Section 4 Survey during construction

4.1.1 Surveyors should discuss and establish with the Builder, a satisfactory routine for quality control and survey throughout the various stages of construction. Records should be kept by the Builders, and made available to the Surveyors.

4.1.2 Builders may apply for approval under the Quality Assurance Scheme for Hull Construction.

4.2.1 The general tolerance and construction standards are to be in accordance with the requirements of this section, and other approved standards agreed.

4.2.2 Tolerances to be used for construction misalignment for all material are to be discussed between Owners/ Builders and the Surveyor, and acceptable Standards agreed, subject to the requirements of this Chapter or Naval Authority requirements where applicable. The permitted degree of inaccuracy/ misalignment will vary according to whether the defect is:

1. In primary structure.

2. In secondary structure.

3. Required for equipment alignment.

4. Cosmetic.

4.2.3 In addition, certain critical locations identified by the plan approval process may be subject to specific construction tolerances which will require to be recorded in accordance with the procedures.

4.2.4 All workmanship is to be of good quality and in accordance with good shipbuilding practice. Any defect is to be rectified to the satisfaction of the Surveyor before the material is covered with paint, cement or other composition. The materials and welding are to be in accordance with the requirements of the Rules for Materials. Plates which have been subjected to excessive heating while being worked are to be satisfactorily heat treated before being erected in the hull.

4.2.5 In shipyards certified under the LR Quality Assurance Scheme, the standards will have received general approval as part of the certification procedures and their application to particular vessels should be included in the Quality Plan submitted to the local Surveyors for approval.

4.3.1 Surveyors will attend in the early stages of construction to ensure that undesirable procedures and faulty workmanship are avoided, and possible consequences minimized. When the existence of defects is noticed, prompt and suitable measures should be taken to ensure rectification. Where, due to circumstances, major prefabrication of units has been carried out without inspection by LR, then Headquarters should be advised immediately, such advice including details of the circumstances.

4.3.2 Throughout the preparation of material and assembly of prefabricated units, workmanship is to be inspected to ensure that correct procedures are being followed. Surveyors will liaise with the Design Offices and the Quality Control Departments to ensure that any plan approval comments are incorporated and that attention is given to details which are not shown on the approved plans (e.g. air and drainage holes, etc.) during early material preparation stages.

4.3.3 Surveyors should bear in mind that visual examination of welds and plating of a finished structure does not necessarily ensure a complete and satisfactory survey. Surveyors should ensure that adequate inspection is made of joint preparation before welding. Attention is drawn to the guidance on welding and structural details in Vol 1, Pt 6, Ch 6 Material and Welding Requirements of the Rules for Naval Ships. Regular examination, in conjunction with the Builder, of radiographic records provides a check on the quality of welding operations and any decline in standards should be investigated, including additional tests as considered necessary.

4.3.4 It is essential that a good standard of cleaning be achieved for these surveys. Welding slag should be removed and rusting of weld deposits should be removed by wire brushing. Work should not be surveyed if presented insufficiently prepared for inspection.

4.4.1 Surveyors must ensure, by regular and systematic examination, that the control exercised up to the stage of block assembly is maintained by the efficient erection of blocks at the berth. It is particularly necessary at this point to ensure that fit up, alignment, adjustment and welding of blocks is in accordance with the approved plans and building standards. Attention is to be given to the sequence of erection and of welding.

4.5.1 For alignment and structural continuity of joints, see Vol 1, Pt 6, Ch 2 Design Tools of the Rules for Naval Ships.

4.5.2  Table 3.4.2 Structural misalignment and fit (see continuation) defines the minimum limits of accuracy required to be achieved in the various welded joint designs. When these values are not achieved, the defects are to be discussed and rectification agreed between the Builder and the Surveyor before remedial action is taken.

4.5.3 Limits for weld undercut and remedial action to be taken depends on plate thickness and are to be discussed and rectification agreed between the Builder and the Surveyor prior to commencement of repairs.

4.5.4 Insert plates are to be in accordance with the requirements of Table 3.4.1 Plate deformation limits.

4.6.1 Post-welding deformation of steel construction should be kept to a minimum.

4.6.2 Deformation outside the limits defined in Table 3.4.1 Plate deformation limits is to be faired by controlled localized heating or the plating renewed.

4.6.3 Controlled and localized heating of steel is not to exceed 900°c (red heat).Where water cooling is employed the steel temperature is to be below 600°c before any water is applied.

4.6.4 With the assembly of large blocks, careful attention should be paid to the areas in way of lifting lugs. It is not unusual to find small fractures in the vicinity of the weld area after removal of lugs. Where lugs are removed, the dressing of the plate must be thorough and magnetic particle or dye penetrant detection of the finished surface is good practice. Repair of any cracks found must be carried out by qualified welders under strict control.

4.6.5 Any unusual incidents during construction, such as fracturing of plates, should be noted and brought to the attention of the local Manager with a view to a suitable report being made. It will be necessary to have full information on the circumstances affecting such cases, such as the position and extent of the fracture relative to adjacent structure and welds, atmospheric temperature, details of joints, precise stage and sequence of welding, type of electrode used, whether or not pre-heating was used, grades of steel involved and any other factors considered to have had a possible influence. Test details of affected plates and proposals for remedial measures should also be reported. Where doubt exists in establishing the source of such incidents, the assistance of LR Headquarters may be sought.

