Section 6 Underwater marking

6.1.1 Where an OIWS notation, for In-water Survey, is to be assigned, see Pt 1, Ch 2 Classification Regulations, the requirements of this Section are to be complied with.

6.1.2 The underwater structure of a unit intended to be surveyed on an In-water basis should have its main frames, bulkheads and joints, etc., clearly identified by suitable marking. Details are to be submitted for approval.

6.1.3 Marking should consist of raised lines, numerals and letters. In general, marking by welding is not to be used on ship units and other surface type units.

6.1.4 If marking is to be carried out by welding, the welds should be made with continuous runs and the quality of the workmanship should be to an equivalent standard as the main hull structure. Substantial runs should be laid, continuously, using large diameter electrodes and avoiding light runs as these are more likely to promote cracking. Sharp corners in the letters are to be avoided. Marking by welding is not permitted in highly stressed areas or over existing butts or seams. The welding procedures and consumables are to be submitted for approval.

6.1.5 On steel of Grade D or E or on higher tensile steel, low hydrogen electrodes should be used of a grade suitable for the steel. In the case of higher tensile steel, see Ch 3, 3 Higher strength steels for ship and other structural applications of the Rules for Materials, pre-heating to about 100°C should be adopted.

6.2.1 The following features are to be incorporated into the unit’s design, where applicable, in order to facilitate the underwater inspection. When verified, they will be noted in the unit’s classification for reference at subsequent surveys.

6.2.2  Stern bearing. For self-propelled units, means are to be provided for ascertaining that the seal assembly on oil-lubricated bearings is intact and for verifying that the clearance or weardown of the stern bearing is not excessive. For oil-lubricated bearings, this may only require accurate oil loss rate records and a check of the oil for contamination by sea-water or white metal. For wood or rubber bearings, an opening in the top of the rope guard and a suitable gauge or wedge would be sufficient for checking the clearance by a diver. For oil-lubricated metal stern bearings, weardown may be checked by external measurements between an exposed part of the seal unit and the sterntube bossing, or by use of the unit’s weardown gauge, where the gauge wells are located outboard of the seals, or the unit can be tipped. For use of the weardown gauges, up-to-date records of the base depths are to be maintained on board. Whenever the stainless steel seal sleeve is renewed or machined, the base readings for the weardown gauge are to be re-established and noted in the unit’s records and in the survey report.

6.2.3  Rudder bearings. For self-propelled units with rudders, means and access are to be provided for determining the condition and clearance of the rudder bearings, and for verifying that all parts of the pintle and gudgeon assemblies are intact and secure. This may require bolted access plates and a measuring arrangement.

6.2.4  Sea suctions. Means are to be provided to enable the diver to confirm that the sea suction openings are clear. Hinged sea suction grids would facilitate this operation.

6.2.5  Sea valves. For the Bottom Surveys associated with the Special Survey, means must be provided to examine any sea valve.

6.2.6 Alternative arrangements to facilitate In-water Surveys will be considered; details are to be submitted to LR for approval.