Code for Design of Vertical Cylindrical Welded Steel Oil Tanks

Transcription

1 Translated English of Chinese Standard: GB UDC GB NATIONAL STANDARD OF THE PEOPLE'S REPUBLIC OF CHINA P Code for Design of Vertical Cylindrical Welded Steel Oil Tanks How to BUY & immediately GET a full-copy of this standard? Search --> Add to Cart --> Checkout (3-steps); 3. No action is required - Full-copy of this standard will be automatically & immediately delivered to your address in 0~60 minutes. 4. Support: Sales@ChineseStandard.net. Wayne, Sales manager Issued on: May 29, 2014 Implemented on: March 1, 2015 Jointly issued by: Ministry of Housing and Urban-Rural Development; General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. Page 1 of 125

2 Contents Foreword General Provisions Terms Basic Requirement Materials General Requirement Steel Plates Steel Pipe Forgings Screw and Nut Structural Steel Welding Materials Bottom Design Size of Bottom Plates Bottom Structure Shell Design Shell Plate's Arrangement and Connection Curb Angle Shell Thickness Wind Girder Fixed Roof General Requirement Allowable Stress of Structural Components Self-supporting Cone Roof Column-Supported Cone Roof Self-supporting Dome Roof Floating Roof General Requirement Structure and Connection of Floating Roof Floating Roof Supports Primary Floating Roof Drains Emergency Roof Drains Rolling Ladder and Track Automatic Bleeder Vents Guiding Devices Peripheral Seals and Static Extracting Devices Floating Roof Manhole Compartment Manhole Wax Scrapers Internal Floating Roof General Requirement Page 4 of 125

3 9.2 Open-Top Bulk-Headed, Single-Deck and Double-deck Internal Floating Roof Internal Floating Roof on Floats Internal Floating Roof Supports Peripheral Seals Automatic Bleeder Vents Vents High Liquid Level Protection Guiding Devices Manhole and Inspection Hatches Appurtenances General Requirement Shell Opening and Reinforcement Shell Manholes Shell Nozzles Flush-type Cleanout Fittings Roof Manholes Roof Nozzles Drain Elbows Water Draw-off Sumps Spiral Stairway, Platforms and Handrails Scaffold Cable Support Protection against Lightning, Static and Others Wind Stable Calculation and Anchorage Design of Oil Tanks Wind Stable Calculation Anchorage Design Prefabrication, Assembling, Welding and Inspection Prefabrication, Assembling and Welding Non-destructive Testing and Tests of Welding Seam Geometry and Dimension Inspection Water Filling Test Fixed Roof Test Appendix A Design of Tank for Small Internal Pressures Appendix B Design of Storage Tank for External Pressure Appendix C Requirements for Tank Operating at Elevated Temperatures Appendix D Seismic Design of Oil Tank Appendix E Basic Requirement of Foundation and Basis for Oil Tank Appendix F Load Combinations Appendix G Variable-design-point Method on Tank Shell Thickness Calculation Appendix H Calculation for Spherical Dome Roof with Rib Reinforcement Appendix J Allowable External Loads on Shell Openings Explanation of Wording in This Code List of Quoted Standards Page 5 of 125

4 Foreword According to the requirements of Ministry of Housing and Urban-Rural Development in Notice on Printing Development and Revision Plan of National Engineering Construction Standards and Codes in 2011 (JIANBIAO [2011] No. 17), the code drafting group summarizes experience from GB Code for Design of Vertical Cylindrical Welded Steel Oil Tanks, refers to relevant international and foreign advanced standards and revises this code based on extensive investigation and solicitation of opinions, discussion and modification. This code covers the design of vertical cylindrical welded steel oil tanks in following main technical aspects, including materials, bottom design, shell design, fixed roof, floating roof, internal floating roof, appurtenances, wind stable calculation and anchorage design of oil tank, tank for small internal pressures, design of storage tank for external pressure, requirements for tank operating at elevated temperatures, seismic design of oil tank, basic requirement of foundation and basis for oil tank, load combinations, variable-design-point method on tank shell thickness calculation, calculation for spherical dome roof with rib reinforcement, allowable external loads on shell openings. There have been some significant changes in this code in the following technical aspects: 1. Chapter 11 "Wind Stable Calculation and Anchorage Design of Oil Tank", Appendix B "Design of Storage Tank for External Pressure", Appendix F "Load Combinations", Appendix G "Variable-design-point Method on Tank Shell Thickness Calculation" and Appendix J "Allowable External Loads on Shell Opening" are added; 2. Design negative pressure of atmospheric pressure storage tank is revised; positive design pressure of fixed-roof oil tank is increased to 18kPa and the maximum design negative pressure is increased to 6.9kPa; 3. Allowable stress of materials is revised; materials of Q235-A.F, Q235-A, Q345-C, Q345-D, 15MnNbR, 07MnNiCrMoVDR are removed; 4. Minimum sketch bottom plate s thickness and lap width limit between bottom plates are revised; extension limit of sketch bottom plates is adjusted; 5. Liquid level and welded joint coefficient are revised in the formula for calculating shell thickness by fixed-design-point method; 6. Calculation formula for top wind girder section modulus is revised; 7. When fixed-roof oil tank roof and shell use weakly connected structure, the requirements, roof thickness and calculation formula of effective sectional area are revised; support guide support structure form and requirements of supporting cone roof and monolayer spherical latticed shell requirements are added; 8. The requirements by which the floating roof structure design shall comply, limitation of floating roof compartment to meet the tightness requirements, the relevant requirements of peripheral seals and static extracting devices are revised; the relevant requirements of wax scrapers are added; 9. Electrical continuity and static extracting of internal floating roof are revised; the relevant requirements of compartment welding are added; 10. Specification and dimension of nozzle reinforcement plate, flanged connection shell Page 6 of 125

