GB50094-98 Code for construction and Acceptance of Spherical Tank

本英文版为内部资料，仅供参考，以中文 版为准。 The Chinese version of standards has precedence to their English translations which are only for internal reference.

GB

UDC

中华人民共和国国家标准 National Standard of the People′s Republic of China P

GB 50094-98

球形储罐施工及验收规范 Code for construction and Acceptance of spherical tanks

Issued on 1998-05-06

Implemented from 1998-12-01

the State Bureau of Technical Supervision Jointly issued by the Ministry of Construction of the People’s Republic of China

Contents 1

General………………………………………………………………………………3

2

Inspection and Acceptance of Parts and Components……………………………4

2.1 Inspection of Quality Certificate of Parts and Components…………………………4 2.2 Inspection of Tank shell Plates and Test Plate………………………………………4 2.3 Inspection of Supports………………………………………………………………8 2.4 Inspection of Assembled Weldments…………………………………………………8 2.5 Inspection of Painting, Package and transportation of Parts and Components……8 3

Site Assembling………………………………………………………………………9

3.1 Inspection and Acceptance of Foundation……………………………………………9 3.2 Assembling of Spherical Tank…………………………………………………………10 3.3 Installation of Parts and Components…………………………………………………13 4

Welding………………………………………………………………………………14

4.1 General Rules…………………………………………………………………………14 4.2 Welding Process Qualification………………………………………………………15 4.3 Selection of Welding Materials and Their Site Control………………………………15 4.4 Welding Application…………………………………………………………………16 4.5 Repair…………………………………………………………………………………20 4.6 Inspection of Size of Spherical Tank Welded………………………………………22 5

Inspection of Welds…………………………………………………………………23

5.1 Visual Inspection of Welds……………………………………………………………23 5.2 Qualification of Non-Destructive Inspection Personnel………………………………23 —1—

5.3 Radiographic Testing and Ultrasonic Testing…………………………………………24 5.4 Magnetic Powder Testing and Dye Penetrant Testing…………………………………25 6

Post Weld Heat Treatment of the Whole……………………………………………27

6.1 General Rules…………………………………………………………………………27 6.2 Heat Treatment Process………………………………………………………………27 6.3 Requirements for Heat Insulation………………………………………………………28 6.4 Temperature Measuring System……………………………………………………29 6.5 Treatment of Support Foot…………………………………………………………29 7

Test Plate of Product Welding………………………………………………………30

7.1 Requirements for Preparation of Test Plate of Product Welding………………………30 7.2 The Preparation and Test of the Test Plate……………………………………………30 8

Pressure Test and Airtight Test……………………………………………………31

8.1 Pressure Test…………………………………………………………………………31 8.2 Airtight Test…………………………………………………………………………33 9

Handing Over and Acceptance………………………………………………………34

Appendix A A.1

Low Temperature Spherical Tanks…………………………………35

General Rules………………………………………………………………………35

A.2 Inspection and Acceptance of Tank Shell Plates……………………………………35 A.3

Assembling…………………………………………………………………………35

A.4

Welding……………………………………………………………………………35

A.5

Post Weld Heat Treatment of the Whole…………………………………………36

A.6

Product Test Plate…………………………………………………………………37

A.7

Inspection of Welds………………………………………………………………37

A.8

Pressure Test………………………………………………………………………37

Appendix B

Name of Different Parts of Spherical Tank, Numbering of Zones, Tank Shell Plates and Welds of Spherical Tank………………………38

Appendix C

Form for Handing Over and Acceptance……………………………41

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1 General 1.0.1 In order to make the spherical tanks (hereinafter referred to as spherical tank) in site construction be advance in technology, reasonable in economy, safe and practical and to guarantee the quality, this Code is worked out. 1.0.2 This Code applies to carbon steel and alloy steel welded spherical tank of orange-petal type or mix type supported with columns with design pressure ≥0.1Mpa but ≯4 Mpa and nominal capacity ≥50M3。 This Code does not apply to following spherical tank: (1) Spherical tank under nuclear radiation; (2) Non-fixed (truck or ship carried) spherical tank; (3) Spherical tank of double-layer structure; (4) St requiring fatigue analysis; (5) Spherical tank expansion formed. 1.0.3 The construction and acceptance of spherical tank shall include following scope: 1.0.3.1 The tank shell and its pressure parts and components connected shall be differentiated in following scope: (1) The first circumferential welds in welding connection of the tank connection pipe and the outer piping; (2) The first thread in thread connection of the tank connection pipe and the outer piping; (3) The first flange seal face in flange connect of the tank connection and the outer piping.. 1.0.3.2 Pressure seal heads, flat covers and their fasteners of the openings of spherical tank. 1.0.3.3 Non-pressure elements of supports, tie rods, pad plates and bottom plates connected to the tank shell. 1.0.4 For spherical tank with design temperature ≤-20℃, stipulation in Appendix A of this Code shall apply. 1.0.5 The contractor of the spherical tank shall have qualification certificate for site assembling and welding of spherical pressure vessels issued by labor department. 1.0.6 Before installation of spherical tank, the contractor must inform the labor departments at provincial, regional and municipal level where the user or installation unit of the spherical tank is. Also the contractor shall make a report to the inspection organization authorized by the safety supervision institution for boilers and pressure vessels under the provincial labor department for inspection and shall accept its site supervision and inspection. 1.0.7 The spherical tank shall be constructed in accordance with design drawings. In case it is necessary to make modification, it must be agreed with original designer and the documents for design modification must be signed. 1.0.8 The construction and acceptance of spherical tank, apart from meeting with this Code, —3—

shall also be in conformity with relevant national standards and specifications in force.

2 Inspection and Acceptance of Parts and Components

2.1 Inspection of Quality Certificate of Parts and Components 2.1.1 The contractor shall inspect technical quality documents of product quality certificates furnished by manufacturers. 2.1.2 Factory certificates for parts and components of tank shell plates, manholes, connection pipes, flanges, reinforcing pieces, supports and tie rods of the spherical tank shall include following contents: (1) Ex-factory Quality Certificates of parts and components; (2) Product inspection reports issued by the supervision organization under labor department; (3) Papers approving material substitution; (4) Quality certificate of materials and reports on re-testing; (5) Non-destructive testing reports on steel plates, forging, parts and components; (6) Ultrasonic testing reports on sides of tank shell; (7) Non-destructive testing reports on bevels and welds; (8) Testing reports on test plates hot-press formed; (9) Testing reports on product welding test plates.

2.2 Inspection of Tank shell Plates and Test Plate 2.2.1 The structural type of tank shell shall be in conformity with requirements of design drawings, no piece of shell plates shall be spliced. 2.2.2 The tank shell plates supplied by manufacturers shall not have defects of crack, bubble, scar, folding or slag inclusion. In case there is, a repair shall be made in accordance with what specified in 4.5 of this Code. 2.2.3 Spot test shall be made to the thickness of tank shell plates. The actual thickness measured shall not be less than nominal thickness minus negative error of the steel plate. The quantity for spot test shall be 20% of quantity of shall plates, and for each zone, it shall not be less than 2 pieces. For upper and lower poles, it shall not be less than 1 piece. For each piece of tank shell plate, the test shall not be less than 5 points. Spot test by double shall be made in case any in-qualification found in the spot test. In case it is still not qualified, test piece by piece shall be made to tank shell plates. —4—

2.2.4 The profile size of tank shell plates shall meet following requirements: 2.2.4.1 The allowable clearance between the sample plate to test the curvature of tank shell plates and tank shell plates and the sample plates shall meet what specified in Table 2.2.4 – 1. (Figure 2.2.4 – 1). Table 2.2.4 – 1 Allowable Clearance between Sample Plate and Tank Shell Plates and Sample Plates Length of chord of tank shell

Length of chord of sample plate

Allowable clearance,

plate (m)

(m)

e (mm)

≥2

2

3

Same as the length of chord of

1mm. (2) The surface shall be smooth and the surface roughness (Ra) shall be ≤25μm; (3) The limit space between defects (Q) shall be ≥0.5m. Table 2.2.4 – 2 Allowable Error for Geometric Size of Tank Shell Plate Item

Allowable error (mm) ±2.5

Length of chord in length direction L1, L2, L3 Length of chord in any width direction, B1, B2, B3

±2

Length of chord of diagonal lines D

±3

Distance between tow diagonal lines

5

—5—

Note: For tank shell plates with less rigidity, length of arc may be inspected. The allowable error shall meet what specified in first three items in the Table.

