processes before installation.
4. Construction Supervision (In-Process Surveys & Quality Assurance)
During shipbuilding, DNV surveyors perform stage inspections to ensure compliance with approved plans:
Hull assembly checks: Verify alignment, welding quality, and coating application.
Machinery installation tests: Confirm proper mounting of engines, pumps, and propulsion systems.
Tank testing: Conduct hydrostatic and pneumatic tests for watertight integrity.
Electrical system inspections: Ensure proper grounding, cable routing, and explosion-proof fittings in hazardous areas.
Non-conformities (e.g., poor welds) trigger corrective actions before proceeding to the next phase.
5. Final Surveys & Sea Trials (Class Certification Before Delivery)
Before delivery, DNV performs final verification, including:
Load line and stability tests to confirm compliance with intact/damage stability criteria.
Sea trials: Assess speed, maneuverability, and emergency systems (e.g., crash-stop tests).
Safety system validations: Test lifeboats, fire pumps, and blackout recovery procedures.
Emission measurements: Verify NOx, SOx, and particulate levels meet IMO limits.
