Materials of Construction and Quality Control

Goal

To identify the required properties, testing standards and stability of metallic and non-metallic materials and fabrication processes used in the construction of cargo containment and piping systems to ensure they serve the functions for which they have been selected, as required in chapters 4 and 5.

6.1 Definitions

6.1.1 Where reference is made in this chapter to A, B, D, E, AH, DH, EH and FH hull structural steels, these steel grades are hull structural steels according to recognized standards.

6.1.2 A piece is the rolled product from a single slab or billet or from a single ingot, if this is rolled directly into plates, strips, sections or bars.

6.1.3 A batch is the number of items or pieces to be accepted or rejected together, on the basis of the tests to be carried out on a sampling basis. The size of a batch is given in the recognized standards.

6.1.4 Controlled rolling (CR) is a rolling procedure in which the final deformation is carried out in the normalizing temperature range, resulting in a material condition generally equivalent to that obtained by normalizing.

LR 6.1-01 Controlled rolling (CR) is also known as Normalising rolling (NR).

6.1.5 Thermo-mechanical controlled processing (TMCP) is a procedure that involves strict control of both the steel temperature and the rolling reduction. Unlike CR, the properties conferred by TMCP cannot be reproduced by subsequent normalizing or other heat treatment. The use of accelerated cooling on completion of TMCP may also be accepted, subject to approval by the Administration. The same applies for the use of tempering after completion of TMCP.

6.1.6 Accelerated cooling (AcC) is a process that aims to improve mechanical properties by controlled cooling with rates higher than air cooling, immediately after the final TMCP operation. Direct quenching is excluded from accelerated cooling. The material properties conferred by TMCP and AcC cannot be reproduced by subsequent normalizing or other heat treatment.

6.2 Scope and general requirements

6.2.1 This chapter gives the requirements for metallic and non-metallic materials used in the construction of the cargo system. This includes requirements for joining processes, production process, personnel qualification, NDT and inspection and testing including production testing. The requirements for rolled materials, forgings and castings are given in 6.4 and tables 6.1, to 6.5. The requirements for weldments are given in 6.5, and the guidance for non-metallic materials is given in appendix 4. A quality assurance/quality control programme shall be implemented to ensure that the requirements of 6.2 are complied with.

LR 6.2-01 Weldment is an assembly of parts which are fusion welded together. They are also referred to as welded joint in LR Rules.

6.2.2 The manufacture, testing, inspection and documentation shall be in accordance with recognized standards and the specific requirements given in the Code.

LR 6.2-02 The manufacture, testing, inspection and certification is to be in accordance with the requirements of the Rules for the Manufacture, Testing and Certification of Materials, and this Chapter of the Code.

6.2.3 Where post-weld heat treatment is specified or required, the properties of the base material shall be determined in the heat-treated condition, in accordance with the applicable table of this chapter, and the weld properties shall be determined in the heat treated condition in accordance with 6.5. In cases where a post-weld heat treatment is applied, the test requirements may be modified at the discretion of the Administration.

LR 6.2-03 A relaxation in the requirements for Charpy V-notch impact tests will be permitted for smaller cargo tanks or process pressure vessels which are post-weld heat treated. The extent of this relaxation will be specially considered for each application and will depend on the grade of steel and thickness involved.

6.3 General test requirements and specifications

6.3.1 Tensile test

6.3.1.1 Tensile testing shall be carried out in accordance with recognized standards.

6.3.1.2 Tensile strength, yield stress and elongation shall be to the satisfaction of the Administration. For carbon-manganese steel and other materials with definitive yield points, consideration shall be given to the limitation of the yield to tensile ratio.

LR 6.3-01 The grades of materials used are, generally, to have mechanical properties complying with the appropriate requirements as given in the Rules for the Manufacture, Testing and Certification of Materials. Provided that the materials have satisfactory ductility, there will be no limitation on the yield to tensile stress ratio, except for carbon–manganese steel grades for low temperature service. For carbon–manganese steel grades for low temperature service, the yield to tensile ratio requirement of Ch 3, 6 Carbon–manganese and nickel alloy steels for low temperature service of the Rules for the Manufacture, Testing and Certification of Materials is to be met.

6.3.2 Toughness test

6.3.2.1 Acceptance tests for metallic materials shall include Charpy V-notch toughness tests, unless otherwise specified by the Administration. The specified Charpy V-notch requirements are minimum average energy values for three full size (10 mm × 10 mm) specimens and minimum single energy values for individual specimens. Dimensions and tolerances of Charpy V-notch specimens shall be in accordance with recognized standards. The testing and requirements for specimens smaller than 5 mm in size shall be in accordance with recognized standards. Minimum average values for subsized specimens shall be:

Charpy V-notch specimen size (mm)	Minimum average energy of three specimens
10 x 10	KV
10 x 7.5	5/6 KV
10 x 5	2/3 KV

where:

KV

=

the energy values (J) specified in tables 6.1 to 6.4.

Only one individual value may be below the specified average value, provided it is not less than 70% of that value.

6.3.2.2 For base metal, the largest size Charpy V-notch specimens possible for the material thickness shall be machined with the specimens located as near as practicable to a point midway between the surface and the centre of the thickness and the length of the notch perpendicular to the surface as shown in figure 6.1.

6.3.2.3 For a weld test specimen, the largest size Charpy V-notch specimens possible for the material thickness shall be machined, with the specimens located as near as practicable to a point midway between the surface and the centre of the thickness. In all cases, the distance from the surface of the material to the edge of the specimen shall be approximately 1 mm or greater. In addition, for double-V butt welds, specimens shall be machined closer to the surface of the second welded section. The specimens shall be taken generally at each of the following locations, as shown in figure 6.2, on the centreline of the welds, the fusion line and 1 mm, 3 mm and 5 mm from the fusion line.

Notch locations in figure 6.2:

.1 Centreline of the weld.
.2 Fusion line.
.3 In heat-affected zone (HAZ), 1 mm from the fusion line.
.4 In HAZ, 3 mm from the fusion line.
.5 In HAZ, 5 mm from the fusion line.

6.3.2.4 If the average value of the three initial Charpy V-notch specimens fails to meet the stated requirements, or the value for more than one specimen is below the required average value, or when the value for one specimen is below the minimum value permitted for a single specimen, three additional specimens from the same material may be tested and the results be combined with those previously obtained to form a new average. If this new average complies with the requirements and if no more than two individual results are lower than the required average and no more than one result is lower than the required value for a single specimen, the piece or batch may be accepted.