4.7.1 Surveyors in building yards should bear in mind the need for accessibility in a vessel in service. Surveyors should ensure, as far as possible, that access is adequate for future maintenance and surveys. In many cases, the only reasonable sized access holes available have access restricted by pipe runs.

4.7.2 While attention is drawn to the need for adequate access, Surveyors should also be alert for additional or enlarged access holes which should not be permitted in highly stressed areas and which are sometimes fitted at a late stage in construction.

4.7.3 It should also be borne in mind that the lack, or bad positioning, of ladders, walkways and manholes may render access under service conditions extremely difficult and dangerous. The Builder’s attention should be drawn to these considerations. In this respect, National Regulations may specify requirements for ladders, walkways and the minimum size of access openings.

4.7.4 Where significant proportions of the ship’s structure are removed for access, the Builder’s calculations demonstrating the adequacy of the remaining structure are to be submitted.

4.8.1 It is the Surveyor’s duty to be alert through all stages of work to ensure that any significant modifications or departures from approved arrangements are noted promptly and dealt with as necessary. It should be clearly understood that deviations from the Rule requirements or approved plans, other than those of a minor nature and not affecting the structural strength of the ship, must not be accepted by the local Surveyor without consultation with the Surveyor-in-charge of the local LR office who, if he considers it appropriate, should submit plans showing the proposed arrangements to the relevant Plan Approval Office.

4.8.2 Large openings not indicated on approved plans are not to be arranged in decks without prior consultation with the Plan Approval Office. Small openings for access, ventilation, etc. may be accepted by the Surveyor who should ensure that they are adequately framed, and when necessary suitably compensated. Requirements for compensation of loss of deck plating, transverse cross-sectional area, and/or edge reinforcement are stated in the appropriate sections of the Rules.

4.8.3 The corners of openings, welded attachments to the sheerstrake (e.g. at bulwark recesses) and small openings cut in decks may not be detailed on approved plans and special attention should be paid to such areas to ensure that no discontinuity, which may produce a notch effect, is built into the structure. Adequate rounding of the corners of openings, with grinding if necessary to a smooth finish, must be ensured to eliminate possible sources of failure in service. The endings of bulwarks should be smoothly tapered without any notch.

4.8.4 Defective welding of seams or butts, with incomplete penetration, omission of sealing runs or craters can result in fractures. When modifications have been made which result in openings having to be closed by welded inserts, particular attention should be paid to welding, with suitable NDE.

4.9.1 Draught marks and paint lines are often permanently indicated on ships’ sides by means of beads of welding or by letters or marks cut from steel plate and welded to the sides.

4.9.2 Lettering on the sheerstrake should be kept below a line 0,1D below the deck, where D is the depth at side. Great care should be taken in the application of the welding, which should be carried out by qualified welders. Substantial runs should be laid continuously, using large diameter low hydrogen electrodes and avoiding light runs as these are more likely to promote fractures. Sharp corners in the letters should be avoided and where the welding crosses a welded butt or seam, the latter should be ground flat for about 75 mm each side of the line of the weld bead before it is laid.

4.9.3 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, pre-heating to about 100°C should be adopted.

4.9.4 In the case of midship draught marks which are located on special quality steel similar precautions should be observed.

4.10.1 Surveyors should ensure compliance with the requirements laid down in Vol 1, Pt 6, Ch 6, 7 Inspection and testing procedures of the Rules for Naval Ships.

4.10.2 Suitable schedules should be produced. It is good practice to first test those tanks which contain supporting structure, so that inspection is made on the smooth, unencumbered sides of the bulkheads.

4.10.3 During testing, the Surveyor should be accompanied by a responsible person and should be satisfied that adequate lighting is available. Particular care is to be exercised if testing is carried out during trial trips.

4.10.4 Attention is drawn to the fact that internal boundary welds made by other than automatic processes should not be coated before leak testing.

4.11.1 Surveyors will normally attend and witness the launch of every vessel being built under Special Survey. This applies also when ships are built in a dry-dock and launching is only a symbolic inlet of water from dock gates.

4.11.2 Under traditional launching methods, if anything occurs which may affect the ship’s structure, the Surveyor should carry out a careful examination for possible damage, as circumstances require. Close attention should be paid to examination of bottom structure in way of launching ways, etc. after launch. Should any damage be found which is not satisfactorily repaired before the completion of the ship, a suitable Condition of Class should be imposed.

4.11.3 Anchors and chain cables supplied for the equipment of a ship in service should not be used as launching drags.

4.12.1 In the period during fitting out of the accommodation, installation of electrical conduits or ventilation trunking, particular vigilance is necessary in order to ensure that the strength of structural members is not impaired by the cutting. Where structural members are cut, adequate reinforcement should be made of girders, brackets, stiffeners, etc. It is also important that watertight or fire rated bulkheads are maintained intact. Any doubts should be referred to the relevant Plan Approval Office.

4.13.1 When a vessel proceeds from the building port to another district for installation of machinery, completion or dry-docking, it is required that the work done be inspected and appropriately tested. This may be done by the Surveyors in the port to which the ship has gone or, if the completing port is within easy access of the building port, by the Surveyors under whose inspection the ship was built. This is a matter for arrangement between the LR offices concerned, the Owners and the Builders.

4.13.2 When the survey is to be completed by the Surveyors at the port to which the ship has gone, the building port Surveyors are to forward to them all necessary plans and a detailed list of items outstanding for completion of the ship and survey. Both offices are to make and agree arrangements for the completion of reports and provision of certificates.