7.3 Preparations for the inclining test
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7.3 Preparations for the inclining test

Parent topic: Chapter 7 - Determination of Lightship Displacement and Centres of Gravity

7.3.1 Notification of the Administration

 Written notification of the inclining test should be sent to the Administration as it requires or in due time before the test. An Administration representative should be present to witness the inclining test and the test results be submitted for review.

The responsibility for making preparations, conducting the inclining test and lightweight survey, recording the data, and calculating the results rests with the shipyard, owner or naval architect. While compliance with the procedures outlined herein will facilitate an expeditious and accurate inclining test, it is recognized that alternative procedures or arrangements may be equally efficient. However, to minimize risk of delay, it is recommended that all such variances be submitted to the Administration for review prior to the inclining test.

7.3.1.1 Details of notification

 Written notification should provide the following information as the Administration may require:

  • .1 identification of the ship by name and shipyard hull number, if applicable;

  • .2 date, time, and location of the test;

  • .3 inclining weight data:

    • .1 type;

    • .2 amount (number of units and weight of each);

    • .3 certification;

    • .4 method of handling (i.e. sliding rail or crane);

    • .5 anticipated maximum angle of heel to each side;

  • .4 measuring devices:

    • .1 pendulums - approximate location and length;

    • .2 U-tubes - approximate location and distance between legs;

    • .3 inclinometers - location and details of approvals and calibrations.

  • .5 approximate trim;

  • .6 condition of tanks;

  • .7 estimated weights to deduct, to complete, and to relocate in order to place the ship in its true lightship condition;

  • .8 detailed description of any computer software to be used to aid in calculations during the inclining test;

  • .9 name and phone number of the person responsible for conducting the inclining test.

7.3.2 General condition of the ship

  7.3.2.1 A ship should be as complete as possible at the time of the inclining test. The test should be scheduled to minimize the disruption in the ship's delivery date or its operational commitments.

  7.3.2.2 The amount and type of work left to be completed (weights to be added) affect the accuracy of the lightship characteristics, so good judgement should be used. If the weight or centre of gravity of an item to be added cannot be determined with confidence, it is best to conduct the inclining test after the item is added.

  7.3.2.3 Temporary material, tool boxes, staging, sand, debris, etc., on board should be reduced to absolute minimum before the inclining test. Excess crew or personnel not directly involved in the inclining test should be removed from on board the ship before the test.

  7.3.2.4 Decks should be free of water. Water trapped on deck may shift and pocket in a fashion similar to liquids in a tank. Any rain, snow or ice accumulated on the ship should be removed prior to the test.

  7.3.2.5 The anticipated liquid loading for the test should be included in the planning for the test. Preferably, all tanks should be empty and clean, or completely full. The number of slack tanks should be kept to an absolute minimum. The viscosity of the fluid, the depth of the fluid and the shape of the tank should be such that the free surface effect can be accurately determined.

  7.3.2.6 The ship should be moored in a quiet, sheltered area free from extraneous forces such as propeller wash from passing vessels, or sudden discharges from shore side pumps. The tide conditions and the trim of the ship during the test should be considered. Prior to the test, the depth of water should be measured and recorded in as many locations as are necessary to ensure that the ship will not contact the bottom. The specific gravity of water should be accurately recorded. The ship should be moored in a manner to allow unrestricted heeling. The access ramps should be removed. Power lines, hoses, etc., connected to shore should be at a minimum, and kept slack at all times.

  7.3.2.7 The ship should be as upright as possible and have sufficient draught so that any abrupt changes in the waterplane will be avoided as the ship is inclined from side to side. A deviation from design trim of up to 1% of L is normally acceptable when using hydrostatic data calculated at design trim. Otherwise, the hydrostatic data should be calculated for the actual trim. Caution should be exercised when applying the “1% rule of thumb” to ensure that excessive error, as would result from a significant change in the waterplane area during heeling, is not introduced into the stability calculations. With inclining weights in the initial position, up to one-half degree of list is acceptable.

  7.3.2.8 The total weight used should be sufficient to provide a minimum inclination of one degree and a maximum of four degrees of heel to each side. The Administration may, however, accept a smaller inclination angle for large ships provided that the requirements on pendulum deflection or U-tube difference in height in 7.3.2.9 are complied with. Test weights should be compact and of such a configuration that the vertical centre of gravity of the weights can be accurately determined. Each weight should be marked with an identification number and its weight. Re-certification of the test weights should be carried out prior to the inclining. A crane of sufficient capacity and reach, or some other means, should be available during the inclining test to shift weights on the deck in an expeditious and safe manner. Water ballast transfer may be carried out, when it is impractical, to incline using solid weights, if acceptable to the Administration.

  7.3.2.9 The use of three pendulums is recommended but a minimum of two should be used to allow identification of bad readings at any one pendulum station. They should each be located in an area protected from the wind. The pendulums should be long enough to give a measured deflection, to each side of upright, of at least 15 cm. To ensure recordings from individual instruments are kept separate, it is suggested that the pendulums be physically located as far apart as practical.

One or more pendulums may be substituted by other measuring devices (U-tubes or inclinometers) at the discretion of the Administration. Alternative measuring devices should not be used to reduce the minimum inclining angles recommended in 7.3.2.8.

  7.3.2.10 Efficient two-way communications should be provided between central control and the weight handlers and between centre control and each pendulum station. One person at a central control station should have complete control over all personnel involved in the test.

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