LR 6.3-02 Material toughness is to be determined by the Charpy V-notch impact test in accordance with the Rules for the Manufacture, Testing and Certification of Materials. In addition, LR may also request other types of tests, such as drop weight or crack tip opening displacement test. When required by Ch 3, 6.1 Scope 6.1.4 of the Rules for the Manufacture, Testing and Certification of Materials, an additional set of Charpy V-notch specimens with axes located on the centreline of thickness of the plate is required.

6.3.3 Bend test

6.3.3.1 The bend test may be omitted as a material acceptance test, but is required for weld tests. Where a bend test is performed, this shall be done in accordance with recognized standards.

LR 6.3-03 Bend tests are to be taken only when such tests are required in the Rules for Materials.

6.3.3.2 The bend tests shall be transverse bend tests, which may be face, root or side bends at the discretion of the Administration. However, longitudinal bend tests may be required in lieu of transverse bend tests in cases where the base material and weld metal have different strength levels.

6.3.4 Section observation and other testing

Macrosection, microsection observations and hardness tests may also be required by the Administration, and they shall be carried out in accordance with recognized standards, where required.

LR 6.3-04 These tests are to be carried out when required by the Rules for Materials and when required according to the scope of approval of the cargo containment system.

6.4 Requirements for metallic materials

6.4.1 General requirements for metallic materials

6.4.1.1 The requirements for materials of construction are shown in the tables as follows:

.1 Table 6.1: Plates, pipes (seamless and welded), sections and forgings for cargo tanks and process pressure vessels for design temperatures not lower than 0°C.
.2 Table 6.2: Plates, sections and forgings for cargo tanks, secondary barriers and process pressure vessels for design temperatures below 0°C and down to -55°C.
.3 Table 6.3: Plates, sections and forgings for cargo tanks, secondary barriers and process pressure vessels for design temperatures below -55°C and down to -165°C.
.4 Table 6.4: Pipes (seamless and welded), forgings and castings for cargo and process piping for design temperatures below 0°C and down to -165°C.
.5 Table 6.5: Plates and sections for hull structures required by 4.19.1.2 and 4.19.1.3.

Table 6.1

PLATES, PIPES (SEAMLESS AND WELDED)^{See notes 1 and 2}, SECTIONS AND FORGINGS FOR CARGO TANKS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES NOT LOWER THAN 0°C
CHEMICAL COMPOSITION AND HEAT TREATMENT
♦ Carbon-manganese steel
♦ Fully killed fine grain steel
♦ Small additions of alloying elements by agreement with the Administration
♦ Composition limits to be approved by the Administration
♦ Normalized, or quenched and tempered ^{See note 4}
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Plates	Each "piece" to be tested
♦ Sections and forgings	Each "batch" to be tested.
Mechanical properties
♦ Tensile properties	Specified minimum yield stress not to exceed 410 N/mm² ^{See note 5}
Toughness (Charpy V-notch test)
♦ Plates	Transverse test pieces. Minimum average energy value (KV) 27J
♦ Sections and forgings	Longitudinal test pieces. Minimum average energy (KV) 41J
♦ Test temperature	Thickness t (mm)	Test temperature (°C)
	t≤20	0
	20<t≤40 ^{See note 3}	-20
*Notes*
1 For seamless pipes and fittings normal practice applies. The use of longitudinally and spirally welded pipes shall be specially approved by the Administration or recognized organization acting on its behalf.
2 Charpy V-notch impact tests are not required for pipes.
3 This table is generally applicable for material thicknesses up to 40 mm. Proposals for greater thicknesses shall be approved by the Administration or recognized organization acting on its behalf.
4 A controlled rolling procedure or TMCP may be used as an alternative.
5 Materials with specified minimum yield stress exceeding 410 N/mm² may be approved by the Administration or recognized organization acting on its behalf. For these materials, particular attention shall be given to the hardness of the welded and heat affected zones.

Table LR 6.1

PLATES, PIPES (SEAMLESS AND WELDED)^{See notes 1 and 2}, SECTIONS AND FORGINGS FOR CARGO TANKS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES NOT LOWER THAN 0°C
CHEMICAL COMPOSITION AND HEAT TREATMENT (See LR 2)
♦ Carbon-manganese steel
♦ Fully killed fine grain steel (See LR 4)
♦ Small additions of alloying elements by agreement with the Administration
♦ Composition limits to be approved by the Administration
♦ Normalized, or quenched and tempered ^{See note 4} (See LR 4)
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Plates	Each "piece" to be tested
♦ Sections and forgings	Each "batch" to be tested.
Mechanical properties
♦ Tensile properties	Specified minimum yield stress not to exceed 410 N/mm² ^{See note 5} (See LR 4)
Toughness (Charpy V-notch test)
♦ Plates	Transverse test pieces. Minimum average energy value (KV) 27J
♦ Sections and forgings	Longitudinal test pieces. Minimum average energy (KV) 41J
♦ Test temperature	Thickness t (mm)	Test temperature (°C)
	t≤20	0 (See LR 4)
	20<t≤40^{See note 3}	-20
*Notes*
1 For seamless pipes and fittings normal practice applies. The use of longitudinally and spirally welded pipes shall be specially approved by the Administration or recognized organization acting on its behalf. (See LR 1).
2 Charpy V-notch impact tests are not required for pipes. (See LR 6).
3 This table is generally applicable for material thicknesses up to 40 mm. Proposals for greater thicknesses shall be approved by the Administration or recognized organization acting on its behalf. (See LR 7).
4 A controlled rolling procedure or TMCP may be used as an alternative.
5 Materials with specified minimum yield stress exceeding 410 N/mm² may be approved by the Administration or recognized organization acting on its behalf. For these materials, particular attention shall be given to the hardness of the welded and heat affected zones. (See LR 3)
LR 1 Welded pressure pipes complying with the requirements of Chapter 6 of the Rules for Materials are acceptable, and special approval is not required. (See LR 3)
LR 2 Generally, the chemical composition and mechanical properties, yield stress, tensile strength and elongation are to comply with the requirements for appropriate grades as given in the Rules for Materials.
LR 3 Stress corrosion cracking can occur in tanks carrying LPG contaminated with hydrogen sulphide. In order to minimise this risk, it is recommended that tanks intended for the carriage of this substance should be constructed in steel with a specified minimum tensile strength not exceeding 410 N/mm². If steels of higher tensile strength are used, it is recommended that the completed cargo tanks or process pressure vessels are given a suitable stress relieving heat treatment in order to reduce the hardness of the weld metal and heat affected zone to 250 Vickers Pyramid Number maximum (HV).
LR 4 Stress corrosion cracking can also occur in tanks carrying high purity anhydrous ammonia, see 17.13. Impact tests are to be made at –20°C for all thicknesses. For pipes, test specimens are to be taken in the longitudinal direction and are to have an average energy value not less than 41J. The hardnesses of welds, including the heat affected zones, are not to exceed 230 HV. Tanks are to be subjected to a stress relieving heat treatment.
LR 5 Steels conforming to grades LT–DH 32, LT–EH 32 and LT–FH 32 of Table 3.6.3 in Chapter 3 of the Rules for Materials are suitable for the construction of tanks for anhydrous ammonia.
LR 6 Charpy V-notch impact tests are to be carried out when required by the Rules for Materials.
LR 7 For plate of thickness greater than 40 mm and up to 50 mm for a design temperature not lower than 0°C, the impact tests are to be conducted in accordance with Table LR 6.1.1

