Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
GB/T 18442 consists of the following seven parts under the general title Static vacuum insulated cryogenic pressure vessels:
——Part 1: General requirements;
——Part 2: Materials;
——Part 3: Design;
——Part 4: Fabrication;
——Part 5: Inspection and testing;
——Part 6: Safety protection;
——Part 7: Rules of pressure strengthening for inner vessels.
This is Part 3 of GB/T 18442.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 18442.3-2011 Static vacuum insulated cryogenic pressure vessel - Part 3: Design, with respect to which, the following main technical changes have been made:
——the normative references are modified;
——two terms and definitions, i.e., calculation pressure and sealing-off vacuum degree are deleted; six terms and definitions, i.e., effective volume, filling rate, specified filling rate, holding time, static evaporation rate and sealing-off vacuum degree, are added;
——the general requirements for design are modified according to the requirements of TSG 21;
——the requirements for design documents are added, and specific requirements for the contents of design documents, general design drawing and those to be indicated in pipeline system drawing are proposed;
——the requirements for design loads are modified and the loads are classified according to the load properties;
——the requirements of exemption criteria for fatigue analysis are modified;
——the requirements for allowable stress of materials are modified; the allowable stress or design stress intensity of corresponding materials are respectively specified by adopting overall design, overall design analysis and stress analysis of local structure; for nonmetallic materials, the safety coefficient for determining the allowable stress of materials is specified;
——the design temperatures of inner vessel and outer jacket are modified;
——the requirements for minimum design metal temperature are added;
——the requirements for design pressure of the inner vessel under external pressure are modified;
——the requirements for outer jacket under internal pressure are modified;
——the requirements for corrosion allowance are modified;
——the requirements for tank thickness are added, and the negative deviation of steel in Edition 2011 is canceled;
——the requirements for filling rate are modified, and the principles for determining the maximum filling rate, specified filling rate and initial filling rate are proposed;
—— the indexes such as static evaporation rate, leakage rate of vacuum annular space, outgassing and leakage rate of vacuum annular space and sealing-off vacuum degree of cryogenic vessels with high vacuum multilayer insulation are modified, the static evaporation rate index of liquefied natural gas (methane) is added, and the requirement that the sealing-off vacuum degree in Table 5 is recommended in Edition 2011 is canceled;
——the requirements for tank leakage test are added;
——the arrangement requirements for adsorbent in vacuum annular space are modified;
——the design requirements for tank are modified.
——the design requirements for welded structure are added;
——the design requirements for annular space bracing and tank support are modified;
——the design requirements for the connection between structural parts and the tank are added;
——the design requirements for insulation are modified;
——the design requirements for pressure build coils are modified;
——the design requirements for vaporizer are added;
——the design requirements for pipeline system are modified; the requirements for design pressure and test pressure of external pipeline are added;
——Annex A "Risk assessment report" is added.
This part was proposed by and is under the jurisdiction of the National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China (SAC/TC 262).
The previous editions of this part are as follows:
——GB/T 18442.3-2011;
——GB 18442-2001.
Static vacuum insulated cryogenic pressure vessels - Part 3: Design
1 Scope
This part of GB/T 18442 specifies the basic requirements such as design documents, design parameters, performance parameters and structural design for the design of static vacuum insulated cryogenic pressure vessels (hereinafter referred to as "cryogenic vessels").
This part is applicable to cryogenic vessels that simultaneously meet the following conditions:
a) cryogenic vessel with the working pressure of inner vessel not less than 0.1MPa;
b) cryogenic vessel with the geometric volume not less than 1m3;
c) cryogenic vessel with the insulation mode of vacuum powder insulation, vacuum composite insulation or high vacuum multilayer insulation;
d) cryogenic vessel storing refrigerated liquefied gas contents with standard boiling point not lower than -196℃.
