4.2.1 For all types of installation, the sea trials are to be of sufficient
duration, and carried out under normal manoeuvring conditions, to prove the
machinery under power. The trials are also to demonstrate that any vibration which
may occur within the operating speed range is acceptable.
4.2.2 The trials are to include demonstrations of the following:
- The adequacy of the starting arrangements to provide the
required number of starts of the main engines.
- The ability of the machinery to reverse the direction of thrust
of the propeller in sufficient time, under normal manoeuvring conditions,
and so bring the unit to rest from maximum service speed. Results of the
trials are to be recorded.
- The ability to permit astern running at 70 per cent of the full power ahead
revolutions corresponding to the maximum continuous ahead power for which
the vessel is classed.
- In steam turbine installations, the ability to permit astern
running at 70 per cent of the ahead revolutions corresponding to the maximum
continuous ahead power for which the vessel is classed. This astern trial
need only be of 15 minutes' duration, but may be extended to 30 minutes at
the Surveyor's discretion.
4.2.3 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.
4.2.4 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.
4.2.5 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
position. Where emergency manual pitch setting facilities are provided, their
operation is to be demonstrated to the satisfaction of the Surveyors.
4.2.6 In geared installations, prior to full power sea trials, the gear teeth
are to be suitably coated to demonstrate the contact markings, and on conclusion of
the sea trials all gears are to be opened up sufficiently to permit the Surveyors to
make an inspection of the teeth. The marking is to indicate freedom from hard
bearing, particularly towards the ends of the teeth, including both ends of each
helix where applicable. The contact is to be not less than that required by Pt 5, Ch 5, 5.2 Meshing tests as applicable.
4.2.7 The following information is to be available on board for the use of the
Master and designated personnel:
- The results of trials to determine stopping times, unit headings
and distance;
- For units having multiple propellers, the results of trials to
determine the ability to navigate and manoeuvre with one or more propellers
inoperative.
- For units 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.
4.2.8 Where the unit is provided with supplementary means for manoeuvring or
stopping, the effectiveness of such means is to be demonstrated and recorded as
referred to in Pt 5, Ch 1, 4.2 Sea trials 4.2.7.
4.2.9 The stopping distance achieved when the unit is initially proceeding
ahead with a speed of at least 90 per cent of the unit’s speed corresponding to 85
per cent of the maximum rated propulsion power, should not exceed 15 unit lengths
after the astern order has been given. However, if the displacement of the unit
makes this criterion impracticable then in no case should the stopping distance
exceed 20 unit lengths.
4.2.10 For main propulsion systems with reversing gears, controllable pitch propellers or
electric propeller drive, running astern is not to lead to the overload of
propulsion machinery.
4.2.11 All trials are to be to the Surveyor’s satisfaction.