5 1 General Provisions This code is formulated to standardize design of vertical cylindrical welded steel oil tanks and make it advanced in technology, cost-effective, safe and applicable and high quality This code is applicable to design of vertical cylindrical welded steel oil tanks at and close to normal pressure for storing petroleum and petrochemical and other similar liquid but it is not applicable to design of buried tank, tank holding extremely and highly hazardous medium and artificial refrigerant fluid tank Design of vertical cylindrical welded steel oil tanks shall comply with not only this code but the current relevant national standards. 2 Terms Annular/sketch bottom plates The outermost bottom plates at the lower part of shell plates Annular bottom plates Annular/sketch bottom plates with polygonal or circular inner edge Bottom plates Bottom plates except edge plate Fixed roofs Roof around which shell ends are fixed and connected, mainly including types as follows: 1 Self-supporting cone roof: with circular cone roof and supported only by the shell periphery; 2 Column-supported cone roof: with circular cone roof and supported by shell, girder, column or other structure; 3 Self-supporting dome roof: with spherical roof and supported only by the shell periphery Floating roofs Roof which lifts with the liquid level, including external floating roof, in an open-top oil tank and internal floating roof, in fixed-roof oil tank. Generally, the floating roof tank refers to external floating roof tank if not specified. There are major floating roofs as follows: 1 Single-deck floating roof: with annular seal cabin around floating roof and single deck in the middle; 2 Double-deck floating roof: entire floating roof is composed of compartments; 3 Open-top bulk-headed floating roof: with annular open-top compartments around the floating roofs and single deck in the middle and this type is only applicable to internal floating roof; 4 Floating roof on floats: plates keep clear of the liquid level, being floated by the float, only applicable to internal floating roof Design pressure Maximum pressure set at the gas phase room on top of tank (gauge pressure, the same Page 8 of 125

6 below) shall not be less than the maximum operating pressure likely to be present in normal use Metal temperature Average temperature of shell plates and pressure components along section thickness Design temperature Metal temperature of shell plates and pressure components given under the normal operation of tanks Calculated thickness Thickness obtained by calculation according to the formulae specified in this code Design thickness The sum of calculation thickness and corrosion allowance Nominal thickness Design thickness with tolerance, which is rounded up to standard thickness of materials Available thickness Nominal thickness minus additional thickness Wind girder Members arranged on the shell to make it stronger to resist wind Stiffening ring Members arranged on the shell to enhance the stability of tank shell and protect it against instability Rolling ladder Walkway which connects shell roof platform and floating roof and lifts with the floating roof Automatic bleeder vent Venting device which opens/closes automatically when the floating roof rises or is restored to bracing state Primary roof drains Equipment which drains the rainwater on external floating roof out of the tank under normal conditions Emergency roof drains Safety devices which discharge excessive seeper on external floating roof in emergency circumstances Circulation vent Venting device which is arranged on the internal floating roof tank shell or fixed roof in a circular manner. 3 Basic Requirement For the atmospheric pressure tank at fixed roof, the negative pressure is designed to be 0.25kPa or less and the lifting force generated from positive pressure shall not exceed the total weight of roof plate and the appurtenances thereon; if as specified in Appendix A of this code, the maximum design pressure may be increased to 18kPa; if as specified in Appendix B of this code, the maximum design negative pressure may be increased to 6.9kPa. The Page 9 of 125

7 Fertilizer Equipment Allowable stress value of seamless steel pipe shall be selected in accordance with Table Table Allowable Stress of Seamless Steel Pipe No. Grade Wall thickness (mm) Room temperature strength index Allowable stress under the following temperatures ( ) MPa R m (MPa) R el (MPa) Q345C Q345D Mn Note: Allowable stress of medium temperature may be calculated by linear interpolation The materials in Table of this code shall meet the following requirements: 1 The chemical composition of 10#, 20# and 16Mn steel pipes, as specified in the current national standard GB 6479 Seamless Steel Tubes for High-Pressure for Chemical Fertilizer Equipment shall be such to make S be % or below; 2 If the design temperature is less than -20, chemical composition of 16Mn steel pipe shall be such to make P be 0.025% or below and S be 0.012% or below The shell opening uses the steel pipes having outer diameter not less than 70mm and wall thickness greater than 10mm, and the steel pipes shall be sampled batch by batch according to the lower allowable temperature limit in Table of this code for Charpy V-notch impact test and shall meet the following requirements: 1 For steel pipes selected from the current national standard GB 6479 Seamless Steel Tubes for High-Pressure for Chemical Fertilizer Equipment, 10# and 20# steel pipes shall be respectively subjected to -10 and 0 impact tests and three longitudinal standard samples shall have an average impact power of 31J or larger; the 16Mn steel pipe shall be subjected to -20 impact test when design temperature is greater than or equal to -20 while it shall be subjected to -40 impact test when the design temperature is less than -20 and three longitudinal standard samples shall have an average impact power of 34J or larger. 2 10# and 20# steel pipes, selected from the current national standard GB 9948 Seamless Steel Tubes for Petroleum Cracking, shall be subjected to -20 and -10 impact tests respectively; three longitudinal standard samples shall have an average impact power of 31J or larger Roof nozzle steel pipe shall meet the requirements of the current national standard GB/T 8163 Seamless Steel Tubes for Liquid Service Steel pipes for tank ladder, platform and other steel structure shall meet the requirements of the current national standard GB/T 3091 Welded Steel Pipes for Low Pressure Liquid Delivery. 4.4 Forgings Page 15 of 125

