CONTENTS:
3. Qualification of personnel
3.1 Qualification of welders
3.2 Qualification of welding procedures
3.3 Qualification of NDE operators
4. Materials
4.1 General requirements to materials
4.2 Equivalency of material grades
5. General requirements to welding
5.1 Correlation of welding consumables to hull structural steels
5.2 General requirements to preheating and drying out
5.3 Dry welding on hull plating below the waterline of vessels afloat
6. Repair quality standard
6.1 Welding, general
6.2 Renewal of plates
6.3 Doubler on plates
6.4 Renewal of internals/stiffeners
1. Scope
1.1 This standard provides guidance on quality of repair of hull structures. The standard covers permanent repairs of existing ships.
1.2 The standard covers typical repair methods and gives guidance on quality standard on the most important aspects of such repairs. Unless explicitly stated elsewhere in the standard, the level of workmanship reflected herein will in principle be acceptable for primary and secondary structure of conventional design. A more stringent standard may however be required for critical and highly stressed areas of the hull, and is to be agreed with the Classification Society in each case. In assessing the criticality of hull structure and structural components, reference is made to ref. 1, 2 and 3.
1.3 Restoration of structure to the original standard may not constitute durable repairs of damages originating from insufficient strength or inadequate detail design. In such cases strengthening or improvements beyond the original design may be required. Such improvements are not covered by this standard, however it is referred to ref. 1, 2 and 3.
2.1 In general, when hull structure covered by classification is to be subjected to repairs, the work is to be carried out under the supervision of the Surveyor to the Classification Society. Such repairs are to be agreed prior to commencement of the work.
2.2 Repairs are to be carried out by workshops, repair yards or personnel who have demonstrated their capability to carry out hull repairs of adequate quality in accordance with the Classification Society’s requirements and this standard.
2.3 Repairs are to be carried out under working conditions that facilitate sound repairs. Provisions are to be made for proper accessibility, staging, lighting and ventilation. Welding operations are to be carried out under shelter from rain, snow and wind.
2.4 Welding of hull structures is to be carried out by qualified welders, according to approved and qualified welding procedures and with welding consumables approved by the Classification Society, see Section 3. Welding operations are to be carried out under proper supervision of the repair yard.
2.5 Where repairs to hull which affect or may affect classification are intended to be carried out during a voyage, complete repair procedure including the extent and sequence of repair is to be submitted to and agreed upon by the Surveyor to the Classification Society reasonably in advance of the repairs. See Ref. 8.
3. Qualification of personnel
3.1 Qualification of welders
3.1.1 Welders are to be qualified in accordance with the procedures of the Classification Society or to a recognised national or international standard, e.g. EN 287, ISO 9606, ASME Section IX, ANSI/AWS D1.1. Recognition of other standards is subject to submission to the Classification Society for evaluation. Repair yards and workshops are to keep records of welders qualification and, when required, furnish valid approval test certificates.
3.1.2 Welding operators using fully mechanised of fully automatic processes need generally not pass approval testing, provided that production welds made by the operators are of the required quality. However, operators are to receive adequate training in setting or programming and operating the equipment. Records of training and production test results shall be maintained on individual operator’s files and records, and be made available to the Classification Society for inspection when requested.
3.2 Qualification of welding procedures
Welding procedures are to be qualified in accordance with the procedures of the Classification Society or a recognised national or international standard, e.g. EN288, ISO 9956, ASME Section IX, ANSI/AWS D1.1. Recognition of other standards is subject to submission to the Classification Society for evaluation. The welding procedure should be supported by a welding procedure qualification record. The specification is to include the welding process, types of electrodes, weld shape, edge preparation, welding techniques and positions.
3.3 Qualification of NDE operators
3.3.1 Personnel performing non destructive examination for the purpose of assessing quality of welds in connection with repairs covered by this standard, are to be qualified in accordance with the Classification Society rules or to a recognised international or national qualification scheme. Records of operators and their current certificates are to be kept and made available to the Surveyor for inspection.
4. Materials
4.1 General requirements for materials
4.1.1 The requirements for materials used in repairs are in general the same as the requirements for materials specified in the Classification Society’s rules for new constructions, (ref. 5).
