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Engine Sea Trial Procedures for New-Build Ships

Engine sea trial is the systematic verification that a marine slow-speed two-stroke diesel engine meets its specified performance, emission, and operational characteristics in actual ship operation. Sea trials follow shop tests at the engine factory and dock trials in the shipyard. The sequence verifies SFOC, peak pressure, exhaust temperatures, turbocharger performance, manoeuvring response, emergency systems, and emission compliance. Class society representatives witness key tests; results form the basis for the engine’s acceptance and the ship’s delivery. This article covers shop test, dock trial, sea trial procedures, key measurements, and the certification documentation. Visit the home page or browse the calculator catalogue for related propulsion engineering tools.

Contents

Background

Before a new-build ship can be delivered to its owner, its engine must be proven to meet specifications. The proving process is a sequence of tests at progressively integrated levels:

  1. Shop test at the engine manufacturer’s factory: engine alone on dynamometer
  2. Dock trial in the shipyard: engine installed in ship, ship moored
  3. Sea trial: engine operating with ship in actual seaway

Each step verifies specific aspects of engine and integrated ship performance. Class society representatives witness key milestones; the engine and ship cannot be delivered until tests are completed satisfactorily.

This article covers the three trial phases, the principal measurements, and the documentation required for class approval and ship delivery.

Shop test

Test environment

Shop tests are performed at the engine manufacturer’s factory:

  • Test bed: dedicated infrastructure for engine operation
  • Dynamometer: water brake or motor-generator absorbing engine power
  • Standard fuel: reference fuel for SFOC determination
  • Standard ambient: air conditions controlled or corrected

Test points

Standard test points (per ISO 3046):

  • 25%, 50%, 75%, 85% (CSR), 100% (MCR), 110% (overload) of rated power

At each point, the engine runs for a minimum time (typically 1 hour at the lower points, 6+ hours at MCR) to reach steady state. Measurements are then taken.

Measurements

At each test point:

  • Power and speed via torque sensor and tachometer
  • Fuel consumption via calibrated flow meter
  • Cylinder pressures at each cylinder (all 720°CA capture)
  • Exhaust temperatures at each cylinder
  • Turbocharger speed, inlet/outlet temperatures, pressures
  • Cooling water temperatures and flow rates
  • Lubricating oil temperature, pressure, flow
  • Charge air pressure, temperature, mass flow
  • Ambient conditions: air temperature, pressure, humidity

SFOC determination

SFOC at each test point is calculated:

SFOC = m_fuel / P_brake × 3600 / 1000

ISO-corrected to standard reference conditions (25°C, 1 bar, 30% RH, fuel LCV 42,700 kJ/kg).

NOx measurement

NOx emission is measured via continuous emission monitoring (CEM):

  • Sample line from exhaust manifold
  • NOx analyser (chemiluminescence)
  • ISO 8178-1 procedure
  • Emission profile across load points
  • Cycle-weighted average for certification

NOx must meet Tier II limit (or Tier III if the engine is Tier III certified).

Documentation

Shop test results documented in:

  • Engine performance test report
  • NOx test report (basis for EIAPP certificate)
  • Cylinder pressure data per cylinder
  • Anomaly reports
  • Class society witness reports

These documents accompany the engine to the shipyard.

Dock trial

Purpose

Dock trial verifies that the engine works correctly in its installed configuration, integrated with ship systems, before going to sea.

Test setup

The ship is moored at the shipyard quay, fully equipped except awaiting sea trial. The engine is connected to:

  • Ship’s fuel system
  • Ship’s cooling water (or shore-side cooling for limited duration)
  • Ship’s electrical system
  • Ship’s lubricating oil system
  • Ship’s bridge controls

Tests performed

Dock trial typically includes:

  • Engine starting: from cold, with bridge command
  • Idle running: prolonged idle to verify stability
  • Reversing: ahead-astern transitions
  • Variable speed: ramp from idle to rated
  • Auxiliary system tests: lubricating oil pumps, cooling water pumps, fuel pumps
  • Telegraph and bridge controls: command transmission and acknowledgement
  • Alarm and shutdown: simulated faults trigger correct responses
  • Cylinder lubricator: feed rate verification
  • Air cooler operation: with ship’s seawater
  • Indicator measurements: at attainable load points (limited by mooring)

Limitations

Dock trial cannot test:

  • Full load operation (mooring lines and ship structure cannot absorb full power)
  • Manoeuvring at speed
  • Sea-state response

These wait for sea trial.