(4) Slag and oxidation scales shall be removed. The surface of the bevel shall not have any defect of crack or lamination. For the tank shell plates made of the steel with standard tensile strength >540 Mpa, the surface of the bevel shall be spot tested with magnetic powder or dye penetrant and there shall be no defect of crack, lamination or slag inclusion. The quantity for spot test shall be 20% of shell plate quantity. In case any unallowable defect is found, re-test shall be made in double. In case there is still unallowable defect, test shall be made piece by piece. 2.2.5.2 The allowable error for geometric size of bevels shall meet following requirements (Figure 2.2.5). (1) The allowable error for the angle of the bevel (α) shall be ±2°30′； (2) The allowable error for the obtuse side (P) and the depth of the bevel (h) shall be ± 1.5mm. 2.2.6 Ultrasonic spot testing shall be made to the full range 100mm from sides of the tank shell plates. The quantity for spot testing shall not be less than 20% of total quantity of tank shell plate, and not less than 2 pieces for each zone, not less than 1 piece for upper and bottom poles. For tank shell plates requiring ultrasonic testing, a spot test of ultrasonic testing shall be made. The quantity for spot test shall be the same as that for the spot test of the sides. The test method and the test results shall meet what specified in the national standard in force the Non-destructive Testing of Pressure Vessels JB4730. The class for qualification shall meet requirements of design drawings. In case there is any unallowable defect, re-test shall be made in double. In case there is still unallowable defect, test shall be made piece by piece. 2.2.7 In case the thickness of adjoining plates is ≥3mm or 1/4 larger than the thickness of thinner plate, the side of thicker plate shall be cut to hypotenuse (Figure 2.2.7). The thickness of the end after cutting shall be the thickness of the thinner plate. 2.2.8 The manufacturer shall provide at least 6 pieces of product welding test plates as well as the test plates necessary for assessing welding process for each spherical tank. The size shall be 180mm x 650mm.The material of test plates shall be qualified and they shall also have same thickness and same steel number of the tank shell plates. The bevel type of the welding test plates shall be same as that of tank shell plates.

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Figure 2.2.4 – 2 Inspection of Geometric Size of Tank Shell Plate (Unit: mm)

Figure 2.2.5 Inspection of Geometric Size of the Bevel of Tank Shell Plate (Unit: mm)

Figure 2.2.7 Requirements for Reducing the Thickness of Thicker Plate in Welding Tank Shell Plates of Different Thickness —7—

2.3 Inspection of Supports 2.3.1 The allowable error for the total length of the supports shall be 3mm. 2.3.2 The supports, after welding to the bottom plate, shall be vertical. The allowable error for the verticality shall be 2mm. (Figure 2.3.2).

Figure 2.3.2 Inspection of Error of Verticality of Support and Bottom Plate (Unit: mm) 2.3.3 The error for the linearity of the total length of the supports shall be ≤1/1000 of total length, and not be > 10mm.

2.4 Inspection of Assembled Weldments 2.4.1 After assemble welding of the upper part of the support of sectors and the equator plate, the curvature shall be inspected by using a sample plate with length of the chord not less than 1m. The clearance must not be >3mm. The allowable error for the linearity of the upper part of the support shall be 1/1000 of the length of upper part of the support. The drift of the position of axis shall not be > 2mm. 2.4.2 After assemble welding of manholes, connection pipes and tank shell plates, the allowable error for the positions of openings of the manholes, connection pipes as well as the allowable error for the length of extension, the curvature of tank shell plates and the installation of the flange of connection pipes shall meet requirements in 3.3.1 of this Code.

2.5 Inspection of Painting, Package and transportation of Parts and Components 2.5.1 Rust shall be removed both from inside and outside of tank shell plates. Both sides shall be applied with two passes of primer. Weldable painting shall be applied within a range of 50mm from the edge inside and outside. The marks of the numbering of tank shell plates the steel number and furnace batch number on each tank shell plate shall be framed with white painted. —8—

2.5.2 In transporting and storing, tank shell plates shall be packed with steel structure supports and closely tied to the supports by using tie yokes. The convex of the tank shell plate shall be upward. Flexible material of wooden blocks shall be cushioned between tank shell plates. The number of plates eclipsed should not be more than 6. Total weight of each package should not be more than 30t. 2.5.3 Flanges, manholes and sample plates should be transported in packages. Tie rods and levers should be bundled. 2.5.4 Anti-rust grease shall be applied to surfaces of all processed pieces. The threads of tie rods shall be protected properly to avoid any damage. 2.5.5 The other requirements for inspection, packing and transportation of parts and components of tank shells, supports and tie rods shall meet relevant stipulations in national standard in force the Painting, Packing and Transportation of Pressure Vessels JB2536.

3 Site Assembling 3.1 Inspection and Acceptance of Foundation 3.1.1 Before installation of spherical tank, inspection and acceptance shall be made to the size of different parts of the foundation. (Figure 3.1.1). The allowable error shall meet what specified in 3.1.1 of this Code. Construction shall not be done until the strength of foundation concrete is not less than 75% of design strength.

Figure 3.1.1 Inspection of Size of Different Parts of Foundation 1—Anchor bolts；2—Reserved holes for anchor bolts

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Table 3.1.1 Allowable Error for Size of Different Parts of Foundation Serial

Item

No.

Allowable error spherical tank capacity

1

Diameter of center circle of foundation

1/4 of nominal thickness of the tank shell plate, and not be >3mm (Figure 3.2.3 -1 and Figure 3.2.3 - 2). In case the thickness of two plates is different, the difference of the thickness of two plates may not be counted.

Figure 3.2.3-1 Displacement of Matching for Assembling Tank Shell Plates of Same Thickness

Figure 3.2.3-2 Displacement of Matching for Assembling Tank Shell Plates of Different Thickness 3.2.3.3 Sharp corners shall be inspected by using a sample plate with length of chord not less than 1m (Figure 3.2.3 – 3). The sharp corner shall be calculated according to following formula, and not be > 7mm: E = l1 – l 2 (3.2.3 – 1) l 2 = |R – R 0| (3.2.3 – 2) In which E ---- value of sharp corner (mm) l1 ---- Radial distance actually measured between the sample plate and the tank — 11 —

shell plate at the place of the largest sharp corned (mm); l 2 ----- Radial distance between the sample plate and standard tank shell plate (mm); R ---- Design inside radius or outside radius of tank shell (mm); R0 ---- Curvature radius of the sample plate (mm).

Figure 3.2.3 – 3 Inspection of Sharp Corner in Assembling Tank Shell Plates (Unit: mm) 3.2.3.4 The inspection of the clearance, displacement and sharp corner in assembling should be made at each 500mm along butt joints as one measuring point. 3.2.4 After assembling of equator zone of spherical tank, the error for the level of equator line of each tank shell plate should not be > 2 mm. The error for the level of equator line of adjoining two tank shell plates should not be > 3 mm. The error for the level of equator line of any two tank shell plates should not be > 6 mm. 3.2.5 When assembling spherical tank, the distance the sides of following welds shall not be less than 3 times of the thickness of tank shell plate, and not less than 100mm: 3.2.5.1 Longitudinal welds of adjoining two zones; 3.2.5.2 Fillet welds of support and tank shell to the butt welds of tank shell plates; 3.2.5.3 The connection welds of spherical tank manholes, connection pipes, reinforcing rings and connection plates and the tank shell to the butt welds of tank shell plates as well as the welds between them. 3.2.6 When assembling spherical tank, the difference of maximum diameter and minimum diameter of the spherical tank shall be controlled. On completion of assembling, the difference should be less than 3 ‰ of design inside diameter of the spherical tank, and not be > 50mm. 3.2.7 The installation of supports shall meet following stipulations:

— 12 —

3.2.7.1 In case the supports are aligned with iron pads, the height of each group of iron pads shall not be less than 25mm, and also should not be more than 3 pieces. The bevel iron pads shall be used in pair and contacted closely. On completion of alignment, tack welding shall be firm. 3.2.7.2 After alignment of the installation of supports, the verticality of supports shall be checked both in radial and circumferential directions of spherical tank. In case the height of the support is ≤8m, the allowable error for the verticality shall be 12mm. In case the height of the support is over 8m, the allowable error for the verticality shall be 1.5‰ of the height of support, and not > 15mm. 3.2.8 When installing tie rods, they shall be tightened symmetrically and uniformly. The deflection at the middle of the tie rods should be controlled according to following calculated value (Figure 3.2.8).

Figure 3.2.8 Measurement of Deflection at the Middle of the Tie Rod 1—Tie line；2—Tie rod；3—Pin shaft Δ = 5.42 × 10 –4·(L4 cosθ ) 1 / 3

(3.2.8)

In which, Δ ---- Deflection at the middle of the tie rod (cm); L ----Distance between pin shafts at two ends of the tie rod (cm); θ ---- Angle of elevation (°).