8 Table Thickness of Annular Edge Plate Thickness of annular edge plate (mm) Nominal thickness of bottom ring shell Lower limit of standard yield strength of bottom ring shell plate (MPa) plate (mm) 390 > ~ ~ ~ ~ ~ ~ l Size of annular edge plate shall meet the following requirements when measure horizontally along the tank radius: 1 Minimum radial clearance of connecting weld from inner surface of shell to edge plate and center plate shall not be less than the calculated value by the following formula and shall not be less than 600mm; L m 215t w b H (5.1.3) L m the minimum radial distance between inner surface of shell to the attachment weld of annular edge plate and center plate, mm; t b the nominal thickness of annular bottom plates (excluding corrosion allowance) mm; H w the design liquid level, m; ρ the relative density of storage liquid. 2 The radial distance between external surface of bottom ring shell and outer edge of edge plate shall not be less than 50mm and should not be greater than 100mm. 3 As for the seismic precaution tank and tank with ring beam foundation, the annular edge plate should be provided with increased radial dimension. 5.2 Bottom Structure If the tank is less than 12.5m for the inner diameter, the bottom may not be provided with annular edge plate; if the tank is greater than or equal to 12.5m for the inner diameter, the bottom should be provided with annular edge plate (Figure 5.2.1). Page 19 of 125

9 additional thickness available for shell, the additional thickness shall be deducted in calculation The design of the intermediate wind girder shall meet the following requirements: 1 As for the fixed-roof oil tank, the stable check interval for wind force shall cover the full height of shell; as for open-top oil tank, the above interval shall cover shell under the top wind girder. 2 Allowable critical pressure for shell cylinder at the check interval shall be calculated according to the following formula: P cr H E = H ei 2.5 D tmin ( ) H E D H ei t hi ti min ( ) [P cr ] the allowable critical pressure for shell cylinder at the check interval, kpa; H E the equivalent height of shell cylinder at check interval, m; t min the available thickness of the thinnest ring of tank shell plate within check interval, mm; t i the available thickness of the i th ring of tank shell plate, mm; h i the actual height of the i th ring of tank shell plate, m; H ei the equivalent height of the i th ring of tank shell plate, m. 3 External design pressure of shell cylinder shall be calculated according to the following formula: As for open floating roof tank: P o =3.375 μ z ω 0 ( ) As for air-connected internal floating roof tank: P o =2.25 μ z ω 0 ( ) As for fixed-roof oil tank with internal pressure: P o =2.25 μ z ω 0 +q ( ) P o the external design pressure of shell cylinder, kpa; ω 0 the reference wind pressure, kpa, valued in accordance with of this code; μ z the height variation coefficient of wind pressure, valued in accordance with of this code; q the design negative vacuum pressure, kpa, which shall not exceed 0.25kPa. 4 The number of intermediate wind girder and its position on the equivalent cylinder shall be arranged in accordance with the following requirements: 1) If [P cr ] P o, the intermediate wind girder may be omitted; 2) If P P o Po cr, one intermediate wind girder shall be arranged at the 1 H E point; Page 27 of 125

10 is a tensile ring when bearing external pressure If weakly connected structure is adopted for roof and shell, the connections shall meet the following requirements: 1 The oil tank, of 15m or less diameter, shall meet the following requirements: 1) Roof gradient at connections shall not be greater than 1/6; 2) Roof's supporting members shall not be connected with roof plate; 3) Consecutive fillet welding is carried out only at outer side for top plate and curb angle and the weld leg size shall not be greater than 5mm and the inner side shall not be welded; 4) The connection structure is only restricted to four conditions as show in Figure 7.1.5(a), (b), (c) and (d) and shall meet the requirements of following formula: A mg t 1415 tan (7.1.6) A the effective cross-section area at roof and shell connection, mm 2 ; m 1 the total mass of tank shell and members supported by shell and tank roof (excluding tank roof plate), kg; θ the included angle between tank roof and horizontal plane at roof and shell connection, ; g the gravity acceleration, taking g=9.81m/s 2. 2 The oil tank, of diameter less than 15m, shall not only meet all the requirements of above and the following requirements: 1) Elastic analysis shall be carried out for confirmation; under the condition of empty tank, the strength at the shell and bottom connection shall not be less than 1.5 times that at the shell and roof connection; under the condition of full tank, the strength at the shell and bottom connection shall not be less than 2.5 times that at the shell and roof connection; 2) The shell-connected appurtenances (including nozzle and manhole) shall be such not to be damaged when the shell moves by 100mm vertically; 3) Bottom plates shall adopt butting structure. 3 The anchored tank shall meet all the requirements of above and in addition, the anchoring and counterweight shall be designed in accordance with three times the roof breakdown pressure The arrangement of venting device of enclosed fixed-roof oil tank shall meet A.2 of this code. 7.2 Allowable Stress of Structural Components Allowable tensile stress shall not be greater than 140MPa Allowable compressive stress shall meet the following requirements: 1 Irrespective of lateral stability of compression rod, it shall not be greater than 140MPa; 2 If lateral stability of compression rod is considered, the allowable compressive stress of compression component shall be calculated in accordance with the following requirements: Page 32 of 125