Table LR 6.1.1

Test temperature	Thickness t (mm)	Test temperature (°C)
	40 < t < 50	−20 (see LR 7a)
	40 < t < 50	−30 (see LR 7b)
LR 7a: Applies to Type C independent tanks and process pressure vessels. In addition, post-weld heat treatment shall be performed. Proposals for exemption of post-weld heat treatment based on an alternative approach (e.g. Engineering Critical Assessment in accordance with BS7910 or an equivalent standard) shall be approved by LR. LR 7b: Applies to cargo tank other than Type C.

Table 6.2

PLATES, SECTIONS AND FORGINGS^{See note1} FOR CARGO TANKS, SECONDARY BARRIERS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES BELOW 0°C AND DOWN TO -55°C Maximum thickness 25 mm^{See note 2}
CHEMICAL COMPOSITION AND HEAT TREATMENT
♦ Carbon-manganese steel
♦ Fully killed, aluminium treated fine grain steel
♦ Chemical composition (ladle analysis)
C		Mn	Si	S	P
0.16%max^{See note 3}		0.7-1.60%	0.1-0.50%	0.025% max	0.025% max
Optional additions: Alloys and grain refining elements may be generally in accordance with the following:
Ni	Cr	Mo	Cu	Nb	V
0.8% max	0.25% max	0.08% max	0.35% max	0.05% max	0.1% max
Al content total 0.02% min (Acid soluble 0.015% min)
♦ Normalized, or quenched and tempered ^{See note 4}
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Plates			Each "piece" to be tested
♦ Sections and forgings			Each "batch" to be tested
Mechanical properties
♦ Tensile properties			Specified minimum yield stress not to exceed 410 N/mm² ^{See note 5}
Toughness (Charpy V-notch test)
♦ Plates			Transverse test pieces. Minimum average energy value (KV) 27J
♦ Sections and forgings			Longitudinal test pieces. Minimum average energy (KV) 41J
♦ Test temperature			5°C below the design temperature or -20°C, whichever is lower

Notes

1 The Charpy V-notch and chemistry requirements for forgings may be specially considered by the Administration.

2 For material thickness of more than 25 mm, Charpy V-notch tests shall be conducted as follows:

Material thickness (mm)	Test temperature (°C)
25 < t ≤ 30	10°C below design temperature or -20°C, whichever is lower
30 < t ≤ 35	15°C below design temperature or -20°C, whichever is lower
35 < t ≤ 40	20°C below design temperature
40 < t	Temperature approved by the Administration or recognized organization acting on its behalf

The impact energy value shall be in accordance with the table for the applicable type of test specimen.
Materials for tanks and parts of tanks which are completely thermally stress relieved after welding may be tested at a temperature 5°C below design temperature or -20°C, whichever is lower.
For thermally stress relieved reinforcements and other fittings, the test temperature shall be the same as that required for the adjacent tank-shell thickness.

3 By special agreement with the Administration, the carbon content may be increased to 0.18% maximum, provided the design temperature is not lower than -40°C.

4 A controlled rolling procedure or TMCP may be used as an alternative.

5 Materials with specified minimum yield stress exceeding 410 N/mm² may be approved by the Administration or recognized organization acting on its behalf. For these materials, particular attention shall be given to the hardness of the welded and heat affected zones

Guidance:

For materials exceeding 25 mm in thickness for which the test temperature is -60°C or lower, the application of specially treated steels or steels in accordance with table 6.3 may be necessary.

Table LR 6.2

PLATES, SECTIONS AND FORGINGS^{See note 1} FOR CARGO TANKS, SECONDARY BARRIERS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES BELOW 0°C AND DOWN TO -55°C Maximum thickness 25 mm^{See note 2}
CHEMICAL COMPOSITION AND HEAT TREATMENT
♦ Carbon-manganese steel
♦ Fully killed, aluminium treated fine grain steel
♦ Chemical composition (ladle analysis)
C		Mn	Si	S	P
0.16%max^{See note 3}		0.7-1.60%	0.1-0.50%	0.025% max	0.025% max
Optional additions: Alloys and grain refining elements may be generally in accordance with the following:
Ni	Cr	Mo	Cu	Nb	V
0.8% max	0.25% max	0.08% max	0.35% max	0.05% max	0.1% max
Al content total 0.02% min (Acid soluble 0.015% min)
♦ Normalized, or quenched and tempered ^{See note 4}
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Plates			Each "piece" to be tested
♦ Sections and forgings			Each "batch" to be tested
Mechanical properties
♦ Tensile properties			Specified minimum yield stress not to exceed 410 N/mm² ^{See note 5}
Toughness (Charpy V-notch test)
♦ Plates			Transverse test pieces. Minimum average energy value (KV) 27J
♦ Sections and forgings			Longitudinal test pieces. Minimum average energy (KV) 41J
♦ Test temperature			5°C below the design temperature or -20°C, whichever is lower

Notes

1 The Charpy V-notch and chemistry requirements for forgings may be specially considered by the Administration.

2 For material thickness of more than 25 mm, Charpy V-notch tests shall be conducted as follows:

Material thickness t (mm)	Test temperature (°C)
25 < t ≤ 30	10°C below design temperature or -20°C, whichever is lower
30 < t ≤ 35	15°C below design temperature or -20°C, whichever is lower
35 < t ≤ 40	20°C below design temperature
40 < t	Temperature approved by the Administration or recognized organization acting on its behalf (see LR 1)

The impact energy value shall be in accordance with the table for the applicable type of test specimen.
Materials for tanks and parts of tanks which are completely thermally stress relieved after welding may be tested at a temperature 5°C below design temperature or -20°C, whichever is lower.
For thermally stress relieved reinforcements and other fittings, the test temperature shall be the same as that required for the adjacent tank-shell thickness.(See LR 1a)