4.1.2 Replacement material is in general to be of the same grade as the original approved material. Alternatively, material grades complying with recognised national or international standards may be accepted by the Classification Societies provided such standards give equivalence to the requirements of the original grade or are agreed by the Classification Society. For assessment of equivalency between steel grades, the general requirements and guidelines in Section 4.2 apply.
4.1.3 Higher tensile steel is not to be replaced by steel of a lesser strength unless specially approved by the Classification Society.
4.1.4 Normal and higher strength hull structural steels are to be manufactured at works approved by the Classification Society for the type and grade being supplied.
4.1.5 Materials used in repairs are to be certified by the Classification Society applying the procedures and requirements in the rules for new constructions. In special cases, and normally limited to small quantities, materials may be accepted on the basis of alternative procedures for verification of the material’s properties. Such procedures are subject to agreement by the Classification Society in each separate case.
4.2.2 When assessing the equivalence between grades of normal or higher strength hull structural steels up to and including grade E40 in thickness limited to 50 mm, the general requirements in Table 4.1 apply.
4.2.3 Guidance on selection of steel grades to certain recognised standards equivalent to hull structural steel grades specified in Classification Societies’ rules is given in Table 4.2
5.1 Correlation of welding consumables with hull structural steels
5.1.1 For the different hull structural steel grades welding consumables are to be selected in accordance with IACS UR W17 (see Ref.6).
5.2.2 A minimum preheat of 50o C is to be applied when ambient temperature is below 0° C. Dryness of the welding zone is in all cases to be ensured.
5.2.3 Guidance on recommended minimum preheating temperature for higher strength steel is given in Table 5.1. For automatic welding processes utilising higher heat input e.g. submerged arc welding, the temperatures may be reduced by 50º C. For re-welding or repair of welds, the stipulated values are to be increased by 25º C.
1)
Combined thickness tcomb = t1+t2+t3+t4, see figure 2)
6.1 Welding, general
Local doublers are normally only allowed as temporary repairs, except as original compensation for openings, within the main hull structure.
6.9 Grinding of shallow cracks
REC 047 Shipbuilding and Repair Quality Standard - Rev.6 May 2012
1. Scope
2. General
requirements to repairs and repairers3. Qualification of personnel
3.1 Qualification of welders
3.2 Qualification of welding procedures
3.3 Qualification of NDE operators
4. Materials
4.1 General requirements to materials
4.2 Equivalency of material grades
5. General requirements to welding
5.1 Correlation of welding consumables to hull structural steels
5.2 General requirements to preheating and drying out
5.3 Dry welding on hull plating below the waterline of vessels afloat
6. Repair quality standard
6.1 Welding, general
6.2 Renewal of plates
6.3 Doubler on plates
6.4 Renewal of internals/stiffeners
6.5 Renewal
of internals/stiffeners - transitions inverted angles/bulb profiles
6.6 Application
of Doubling Straps
6.7 Welding
of pitting corrosion
6.8 Welding
repairs of cracks
6.9 Grinding of shallow cracks
1. Scope
1.1 This standard provides guidance on quality of repair of hull structures. The standard covers permanent repairs of existing ships.
Whereas
the standard generally applies to
- conventional
ship types,
- parts of hull
covered by the rules of the Classification Society,
- hull structures constructed from normal
and higher strength hull structural steel, the applicability of the standard is
in each case to be agreed upon by the Classification Society.
The
standard does generally not apply to repair of
- special types
of ships as e.g. gas tankers
- structures
fabricated from stainless steel or other, special types or grades of steel
1.2 The standard covers typical repair methods and gives guidance on quality standard on the most important aspects of such repairs. Unless explicitly stated elsewhere in the standard, the level of workmanship reflected herein will in principle be acceptable for primary and secondary structure of conventional design. A more stringent standard may however be required for critical and highly stressed areas of the hull, and is to be agreed with the Classification Society in each case. In assessing the criticality of hull structure and structural components, reference is made to ref. 1, 2 and 3.
1.3 Restoration of structure to the original standard may not constitute durable repairs of damages originating from insufficient strength or inadequate detail design. In such cases strengthening or improvements beyond the original design may be required. Such improvements are not covered by this standard, however it is referred to ref. 1, 2 and 3.
2. General
requirements for repairs and repairers
2.1 In general, when hull structure covered by classification is to be subjected to repairs, the work is to be carried out under the supervision of the Surveyor to the Classification Society. Such repairs are to be agreed prior to commencement of the work.