11 t cr The calculation thickness of roof plate, mm; T the load combination, kpa, determined in accordance with Line e, Table F.0.1; D the inner diameter of oil tank, m; θ the included angle between tank roof and horizontal plane at roof and shell connection, The effective tensile or compressive section area of the roof and shell plate connections shall meet the requirements of the following formula: 2 3 TD 10 A 8 tan (7.3.3) A the effective area determined according to Figure of this code, mm 2 ; [σ] the allowable stress of material, MPa, which shall be 1/1.6 of the lower limit of yield strength under design temperature; T the load combination, kpa, determined in accordance with Line e, Table F.0.1; D the inner diameter of oil tank, m; θ the included angle between tank roof and horizontal plane at roof and shell connection,. 7.4 Column-Supported Cone Roof The roof gradient shall not be less than 1/ Purline is major supporting members of roof, including section steel, steel pipes, welded assembly parts or truss and the allowable stress of the strength and stability calculation shall comply with 7.2 of this code The purline, directly exposed to roof plate, shall be equipped with lateral support under the following conditions: 1 Truss or thin webbed girder assembly purline; 2 Purline of over 380mm high; 3 Purline of roof gradient greater than 1/ The roof support base shall be limited by a guide bracket, and shall not be welded with the bracket. If the roof support is made of steel pipes, the support shall be drilled a vent hole, fluid hole or made into a closed support Structural type of guide bracket (Figure 7.4.5) shall meet the following requirements: 1 The structure shown as Figure 7.4.5(a) may also be used as a sub-plate when the loading plate is 12mm thick or larger and no additional sub-plate will be arranged; 2 The structure shown as Figure (b) and (c) shall be arranged with a sub-plate of 6mm thick or larger; 3 The support shall be able to freely move in a vertical direction along the guide sleeve; 4 The guide sleeve shall not be directly welded with bottom plates. When the relative displacement between the support and bottom plates reaches 75mm, the guide sleeve shall effectively prevent the support from transverse slide along the support. Page 35 of 125

12 beam, the external surface shall be subjected to continuous fillet weld with the leg being 5mm or less; the inner surface shall not be welded. 8 Floating Roof 8.1 General Requirement This chapter is applicable to design of single-deck floating roof and double-deck floating roof and their accessories Structural design of compartment shall not only reach the strength, stability and resistance to sinking but also be convenient for construction and can reduce the welding works in the compartment The floating roof shall not contact with the accessories in the tank when floating between the maximum liquid level and minimum liquid level; the sparkless materials shall be used if elements need rubbing each other All the metal components of floating roof shall be electrically connected and the movable cover plate, if equipped with opening on the floating roof, shall be electrically connected with floating roof When the floating roof is floating, its lower surface shall be in full contact with the stock solution Floating roof shall meet the following requirements for buoyancy calculation: 1 When stock solution's density is greater than or equal to 700kg/m 3, subject to 700kg/m 3 ; 2 When stock solution's density is less than 700kg/m 3, calculate it in accordance with actual density; 3 In the design of single-deck installation height, subject to the actual stock solution density The structural design of single-deck floating roof shall meet the following requirements: 1 When the drain pipe fails, the floating roof shall be able to bear 250mm of rainfall within 24h without sinking; 2 If the floating roof has no rain loads and live loads, it shall be able to float on the liquid surface without sinking when the single-deck plate and any two compartments are leaking simultaneously; 3 Under the two cases, the floating roof shall not have strength or stability damaged The structural design of double-deck floating roof shall meet the following requirements: 1 If drain pipe fails, the floating roof shall not be submersed when bearing 250mm rainfall within 24h; if the floating roof is equipped with emergency drain facilities, the above limitation may be ignored, but the drainage capacity of such facilities shall enable the floating roof to maintain accumulated water whose load is less than the permissible load by the design. 2 If the floating roof has no rain loads and live loads, it shall be able to float on the Page 38 of 125