3.3 Installation of Parts and Components 3.3.1 The installation of pressure elements of manholes and connection pipes shall meet following requirements: 3.3.1.1 Allowable error for the position of the opening shall be 5mm; 3.3.1.2 The difference of the diameter of the opening and the diameter of the assembled piece should be 2 ~ 5 mm;

— 13 —

3.3.1.3 Allowable error for the extended length and the position of the connection pipe shall be 5mm; 3.3.1.4 The flange face of the connection pipe shall be vertical to the center axis of the connection pipe, unless the design specifies. The flange faces shall be horizontal or vertical. The error must not exceed 1% of outside diameter of the flange (in case the outside diameter of the flange is 3mm; 3.3.1.5 With the center of the opening as a circle, and with the diameter of the opening as the radius, beyond this range, check the curvature by using a sample plate with the length of chord not less than 1m, the clearance must not be > 3mm; 3.3.1.6 The reinforcing rings shall be close to the tank shell plates. 3.3.2 The connection plates of the spherical tank shall be close to the tank shell and shall be welded before heat treatment. In case the fillet welds between the connection plates and the tank shell is continuous welds, vent gap of 10mm shall be reserved at the place where rain is not easy to flow in. The allowable error for the installation of the connection plates shall be 10mm. 3.3.3 The parts and components, which shall affect the entire heat treatment of the spherical tank and affect the water-filling settlement, shall be fixed to the spherical tank after heat treatment and after settlement test.

4 Welding 4.1 General Rules 4.1.1 The welder engaging spherical tank welding must have valid certificate issued by labor department. The type of steel, the welding process and the welding position the welder is going to apply welding shall be in conformity with the items the welder was tested. 4.1.2 The welding machine selected shall meet the requirements of welding process. 4.1.3 In any of following cases, welding shall not be applied until effective measures are taken. 4.1.3.1 In raining or snowing weather; 4.1.3.2 Wind velocity exceeds 8m/s; in case of gas shielded welding, wind velocity exceeds 2m/s; 4.1.3.3 Ambient temperature is -5℃ or below; 4.1.3.4 Relative humidity is 90% or over. Note:

The ambient temperature and relative humidity for welding shall be measured 0.5 ~ 1m from the surface of the spherical tank.

4.1.4 The welding method for the spherical tank should be hand arc welding, automatic welding with cored welding wire, semi-automatic welding with cored welding wire and — 14 —

submerged arc welding.

4.2 Welding Process Qualification 4.2.1 Before welding spherical tank, welding process shall be evaluated in according with the national standard in force the Evaluation of Welding Process for Steel Pressure Vessels JB4708.

4.3 Selection of Welding Materials and Their Site Control 4.3.1 The selection of welding materials shall meet following stipulation: 4.3.1.1 Welding materials shall have quality certificates with them. The quality certificates of the electrodes and cored welding wires for hand arc welding shall include chemical composition, physical performance and content of diffusion hydrogen of melt metal. 4.3.1.2 The electrodes for hand arc welding shall meet what specified in the national standard in force the Carbon Steel Electrodes GB/T5117 and the Low Alloy Steel Electrodes GB/T5118. The cored welding wires shall meet what specified in the national standard in force the Carbon Steel Cored welding wires GB10045. The welding wires for submerged arc welding shall meet what specified in the national standard in force the Wires for Melt Welding GB/T14957 and the Welding Wires for CO2 Shielded Welding GB/T8110. 4.3.1.3 For butt welds of the tank shell and the welds directly welded to the tank shell, coated electrodes of low hydrogen must be used. The electrodes and cored welding wires shall be re-tested for hydrogen diffusion according batch numbers. The test method for hydrogen diffusion shall be in accordance with the national standard in force the Method for Measuring Hydrogen in Electrode Melting Metal GB/T3965. The actual content of hydrogen diffusion after baking shall meet what specified in Table 4.3.1. Table 4.3.1 Content of Diffusion Hydrogen in Low Hydrogen Electrodes and Cored welding wires Type of electrodes and cored welding wires

Content of hydrogen diffusion (ml/100g)

E4315 E4316

≤8

E5015 E5016

≤8

E5515 – X E5516 – X

≤6

E6015 – X E6016 - X

≤4

Cored welding wire

≤6

4.3.1.4 The flux shall match the type of steel. The flux used in submerged arc welding shall — 15 —

meet what specified in the national standard in force the Flux for Carbon Steel Submerged Arc Welding GB5293 and the Flux for Low Alloy Submerged Arc Welding GB12470. 4.3.1.5 CO2 for shielding shall meet what specified in the national standard in force the CO2 for Welding HG/T2537. Argon for shielding shall meet what specified in the national standard in force the Argon GB4842. Before using, CO2 cylinder should be put upside down for 24 hours and all water drained. 4.3.2 Site control of welding materials shall meet following stipulations: 4.3.2.1 Welding material shall be kept, baked and issued by assigned special person; 4.3.2.2 Before using, the welding material shall be baked according to product instructions, It may also be baked according to baking temperature and time set in Table 4.3.2. The electrodes baked shall be kept in a oven at temperature of 100 ~ 150℃ and when it is to be used , take it out. The coating of the electrodes shall have no peeling or notable crack. Table 4.3.2 Baking Temperature and Time for Electrodes and Fluxes Type

Baking temperature (℃)

Baking time (h)

Low hydrogen coated electrode

350 ~ 400

1

Melting type

150 ~ 300

1

Sintering type

200 ~ 400

1

Flux

4.3.2.3 For hand arc welding, an oven of constant temperature, which is up to product standard, shall be provided at site. The electrodes shall not be kept in the oven for more than 4 hours. If it is over 4 hours, they shall be re-baked at original baking temperature. The electrodes shall not be re-baked for more than two times. 4.3.2.4 No foreign material shall be mixed in the flux. In case there is any foreign material in the flux, the flux shall be cleaned or replaced. 4.3.2.5 Before using, any rust or dirt shall be removed from the welding wires.

4.4 Welding Application 4.4.1 Before welding, bevels shall be inspected. Rust, water, oil or dust shall be removed from the surface and from the range at least 20mm from both sides of the bevel. 4.4.2 Pre-heating and post heating shall meet following stipulations: 4.4.2.1 The pre-heating temperature shall be in accordance with the WPS. For the steel of common use, it may be selected according to Table 4.4.2.

— 16 —

Table 4.4.2 Pre-heating Temperature for Common Use Steel ( ℃ ) Steel type 20R

16MnR

15MnVR

15MnVNR

20

—

—

—

75 ~ 125

25

—

—

75 ~ 125

100 ~ 150

32

—

75 ~ 125

100 ~ 150

125 ~ 175

38

75 ~ 125

100 ~ 150

125 ~ 175

150 ~ 200

50

100 ~ 150

125 ~ 175

150 ~ 200

150 ~ 200

Thickness

07MnCrMoVR

of steel (mm)

75 ~ 100

4.4.2.2 The welds requiring pre-heating before welding, the temperature of inter-layer in welding application shall not be lower than lower limit of pre-heating temperature. 4.4.2.3 Any of following welds shall be post weld heat treated immediately after welding: (1) Thickness is over 32mm, and the standard tensile strength of the material is >540Mpa; (2) Low alloy steel of thickness over 38mm; (3) Butt welds of insert type connection pipe and tank shell; (4) Post weld heat treatment specified by WPS. 4.4.2.4 Post weld heat treatment shall be in accordance with WPS as well as following requirements: (1) Post weld heat treatment temperature shall be: 200 ~ 250℃; (2) Post weld heat treatment time shall: 0.5 ~ 1 hour. 4.4.2.5 Temperature for pre-heating and post- heating shall be uniform. The width at the two sides of welds center, at pre-heating zone and post-heating zone shall be 3 times of plate thickness, and not be < 100mm. 4.4.2.6 The temperature for pre-heating, post-heating and inter-layer temperature shall be measured symmetrically at 50mm away from welds center. For each piece of welds, the measuring points shall not be less than 3 pairs. 4.4.2.7 For welds not requiring pre-heating, in case the temperature of the wledment is lower than 0℃, welding shall not be applied until the range 100mm from the place to weld is pre-heated to 15℃. 4.4.2.8 For connection pipes and manholes which have high restrain, and the ambient temperature is lower than 5℃, the range for pre-heating shall be expanded. 4.4.2.9 In accordance with energy condition in the area of construction, pre-heating and post-heating may be electric heating or flame heating. Pre-heating and post-heating may be done at the back of welds. — 17 —

4.4.3 Positioning welding and the welding of tools and calipers shall meet following requirements: 4.4.3.1 Welding shall be applied in accordance with WPS; 4.4.3.2 If pre-heating is necessary, it shall be done in the range at least 150mm from the center of welding; 4.4.3.3 The positioning welding shall be applied to the back of preliminary welding layer. The quality requirements for positioning welding shall be the same as the formal welding. In case there is any crack, it must be removed. 4.4.3.4 The length of positioning welding shall be over 50mm and the space should be 250 ~ 300mm. The arc striking and arc closing of positioning welding shall be in the bevel. 4.4.3.5 When welding temporary welds of tools and calipers, the arc striking and arc closing shall all be in tools, calipers or in welds. It is strictly prohibited to strike arc or close arc in non-welding position. 4.4.4 The determination and control of the energy of welding line shall meet following requirements: 4.4.4.1 The energy of welding line shall be set in the WPS according to the material, thickness, welding position and pre-heating temperature of the tank shell. For the steel plate with standard tensile strength over 540Mpa and the carbon steel with thickness over 38mm as well as the low alloy steel with thickness over 25mm, the energy of welding line must be measured and controlled strictly. 4.4.4.2 The control of energy of welding line shall be calculated according to following formula: Q = 60 I U V In which,

(4.4.4)

Q ---- Energy of welding line (J/cm); I ---- Current in welding (A); U ---- Voltage of arc (V); V ---- Welding speed (cm/min).