Duration

Dock trial typically takes 2-5 days, including any troubleshooting and recommissioning of items revealed during testing.

Sea trial

Purpose

Sea trial verifies engine performance and ship operation in actual seaway. The trial is the final acceptance test before ship delivery to the owner.

Test setup

The ship sails from the shipyard with:

  • Owner’s representatives aboard
  • Class society representatives aboard
  • Yard test engineers and crew
  • Manufacturer service engineers
  • Test instrumentation

The trial is typically 2-7 days at sea, depending on test scope.

Standard test program

A typical sea trial program:

Day 1: Light operation

  • Departure from yard
  • Stable cruise at moderate load (50-70%)
  • Initial system checks
  • Fuel consumption baseline

Day 2: Power and speed

  • Speed-power curve (15, 20, 25, 30 minutes at increasing speeds)
  • Bollard pull verification (if applicable)
  • Maximum speed determination
  • Fuel consumption at each speed

Day 3: Performance verification

  • Continuous service rating run (4-8 hours at CSR)
  • SFOC determination at multiple loads
  • Cylinder pressure measurements
  • Exhaust temperature mapping
  • Turbocharger performance
  • ISO correction calculations

Day 4: Manoeuvring

  • Steering trials
  • Crash stop trials
  • Astern trials
  • Emergency stop trials
  • Pilot ladder operations

Day 5: Emission verification

  • NOx measurement at multiple loads
  • Smoke level verification
  • Emission compliance documentation

Days 6-7: Misc

  • Auxiliary system performance
  • Fuel switching tests (if multi-fuel)
  • Sister ship comparison (if applicable)
  • Final adjustments and rerun of any failed items

Specific tests

Speed-power test

Ship runs at various speeds; engine power and ship speed measured. Comparison to design predicts confirms hull performance.

Crash stop test

Ship at full speed; emergency astern command issued. Stopping distance and time measured. Verifies emergency response capability.

NOx test

Continuous emission monitoring during specific load points. Cycle-weighted NOx calculated and compared to certification.

Cylinder balance verification

PMI data collected at multiple operating points. Cylinder-to-cylinder variation measured. Adjustments made if needed.

Trials in different conditions

Sea trial may include:

  • Calm sea conditions (baseline performance)
  • Sea state 4-5 (operational seakeeping)
  • Various headings (effect of wave direction)
  • Various propulsion modes (if applicable)

Documentation

Sea trial results documented in:

  • Sea trial report (full performance data)
  • ISO-corrected SFOC curve
  • Cylinder pressure baseline records
  • Emission test report
  • Anomaly log
  • Class society witness statements
  • Owner acceptance

Independent verification

Class society survey

Class society representatives:

  • Witness shop test at engine factory
  • Witness key dock trial tests
  • Witness key sea trial tests
  • Approve test reports
  • Issue certificates

Owner inspection

Owner’s representatives accompany the test process:

  • Verify specifications met
  • Identify any commissioning items
  • Record final condition
  • Authorise delivery

Sister ship comparison

For ships in series, sea trial results are compared to sister ships:

  • Identifies systematic issues
  • Confirms expected performance reproducibility
  • Supports optimization across the series

Acceptance and delivery

Acceptance criteria

The ship/engine is accepted if:

  • All measured parameters within specification
  • All ISO-corrected SFOC values within specification
  • NOx emissions meet certification levels
  • All safety systems function correctly
  • Class society approval received
  • Owner satisfaction confirmed

Delivery documents

Documents accompany delivery:

  • Engine performance test reports
  • EIAPP certificate (NOx compliance)
  • Class society certificates
  • Operating and maintenance manuals
  • Spare parts inventory
  • Ship’s classification documents

Post-delivery monitoring

After delivery, the engine undergoes initial service period (typically 6-12 months) with:

  • Manufacturer service support
  • Detailed performance monitoring
  • Resolution of any commissioning issues
  • Establishment of in-service baselines

This period validates the trial results and establishes the engine’s true operational baseline.

See also

References

  • ISO 3046-1:2002. Reciprocating internal combustion engines: Performance.
  • ISO 8178-1:2017. Reciprocating internal combustion engines — Exhaust emission measurement.
  • IMO. (2008). NOx Technical Code 2008.
  • MAN Energy Solutions. (2023). Engine Sea Trial Procedures Manual. MAN Energy Solutions.
  • Lloyd’s Register. (2023). Sea Trials and Performance Tests Guide.