2.2 Repairs are to be carried out by workshops, repair yards or personnel who have demonstrated their capability to carry out hull repairs of adequate quality in accordance with the Classification Society’s requirements and this standard.
2.3 Repairs are to be carried out under working conditions that facilitate sound repairs. Provisions are to be made for proper accessibility, staging, lighting and ventilation. Welding operations are to be carried out under shelter from rain, snow and wind.
2.4 Welding of hull structures is to be carried out by qualified welders, according to approved and qualified welding procedures and with welding consumables approved by the Classification Society, see Section 3. Welding operations are to be carried out under proper supervision of the repair yard.
2.5 Where repairs to hull which affect or may affect classification are intended to be carried out during a voyage, complete repair procedure including the extent and sequence of repair is to be submitted to and agreed upon by the Surveyor to the Classification Society reasonably in advance of the repairs. See Ref. 8.
3. Qualification of personnel
3.1 Qualification of welders
3.1.1 Welders are to be qualified in accordance with the procedures of the Classification Society or to a recognised national or international standard, e.g. EN 287, ISO 9606, ASME Section IX, ANSI/AWS D1.1. Recognition of other standards is subject to submission to the Classification Society for evaluation. Repair yards and workshops are to keep records of welders qualification and, when required, furnish valid approval test certificates.
3.1.2 Welding operators using fully mechanised of fully automatic processes need generally not pass approval testing, provided that production welds made by the operators are of the required quality. However, operators are to receive adequate training in setting or programming and operating the equipment. Records of training and production test results shall be maintained on individual operator’s files and records, and be made available to the Classification Society for inspection when requested.
3.2 Qualification of welding procedures
Welding procedures are to be qualified in accordance with the procedures of the Classification Society or a recognised national or international standard, e.g. EN288, ISO 9956, ASME Section IX, ANSI/AWS D1.1. Recognition of other standards is subject to submission to the Classification Society for evaluation. The welding procedure should be supported by a welding procedure qualification record. The specification is to include the welding process, types of electrodes, weld shape, edge preparation, welding techniques and positions.
3.3 Qualification of NDE operators
3.3.1 Personnel performing non destructive examination for the purpose of assessing quality of welds in connection with repairs covered by this standard, are to be qualified in accordance with the Classification Society rules or to a recognised international or national qualification scheme. Records of operators and their current certificates are to be kept and made available to the Surveyor for inspection.
4. Materials
4.1 General requirements for materials
4.1.1 The requirements for materials used in repairs are in general the same as the requirements for materials specified in the Classification Society’s rules for new constructions, (ref. 5).
4.1.2 Replacement material is in general to be of the same grade as the original approved material. Alternatively, material grades complying with recognised national or international standards may be accepted by the Classification Societies provided such standards give equivalence to the requirements of the original grade or are agreed by the Classification Society. For assessment of equivalency between steel grades, the general requirements and guidelines in Section 4.2 apply.
4.1.3 Higher tensile steel is not to be replaced by steel of a lesser strength unless specially approved by the Classification Society.
4.1.4 Normal and higher strength hull structural steels are to be manufactured at works approved by the Classification Society for the type and grade being supplied.
4.1.5 Materials used in repairs are to be certified by the Classification Society applying the procedures and requirements in the rules for new constructions. In special cases, and normally limited to small quantities, materials may be accepted on the basis of alternative procedures for verification of the material’s properties. Such procedures are subject to agreement by the Classification Society in each separate case.
4.2 Equivalency
of material grades
4.2.1 Assessment of equivalency between
material grades should at least include the following aspects;
- heat
treatment/delivery condition
- chemical
composition
- mechanical
properties
- tolerances
4.2.2 When assessing the equivalence between grades of normal or higher strength hull structural steels up to and including grade E40 in thickness limited to 50 mm, the general requirements in Table 4.1 apply.
4.2.3 Guidance on selection of steel grades to certain recognised standards equivalent to hull structural steel grades specified in Classification Societies’ rules is given in Table 4.2
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| Table 4.1 Minimum extent and requirements to assessment of equivalency between normal or higher strength hull structual steel grades |
 |
Note: In selecting
comparitable steels from this table, attention should be given to the
requirements of Table 4.1 and the dimension requirements of the product with
respect to Classification Sociey rules.