LR 1 For plates of thickness greater than 40 mm and up to 50 mm for a design temperature lower than 0°C and down to −55°C, the impact tests are to be conducted in accordance with Table LR 6.2.1:

Table LR 6.2.1

Test temperature	Thickness t (mm)	Test temperature (°C)
	40 < t < 50	5°C below design temperature or –20°C, whichever is lower (see LR 1a)
	40 < t < 45	25°C below design temperature (see LR 1b)
	45 < t < 50	30°C below design temperature (see LR 1b)
LR 1a: Applies to Type C independent tanks and process pressure vessels. Post-weld heat treatment shall be performed. Proposals for exemption of post-weld heat treatment based on an alternative approach (e.g. Engineering Critical Assessment in accordance with BS7910 or an equivalent standard) shall be approved by LR. LR 1b: Applies to cargo tank other than Type C.

3 By special agreement with the Administration, the carbon content may be increased to 0.18% maximum, provided the design temperature is not lower than -40°C.

4 A controlled rolling procedure or TMCP may be used as an alternative.

5 Materials with specified minimum yield stress exceeding 410 N/mm² may be approved by the Administration or recognized organization acting on its behalf. For these materials, particular attention shall be given to the hardness of the welded and heat affected zones

LR 2 Stress corrosion cracking can occur in tanks carrying high purity anhydrous ammonia or LPG contaminated with hydrogen sulphide, see 17.12. If steels of higher tensile strength are used, it is recommended that the completed cargo tanks or process pressure vessels are given a suitable stress relieving heat treatment in order to reduce the hardness of the weld metal and heat affected zone to 250 HV maximum.

Guidance:

For materials exceeding 25 mm in thickness for which the test temperature is -60°C or lower, the application of specially treated steels or steels in accordance with table 6.3 may be necessary.

Table 6.3

PLATES, SECTIONS AND FORGINGS ^{See note 1} FOR CARGO TANKS, SECONDARY BARRIERS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES BELOW -55°C AND DOWN TO -165°C^{See note 2} Maximum thickness 25 mm^{See notes 3 and 4}
Minimum design temperature (°C)	Chemical composition See note 5 and heat treatment	Impact test temperature (°C)
-60	1.5% nickel steel – normalized or normalized and tempered or quenched and tempered or TMCP See note 6	-65
-65	2.25% nickel steel – normalized or normalized and tempered or quenched and tempered or TMCP See notes 6 and 7	-70
-90	3.5% nickel steel – normalized or normalized and tempered or quenched and tempered or TMCP See notes 6 and 7	-95
-105	5% nickel steel – normalized or normalized and tempered or quenched and tempered See notes 6, 7 and 8	-110
-165	9% nickel steel – double normalized and tempered or quenched and tempered See note 6	-196
-165	Austenitic steels, such as types 304, 304L, 316, 316L, 321 and 347 solution treated See note 9	-196
-165	Aluminium alloys; such as type 5083 annealed	Not required
-165	Austenitic Fe-Ni alloy (36% nickel). Heat treatment as agreed	Not required
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Plates	Each "piece" to be tested
♦ Sections and forgings	Each "batch" to be tested
Toughness (Charpy V-notch test)
♦ Plates	Transverse test pieces. Minimum average energy value (KV) 27J
♦ Sections and forgings	Longitudinal test pieces. Minimum average energy (KV) 41J

Notes

1 The impact test required for forgings used in critical applications shall be subject to special consideration by the Administration.

2 The requirements for design temperatures below -165°C shall be specially agreed with the Administration.

3 For materials 1.5% Ni, 2.25% Ni, 3.5% Ni and 5% Ni, with thicknesses greater than 25 mm, the impact tests shall be conducted as follows:

Material thickness (mm)	Test temperature (°C)
25 < t ≤ 30	10°C below design temperature
30 < t ≤ 35	15°C below design temperature
35 < t ≤ 40	20°C below design temperature

The energy value shall be in accordance with the table for the applicable type of test specimen. For material thickness of more than 40 mm, the Charpy V-notch values shall be specially considered.

4 For 9% Ni steels, austenitic stainless steels and aluminium alloys, thickness greater than 25 mm may be used.

5 The chemical composition limits shall be in accordance with recognized standards.

6 TMCP nickel steels will be subject to acceptance by the Administration.

7 A lower minimum design temperature for quenched and tempered steels may be specially agreed with the Administration.

8 A specially heat treated 5% nickel steel, for example triple heat treated 5% nickel steel, may be used down to -165°C, provided that the impact tests are carried out at -196°C.

9 The impact test may be omitted, subject to agreement with the Administration.

Table LR 6.3

PLATES, SECTIONS AND FORGINGS^{See note 1} FOR CARGO TANKS, SECONDARY BARRIERS AND PROCESS PRESSURE VESSELS FOR DESIGN TEMPERATURES BELOW -55°C AND DOWN TO -165°C^{See note 2} Maximum thickness 25 mm^{See notes 3 and 4}
Minimum design temperature (°C)	Chemical composition See note 5 and heat treatment	Impact test temperature (°C)
-60	1.5% nickel steel – normalized or normalized and tempered or quenched and tempered or TMCP See note 6	-65
-65	2.25% nickel steel – normalized or normalized and tempered or quenched and tempered or TMCP See notes 6 and 7	-70
-90	3.5% nickel steel – normalized or normalized and tempered or quenched and tempered or TMCP See notes 6 and 7	-95
-105	5% nickel steel – normalized or normalized and tempered or quenched and tempered See notes 6, 7 and 8	-110
-165	9% nickel steel – double normalized and tempered or quenched and tempered See note 6	-196
-165	Austenitic steels, such as types 304, 304L, 316, 316L, 321 and 347 solution treated See note 9 (see LR 4)	-196
-165	Aluminium alloys; such as type 5083 annealed	Not required
-165	Austenitic Fe-Ni alloy (36% nickel). Heat treatment as agreed	Not required
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Plates	Each "piece" to be tested
♦ Sections and forgings	Each "batch" to be tested
Toughness (Charpy V-notch test)
♦ Plates	Transverse test pieces. Minimum average energy value (KV) 27J
♦ Sections and forgings	Longitudinal test pieces. Minimum average energy (KV) 41J

Notes

1 The impact test required for forgings used in critical applications shall be subject to special consideration by the Administration.