13 liquid surface without sinking when any two compartments are leaking simultaneously. 3 Under the two cases, the floating roof shall not have strength or stability damaged If diameter of holes in floating roof is greater than 80mm, the reinforcement shall be carried out. 8.2 Structure and Connection of Floating Roof For top plate and bottom plate of compartments and single-deck plate, the nominal thickness shall not be less than 5mm and the actual overlap width shall not be less than 25mm; the compartments' top plate shall be provided with drainage slope of 15/1000 or more and the drainage slope of outermost circle of top plate shall point to center of floating roof For the bottom plate and top plate of compartments and single-deck plate, the consecutive full fillet weld shall be adopted for the upper surface of lap weld and intermittent weld may be adopted at the lower surface; consecutive full fillet welding shall be adopted inside and outside the lap weld within the range of 300mm around support and other larger rigid members All the compartments of single-deck floating roof shall be in accordance with air-tightness requirements. The number of sealing compartments of double-deck floating roof shall be in accordance with of this code and outermost circle of compartments shall be sealed as a minimum and the sealed ones shall be in accordance with air-tightness requirements; the rest compartments shall use continuous weld at one surface as a minimum besides connecting weld between ring plate and top plate and partition and top plate Continuous welding by both sides shall be adopted between outer edge plate and floating roof bottom plate Full penetration butt weld shall be adopted within compartments and for outer annular plate. 8.3 Floating Roof Supports Floating roof supports shall be able to bear floating roof weight and 1.2kPa evenly-distributed additional loads For floating roof supports, its minimum installation height shall realize construction and maintenance and its slenderness ratio shall not be greater than 150; outer edge bottom of floating roof should not be distanced by 1.8m or less from upper surface of tank bottom in a vertical manner The support sleeve shall be extended out of the upper surface of floating roof which is higher than liquid level of floating roof at the permissible water accumulation and shall not enable the stock solution to overflow on floating roof. The support sleeve shall be immerged into the stock solution by 100mm or more The support shall be locally reinforced when passing through the floating roof At the bottom plates in contact with the support shall be arranged with a sub-plate which is 5mm or thicker and 500mm or more in diameter. The sub-plate shall be treated into continuous fillet weld with the bottom plates at the periphery Upper end of support made of steel pipes shall be blind; the lower end of support shall Page 39 of 125

14 during rubbing or crash When the rolling ladder is located at the lowest position and highest position, the track must have sufficient length at both ends. The track shall be able to prevent the roller wheel from deorbit Rolling ladder track shall be provided with sufficient rigidity and supported by a proper height. 8.7 Automatic Bleeder Vents The floating roof shall be installed with automatic bleeder vent whose quantity and flow area shall be dependent on the maximum flow of oil; when the floating roof is supported, the bleeder vent shall be opened itself; when the floating roof is floating, the bleeder vent shall be able to be closed itself and well-sealed Automatic bleeder vent cover shall be such opened to make the flow area between vent cover and body higher than that formed by vent diameter. The steel pipe valve stem shall be blind at both ends or blind on the upper end and opened a gap to remove liquid loading at the lower end If two parts rub, at least one of them shall be made of spark-free material during the rubbing. 8.8 Guiding Devices Floating roof shall be arranged with guiding devices to keep it at center position and prevent from rotation Guiding device should adopt rolling friction Floating roof shall be arranged with limit function apparatus at the outer edge. 8.9 Peripheral Seals and Static Extracting Devices Sealing device shall be peripherally installed between floating roof and shell and able to keep good sealing effect when the periphery between edge plate and shell is radially deviated from ±100mm Primary sealing should adopt the following types: 1 Flexible foam; 2 Filling pipe; 3 Mechanical type During mechanical steel slide sealing, the slide shall be inserted into liquid level by more than 100mm when the floating roof is floating; the slide should be made of 1.5mm ~ 2mm zinced sheet or 1.0mm ~ 1.5mm stainless steel sheet. Slide and floating roof shall be connected by the soft copper cable whose sectional area is not less than 10mm 2 and the spacing apart from the inner-wall should not be greater than 3m When nonmetallic material soft-seal is used as primary sealing, immersion liquid should be adopted Floating roof and shell shall be connected by at least two soft copper cables whose Page 41 of 125

15 9.2.2 Compartments of single-deck and double-deck internal floating roof shall be arranged with manholes For the bottom plate and top plate of compartments and single-deck plate, the consecutive full fillet weld shall be adopted for the upper surface of lap weld and intermittent weld may be adopted at the lower surface; consecutive full fillet welding shall be adopted inside and outside the lap weld within the range of 300mm around support and other larger rigid members Continuous welding by both sides shall be adopted between outer edge plate and floating roof bottom plate Compartment weld of open-top bulk-headed internal floating roof shall meet tightness requirements; All the compartments of single-deck floating roof shall be in accordance with air-tightness requirements. The number of sealing compartments of double-deck floating roof shall be in accordance with design requirements of internal floating roof and outermost circle of compartments shall be sealed as a minimum and the sealed ones shall be in accordance with air-tightness requirements; the rest compartments shall use continuous weld at one surface as a minimum besides connecting weld between ring plate and top plate and partition and top plate. 9.3 Internal Floating Roof on Floats Buoyancy elements of internal floating roof shall meet tightness requirements Internal floating roof shall be still able to float on the liquid surface and not to generate additional hazards after any two buoys leak For the internal floating roof, the outer edge plate and all the nozzles through floating deck shall be immerged into the stock solution by 100mm or deeper. 9.4 Internal Floating Roof Supports Internal floating roof shall be arranged with fixed or regulable floating roof supports. When the internal floating roof is located at the lowest support height, the floating roof and appurtenance thereunder shall not crash each other; when the floating roof is located at the highest design liquid level, the support shall not crash with the fixed roof When the internal floating roof is not provided with draining device or other measures to prevent the gathering of stock solution, the internal floating roof supports shall be able to support the deadweight of floating roof and 0.6 KPa evenly-distributed additional loads The upper end of support shall be sealed and the lower end shall be blind or opened a vent hole At the bottom plates in contact with the support shall be arranged with a sub-plate which is 5mm or thicker and 500mm or more in diameter. The sub-plate shall be treated into continuous fillet weld with the bottom plates at the periphery. 9.5 Peripheral Seals Sealing device shall be arranged at the periphery between outer edge of internal Page 44 of 125