This part is not applicable to cryogenic vessels that meet the following conditions:
a) cryogenic vessel with the inner vessel and outer jacket made of non-ferrous metal or non-metallic materials;
b) cryogenic vessel with spherical structure;
c) cryogenic vessel with stacked insulation;
d) transportable cryogenic vessel;
e) cryogenic vessel storing refrigerated liquefied gas contents with standard boiling point lower than -196℃;
f) cryogenic vessel storing toxic gas as specified in GB 12268;
g) cryogenic vessel with special requirements such as national defense military equipment.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 150-2011
(All parts) Pressure vessels
GB/T 1448 Fiber-reinforced plastics composites - Determination of compressive properties
GB/T 1450.1 Fiber-reinforced plastics composites - Determination of interlaminar strength
GB/T 9341 Plastics - Determination of flexural properties
GB/T 18442.1 Static vacuum insulated cryogenic pressure vessels - Part 1: General requirements
GB/T 20801.3-2006 Pressure piping code - Industrial piping - Part 3: Design and calculation
GB/T 20801.5 Pressure piping code - Industrial piping - Part 5: Inspection and testing
GB/T 24511 Stainless steel and heat resisting steel plate, sheet and strip for pressure equipments
GB/T 26929 Terminology for pressure vessels
GB/T 31481 Guidance for gas/materials compatibility of cryogenic vessels
HG/T 21574 Standard for design and selection of chemical equipment lifting lugs
BJ 4732 Steel pressure vessels - Design by analysis
NB/T 47041 Vertical vessels supported by skirt
NB/T 47065.1 Vessel supports - Part 1: Saddle support
NB/T 47065.2 Vessel supports - Part 2: Leg support
NB/T 47065.4 Vessel supports - Part 4: Bracket support
TSG 21 Supervision regulation on safety technology for stationary pressure vessel
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 150, GB/T 18442.1 and GB/T 26929 as well as the following apply.
3.1
effective volume
maximum liquid volume of refrigerated liquefied gas that is allowed to be filled in a cryogenic vessel in use
3.2
filling rate
ratio of the liquid volume of the refrigerated liquefied gas filled in a cryogenic vessel to the geometric volume of the inner vessel
3.3
specified filling rate
ratio of the liquid volume to the geometric volume of the inner vessel where the filled liquid volume reaches the highest liquid level specified in the design during cryogenic vessel filling
3.4
holding time
time taken for the inner vessel to rise from the ambient atmospheric pressure to the set pressure of the safety discharge device when replenishing liquid to the specified filling rate after the internal refrigerated liquefied gas reaches thermal equilibrium with the external ambient temperature under atmospheric pressure and then closing the gas valve, where the refrigerated liquefied gas is filled according to the specified filling rate; it is converted into the time under the standard atmospheric pressure (1.013 25×105Pa) at the set ambient temperature (20℃)
Note: the unit is hour (h).
3.5
static evaporation rate
percentage of the mass loss of refrigerated liquefied gas due to natural evaporation within 24h after the cryogenic vessel is kept still to reach thermal equilibrium under the specified filling rate to the mass of refrigerated liquefied gas under the effective volume of the inner vessel, which is converted into the evaporation rate under the standard atmospheric pressure (1.013 25×105Pa) at set ambient temperature (20℃)
3.6
annular space vacuum degree
absolute pressure of gas in annular space of cryogenic vessel
3.7
sealing-off vacuum degree
vacuum degree where the pressure of the vacuum annular space is relatively stable at normal temperature after vacuumizing the tank annular space and closing the vacuumizing interface
3.8
leakage rate of vacuum annular space
amount of gas leaking into the vacuum annular space in unit time
3.9
outgassing rate of vacuum annular space
amount of gas released by the material in vacuum annular space, the vessel wall surface, etc. in unit time
3.10
outgassing and leakage rate of vacuum annular space
sum of leakage rate of vacuum annular space and outgassing rate of vacuum annular space
4 General requirements
4.1 The design of cryogenic vessels shall not only meet the requirements of this part, but also comply those specified in TSG 21 and GB/T 150.3.
4.2 The design unit shall, in strict accordance with the design conditions of the cryogenic vessel provided by the design entrusting party, comprehensively consider all relevant factors, failure modes and sufficient safety allowance to ensure that the cryogenic vessel has sufficient strength, rigidity, stability and corrosion resistance. Meanwhile, the strength requirements for welded joints between the main stressed members such as annular space bracings, supports and lifting lugs of cryogenic vessels and the tanks shall be considered to ensure the safety of cryogenic vessels within the design service life.
4.3 The arrangement of tanks, pipelines, safety accessories, instruments and handling accessories shall meet the requirements of use and safety.
4.4 The basic contents of the risk assessment report shall meet the requirements of Annex A. See Annex B for thermodynamic data of common refrigerated liquefied gases.