2 The requirements for design temperatures below -165°C shall be specially agreed with the Administration.

3 For materials 1.5% Ni, 2.25% Ni, 3.5% Ni and 5% Ni, with thicknesses greater than 25 mm, the impact tests shall be conducted as follows:

Material thickness (mm)	Test temperature (°C)
25 < t ≤ 30	10°C below design temperature
30 < t ≤ 35	15°C below design temperature
35 < t ≤ 40	20°C below design temperature

The energy value shall be in accordance with the table for the applicable type of test specimen. For material thickness of more than 40 mm, the Charpy V-notch values shall be specially considered (see LR 1).

LR 1 In no case should the test temperature exceed that shown in the main table above. For materials 1,5% Ni, 2,25% Ni, 3,5% Ni and 5% Ni, with thicknesses greater than 40 mm and up to 50 mm, the impact tests are to be conducted in accordance with Table LR 6.3.1:

Table LR 6.3.1

Material thickness t (mm)	Test temperature (°C)
40 < t < 45	25°C below design temperature
45 < t < 50	30°C below design temperature

4 For 9% Ni steels, austenitic stainless steels and aluminium alloys, thickness greater than 25 mm may be used.

5 The chemical composition limits shall be in accordance with recognized standards.

6 TMCP nickel steels will be subject to acceptance by the Administration.

7 A lower minimum design temperature for quenched and tempered steels may be specially agreed with the Administration.

8 A specially heat treated 5% nickel steel, for example triple heat treated 5% nickel steel, may be used down to -165°C, provided that the impact tests are carried out at -196°C.

9 The impact test may be omitted, subject to agreement with the Administration. (See LR 2)

LR 2 Generally, impact tests are not required.

LR 3 Stress corrosion cracking can occur in tanks carrying high purity anhydrous ammonia or LPG contaminated with hydrogen sulphide, see 17.12. If steels of higher tensile strength are used, it is recommended that the completed cargo tanks or process pressure vessels are given a suitable stress relieving heat treatment in order to reduce the hardness of the weld metal and heat affected zone to 250 HV maximum.

LR 4 Grades 304 and 316 are not to be used for welded construction.

Table 6.4

PIPES (SEAMLESS AND WELDED)^{See note 1}, FORGINGS^{See note 2} AND CASTINGS^{See note 2} FOR CARGO AND PROCESS PIPING FOR DESIGN TEMPERATURES BELOW 0°C AND DOWN TO -165°C^{See note 3} Maximum thickness 25 mm
Minimum design temperature (°C)	Chemical composition See note 5 and heat treatment	Impact test
		Test temp. (°C)	Minimum average energy (KV)
-55	Carbon-manganese steel. Fully killed fine grain. Normalized or as agreed ^{See note 6}	^{See note 4}	27
-65	2.25% nickel steel. Normalized, normalized and tempered or quenched and tempered ^{See notes 6 and 7}	-70	34
-90	3.5% nickel steel. Normalized, normalized and tempered or quenched and tempered^{See note 6}	-95	34
	9% nickel steel^{See note 7}. Double normalized and tempered or quenched and tempered	-196	41
-165	Austenitic steels, such as types 304. 304L, 316, 316L, 321 and 347. Solution treated^{See note 8}	-196	41
	Aluminium alloys; such as type 5083 annealed		Not required
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Each "batch" to be tested.
Toughness (Charpy V-notch test)
♦ Impact test: Longitudinal test pieces
*Notes*
1 The use of longitudinally or spirally welded pipes shall be specially approved by the Administration.
2 The requirements for forgings and castings may be subject to special consideration by the Administration.
3 The requirements for design temperatures below -165°C shall be specially agreed with the Administration.
4 The test temperature shall be 5°C below the design temperature or -20°C, whichever is lower.
5 The composition limits shall be in accordance with recognized standards.
6 A lower design temperature may be specially agreed with the Administration for quenched and tempered materials.
7 This chemical composition is not suitable for castings.
8 Impact tests may be omitted, subject to agreement with the Administration.

Table LR 6.4

PIPES (SEAMLESS AND WELDED)^{See note 1}, FORGINGS^{See note 2} AND CASTINGS^{See note 2} FOR CARGO AND PROCESS PIPING FOR DESIGN TEMPERATURES BELOW 0°C AND DOWN TO -165°C^{See note 3} Maximum thickness 25 mm
Minimum design temperature (°C)	Chemical composition^{See note 5} and heat treatment	Impact test
		Test temp. (°C)	Minimum average energy (KV)
-55	Carbon-manganese steel. Fully killed fine grain. Normalized or as agreed^{See note 6}	^{See note 4}	27
-65	2.25% nickel steel. Normalized, normalized and tempered or quenched and tempered^{See note 6 and 7}	-70	34
-90	3.5% nickel steel. Normalized, normalized and tempered or quenched and tempered^{See note 6}	-95	34
	9% nickel steel^{See note 7}. Double normalized and tempered or quenched and tempered	-196	41
-165	Austenitic steels, such as types 304. 304L, 316, 316L, 321 and 347. Solution treated^{See note 8} (see LR 3)	-196	41
	Aluminium alloys; such as type 5083 annealed		Not required
TENSILE AND TOUGHNESS (IMPACT) TEST REQUIREMENTS
Sampling frequency
♦ Each "batch" to be tested.
Toughness (Charpy V-notch test)
♦ Impact test: Longitudinal test pieces
*Notes*
1 The use of longitudinally or spirally welded pipes shall be specially approved by the Administration. (See LR 1).
2 The requirements for forgings and castings may be subject to special consideration by the Administration.
3 The requirements for design temperatures below -165°C shall be specially agreed with the Administration.
4 The test temperature shall be 5°C below the design temperature or -20°C, whichever is lower.
5 The composition limits shall be in accordance with recognized standards.
6 A lower design temperature may be specially agreed with the Administration for quenched and tempered materials.
7 This chemical composition is not suitable for castings.
8 Impact tests may be omitted, subject to agreement with the Administration. (SeeLR 2).
LR 1 Welded pressure pipes complying with the requirements of Chapter 6 of the Rules for Materials are acceptable and special approval is not required.
LR 2 Impact tests are not required except for austenitic steel castings intended for applications where the design temperature is lower than –55°C.
LR 3 Grades 304 and 316 are not to be used for welded pipework.