16 9.8 High Liquid Level Protection Internal floating roof tanks should be arranged with high liquid level alarm or long overflow orifice When long overflow orifice is used, the dimension of overflow orifice shall be dependent on the maximum feeding speed of tank; if the oil tanks leak, the floating roof and other appurtenances shall not be damaged The floating roof shall be sealed such not to influence the normal action of liquid level indicating device and overflow orifice. 9.9 Guiding Devices Internal floating roof shall be arranged with guiding device which may use steel pipe, cable or other suitable mechanism Guiding device shall be well sealed when passing through floating roof Manhole and Inspection Hatches Fixed roof and internal floating roof of internal floating roof tanks shall be each arranged with one manhole with inner diameter not less than 600mm Shell shall be arranged with one low-position manhole and one high-position manhole whose inner diameter shall not be less than 600mm. The high-position manhole shall be above maximum bracing height of internal floating roof and shall not interfere with the operation of floating roof. The low-position manhole shall be below the minimum bracing height of internal floating roof and be convenient for the access of personal Fixed roof should be arranged with visual inspection hatches whose maximum spacing shall not be greater than 20m and which shall be evenly-distributed along periphery and shall not be less than 4. When the circulation vents are arranged on the tank roof, they can be used also as inspection hatches. 10 Appurtenances 10.1 General Requirement The design of opening appurtenances and their connection with tank body shall meet the requirements of this chapter The nozzles bearing relatively large additional loads of external pipeline or equipment shall not only meet the requirements of this chapter, but also be provided with measures to reduce part additional loads. The loads for pipeline connected with tank body shall not exceed the permissible external load of shell opening specified in Appendix J of this code The materials of shell opening reinforcement plate shall be the same as those of shell plate at opening. The materials of nozzle should be the same as or similar with those of shell Page 46 of 125

17 at the edges In case the distance between any two openings fails to meet the requirements of in this code, the joint reinforcement shall be adopted and shall meet the following requirements: 1 The joint reinforcement plate shall be capable of covering the reinforcement plate in case of separate setting for each opening, and shall be with smooth outer edges; 2 In case the vertical center line of any opening intersects with other openings, the effective reinforcement area along of vertical center line of joint reinforcement plate shall not be less than the total of reinforcement area in case of separate opening for each opening In case the distance from outer edge of fillet weld for shell openings (outer edge of fillet weld for reinforcement plate if equipped with reinforcement plate) to center line of shell longitudinal and circumferential welds shall be: 1 No less than 150mm from the longitudinal weld as well as no less than 2.5 times the nominal thickness of wall-board and no less than 75mm from the circumferential weld in case the shell thickness is no greater than 12mm or the nozzle and shell plates are subjected to stress relief heat treatment after welding. 2 Greater than 8 times the relatively large weld leg size and no less than 250mm in case the shell thickness is greater than 12mm or the nozzle and shell plates are not subjected to stress relief heat treatment after welding The distance from shell opening to shell bottom shall meet the following requirements: 1 In case the lower limit of standard yield strength of shell plates is less than or equal to 390MPa, the shell manhole shall meet those specified in 10.3 of this Code; the shell opening shall meet those specified in 10.4 of this Code. 2 In case the lower limit of standard yield strength of shell plates is greater than 390MPa, the distance from outer edge of fillet weld for shell opening (outer edge of fillet weld for reinforcement plate if equipped with reinforcement plate) to outer edge of fillet weld at shell bottom shall not be less than 2.5 times the nominal thickness of wall-board and shall not be less than 75mm The shell nozzle, shell plates and reinforcement plates, after being welded and qualified through inspection, shall be subjected to overall stress relief heat treatment under the following conditions: 1 The lower limit of standard yield strength is less than or equal to 390MPa, the plate thickness is greater than 32mm and the nominal diameter of nozzle is greater than 300mm; 2 The lower limit of standard yield strength is greater than 390MPa, the plate thickness is greater than 12mm and the nominal diameter of nozzle is greater than 50mm; 3 16MnDR with the plate thickness greater than 25mm Shell Manholes The dimension of shell manhole (Figure ) flange cover, flange and reinforcement plate should meet those specified in Table Page 48 of 125