4.4.4.3 In hand arc welding, the energy of line may be controlled through the range of the length of welding pass of each electrode which is pre-determined by the range of allowable energy of line. 4.4.4.4 In automatic welding and submerged arc welding with cored welding wires, energy of line may be controlled in accordance with the WPS by selecting proper welding speed. 4.4.5 In hand arc welding, the welding sequence of the spherical tank and the arrangnent of welders shall meet following requirements: 4.4.5.1 In case the spherical tank is assembled in zones, the longitudinal joints of the zones should be welded on a platform. Assemble them to be a whole one and then weld — 18 —

circumferential joints between zones. 4.4.5.2 In case the spherical tank is assembled in sectors, the welding sequence shall follow the principle of longitudinal joints firstly and then circumferential joints. 4.4.5.3 The arrangement of welders shall be uniform and welding shall be applied synchronously. 4.4.6 When welding double-face butt welds with hand arc welding, after welding one side, the root of the back shall be cleaned. In case carbon arc air planner is used in cleaning, after root cleaning, sand wheel shall be used to rectify planed channel and carbon penetration layer shall be ground off. Visual inspection, magnetic powder and dye penetrant testing shall be used for inspection. For steel with standard tensile strength over 540Mpa, after root cleaning, it is a must to use magnetic powder and dye penetrant testing to inspect. In root cleaning of the welds, the metal of welds of positioning welding shall be removed. The shape of the bevel after root cleaning shall be same. 4.4.7 In auto and semi-auto welding with cored welding wires, the welding sequence in welding the spherical tank shall meet following requirements: 4.4.7.1 On completion of the assembling of the spherical tank, the welding sequence shall be arranged follow the principle of longitudinal joints first and then circumferential joints. 4.4.7.2 When welding longitudinal joints, the arranging of welding machines shall be uniform and symmetrically and the welding shall be applied synchronously. 4.4.7.3 When welding circumferential joints, the arranging of welding machines shall be symmetrically and welding shall be applied in same rotation direction. 4.4.8 In welding, the side of arc striking shall be backward arc striking method. At arc closing side, the arc pit shall be fully filled. The connections of multi-layer welding layers shall be staggered. 4.4.9 In the case of the interruption of any pass of the welding, measures to avoid any crack shall be taken in accordance with the process requirement. Before re-welding, a check shall be made to confirm that there is no crack, then the welding can be applied. 4.4.10 Steel stamp of welder’s code shall be made at the assigned place 50mm away from the welds of the spherical tank and a record shall be made. For the spherical tank which allows no stamp, it shall be recorded in arrangement drawings. 4.4.11 The welding of the parts and components of manholes, connection pipes and supports shall meet following requirements: 4.4.11.1 The welding for the butt welding of forged flange and the tank shell, apart from that the welding materials shall be same as that for the welding of the tank shell, the welding process shall be same as that for the steel of higher strength. 4.4.11.2 The welding of the supports, connection plates and the tank shell, apart from that the welding materials should be the one matching the steel of lower strength, the welding process shall be same as that that for the steel of higher strength. — 19 —

4.4.11.3 The fillet welds of the tank shell and the reinforcing rings, connection pipes and supports shall be transited smoothly.

4.5 Repair 4.5.1 Any defect of the spherical tank caused in manufacturing, storage or transportation shall be repaired. 4.5.2 The repair of surface defect shall meet following requirements: 4.5.2.1 The surface defect of the spherical tank and the welding trace of tools and calipers shall be removed by sand wheel grinding. The actual thickness after grinding shall not be < design thickness. The depth of grinding shall be < 5% of nominal thickness of tank shell plate, and not exceeding 2mm. If it exceeds, remedy welding shall be applied. 4.5.2.2 In welding repairing surface defect of tank shell plate, the area of each repair shall be within 50 cm2. In case there are two or more places repaired, the distance between sides of any two repairs shall be > 50mm. The total area of repair of surface of each tank shell plate shall be 0.5 mm, and the actual thickness of the tank shell after grinding must not be < design thickness. In case it is not up to this requirement, a remedy welding shall be applied.

Figure 4.5.2 – 1 Grinding off the Welding Defects Along Both Side of Welds by Using a Sand Wheel 1—Base metal；2—Welds metal；3—Surface after grinding — 20 —

4.5.2.5 In welding repairing defects of welds over cut and welds foot crack, a sand wheel shall be used to grind off the defects to make it a concave channel facilitating welding, and then welding shall be applied. The length of remedy welding shall not be < 50mm. For the spherical tank with standard tensile strength over 540 Mpa, one pass of tempered welding pass shall be added onto the remedy welding pass (Figure 4.5.2 – 2). After welding, grind off surplus metal of welds.

Figure 4.5.2 - 2 Tempered Welding Pass in Remedy Welding 1—Remedy welding pass；2—Tempered welding pass；3—Base metal；4—Welds metal 4.5.2.6 In case preheating is necessary in remedy welding, preheating shall be done in a range with repairing place as the center and a radius of 150mm. The preheating temperature shall take the upper limit. The energy of welding line shall be within specified scope. In welding short welds, the energy of line shall not take the lower limit. After remedy welding, post weld heat treatment, if required, shall be done immediately. 4.5.3 The repair of the inside defects in welds shall meet following requirements: 4.5.3.1 An appropriate welding method shall be selected according to the reason causing the defects and the repair process shall be worked out. 4.5.3.2 Before repairing, ultrasonic testing should be used to determine the position and depth of the defect and to determine the side to repair. 4.5.3.3 In case the removal of the inside defect uses carbon arc air planner, a sand wheel shall be used to remove carbon penetration layer and grind the welds to be transited smoothly. Remedy welding shall not be applied until it is magnetic powder tested or dye penetrant tested and qualified. The depth air planned shall not exceed 2/3 of plate thickness. In case the defect still not yet removed, after remedy welding, air planning shall be made at another side. 4.5.3.4 The length of remedy welding shall not be < 50mm. 4.5.3.5 In case pre-heating is necessary in remedy welding, the pre-heating temperature shall be the upper limit of the required value. After remedy welding, post weld heat treatment, if required, shall be done immediately. The energy of line shall be within specified scope. In welding short welds, the energy of line shall not take the lower limit. 4.5.3.6 At same position (inside and outside of the welds shall be deemed as one position separately), the time of repairing shall not exceed two. For the welds repaired for two times and not yet qualified, reliable technical measures shall be taken and repair shall not be done until it is approved by the person in charge of technique of the organization. — 21 —

4.5.3.7 The positions, times and test results of remedy welding shall be recorded. 4.5.4 Non-destructive testing shall be made to the spherical tank after repairing in accordance with following stipulations:: 4.5.4.1 After removal of all defects and after remedy welding, magnetic powder testing and dye penetrat testing shall be made. 4.5.4.2 In case the depth for remedy welding of the surface defects exceeds 3mm (calculated from the surface of the tank shell plate), a radiographic testing shall be made. 4.5.4.3 After repairing of inside defects of the welds, a radiographic testing or ultrasonic testing shall be made. The method selected shall be the same as the method with which the defect was found.

4.6 Inspection of Size of Spherical Tank Welded 4.6.1 After welding, the sharp corners shall be inspected in accordance with the method in 3.2.3.3 of this Code. The value of the sharp corner shall not be > 10mm. 4.6.2 After welding, the inside diameters of the sections at two poles and at equator section shall be inspected and they shall meet following requirements: 4.6.2.1 The difference of the three, the ID at two poles, the maximum ID at equator and the minimum ID, shall be < 7/1000 of design ID, and not be > 80mm; 4.6.2.2 The difference of the ID at two poles, the maximum ID at equator and the minimum ID and the design ID shall all be < 7/1000 of design ID, and not be > 80mm. 4.6.3 The verticality of the supports of spherical tank after welding shall meet what specified in 3.2.7.2 of this Code. 4.6.4 After welding, manholes and connection pipes shall meet what specified in 3.3.1 of this Code.

— 22 —

5 Inspection of Welds 5.1 Visual Inspection of Welds 5.1.1 After welding, a visual inspection shall be made to the welds. Before inspection, fused slag and scales, spatters shall be removed. 5.1.2 The surface quality of welds shall meet following stipulations: 5.1.2.1 The welds and the heat-affected zone shall not have any defect of crack, bubble, over cut, slag inclusion, pit or in-full welding. 5.1.2.2 The size of welding foot of fillet welds shall meet requirements of design drawings. 5.1.2.3 The width of welds shall be 1 ~ 2mm wider than each side of the bevel. 5.1.2.4 The surplus height of but welds shall meet the requirements in Table 5.1.2. Table 5.1.2

Surplus Height of Butt Welds (mm) Surplus height of welds

Depth of welds (δ) Hand arc welding

Submerged arc

Gas shielded welding with

welding

cored welding wires

≤12

0 ~ 1.5

0~3

0~3

12 2mm. 5.4.5 Any defect found in magnetic powder or dye penetrant testing shall be ground or repaired in accordance with what specified in 4.5.2 of this Code and a re-test shall be made to that location by using original test method till it is qualified.