Table 6.5

PLATES AND SECTIONS FOR HULL STRUCTURES REQUIRED BY 4.19.1.2 AND 4.19.1.3
Minimum design temperature of hull structure (°C)	Maximum thickness (mm) for steel grades
Minimum design temperature of hull structure (°C)	A	B	D	E	AH	DH	EH	FH
0 and above^{See note 1}	Recognized standards
-5 and above^{See note 2}	Recognized standards
down to -5	15	25	30	50	25	45	50	50
down to -10	x	20	25	50	20	40	50	50
down to -20	x	x	20	50	x	30	50	50
down to -30	x	x	x	40	x	20	40	50
Below -30	In accordance with table 6.2, except that the thickness limitation given in table 6.2 and in note 2 of that table does not apply.
*Notes*
"x" means steel grade not to be used.
1 For the purpose of 4.19.1.3.
2 For the purpose of 4.19.1.2.

Hull Structure

LR 6.4-01 The materials of the hull structure are to comply with the requirements of the Rules for Materials. The requirements of Pt 3, Ch 2 of the Rules for Ships are also to be complied with, except as indicated otherwise by the requirements of these Rules, see also 4.19.1.

LR 6.4-02 Single strakes required to be of Grade E/EH and within 0,4L amidships are to have breadths not less than 800 + 5L mm, but need not be greater than 1800 mm, unless limited by the geometry of the ship’s design, see also Note 10 of Table 2.2.1, in Pt 3, Ch 2 of the Rules for Ships.

LR 6.4-03 Where higher tensile steel is used in the hull structure, the scantling and arrangements are to be as required by Part 3 and Part 4 of the Rules for Ships.

LR 6.4-04 Plans illustrating the means of protection for the ship steelwork, e.g. drip trays, cladding, etc., at loading manifolds; deck tanks, cargo handling system, etc., are to be submitted for approval.

6.5 Welding of metallic materials and non-destructive testing

6.5.1 General

6.5.1.1 This section shall apply to primary and secondary barriers only, including the inner hull where this forms the secondary barrier. Acceptance testing is specified for carbon, carbon-manganese, nickel alloy and stainless steels, but these tests may be adapted for other materials. At the discretion of the Administration, impact testing of stainless steel and aluminium alloy weldments may be omitted and other tests may be specially required for any material.

LR 6.5-01 Unless otherwise specified below, all welded construction is to be in accordance with Chapter 13 of the Rules for Materials.

LR 6.5-02 Unless otherwise specified in these Rules, welding procedure tests are to be performed in accordance with the requirements of Chapter 12 of the Rules for Materials. Generally, impact tests from aluminium welded joint are not required. For austenitic stainless steel welded joint, impact tests are not required from the heat affected zone.

6.5.2 Welding consumables

6.5.2.1 Consumables intended for welding of cargo tanks shall be in accordance with recognized standards. Deposited weld metal tests and butt weld tests shall be required for all consumables. The results obtained from tensile and Charpy V-notch impact tests shall be in accordance with recognized standards. The chemical composition of the deposited weld metal shall be recorded for information.

LR 6.5-03 Welding consumables are to be approved by LR in accordance with Chapter 11 of the Rules for Materials.

6.5.3 Welding procedure tests for cargo tanks and process pressure vessels

6.5.3.1 Welding procedure tests for cargo tanks and process pressure vessels are required for all butt welds.

6.5.3.2 The test assemblies shall be representative of:

.1 each base material;
.2 each type of consumable and welding process; and
.3 each welding position.

6.5.3.3 For butt welds in plates, the test assemblies shall be so prepared that the rolling direction is parallel to the direction of welding. The range of thickness qualified by each welding procedure test shall be in accordance with recognized standards. Radiographic or ultrasonic testing may be performed at the option of the fabricator.

LR 6.5-04 Welding procedure tests are to be performed in accordance with the requirements of Chapter 12 of the Rules for Materials, except where indicated otherwise in these Rules. Mechanical tests for butt welds are to be in accordance with 6.5.3.4

6.5.3.4 The following welding procedure tests for cargo tanks and process pressure vessels shall be carried out in accordance with 6.3, with specimens made from each test assembly:

.1 cross-weld tensile tests;
.2 longitudinal all-weld testing, where required by the recognized standards;
.3 transverse bend tests, which may be face, root or side bends. However, longitudinal bend tests may be required in lieu of transverse bend tests in cases where the base material and weld metal have different strength levels;
.4 one set of three Charpy V-notch impacts, generally at each of the following locations, as shown in figure 6.2:
- .1 centreline of the weld;
- .2 fusion line;
- .3 1 mm from the fusion line;
- .4 3 mm from the fusion line; and
- .5 5 mm from the fusion line; and
.5 macrosection, microsection and hardness survey may also be required.

LR 6.5-05 Additionally, an all-weld metal tensile test is required from welding procedure tests for type C independent cargo tanks. A macrosection and hardness survey is required for all welding procedure tests, except that hardness survey is not required for austenitic stainless steel. Generally, microsections are not required.

LR 6.5-06 For alloys where the weld metal has a lower tensile strength than that of the parent metal, and such an application has prior approval by LR, the transverse weld tensile strength is not to be less than the specified design tensile strength.

6.5.3.5 Each test shall satisfy the following requirements:

.1 tensile tests: cross-weld tensile strength shall not be less than the specified minimum tensile strength for the appropriate parent materials. For aluminium alloys, reference shall be made to 4.18.1.3 with regard to the requirements for weld metal strength of under-matched welds (where the weld metal has a lower tensile strength than the parent metal). In every case, the position of fracture shall be recorded for information;
.2 bend tests: no fracture is acceptable after a 180° bend over a former of a diameter four times the thickness of the test pieces; and
.3 Charpy V-notch impact tests: Charpy V-notch tests shall be conducted at the temperature prescribed for the base material being joined. The results of weld metal impact tests, minimum average energy (KV), shall be no less than 27 J. The weld metal requirements for subsize specimens and single energy values shall be in accordance with 6.3.2. The results of fusion line and heat-affected zone impact tests shall show a minimum average energy (KV) in accordance with the transverse or longitudinal requirements of the base material, whichever is applicable, and for subsize specimens, the minimum average energy (KV) shall be in accordance with 6.3.2. If the material thickness does not permit machining either full-size or standard subsize specimens, the testing procedure and acceptance standards shall be in accordance with recognized standards.

LR 6.5-07 For aluminium alloys, the bend test required in 6.5.3.4.3 is to be carried out over a former with D/t according to Ch 12, 4 of the Rules for Materials.

LR 6.5-08 Bend tests revealing small openings up to a maximum of 3 mm in any direction are acceptable.

6.5.3.6 Procedure tests for fillet welding shall be in accordance with recognized standards. In such cases, consumables shall be so selected that exhibit satisfactory impact properties.