18 2 The lift angle of spiral stairway should be 45 and the maximum lift angle shall not exceed 50 ; the lift angle of spiral stairways in same tank field should be the same; 3 The width of stairstep shall not be less than 200mm; 4 The sum of horizontal distance between two adjacent stairsteps and 2 times the height between two stairsteps shall be no less than 600mm and no greater than 660mm; the height among stairsteps of the whole spiral stairway shall keep consistent; 5 The grid plate or tread plate shall be used for the stairstep; 6 Outside of the spiral stairway must be arranged with hand rails; in case the distance between inside of spiral stairway and shell is greater than 150mm, inside must also be arranged with hand rails; 7 The upper hand rails of the spiral stairway shall be center-connected with hand rails of the platform; 8 The maximum spacing of rail posts shall be 2400mm if measured along axis of the hand rails; 9 The spiral stairway shall be able to bear 5kN concentrated live load and any point on upper part of hand rails shall be able to bear 1kN concentrated load at any direction; 10 All the spiral stairways shall be supported on the shell, and appropriate distance shall be left between lower end of spiral stairway side plate and upper surface of tank base In case the height of top platform to the ground exceeds 10m, the intermediate rest platform shall be arranged The design of platforms and handrails shall meet the following requirements: 1 The clear width of platform and walkway shall be no less than 650mm. 2 The floor shall adopt grid plate or tread plate. In case tread plates are adopted, the drain holes shall be set. 3 In case the height of platform and walkway to the ground is less than 20m, the height from upper surface of floor plate to top of hand rails shall be no less than 1050mm; in case the height of platform and walkway to the ground is no less than 20m, the height from upper surface of floor plate to top of hand rails shall be no less than 1200mm. 4 The width of foot baffle shall be no less than 75mm. 5 The maximum clearance between floor plate and foot baffle is 6mm. 6 The space between waist supports of hand rails shall not be greater than 500mm. 7 The space between rail posts shall not be greater than 2400mm. 8 The platform and walkway shall be able to bear 5kN concentrated live load and any point on upper part of hand rails shall be able to bear 1kN concentrated load at any direction In case the operations are conducted on fixed roof, the fixed roof must be arranged with hand rails. The anti-slip strip or tread-board shall be arranged on the passage way The wind girder, if used as operating platform and walkway, must be arranged with hand rails around Scaffold Cable Support The scaffold cable support may be arranged for fixed roof oil tank near center of the Page 66 of 125

19 Material substitution shall be agreed by the design unit. The substitute material shall be of same or similar chemical components, mechanical properties, delivery state, surface quality, inspection items and inspection rate as well as dimensional tolerance with substituted material Installation of steel structures of oil tank, such as ladder, platform, wind girder, floating roof and fixed roof, shall be in accordance with relevant requirements of the current national standard GB Code for Acceptance of Construction Quality of Steel Structures The tank shell, edge plate and shell opening with the design temperature below -20 and lower limit of standard yield strength above 390MPa shall not be assembled with force method like hammering or hammered for marks Qualified welding procedure qualification report shall be provided before welding. The welding procedure qualification shall meet relevant requirements of the current professional standard NB/T Welding Procedure Qualification for Pressure Equipment; in case the thickness of single-pass welding is greater than 19mm, the welded joints for each thickness shall be assessed separately Except as above requirements are satisfied, prefabrication, assembling and welding of the oil tank shall also meet relevant requirements of the design document and the current national standard GB Code for Construction and Acceptance of Vertical Cylindrical Steel Welded Storage Tanks Non-destructive Testing and Tests of Welding Seam Testing of tank bottom welding seam shall meet the following requirements: 1 The butt welding seam of bottom edge plates made of steels with the lower limit of standard yield strength greater than 390MPa, after root pass welding is completed, shall be subjected to penetration testing and shall be subjected to penetration testing again or magnetic particle testing after last layer of welding is completed, 2 After the root pass of overlap joint welding seam at overlap section of three layers of bottom steel plates and that of T-shape welding seam of butt joint bottom plates are welded, the penetration testing shall be conducted within the scope of 200mm along three directions; after all welding seams are welded, penetration or magnetic particle testing shall be conducted. 3 For the bottom edge plates with the thickness greater than or equal to 10mm, 300mm at outer end of each butt welding seam shall be subjected to radiographic testing; for the bottom edge plates with the thickness less than10mm, at least one of the welding seams welded by each welder shall be randomly inspected in accordance with above-mentioned method. 4 All the bottom welding seams shall be subjected to leakage test with vacuum tank, and negative pressure of the test shall not be less than 53kPa, if there is no leakage, it will be regarded as qualified The testing of inside fillet weld of bottom ring shell and T joint of bottom plates shall meet the following requirements: 1 In case the thickness of bottom edge plates is greater than or equal to 8mm, the thickness of bottom ring shell plate is greater than or equal to 16mm or for the shell plates and Page 72 of 125