— 26 —

6

Post Weld Heat Treatment of the Whole 6.1 General Rules

6.1.1 In any of following cases, spherical tank shall be post weld heat treated for the whole before pressure test: 6.1.1.1 Post weld heat treatment required by design drawing; 6.1.1.2 Spherical tank to contain LPG, liquefied ammonia and other medium of stress corrosive; 6.1.1.3 Spherical tank made of carbon steel with nominal thickness over 34mm (in case the preheating temperature is over 100℃, nominal thickness is over 38mm) and spherical tank made of 07MnCrMoVR steel; 6.1.1.4 Spherical tank made of 16MnR steel with nominal thickness over 30mm (in case the preheating temperature is over 100℃, nominal thickness is over 34mm); 6.1.1.5 Spherical tank made of 15MnVR steel with nominal thickness over 28mm (in case the preheating temperature is over 100℃, nominal thickness is over 32mm); 6.1.1.6 Spherical tank of other low alloy steel of any thickness. 6.1.2 Following conditions shall be ready before post weld heat treatment: 6.1.2.1

Welding connecting pressure pieces of spherical tank is completed;

6.1.2.2

Non-destructive inspection before heat treatment is completed;

6.1.2.3 The product welding test plate is put at the outer side of the high temperature zone of the spherical tank heat treatment; 6.1.2.4

Heating system is adjusted and qualified;

6.1.2.5

Connection pipe not related to heat treatment is blind blocked;

6.1.2.6

The bolts connecting spherical tank and ladders, platforms have been loosened;

6.1.2.7 taken.

Measures for anti rain, anti wind, anti fire and power failure prevention have been

6.2

Heat Treatment Process

6.2.1 Temperature for heat treatment shall meet requirements of design drawings. In case the design drawings have not requirements for it, the temperature for heat treatment for common use steels may be selected according to Table 6.2.1.

— 27 —

Table 6.2.1 Temperature for Heat Treatment for Common Use Steel Steel number

Temperature for heat treatment (℃)

20R

625±25

16MnR

625±25 +25

15MnVR

570 -20

15MnVNR

565±15

07MnCrMoVR

565±20

6.2.2 The minimum holding time in heat treatment shall be calculated according to the thickness of butt welds of thickest steel plate as 1 hour for every 25mm, and shall not be 130℃.

6.3 Requirements for Heat Insulation 6.3.1 In heat treatment, insulation materials, which may resist highest temperature, have no corrosive to spherical tank, lower unit weight, less heat conduction coefficient and is easy for construction, shall be selected. 6.3.2 The insulation materials shall be dry and not damped. 6.3.3 The insulation layer shall be close to the tank shell surface and the local gap should not be > 20mm. The joints shall be tight. In multi-layer insulation, the joints of different layers shall be staggered. During heat treatment, the insulation layers shall not be loose or peeling off. 6.3.4 All manholes, connection pipes and connection plates of spherical tank shall be insulated. Insulation shall be made to the supports within a range not less than 1 meter calculated down from the lower side of the welds of the supports and the tank shell. 6.3.5 During temperature holding time, the temperature at outer surface of the insulation layer should not be > 60℃.

— 28 —

6.4 Temperature Measuring System 6.4.1 The temperature measuring points shall be arranged on the tank shell surface evenly. The space between adjoining temperature measuring points should be < 4.5m. One temperature measuring point shall be arranged respectively in a range 200mm away from the upper and lower manholes and from the side of circumferential welds of the tank shell plate. One temperature measuring point shall be arranged to the product welding test plate. The total temperature measuring points shall not be less than what specified in Table 6.4.1. Table 6.4.1 Quantity of Temperature Measuring Point Volume of spherical tank (m3)

50

120

200

400

650

1 000

2 000

≥4 000

Quantity of temperature measuring point

8

8

12

12

12

16

24

36

6.4.2 The thermocouple used in temperature measuring may be fixed onto the outer surface of the tank shell by percussion welding or bolts (Figure 6.4.2). The thermocouple and compensation wire shall be fixed.

Figure 6.4.2 Method for Fixing Thermocouple in Temperature Measuring 1—Channeled nut；2—Tack welds；3—Tank shell；4—Bolt；5—Thermocouple 6.4.3 Temperature shall be recorded continuously and automatically. The thermocouple and recording instruments shall be adjusted and in valid period. The accuracy shall be up to ± 1%.

6.5 Treatment of Support Foot 6.5.1 During heat treatment, tie rods and anchor bolts shall be loosened. Moving device and displacement measuring unit shall be installed to the bottom of anchor plate of the supports. 6.5.2 During heat treatment, actual displacement shall be monitored and the displacement of the support foot shall be adjusted according to the calculated value of displacement. For changing of temperature of each 100℃, one adjustment shall be made. The moving of support foot shall be mild and slow. 6.5.3 After heat treatment, verticality of supports and deflection of tie rods shall be measured and adjusted. The allowable error shall meet the requirements in 3.2.7 and 3.2.8 in this Code. — 29 —

7 Test Plate of Product Welding 7.1 Requirements for Preparation of Test Plate of Product Welding 7.1.1 The steel number, thickness and the heat treatment process of the test plate shall be same as that for the tank shell. 7.1.2 The test plate shall be welded by the welder who is going to weld the spherical tank under same welding condition and with same welding process. 7.1.3 According to the position of welding application, for each spherical tank, one piece of test plate shall be prepared respectively for horizontal welding, vertical welding, flat welding and overhead welding. The size of the test plate shall be 360mm x 650mm. 7.1.4 Visual inspection and 100% radiographic or ultrasonic testing shall be made to welds of the test plate. When cutting the test plate, the defect may be kept away. 7.1.5 For the spherical tank needs post weld heat treatment, the product test plate shall be heat treated together with the spherical tank.

7.2 The Preparation and Test of the Test Plate 7.2.1 The size, cutting, test method of the test plate and the criteria for qualification shall meet relevant stipulations in the national standard in force the Steel Made Pressure Vessels GB150. 7.2.2 For spherical tank made of 20R steel with thickness over 25mm, of 16MnR steel, 15MnVR steel, 15MnVNR steel and 07MnCrMoVR steel with thickness over 38mm, in case the design temperature is lower than 0℃, a low temperature Charpy（V-notch）impact test shall be made to the heat affected zone and the welded metal according to the design temperature of spherical tank and the test temperature specified in drawings. 7.2.3 Re-test shall meet following requirements: 7.2.3.1 In case the product test plate is not qualified in the tensile test or bend test, it is allowable to cut double test plates for unqualified item from the original test piece or from another test piece welded at same time with the spherical tank for re-test. 7.2.3.2 In case the impact test is not up to requirements, another group (3 pieces) of test plate may be cut from original test plate to test. The criteria for qualification shall be: the average value of impact power for the 6 test pieces of 2 groups shall not be lowered than specified value. It is allowable that the impact power for 2 test pieces may be lower than specified values, in which, it is allowable that only one can be 70% lowered than the specified value. 7.2.3.3 In case the result of re-test is still not qualified, the welding test plate of the spherical tank shall be judged as not qualified. In this case, reasons shall be analyzed. It is allowed to re-heat treat the test plate and the spherical tank it represented. However, the heat treatment — 30 —

process shall be worked out again and then re-test in accordance with the requirements of this Code.

8 Pressure Test and Airtight Test 8.1 Pressure Test 8.1.1 Before pressure test, the spherical tank shall have following conditions: (1) The welding of the spherical tank and the connection with parts and components have been completed and they are qualified after inspection; (2) The strength of secondary grouting of the foundation is up to the requirements for the strength; (3) Post weld heat treatment has been done to spherical tank, which needs post weld heat treatment. The product welding test plate is qualified after inspection; (4) The welds of reinforcing rings have been leakage tested with compressed air of 0.4 ~ 0.5 Mpa and qualified; (5) The alignment of the supports and the adjustment of the tie rods have been completed. 8.1.2 Gases must not be used to replace the liquid in pressure test, unless it is specified in design drawings. 8.1.3 During pressure, a pressure gauge of same scale and qualified after calibration shall be installed respectively at the top and bottom of the spherical tank. The accuracy shall not be less than 1.5 grade. The range of scale of pressure gauges should be 2 times of test pressure, and shall not be < 1.5 times of and not be > 4 times of test pressure. The diameter of the pressure gauge should not be < 150mm. 8.1.4 During pressure test, it is strictly prohibited to impact or strike the spherical tank. 8.1.5 Hydraulic test shall meet following stipulations: 8.1.5.1 For hydraulic test, clean water shall be used as the medium; 8.1.5.2 For hydraulic test of spherical tank of carbon steel, 16MnR steel and normalized 15MnVR steel, the temperature of water used in the test shall not be lower than 5℃. For spherical tank of other low alloy steel (except low temperature spherical tank) the temperature of water used in the test shall not be lower than 15℃. In case the temperature is risen due to the lacking of ductility of material caused by the thickness of the plate, the temperature of water used in the test shall also be raised correspondingly. 8.1.5.3 The test pressure in hydraulic test shall be specified by the design drawings, and not lower than 1.25 times of design pressure of the spherical tank. For the reading of the test pressure, the one of the pressure gauge at the top of the spherical tank shall apply. 8.1.5.4 The hydraulic test shall be done in accordance with following steps:

— 31 —

(1) During test, a vent port shall be provided at the top of the spherical tank. Air in the spherical tank shall be completely vented when filling the liquid. During the test, the outer surface of the spherical tank shall be dry; (2) During test, the pressure shall be risen slowly. Keep the pressure for 15 minutes when the pressure is up to 50% of test pressure. Check all welds and connection places of the spherical tank. Continue the pressure rising after confirming that there isn’t any leakage; (3) Keep the pressure for 15 minutes when the pressure is up to 90% of test pressure. Check it again and continue the pressure rising after confirming there isn’t any leakage; (4) Keep the pressure for 30 minutes when the pressure is up to the test pressure. Then fall the pressure to 80% of test pressure and check. If there isn’t any leakage or abnormal, it is qualified; (5) On completion of the hydraulic test, water shall be drained completely. Water shall not be drained to the ground locally. 8.1.6 Air pressure test shall meet following stipulations: 8.1.6.1 Safety measures shall be taken for air pressure test, which shall be approved by the person in charge of safety work of the organization. The test shall be supervised and checked by the safety department of the organization. Two or more safety valves and emergency vent valves shall be provided in air pressure test. 8.1.6.2 The test pressure of the air pressure test shall meet what specified in design drawings. 8.1.6.3 Air or nitrogen shall be used as the medium of the air pressure test. The temperature of the medium shall not be less than 15℃. 8.1.6.4 The air pressure test shall be done in accordance with following steps: (1) Keep the pressure for 5 ~ 10 minutes when the pressure is up to 10% of test pressure. A preliminary check for leakage shall be made to all welds and connection places of spherical tank. Continue the pressure rising after confirming there isn’t any leakage; (2) Keep the pressure for 10 minutes when the pressure is up to 50% of test pressure. When it is confirmed that there isn’t any abnormal, the test pressure shall be risen stage by stage at a pressure of 10% of test pressure for each stage. Keep it for 10 ~ 30 minutes. Then fall to design pressure to check. If there isn’t any leakage or abnormal, it is qualified; (3) The pressure shall be unloaded slowly. 8.1.6.5 In air pressure test, the fluctuation of the environment temperature shall be monitored as well as the reading of the pressure gauge. No over pressure shall happen. 8.1.6.6 The safety valves used in the air pressure test shall meet following requirements: (1) Safety valves shall be the products manufactured by the manufacturer having manufacturing license and the products are up to technical standard; (2) The safety valves must be calibrated and qualified; (3) The begin-to-open pressure of the safety valves shall be set at 0.05Mpa of the test pressure. 8.1.7

During water filling and water draining of the spherical tank, foundation settlement — 32 —

shall be observed and actually recorded and it shall meet following stipulations: 8.1.7.1 The settlement observation shall be done at following stages: (1) Before water filling; (2) At the time when water is filled up to 1/3 of ID of the tank shell; (3) At the time when water is filled up to 2/3 of ID of the tank shell; (4) At the time when water it fully filled; (5) 24 hours after fully water filling; (6) After water is drained. 8.1.7.2 Settlement of each foundation of support shall be measured. Permanent plate for measuring level shall be welded to supports as specified. 8.1.7.3 The settlement of foundation shall be even. After water draining, the uneven settlement shall not be > 1/1000 of center circle of the foundation. The difference of the settlement of adjoining supports shall not be > 2mm. 8.1.7.4 In case the uneven settlement is > above requirement, measures shall be taken to handle it.

8.2 Airtight Test 8.2.1 Airtight test shall be done when the hydraulic test is done and qualified to those spherical tank requiring airtight test. 8.2.2 Air or nitrogen shall be used as the medium of the airtight test. The temperature of the medium shall not be lowered than 5℃. 8.2.3 The pressure gauges and safety valves used in the test shall be calibrated. The requirements for pressure gauges and valves shall meet what specified in 8.1.3 and 8.1.6.6 of this Code. 8.2.4 The test pressure of the airtight test shall meet what specified in design drawing. 8.2.5 The airtight test shall be done in accordance with following steps: 8.2.5.1 Keep the pressure for 10 minutes when the pressure is up to 50% of test pressure. Check all welds and connection places of the spherical tank. Continue pressure rising after confirming there isn’t any leakage. 8.2.5.2 Keep the pressure for 10 minutes when the pressure is up to the test pressure. Check all welds and connection places of the spherical tank. If there isn’t any leakage, it is qualified. In case there is leakage, re-airtight test it after the leakage is handled. 8.2.5.3 Pressure shall be unloaded slowly. 8.2.6 During airtight test, the fluctuation of the environment temperature shall be monitored as well as the reading of the pressure gauge. No over pressure shall happen. 8.2.7 For the spherical tank requiring air pressure test specified by the design drawings, the airtight test may be done with air pressure test simultaneously. — 33 —

9 Handing Over and Acceptance 9.0.1 On completion of the construction of spherical tank, the contractor shall hand over as-built drawings and other technical documents to the Employer. The Employer, together with other departments, shall inspect according to stipulations in this Code. It shall not be handed over until it is confirmed to be qualified. 9.0.2 When handing over the spherical tank, the contractor shall submit following technical documents, of which the format should meet what specified in Appendix C of this Code: (1) Certificate for Handing Over and Acceptance of the spherical tank; (2) Certificate for Supervised Inspection: (3) As-built drawings; (4) Product Quality Certificate from spherical tank manufacturer; (5) Test reports on delivered goods of tank shell plates and supports; (6) Inspection Reports on spherical tank foundation; (7) Test Reports on product welding test plates; (8) Welds and welder arrangement drawings; (9) Quality Certificate for welding materials and their re-test reports; (10) Reports on inspection of geometric size of spherical tank after welding; (11) Inspection Records of spherical tank supports; (12) Reports on Radiographic Testing of welds (Sketch of tested position shall be attached); (13) Reports on Ultrasonic Testing of welds (Sketch of tested position shall be attached); (14) Reports on Magnetic Powder Testing of welds (Sketch of tested position shall be attached); (15) Reports on Dye Penetrant Testing of welds (Sketch of tested position shall be attached); (16) Records of welds repairing; (17) Reports on post weld heat treatment of the whole, the arrangement drawing of the temperature measuring points and temperature curve automatically recorded; (18) Records of pressure test; (19) Records of airtight test; (20) Records of foundation settlement; (21) Notices for design alterations 9.03 A product name plate and registered name plate shall be installed on spherical tank at the position the design drawing specified.

— 34 —

Appendix A

Low Temperature Spherical Tanks A.1 General Rules

A.1.1 This appendix applies to the assembling, welding, inspection and acceptance of spherical tank made of carbon steel and low alloy steel with design temperature lower than 20℃ (abbreviated as “low temperature spherical tanks”). A.1.2 Those not specified in this appendix shall also meet requirements specified in different chapters and sections of this Code.

A.2 Inspection and Acceptance of Tank Shell Plates A.2.1 The tank shell plates of thickness over 20mm shall be ultrasonic spot tested in accordance with 2.2.6 of this Code. The quantity for spot test shall not be less than 40% of total quantity of tank shell plates. The spot test shall include all upper and lower pole plates and the equator plates connected with supports. The quantity for spot test for each zone shall not be less than 2 pieces.

A.3 Assembling A.3.1 Forming means such as hammering the tank shell plates shall not be used in form adjusting or assembling. A.3.2 Material marks or welder seal, which may cause notch effectiveness, shall not be engraved or stamped on pressure elements.

A.4 Welding A.4.1 The welding materials shall meet following requirements: A.4.1.1 The welding materials used for low temperature spherical tank shall be those matching the performance of the base material. A.4.1.2 The technical requirements, test method and rules for inspection for welding materials shall meet relevant stipulation of national standard in force. A.4.1.3 Electrodes shall be tested for water content in coating and diffusion hydrogen content in melting metal in batches. The method for testing shall be as per relevant technical standards or technical requirements for electrodes. — 35 —

A.4.2 Welding process shall be evaluated before welding application in accordance with the national standard in force the Evaluation of Welding Process of Steel Made Pressure Vessels JB4708. The standard for qualification of low temperature Charpy （V-notch）impact test shall be determined according to the national standard the Steel Made Pressure Vessels GB150, and not lower than the performance of the base material. A.4.3 The WPS shall be worked out in accordance with drawing requirements and qualified welding process in the light of structural feature of the spherical tank and the practical experience. In application of welding, the WPS must be followed. A.4.4 The pre-heating temperature for low temperature steels shall execute the WPS. It may also be selected according to Table A.4.4. Table A.4.4 Pre-heating Temperature for Low Temperature Steel Steel type

16MnDR

07MnNiCrMoVDR

09Mn2VDR

20

—

75 ~ 100

—

25

—

75 ~ 100

—

32

75 ~ 125

75 ~ 100

—

38

100 ~ 150

75 ~ 100

—

50

125 ~ 175

75 ~ 100

—

Plate thickness (mm)

A.4.5 Welding line energy must be controlled. Within the range specified by the WPS, welding line of less energy should be selected and the welding shall be applied in multi-pass. A.4.6 The surplus height of butt welds, shall not be larger than 10% of thickness of the weldment, and not be > 3mm. The height exceeded shall be ground off. A.4.7 The damage or defect of scraping, welding scar, arc pit on the tank shell shall be ground off and repaired. The grinding and repairing shall meet what specified in 4.5.2 of this Code.

