Annex -Unified interpretations concerning the arrangements for steering capability and
function on ships fitted with propulsion and steering systems other than traditional
arrangements for a ship's directional control
Introduction
The SOLAS requirements for steering gears have been
established for ships having a traditional propulsion system and one rudder. For ships fitted
with alternative propulsion and steering arrangements, such as but not limited to, azimuthing
propulsors or water jet propulsion systems, SOLAS regulations II-1/28.2, 28.3, 29.1, 29.2.1,
29.3, 29.4, 29.6.1 and 29.14 should be interpreted as follows, except 29.14, which is limited
to the steering systems having a certain steering capability due to ship speed also in case
propulsion power has failed.
Regulation 28 – Means of going astern
Paragraph 2
The ability of the machinery to reverse the direction
of thrust in sufficient time, and so to bring the ship to rest within a reasonable distance
from maximum ahead service speed, should be demonstrated and recorded.
Paragraph 3
The stopping times, ship headings and distances
recorded on trials, together with the results of trials to determine the ability of ships
having multiple propulsion/steering arrangements to navigate and manoeuvre with one or more of
these devices inoperative, should be available on board for the use of the master or
designated personnel.
Regulation 29 – Steering gear
Paragraph 1
For a ship fitted with multiple steering systems, such
as but not limited to azimuthing propulsors or water jet propulsion systems, the requirement
in SOLAS regulation II-1/29.1 is considered satisfied if each of the steering systems is
equipped with its own dedicated steering gear.
Paragraph 2.1
All components used in steering arrangements for
ship directional control should be of sound reliable construction to the satisfaction of the
classification society. Special consideration should be given to the suitability of any
essential component which is not duplicated. Any such essential component should, where
appropriate, utilize anti-friction bearings such as ball bearings, roller bearings or sleeve
bearings which should be permanently lubricated or provided with lubrication fittings.
Paragraph 3
The main steering arrangements for ship directional
control should be:
- of adequate strength and capable of steering the ship at maximum ahead service speed which
should be demonstrated;
- capable of changing direction of the ship's directional control system from one side to
the other at declared steering angle limits at an average rotational speed of not less than
2.3°/s with the ship running ahead at maximum ahead service speed;
- for all ships, operated by power; and
- so designed that they will not be damaged at maximum astern speed.
Definition:
Declared steering angle limits are the operational limits in terms of maximum
steering angle, or equivalent, according to manufacturers guidelines for safe operation, also
taking into account the ship's speed or propeller torque/speed or other limitation; the
"declared steering angle limits" are to be declared by the directional control system
manufacturer for each ship specific non-traditional steering mean; ship's manoeuvrability
tests, such as those in the Standards for ship manoeuvrability (resolution MSC.137(76)) should
be carried out with steering angles not exceeding the declared steering angle limits.
Paragraph 4
The auxiliary steering arrangements for ship
directional control should be:
- of adequate strength and capable of steering the ship at navigable speed and of being
brought speedily into action in an emergency;
- capable of changing direction of the ship's directional control system from one side to
the other at declared steering angle limits at an average rotational speed, of not less than
0.5°/s; with the ship running ahead at one half of the maximum ahead service speed or 7
knots, whichever is the greater; and
- for all ships, operated by power where necessary to meet the requirements of 29.4.2 and in
any ship having power of more than 2,500 kW propulsion power per thruster unit.
The definition of "declared steering angle limits", given under the interpretation of
paragraph 3 above, applies.
Paragraph 6.1
In a ship fitted with multiple steering systems,
such as but not limited to azimuthing propulsors or water jet propulsion systems, an auxiliary
steering gear need not be fitted, provided that:
- in a passenger ship, each of the steering systems is fitted with two or more identical
power units, capable of satisfying the requirements in regulation 29.3.2 while anyone of the
power units is out of operation;
- in a cargo ship, each of the steering systems is fitted with one or more identical power
units, capable of satisfying the requirements in regulation 29.3.2 while operating with all
power units;
- each of the steering systems is arranged so that after a single failure in its piping or
in one of the power units, ship steering capability (but not individual steering system
operation) can be maintained or speedily regained (e.g. by the possibility of positioning the
failed steering system in a neutral position in an emergency, if needed).
Definition:
Steering gear power unit – For the purposes of alternative steering arrangements, the
steering gear power unit should be considered as defined in SOLAS regulation II-1/3. For
electric steering gears, refer to SOLAS regulation II-1/3; electric steering motors should be
considered as part of the power unit and actuator.
Paragraph 14
This interpretation is valid for steering systems
having a certain proven steering capability due to ship speed also in case propulsion power
has failed.
Where the propulsion power exceeds 2,500 kW per thruster unit, an alternative power supply,
sufficient at least to supply the steering arrangements which complies with the requirements
of paragraph 4.2 and also its associated control system and the steering system response
indicator, should be provided automatically, within 45 s, either from the emergency source of
electrical power or from an independent source of power located in the steering gear
compartment. This independent source of power should be used only for this purpose. In every
ship of 10,000 gross tonnage and upwards, the alternative power supply should have a capacity
for at least 30 min of continuous operation and in any other ship for at least 10 min.