Table 4.2 Guidance
on steel grades comparable to the normal and high strength hull structural
steel grades given in Classification Society rules
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5. General
requirements to welding
5.1 Correlation of welding consumables with hull structural steels
5.1.1 For the different hull structural steel grades welding consumables are to be selected in accordance with IACS UR W17 (see Ref.6).
5.2 General
requirements to preheating and drying out
5.2.1 The need for preheating is to be
determined based on the chemical composition of the materials, welding process
and procedure and degree of joint restraint.
5.2.2 A minimum preheat of 50o C is to be applied when ambient temperature is below 0° C. Dryness of the welding zone is in all cases to be ensured.
5.2.3 Guidance on recommended minimum preheating temperature for higher strength steel is given in Table 5.1. For automatic welding processes utilising higher heat input e.g. submerged arc welding, the temperatures may be reduced by 50º C. For re-welding or repair of welds, the stipulated values are to be increased by 25º C.
 |
| Table 5.1 Preheating temperature |
5.3 Dry
welding on hull plating below the waterline of vessels afloat
5.3.1
Welding on hull plating below the waterline of vessels afloat is acceptable
only on normal and higher strength steels with specified yield strength not
exceeding 355 MPa and only for local repairs. Welding involving other high
strength steels or more extensive repairs against water backing is subject to
special consideration and approval by the Classification Society of the welding
procedure.
5.3.2
Low-hydrogen electrodes or welding processes are to be used when welding on
hull plating against water backing. Coated low-hydrogen electrodes used for
manual metal arc welding should be properly conditioned to ensure a minimum of
moisture content.
5.3.3 In order to ensure dryness and to reduce the cooling rate, the structure is to be preheated by a torch or similar prior to welding, to a temperature of minimum 5º C or as specified in the welding procedure.
Notes:
1)Combined thickness tcomb = t1+t2+t3+t4, see figure 2)
6. Repair quality
standard
6.1 Welding, general
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Fig 6.1 Groove roughness
|
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Note:
Slag, grease, loose
mill scale, rust and paint, other than primer, to be removed.
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6.2 Renewal of plates
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Fig 6.2 Welding sequence for inserts
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6.3 Doublers on
plating
Local doublers are normally only allowed as temporary repairs, except as original compensation for openings, within the main hull structure.
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Fig 6.3 Doublers on plates
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6.4 Renewal of
internals/stiffeners
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Fig 6.4 Welding sequence for inserts of stiffeners
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6.5 Renewal of internals/stiffeners –
transitions inverted angle/bulb profile
The application of the transition is
allowed for secondary structural elements.
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Fig 6.5 Transition between inverted angle and bulb profile
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6.6 Application of Doubling Straps
In
certain instances, doubling straps are used as a means to strengthen and
reinforce primary structure. Where this has been agreed and approved,
particular attention should be paid to:
- the end termination points of the straps, so that toe support is such that no isolated hard point occurs.
- in the case of application of symmetrical or asymmetrical-ended straps, the corners at the end of the tapering should be properly rounded.
- any butts between lengths of doubling straps, so that there is adequate separation of the butt weld from the primary structure below during welding, and so that a high quality root run under controlled circumstances is completed prior to completing the remainder of the weld. Ultrasonic testing should be carried out on completion to verify full penetration.
- in the case of application of symmetrical or asymmetrical-ended straps, the corners at the end of the tapering should be properly rounded.
- any butts between lengths of doubling straps, so that there is adequate separation of the butt weld from the primary structure below during welding, and so that a high quality root run under controlled circumstances is completed prior to completing the remainder of the weld. Ultrasonic testing should be carried out on completion to verify full penetration.
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Fig 6.6 Application of Doubling Straps
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6.7 Welding of pitting corrosion
Notes:
Shallow pits may be filled by applying
coating or pit filler. Pits can be defined as shallow when their depth is less
that 1/3 of the original plate thickness.
6.8 Welding repairs for cracks
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Fig 6.8.a Step back technique
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Fig 6.8.b End crack termination
|
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Fig 6.8.c Welding
sequence for cracks with length less than 300 mm
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Fig 6.8.d Groove
preparation (U-groove left and V-groove right)
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6.9 Grinding of shallow cracks
REC 047 Shipbuilding and Repair Quality Standard - Rev.6 May 2012