LR 6.5-09 Ch 12 of Rules for Materials is to be followed for procedure tests for fillet welding, and LR approved welding consumables are to be used.

6.5.4 Welding procedure tests for piping

Welding procedure tests for piping shall be carried out and shall be similar to those detailed for cargo tanks in 6.5.3.

6.5.5 Production weld tests

6.5.5.1 For all cargo tanks and process pressure vessels, except integral and membrane tanks, production weld tests shall generally be performed for approximately each 50 m of butt-weld joints and shall be representative of each welding position. For secondary barriers, the same type production tests as required for primary tanks shall be performed, except that the number of tests may be reduced subject to agreement with the Administration. Tests, other than those specified in 6.5.5.2 to 6.5.5.5 may be required for cargo tanks or secondary barriers.

6.5.5.2 The production tests for type A and type B independent tanks and semi-membrane tanks shall include bend tests and, where required for procedure tests, one set of three Charpy V-notch tests. The tests shall be made for each 50 m of weld. The Charpy V-notch tests shall be made with specimens having the notch alternately located in the centre of the weld and in the heat-affected zone (most critical location based on procedure qualification results). For austenitic stainless steel, all notches shall be in the centre of the weld.

LR 6.5-10 The production weld tests shall satisfy the applicable requirements of 6.5.3.5.

6.5.5.3 For type C independent tanks and process pressure vessels, transverse weld tensile tests are required in addition to the tests listed in 6.5.5.2. Tensile tests shall meet the requirements of 6.5.3.5.

LR 6.5-11 In addition, an all-weld metal tensile test for type C independent cargo tanks and Class 1 and Class 2/1 process pressure vessels is required.

LR 6.5-12 In addition, macrosection examination and hardness survey are required according to Ch 13,4.8 of the Rules for Materials.

6.5.5.4 The quality assurance/quality control programme shall ensure the continued conformity of the production welds as defined in the material manufacturers quality manual.

6.5.5.5 The test requirements for integral and membrane tanks are the same as the applicable test requirements listed in 6.5.3.

LR 6.5-13 Requirements for production tests from integral or membrane cargo tanks are to be agreed with LR prior to manufacture.

LR 6.5-14 Unless otherwise stated below, all welds are to be subject to non-destructive examination in accordance with the requirements of Chapter 13 of the Rules for Materials.

6.5.6 Non-destructive testing

6.5.6.1 All test procedures and acceptance standards shall be in accordance with recognized standards, unless the designer specifies a higher standard in order to meet design assumptions. Radiographic testing shall be used, in principle, to detect internal defects. However, an approved ultrasonic test procedure in lieu of radiographic testing may be conducted, but, in addition, supplementary radiographic testing at selected locations shall be carried out to verify the results. Radiographic and ultrasonic testing records shall be retained.

6.5.6.2 For type A independent tanks and semi-membrane tanks, where the design temperature is below -20°C, and for type B independent tanks, regardless of temperature, all full penetration butt welds of the shell plating of cargo tanks shall be subjected to non-destructive testing suitable to detect internal defects over their full length. Ultrasonic testing in lieu of radiographic testing may be carried out under the same conditions as described in 6.5.6.1.

6.5.6.3 Where the design temperature is higher than -20°C, all full penetration butt welds in way of intersections and at least 10% of the remaining full penetration welds of tank structures shall be subjected to radiographic testing or ultrasonic testing under the same conditions as described in 6.5.6.1.

6.5.6.4 In each case, the remaining tank structure, including the welding of stiffeners and other fittings and attachments, shall be examined by magnetic particle or dye penetrant methods, as considered necessary.

6.5.6.5 For type C independent tanks, the extent of non-destructive testing shall be total or partial according to recognized standards, but the controls to be carried out shall not be less than the following:

.1 Total non-destructive testing referred to in 4.23.2.1.3:
- Radiographic testing:
- .1 all butt welds over their full length;
- Non-destructive testing for surface crack detection:
- .2 all welds over 10% of their length;
- .3 reinforcement rings around holes, nozzles, etc., over their full length.
- As an alternative, ultrasonic testing as described in 6.5.6.1 may be accepted as a partial substitute for the radiographic testing. In addition, the Administration may require total ultrasonic testing on welding of reinforcement rings around holes, nozzles, etc.
.2 Partial non-destructive testing referred to in 4.23.2.1.3:
- Radiographic testing:
- .1 all butt-welded crossing joints and at least 10% of the full length of butt welds at selected positions uniformly distributed;
- Non-destructive testing for surface crack detection:
- .2 reinforcement rings around holes, nozzles, etc., over their full length;
- Ultrasonic testing:
- .3 as may be required by the Administration or recognized organization acting on its behalf in each instance.

LR 6.5-15 Non-destructive examination (NDE) is to meet the requirements of Chapter 13, 4 of the Rules for Materials for Class 1 pressure vessels.

LR 6.5-16 General NDE requirements shall be in accordance with the Rules for the Manufacture, Testing and Certification of Materials, Ch 1, 5 Non-destructive examination, and suppliers of NDE services (e.g. NDE firms or internal shipyard NDE department) shall comply with Rules for the Manufacture, Testing and Certification of Materials, Ch 1, 5.3 Requirements for suppliers of NDE services.

6.5.6.6 The quality assurance/quality control programme shall ensure the continued conformity of the non-destructive testing of welds, as defined in the material manufacturer's quality manual.

6.5.6.7 Inspection of piping shall be carried out in accordance with the requirements of chapter 5.

6.5.6.8 The secondary barrier shall be non-destructive tested for internal defects as considered necessary. Where the outer shell of the hull is part of the secondary barrier, all sheer strake butts and the intersections of all butts and seams in the side shell shall be tested by radiographic testing.

6.6 Other requirements for construction in metallic materials

6.6.1 General

6.6.1.1 Inspection and non-destructive testing of welds shall be in accordance with the requirements of 6.5.5 and 6.5.6. Where higher standards or tolerances are assumed in the design, they shall also be satisfied.

6.6.2 Independent tank

6.6.2.1 For type C tanks and type B tanks primarily constructed of bodies of revolution, the tolerances relating to manufacture, such as out-of-roundness, local deviations from the true form, welded joints alignment and tapering of plates having different thicknesses, shall comply with recognized standards. The tolerances shall also be related to the buckling analysis referred to in 4.22.3.2 and 4.23.3.2.

LR 6.6-01 Manufacture and workmanship are to satisfy the requirements of Ch 13, 4 Specific requirements for fusion welded pressure vessels in the Rules for the Manufacture, Testing and Certification of Materials.

