Annex 12 – Procedural Requirements for Thickness Measurements
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Annex 12 – Procedural Requirements for Thickness Measurements

1 General

 Thickness measurements required in the context of hull structural surveys, if not carried out by the society itself should be witnessed by a surveyor. The attendance of the surveyor should be recorded. This also applies to thickness measurements taken during voyages.

2 Survey meeting

  2.1 Prior to commencement of the renewal or intermediate survey, a meeting should be held between the attending surveyor(s), the owner’s representative(s) in attendance and the thickness measurement firm’s representative(s) so as to ensure the safe and efficient execution of the surveys and thickness measurements to be carried out on board.

  2.2 Communication with the thickness measurement operator(s) and owner’s representative(s) should be agreed during the meeting, with respect to the following:

  • .1 reporting of thickness measurements on regular basis;

  • .2 prompt notification to the surveyor in case of findings such as:

    • .2.1 excessive and/or extensive corrosion or pitting/grooving of any significance;

    • .2.2 structural defects like buckling, fractures and deformed structures;

    • .2.3 detached and/or holed structure; and

    • .2.4 corrosion of welds.

  2.3 The survey report should indicate where and when the meeting took place and who attended (the name of the surveyor(s), the owner’s representative(s) and the thickness measurement firm’s representative(s)).

3 Monitoring of the thickness measurement process onboard

  3.1 The surveyor should decide final extent and location of thickness measurements after overall survey of representative spaces onboard.

  3.2 In case the owner prefers to commence the thickness measurements prior to the overall survey, then the surveyor should advise that the planned extent and locations of thickness measurements are subject to confirmation during the overall survey. Based on findings, the surveyor may require additional thickness measurements to be taken.

  3.3 The surveyor should direct the gauging operation by selecting locations such that readings taken represent, on average, the condition of the structure for that area.

  3.4 Thickness measurements taken mainly to evaluate the extent of corrosion, which may affect the hull girder strength, should be carried out in a systematic manner such that all longitudinal structural members are gauged, as required.

  3.5 Where thickness measurements indicate substantial corrosion or wastage in excess of allowable diminution, the surveyor should direct locations for additional thickness measurements in order to delineate areas of substantial corrosion and to identify structural members for repairs/renewals.

  3.6 Thickness measurements of structures in areas where close-up surveys are required should be carried out simultaneously with close-up survey.

4 Review and verification

  4.1 Upon completion of the thickness measurements, the surveyor should confirm that no further gaugings are needed, or specify additional gaugings.

  4.2 Where these guidelines allow the extent of thickness measurements to be reduced after special considerations by the surveyor, these special considerations should be reported, where appropriate.

  4.3 In case thickness measurements are partly carried out, the extent of remaining thickness measurements should be reported for the use of the next surveyor.”

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