A.5 Post Weld Heat Treatment of the Whole A.5.1 Post weld heat treatment shall be done for low temperature spherical tank with plate thickness ≥16mm. A.5.2 The temperature for heat treatment of low temperature spherical tank shall meet requirements of the design drawings. In case there isn’t requirement in the design drawing, Table A.5.2 may apply.

— 36 —

Table A.5.2 Temperature for Heat Treatment of Low Temperature Spherical Tank Steel number

Temperature for heat treatment (℃)

16MnDR

625±25

07MnNiCrMoVDR

565±20

09Mn2VDR

600±20

A.6 Product Test Plate A.6.1 The size of the test plate, the cutting of the sample, the test items, method of test and the criteria for qualification shall implement what specified in Chapter 7 of this Code. A.6.2 A low temperature Charpy impact test shall done to the welds metal and heat affected zone of the product welding test plate. The temperature for impact test and the criteria for qualification shall meet the requirements in the national standard in force the Steel Made Pressure Vessels GB150.

A.7 Inspection of Welds A.7.1 Any of following butt welds shall be 100% radiographic or ultrasonic tested: (1) Spherical tank with design temperature lower than -40℃; (2) Spherical tank with design temperature ≥-40℃, however the tank shell thickness is > 25mm; (3) The one meets requirements for 100% radiographic or ultrasonic testing in 5.3.2 of this Code; (4) Those the design drawing specified. A.7.2 When local non-destructive inspection is made to welds, the length of inspection for each piece of welds shall not be less than 50% of total length of welds.

A.8 Pressure Test A.8.1 The temperature of the liquid in hydraulic test of low temperature spherical tank shall not be lower than 0℃.

— 37 —

Appendix B Name of Different Parts of Spherical Tank, Numbering of Zones, Tank Shell Plates and Welds of Spherical Tank B.0.1 Names of different parts of spherical tank should meet what specified in Figure B.0.1.

Figure B.0.1 Names of Different Parts of Spherical Tank 1—Upper pole；2—Upper frigid zone；3—Upper temperate zone；4—Equator zone； 5—Lower temperate zone；6—Lower frigid zone；7—Lower pole B.0.2 Names of different parts of the supports of spherical tank should meet what specified in Figure B.0.2.

Figure B.0.2 Name of Different Parts of Supports of Spherical Tank 1—Tank shell；2—Cover plate；3—Support of upper section； 4—Bracket plate；5—Upper ear plate；6—Support of lower section；7—Anti-fire layer； 8—Grounding plate；9—Anchor bolt；10—Bottom plate；11—Lower ear plate； 12—Pin；13—Tie rod；14—Adjustment knot；15—Vent port. — 38 —

B.0.3 Names of different parts of manholes and connection pipes of spherical tank should meet what specified in Figure B.0.3.

Figure B.0.3. Names of Different Parts of Manholes and Connection Pipes of Spherical Tank 1—Flange cover or manhole cover; 2—Flat welded flange; 3—Connection pipe or sections of manhole; 4—Reinforcing ring; 5—Tank shell; 6—Forged flange wholly made; 7—Butt welded flange; 8—Washer; 9—Nut; 10—Bolt 11—Gasket. B.0.4 The numbering of different zones, the tank shell plates and the welds of spherical tank should meet what specified in Table B.0.4.

— 39 —

Table B.0.4 Numbering of Different Zones, Tank Shell Plates and Welds of Spherical Tank Sketch of structure of tank shell

Name of different zones of tank shell

Numbering of different zones of tank shell

Upper pole

F

Upper frigid zone

D

DF BD

Upper AB

temperate

zone Equator zone

B A

AC

Lower temperate CE

zone

C

Lower frigid zone

E

Lower pole

G

Upper pole

F

EG

BF

Upper AB

temperate

zone Equator zone

B A

AC

Lower temperate CG

zone

C

Lower pole

G

Upper pole

F

BF

Upper AB

temperate

zone

B

Equator zone

A

Lower pole

G

Upper pole

F

Equator zone

A

Lower pole

G

AG

AF AG

— 40 —

Numbering of tank shell plates F01 F02 -----D01 D02 -----B01 B02 -----A01 A02 -----C01 C02 -----E01 E02 -----G01 G02 -----F01 F02 -----B01 B02 -----A01 A02 -----C01 C02 -----G01 G02 -----F01 F02 -----B01 B02 -----A01 A02 -----G01 G02 -----F01 F02 -----A01 A02 -----G01 G02 ------

Numbering of longitudinal welds of different zones F1×2 F2×3 -------D1×2 D2×3 -------B1×2 B2×3 -------A1×2 A2×3 -------C1×2 C2×3 -------E1×2 E2×3 -------G1×2 G2×3 -------F1×2 F2×3 -------B1×2 B2×3 -------A1×2 A2×3 -------C1×2 C2×3 -------G1×2 G2×3 -------F1×2 F2×3 -------B1×2 B2×3 -------A1×2 A2×3 -------G1×2 G2×3 -------F1×2 F2×3 -------A1×2 A2×3 -------G1×3 G2×2 --------

Numbering of circumferenti al welds

Appendix C Form for Handing Over and Acceptance C.0.1 The certificate for handing over and acceptance of spherical tank should meet what specified in Table C.0.1. Table C.0.1 Certificate for Handing Over and Acceptance of Spherical Tank Title of project

Name of spherical tank

Serial number of spherical tank

Nominal capacity

ID of tank shell

Material of tank shell

Thickness of tank shell

Material contained

Design pressure

Design temperature

Designer

Manufacturer License

Contractor

number

for

assembly welding Date

Type of vessel

of

commence/

completion

Description of construction

The inspection shows that the spherical tank meets the requirements of drawings and GB50094 – 98. It is agreed for handing over and acceptance of the spherical tank after Employer: (seal)

Contractor (seal)

Representative of Employer

Representative of Contractor

Year ---- Month ---- Date ----

Year ---- Month ---- Date ----

— 41 —

C.0.2 The Report on inspection of delivered goods of tank shell plates and supports should meet what specified in Table C.0.2. C.0.3 Record for inspection of foundation for tank shell should meet what specified in Table C.0.3. Table C.0.2 Report on Inspection of Delivered Goods of Tank Shell Plates and Supports Title of project: Name of Spherical Tank: Items to inspect

Serial No. of Spherical Tank: Date:

Quantity to inspect

Quantity qualified

Piece

Piece

Geometric size of tank shell plate Serial number

Rate of qualification

Remarks

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Error of linearity (mm) Support

Length (mm) Serial number Error of linearity (mm) Length (mm)

Items to test Ultrasonic

Quantity to inspect testing

of

sides of tank shell plates Ultrasonic testing of full area of tank shell plate Dye penetrant (magnetic powder) testing of bevel Measurement plate

Piece

Piece

Piece

Minimum thickness

mm

Engineer in charge of process: Year ---- Month ---- Date ----

Engineer in charge of quality inspection: Year ---- Month ---- Date----

Engineer in charge of material:

Judgement

Piece

of

thickness of tank shell

Test result

Year ---- Month ---- Date ----

— 42 —

Maximum thickness

mm

Result of Inspection:

Table C.0.3 Record for Inspection of Foundation for Tank Shell

inspect

Error of

foundation

foundation

position

elevation

(°)

(mm)

Error of foundation level (mm)

Distance

between

between

center of

center of

anchor bolt

reserved

Distance

and center

hole and

between

circle of

center

centers of

foundation,

circle of

adjoining

S1 (mm)

Inside

Error of

Allowable

Date:

foundation

supports, S,

S2 (mm)

(mm)

Difference of

Error of D

elevations of

of

foundation of

foundation

adjoining

center

supports (mm)

circle (mm)

error Serial No. of foundations 1

1~2

1~2

2

2~3

2~3

3

3~4

3~4

4

4~5

4~5

5

5~6

5~6

6

6~7

6~7

7

7~8

7~8

8

8~9

8~9

9

9~10

9~10

10

10~11

10~11

11

11~12

11~12

12

12~13

12~13

13

13~14

13~14

14

14~1

14~1

Quality Inspector: Year --- Month --- Date ---— 43 —

Surveyor: Year --- Month --- Date ----

Remarks

Distance

Serial No. of spherical tank:

Outside

to

Outside

Items

Name of spherical tank:

Inside

Title of project:

C.0.4 Record of welds repairing should meet what specified in Table C.0.4 Table C.0.4

Record of Welds Repairing

Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

ID of tank shell Series No.