6.6.2.2 For type C tanks of carbon and carbon-manganese steel, post-weld heat treatment shall be performed after welding, if the design temperature is below -10°C. Post-weld heat treatment in all other cases and for materials other than those mentioned above shall be to recognized standards. The soaking temperature and holding time shall be to the recognized standards.

LR 6.6-02 For Type C tanks of carbon and carbon-manganese steel with plate thickness up to 40 mm, post-weld heat treatment shall be performed after welding, if the design temperature is equal to or less than −10°C.

For Type C independent tanks with plate thickness up to 40 mm, if the design temperature is higher than −10°C, and for any other carbon and carbon-manganese tanks, the post-weld heat treatment is to conform to the requirements of Ch 13, 4.10 Post-weld heat treatment in the Rules for the Manufacture, Testing and Certification of Materials.

For Type C tanks of carbon and carbon-manganese steel with plate thickness greater than 40 mm and up to 50 mm, post-weld heat treatment shall be performed after welding. Any proposal for exemption of post-weld heat treatment is to be based on an alternative approach as approved by LR (e.g. Engineering Critical Assessment in accordance with BS7910 or an equivalent standard). Mechanical stress relieving as permitted under Ch 6, 6.6 Other requirements for construction in metallic materials 6.6.2.3 is not applicable for Type C tanks of carbon and carbon-manganese steel with plate thickness greater than 40 mm and up to 50 mm.

The requirements of Ch 13, 1.16 Post-weld heat treatment and Ch 13, 4.11 Basic requirements for post-weld heat treatment of fusion welded pressure vessels in the Rules for the Manufacture, Testing and Certification of Materials are to be followed for the method and technique of post-weld heat treatment.

6.6.2.3 In the case of type C tanks and large cargo pressure vessels of carbon or carbon-manganese steel, for which it is difficult to perform the heat treatment, mechanical stress relieving by pressurizing may be carried out as an alternative to the heat treatment and subject to the following conditions:

.1 complicated welded pressure vessel parts such as sumps or domes with nozzles, with adjacent shell plates shall be heat treated before they are welded to larger parts of the pressure vessel;
.2 the mechanical stress relieving process shall preferably be carried out during the hydrostatic pressure test required by 4.23.6, by applying a higher pressure than the test pressure required by 4.23.6.1. The pressurizing medium shall be water;
.3 for the water temperature, 4.23.6.2 applies;
.4 stress relieving shall be performed while the tank is supported by its regular saddles or supporting structure or, when stress relieving cannot be carried out on board, in a manner which will give the same stresses and stress distribution as when supported by its regular saddles or supporting structure;
.5 the maximum stress relieving pressure shall be held for 2 h per 25 mm of thickness, but in no case less than 2 h;
.6 the upper limits placed on the calculated stress levels during stress relieving shall be the following:
- .1 equivalent general primary membrane stress: 0.9 R_e ;
- .2 equivalent stress composed of primary bending stress plus membrane stress: 1.35 R_e , where R_e is the specific lower minimum yield stress or 0.2% proof stress at test temperature of the steel used for the tank;
.7 strain measurements will normally be required to prove these limits for at least the first tank of a series of identical tanks built consecutively. The location of strain gauges shall be included in the mechanical stress relieving procedure to be submitted in accordance with 6.6.2.3;
.8 the test procedure shall demonstrate that a linear relationship between pressure and strain is achieved at the end of the stress relieving process when the pressure is raised again up to the design pressure;
.9 high-stress areas in way of geometrical discontinuities such as nozzles and other openings shall be checked for cracks by dye penetrant or magnetic particle inspection after mechanical stress relieving. Particular attention in this respect shall be paid to plates exceeding 30 mm in thickness;
.10 steels which have a ratio of yield stress to ultimate tensile strength greater than 0.8 shall generally not be mechanically stress relieved. If, however, the yield stress is raised by a method giving high ductility of the steel, slightly higher rates may be accepted upon consideration in each case;
.11 mechanical stress relieving cannot be substituted for heat treatment of cold formed parts of tanks, if the degree of cold forming exceeds the limit above which heat treatment is required;
.12 the thickness of the shell and heads of the tank shall not exceed 40 mm. Higher thicknesses may be accepted for parts which are thermally stress relieved;
.13 local buckling shall be guarded against, particularly when tori-spherical heads are used for tanks and domes; and
.14 the procedure for mechanical stress relieving shall be to a recognized standard.

LR 6.6-03 The post-weld heat treatment requirements contained within Rules for the Manufacture, Testing and Certification of Materials, Ch 13, 4.10 Post-weld heat treatment and Ch 13, 4.11 Basic requirements for post-weld heat treatment of fusion welded pressure vessels are to be complied with where applicable.

6.6.3 Secondary barriers

During construction, the requirements for testing and inspection of secondary barriers shall be approved or accepted by the Administration or recognized organization acting on its behalf (see 4.6.2.5 and 4.6.2.6).

6.6.4 Semi-membrane tanks

For semi-membrane tanks, the relevant requirements in section 6.6 for independent tanks or for membrane tanks shall be applied as appropriate.

6.6.5 Membrane tanks

The quality assurance/quality control programme shall ensure the continued conformity of the weld procedure qualification, design details, materials, construction, inspection and production testing of components. These standards and procedures shall be developed during the prototype testing programme.

6.7 Non-metallic materials

6.7.1 General

The information in the attached appendix 4 is given for guidance in the selection and use of these materials, based on the experience to date.

LR 6.8 Materials in the containment system

LR 6.8-01 This Section gives requirements for the component materials of the containment system and applies to each series of ships.

LR 6.8-02 Specifications of the component materials are to be submitted for approval, see also LR IV.1.

LR 6.8-03 Metallic and non-metallic components of the containment system are to comply with the requirements of this Chapter and the Rules for Materials where applicable.

LR 6.8-04 The Surveyors are to be allowed access to all relevant parts of the works and are to be provided with the necessary facilities and information to enable them to verify the component materials of the containment system comply with the approved specifications.

LR 6.8-05 In the event of any material proving unsatisfactory, during subsequent working, machining or fabrication, it is to be rejected, notwithstanding any previous certification.

LR 6.8-06 The requirements of this Section are also to be applied to assembled components of the containment system.

LR 6.8-07 Approval and supply of materials intended to be used in cargo containment systems are to comply with the Lloyd’s Register ShipRight Procedure Additional Design Procedures - Approval Scheme for Gas Ship Containment Systems.