20 bottom plates of any thickness with the lower limit of standard yield strength greater than 390MPa, after welding of the inside and outside fillet welds, the inside fillet weld shall be subjected to magnetic particle or penetration testing; after water filling test of the storage tank, re-testing shall be conducted with the same method; 2 The root weld pass of inside fillet weld, after being welded, shall be subjected to penetration testing in case the steel plates with lower limit of standard yield strength greater than 390MPa are adopted for bottom ring shell and bottom plates The testing of shell welding seam shall meet the following requirements: 1 The testing of shell longitudinal weld shall meet the following requirements: 1) In case the thickness of bottom ring shell plate is less than or equal to 10mm, the radiographic testing [Figure (a)] shall be conducted by randomly taking 300mm from each welding seam; in case the plate thickness is greater than 10mm and less than 25mm, the radiographic testing shall be conducted by randomly taking two 300mm from each welding seam, of which the position of one shall be close to bottom plate [Figure (b)]; in case the plate thickness is greater than or equal to 25mm, each welding seam shall be subjected to 100% radiographic testing [Figure (c)]. 2) In case the thickness of other ring shell plates is less than 25mm, the radiographic testing [Figure (a)] shall be conducted to each plate thickness (may be regarded as same thickness in case the plate thickness difference is no greater than 1mm) welded by each welder by randomly taking 300mm from 3m welding seam welded at first. Without regard to the number of welders, the radiographic testing [Figure (b)] shall be conducted by taking 300mm at any part of each 30m welding seam and its mantissa; in case the plate thickness is greater than or equal to 25mm, each welding seam shall be subjected to 100% radiographic testing [Figure (c)]. 2 The testing of shell circumferential weld shall meet the following requirements: The radiographic testing for each plate thickness (subject to thinner plate thickness) shall be conducted by taking 300mm at any part of 3m welding seam welded at first, thereafter, the radiographic testing [Figure ] for each plate thickness shall be conducted by taking 300mm at any part of 60m welding seam and its mantissa. 3 The testing of T-shape welding seam shall meet the following requirements: 1) In case the plate thickness (subject to thinner plate thickness of T-shape welding seam) is less than or equal to 10mm, the bottom ring shell plate shall meet the requirements of Clause 1 Item 1 in this article, and 25% T-shape welding seam shall be subjected to radiographic testing [Figure (a)]; for other ring shell plates, 25% of the radiographic testing parts shall be located at T-shape welding seam; in case the plate thickness is greater than 10mm, all the T-shape welding seams shall be subjected to radiographic testing. 2) The testing position for T-shape welding seam of shell shall include 300mm of longitudinal and circumferential welds. 4 The testing of welding seams for shell nozzle shall meet the following requirements: 1) The butt welding seam of shell plates where assembly parts of flush-type cleaning hole are located and adjacent shell plates shall be subjected to 100% radiographic testing. 2) The welding seams of openings and reinforcement plates on shell plates with the Page 73 of 125

21 and single-deck plate, the leakage test shall be conducted with vacuum tank, the negative pressure of test shall not be less than 53kPa and held for at least 5S, and if there is no leakage, it will be regarded as qualified. 2 In case the two-side continuous welds are adopted for floating roof bottom plate, the continuous weld of lower part shall be welded after the welding seams of upper part are welded and pass inspection according to the requirements of Clause l in this Article; after all welding seams are welded, the kerosene leakage test shall be adopted to make a test, and if there is no leakage, it will be regarded as qualified. 3 The welding seams of ring plate and division plate for compartment shall be tested with kerosene leakage test. The welding seam of compartment roof shall be subjected to leakage test with vacuum tank or tightness test by means of blowing into compressed air with the pressure of 785Pa compartment by compartment; the pressure stabilization time shall not be less than 5min, if there is no leakage, it will be regarded as qualified. 4 All the compartments with single deck floating roof and compartments with double-deck floating roof and seal structure shall meet air-tightness requirements. 5 In case the vacuum tank cannot be adopted for leakage test due to structural constraint, the kerosene leakage test may be adopted In case the plate thickness is greater than 12mm, ultrasonic time of flight diffraction technique may be adopted The method and acceptance criteria for non-destructive testing of welding seam shall meet the following requirements: 1 The radiographic testing shall be conducted according to those specified in the current professional standard JB/T Nondestructive Testing of Pressure Equipment - Part 2: Radiographic Testing, and the testing technique grade shall not be less than Grade AB; the acceptance level for welding seam of steel shell with the lower limit of standard yield strength greater than 390MPa or carbon steel shell with the thickness no less than 25mm or low alloy steel shell with the thickness no less than 16mm shall be Level II; for others, the acceptance level shall be Level III. 2 The ultrasonic testing shall be conducted according to those specified in the current professional standard JB/T Nondestructive Testing of Pressure Equipment - Part 3: Ultrasonic Testing, and the acceptance level shall be Level II. 3 The magnetic particle testing & penetration testing parts shall be free from any crack and white spot and shall be subjected to defect classification assessment according to those specified in the current professional standards JB/T Nondestructive Testing of Pressure Equipment - Part 4: Magnetic Particle Testing and JB/T Nondestructive Testing of Pressure Equipment - Part 5: Penetrant Testing, and the acceptance level shall be Level II. 4 The ultrasonic time-of-flight diffraction technique (TOFD) shall be conducted according to relevant requirements of the current professional standard JB/T Nondestructive Testing of Pressure Equipment - Part 10: Ultrasonic Time-of-flight Diffraction Technique, and the acceptance level shall be Level II Geometry and Dimension Inspection Geometry dimension and shape of the tank body after assembling and welding shall Page 75 of 125