Location of repairing

mm

Thickness of tank shell

mm

Nature of

Time of

Length of

Date of

defect

repairing

repairing

repairing

Material of tank shell Steel seal number of welder

Engineer in charge of welding:

Year ---- Month ---- Date ----

Inspector:

Year ---- Month ---- Date ----

Recorded by:

Year ---- Month ---- Date ---— 44 —

Result of repairing

C.0.5 Report on inspection of geometric size of spherical tank after welding should meet what specified in Table C.0.5. Table C.0.5 Report on Inspection of Geometric Size of Spherical Tank after Welding Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date: Result of inspection

Items to inspect

Quantity of total

Quantity of

Rate of

Maximum error actually

measuring points

qualified points

qualification

measured (mm)

Width of welds Surplus height of welds Sharp corner of welds Maximum ID of equator

section

(mm) Minimum ID of equator

section

(mm) ID

actually

measured at two poles (mm) Difference

of

Max. and Min IDs (mm) Difference Max.

ID

of and

design ID (mm) Difference Min.

ID

of and

design ID (mm) Conclusion:

Engineer in charge of inspection:

Year ---- Month ---- Date ----

Engineer in charge of process:

Year ---- Month ---- Date ----

Inspector :

Year ---- Month ---- Date ---— 45 —

C.0.6 C.0.6.

Record of inspection of spherical tank supports should meet what specified in Table

Table C.0.6 Record of Inspection of Spherical Tank Support Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Error of linearity of total

inspect

length of supports (mm)

Serial No.

Radial

Circumferential

Error of verticality of supports (mm) Radial a1

a2

Circumferential a1- a2

a1

a2

of support 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Engineer in charge of process: Inspector: Construction team (group) leader:

Year ---- Month ---- Date ---Year ---- Month ---- Date ---Year ---- Month ---- Date ---— 46 —

a1- a2

Remarks

Items to

C.0.7 Reports on radiographic, ultrasonic, magnetic powder and dye penetrant testing of welds should meet what specified in Tables C.0.7- 1 ~ C.0.7 – 4 respectively. Table C.0.7 – 1

Report on Radiographic Testing of Welds

Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal

m3

capacity Type of

Focal distance

equipment

Material of

Thickness of tank shell

tank shell mm

Tube voltage

Type of ray

Size of ray

Type of

source

source

amplification

Time of exposure

min

Index of image quality

Scope of

Temperature

blackness

of developing

Total length of welds:

Type of film ℃

m, Ratio of testing :

%

KV

mm

Tube current

mA

Activity

TBq

Type of developing

Applicable

Class of

standard

qualification

Length tested: m

Radiographic tested -------pieces, longitudinal joints ------ pieces, circumferential joints ---- pieces, other position ---- pieces In which, Class I ---- pieces, making up ---% of total films Class II ---- pieces, making up ---% of total films, Repairing --- pieces, repairing one time ---- pieces, repairing two times ---- pieces Rate of qualification for one time ----% Description:

Drawing of film arrangement and record of evaluation are attached

Engineer in charge of non-destructive inspection:

Year ---- Month ---- Date ----

Re-evaluator:

Year ---- Month ---- Date ----

Image evaluator:

Year ---- Month ---- Date ---— 47 —

Table C.0.7 – 2 Report on Ultrasonic Testing of Welds Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal capacity

m3

Type of

search unit

Thickness of

tank shell

tank shell Frequency of

Couplant

equipment Diameter of

Material of

mm

searching Type of

K value of

moving of

search unit

search unit

Method of

Type of bevel

welding Applicable

Class for

standard

qualification

Total length of welds:

m, Ratio of testing :

%

Length tested: m

Record of defects: (Sketches of positions tested attached)

Result of evaluation:

Engineer in charge of non-destructive inspection:

Year ---- Month ---- Date ----

Checked by:

Year ---- Month ---- Date ----

Inspector:

Year ---- Month ---- Date ---— 48 —

mm

Table C.0.7 – 3 Report on Magnetic Powder Testing of Welds Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal capacity

m3

Material of

Thickness of

tank shell

tank shell

Method of

Type of equipment

Sensitivity

excitation

Concentration of

Status of

Carrier liquid

suspension liquid

surface

Applicable standard Total length of welds:

m, Ratio of testing :

%

Length tested: m

Positions tested :

Result of evaluation:

Notes: Records of defects attached Remarks:

Engineer in charge of non-destructive inspection:

Year ---- Month ---- Date ----

Checked by:

Year ---- Month ---- Date ----

Inspector:

Year ---- Month ---- Date ---— 49 —

mm

Table C.0.7 – 4

Report on Dye Penetrant Testing of Welds

Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal capacity

m3

Material of

Thickness of

tank shell

tank shell

Penetrant

Developer

Status of

Applicable

surface

standard

Total length of welds:

m, Ratio of testing :

Time for penetration

%

mm min

Length tested: m

Positions tested :

Result of evaluation:

Notes: Records of defects attached Remarks:

Engineer in charge of non-destructive inspection:

Year ---- Month ---- Date ----

Checked by:

Year ---- Month ---- Date ----

Inspector:

Year ---- Month ---- Date ---— 50 —

C.0.8 Post weld heat treatment of the whole should meet what specified in Table C.0.8. Table C.0.8 Report on post weld heat treatment of the Whole Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal capacity

m3

ID of spherical tank

mm

Material of tank shell Thickness of spherical tank

mm

Type of heating Position of product

Total

test plate

thermocouple

Average

speed

of

℃/h

Holding temperature

℃/h

Holding time

temperature rising Average

speed

of

quantity

temperature falling

of

℃

h

Description:

Note： Automatic curve of heat treatment temperature and drawings of arrangement of thermocouples are attached. Result of heat treatment: Person responsible for technique of heat treatment: Year ---- Month ---- Date ---Engineer responsible for heat treatment: Year ---- Month ---- Date ---Engineer responsible for quality inspection: Year ---- Month ---- Date ---Representative from organization of inspection supervision: Year ---- Month ---- Date ----

— 51 —

C.0.9 Report on pressure test should meet what specified in Table C.0.9. Table C.0.9 Report on Pressure Test Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal capacity

m3

Material of tank shell

Design pressure

MPa

Medium of test

Test pressure Temperature of medium

Mpa ℃

Steps of test: 1． Rise the pressure up to ---- % of the test pressure, i.e. ---- Mpa, and held for ---- minutes to inspect all welds and connection places of the spherical tank. 2． Rise the pressure up to ---- % of the test pressure, i.e. ---- Mpa, and held for ---- minutes to inspect all welds and connection places of the spherical tank. 3． Rise the pressure stage by stage with 10% of the test pressure for each stage (This does not apply to air pressure test.). 4． Rise the pressure up to the test pressure, ---- Mpa and held for ---- minutes. Fall the pressure to 80% of the test pressure, ---- Mpa to inspect all welds and connection places of the spherical tank. Result of test:

Inspection supervising organization

Employer

Contractor

Representative

Representative

Representative

Year ---- Month ---- Date

Year ---- Month ---- Date

Year ---- Month ---- Date

— 52 —

C.0.10 Report on airtight test should meet what specified in Table C.0.10. Table C.0.10

Report on Pressure Test

Title of project:

Serial No. of spherical tank:

Name of spherical tank:

Date:

Nominal

m3

capacity Material

of

tank shell

Design

MPa

pressure Medium

Test pressure Temperature

of

Mpa ℃

of medium

test

Steps of test: 1． Rise the pressure up to 50% of the test pressure, i.e. ---- Mpa, and held for ---- minutes to inspect all welds and connection places of the spherical tank. 2． Rise the pressure up the test pressure, i.e. ---- Mpa, and held for ---- minutes to inspect all welds and connection places of the spherical tank.

Result of test:

Inspection supervising organization

Employer

Contractor

Representative

Representative

Representative

Year ---- Month ---- Date

Year ---- Month ---- Date

Year ---- Month ---- Date

— 53 —

C.0.11 Record for observation of foundation settlement should meet what specified in Table C.0.11. Table C.0.11 Record for Observation of Foundation Settlement Title of project:

Serial No. of spherical tank

Name of spherical tank:

Date:

Stages of observation

Observation time

Serial number of foundations and measuring points 1

2

3

4

5

6

7

8

Before water filling Water

filled

to 1/3 of ID of tank shell Water

filled

to 2/3 of ID of tank shell Water

fully

filled 24 hours after fully

water

filled After

water

drained

Sketch of foundation plan

Engineer in charge of process:

Year ---- Month ---- Date ----

Inspector:

Year ---- Month ---- Date ----

Surveyor:

Year ---- Month ---- Date ---— 54 —

9

10

11

12

13

14