Section 17 Sea trials

17.1.1 Sea trials are to be of sufficient duration and carried out under normal operating conditions applicable to the intended class notation. Individual Chapters give specific requirements.

17.2.1 Sea trials are to include the demonstration of:

1. The adequacy of the starting arrangements of the main engines, auxiliary systems and emergency generators.

2. The effectiveness of the steering gear control systems, see Vol 2, Pt 1, Ch 3, 16.4 Testing 16.4.2.

3. Manoeuvring, to include:

   • starting;
   • normal and emergency stopping;
   • reversing;
   • governor testing;
   • safety devices and associated indicators; and
   • alarms.

4. The redundancy arrangements.

5. Tooth contact markings in geared installations using a recognised technique. The marking is to be as detailed in Vol 2, Pt 1, Ch 3, 10.6 Meshing tests

6. For controllable pitch propellers, the pitch setting under failure conditions.

7. Operation of sliding watertight doors under working conditions.

8. Anchoring test to demonstrate that the windlass with brakes, etc. functions satisfactorily, and that the power to raise the anchor can be developed and satisfies the Rule requirements. See Vol 1, Pt 3, Ch 5, 7 Towing arrangements.

9. Operation of bilge and dewatering systems to dry compartments.

17.2.2 Main propulsion systems are to undergo tests to demonstrate the astern response characteristics. The tests are to be carried out over at least the manoeuvring range of the propulsion system and from all control positions. A test plan is to be provided by the yard and accepted by the Surveyor. If specific operational characteristics have been defined by the manufacturer, then these are to be included in the test plan.

17.3.1 The performance of main propulsion machinery is to be demonstrated at full power in accordance with an agreed trials schedule. Engine changeover arrangements are to be demonstrated where applicable.

17.3.2 The reversing characteristics of the propulsion plant, including the blade pitch control system of controllable pitch propellers, are to be demonstrated and recorded during trials.

17.3.3  It is to be verified that the propeller performs satisfactorily under ahead and astern conditions. Where controllable pitch propellers are fitted, the free route astern trial is to be carried out with the propeller blades set in the full pitch astern condition.

17.3.4 It is to be verified that large movements of resiliently mounted machinery do not occur during start up and stop, or during normal operating conditions.

17.3.5 The installation should be tested to ensure that gas turbines cannot be continuously operated within any speed range where excessive vibration, stalling or surging may be encountered.

17.3.6 For main propulsion systems with reversing gears, controllable pitch propellers or electric propeller drive, running astern is not to lead to the overload of any systems.

17.3.7 Steam turbine test requirements are to be agreed with LR, consideration is to be given to ventilation and intake arrangements in the astern direction. The duration of the astern trial is to be limited in accordance with manufacturer’s recommendations to avoid overheating of the turbine due to the effects of ‘windage’ and friction.

17.3.8 The following information is to be available on board for the use of designated personnel:

• The results of trials to determine stopping times, ship headings and distance;
• For ships having multiple propellers or multiple steering-propulsion arrangements, the results of trials to determine the ability to navigate and manoeuvre with one or more propellers or steering-propulsion units inoperative;
• For ships having a single propulsor driven by multiple engines or electric motors, the results of trials to determine the ability to navigate and manoeuvre with the largest engine or electric motor inoperative.

17.3.9 It is to be demonstrated at the sea trial that the stopping distance achieved when the ship is initially proceeding ahead with a speed of at least 90 per cent of the ship's speed corresponding to 85 per cent of the maximum rated propulsion power should not exceed 15 ship lengths after the astern order has been given. However, if the displacement of the ship makes this criterion impracticable then in no case should the stopping distance exceed 20 ship lengths.