5 Design documents
5.1 The design documents of cryogenic vessels shall at least include the following items:
a) risk assessment report, including the main failure modes and risk control at the design, fabrication and use stages;
b) design specifications, including the main physical and chemical properties (number, name, category and saturated vapor pressure and density corresponding to the working temperature, etc.) and hazardous characteristics of filling contents, content limits for restricted components and harmful impurities of the mixed contents, the compatibility with tank materials; moreover, the selection of design specifications and standards, principles for determination of main design structures and main design parameters as well as the selection of materials, safety accessories, instruments, handling accessories and pressure build coils shall also be included;
c) design calculation sheet, including the calculation of tank strength, rigidity, external pressure stability, structural strength stress analysis report (where necessary), volume, heat transfer, safe discharge volume and capacity of overpressure capacity device as well as the strength calculation of annular space bracing and tank support, etc.;
d) design drawings, at least including general drawing, inner vessel drawing, pipeline system drawing and flow chart, etc.; the basic condition drawing for cryogenic vessel shall also be provided where necessary;
e) technical conditions for fabrication, including main fabrication process requirements, inspection and test methods, etc.;
f) instructions for installation, use and maintenance, including main technical performance parameters, characteristics of filled contents, specifications and connection methods of safety accessories, instruments and handling accessories, operation instructions, maintenance instructions, precautions for use, necessary warnings and emergency measures.
5.2 The general design drawing shall at least cover the following information:
a) product name, model, vessel type, safety technical specifications and product standards for design and fabrication;
b) working conditions, including working pressure, working temperature and content characteristics (toxicity, explosion hazard degree, oxidation, etc.);
c) design conditions, including design temperature, minimum design metal temperature, design load (including pressure load and other loads to be considered), contents (composition), welded joint coefficient, corrosion allowance, natural conditions (ambient temperature, seismic fortification intensity, basic wind pressure or wind speed, basic snow pressure, etc.), and the limited content of corrosion contents shall also be indicated for those vulnerable to stress corrosion;
d) designations and standards of materials for main pressure elements, outer jackets and pipelines of inner vessels;
e) main characteristic parameters, including the geometric volume of the inner vessel of the cryogenic vessel, specified filling rate, geometric volume of annular space, dead weight of the cryogenic vessel and the weight of contents, etc.;
f) the required thickness, nominal thickness and minimum forming thickness of the seal head and cylinder of inner vessel, and the nominal thickness and minimum forming thickness of the seal head and cylinder of outer jacket;
g) overall dimensions;
h) design service life of the cryogenic vessel;
i) requirements for pressure test and leakage test;
j) fabrication requirements, including non-destructive testing requirements, heat treatment requirements (where necessary), surface cleaning and treatment requirements, nitrogen or inert gas replacement requirements, outer jacket surface treatment and coating requirements, etc.;
k) tank insulation mode, vacuum insulation performance index and annular space vacuum performance index, etc.;
l) specifications, performance parameters and connection methods of tank safety accessories, instruments and handling accessories;
m) nozzle orientation, specifications, connecting flange standards, etc.;
n) position of product nameplate;
o) packaging, transportation and installation requirements.
5.3 The pipeline system drawing shall at least cover the following information:
a) standards for the design and fabrication of pipeline system;
b) design parameters, including design temperature, design pressure, welded joint coefficient, etc.;
c) designations, standard numbers, specifications, etc. of materials for the pressure elements of pipelines;
d) models, specifications, performance parameters, connection methods, nozzle orientation, etc. of safety accessories (including pipeline overpressure discharge devices), instruments and handling accessories;
e) requirements for non-destructive testing;
f) requirements for pressure test;
g) requirements for leakage test.
6 Loads
6.1 General requirements
The cryogenic vessels shall be able to withstand mechanical loads (including pressure load, gravity load, inertia force load and dynamic load) and thermal stress load under various conditions that may occur during normal operation and empty tank transportation, and the most severe combination of these loads shall be considered. The structural fatigue failure due to pressure fluctuation, etc. of the inner vessel within the design service life shall also be considered at the same time.
6.2 Design loads of inner vessel
6.2.1 The following pressure loads shall be considered:
a) the internal pressure, external pressure or maximum differential pressure;
b) the static pressure of liquid column generated by the content filled to the specified filling rate, which is calculated according to the density of content at the boiling point at standard atmospheric pressure.
6.2.2 The following gravity loads shall be considered:
a) the dead weight of inner vessel and the gravity loads of the accessories attached thereto, such as insulation materials and annular space pipelines;
b) the gravity load of content contained in the inner vessel under normal working conditions or pressure test conditions.
6.2.3 The dynamic loads caused by the followings shall be considered:
a) the impact force of liquid flow on the inner vessel where filled with liquid;
b) the impact load caused by sharp fluctuation of content pressure;
c) the seismic load.
6.2.4 For the thermal stress load, at least the uneven strain load caused by temperature gradient and the pipeline reactive force caused by thermal expansion or cold contraction of the inner vessel and annular space pipeline under the following conditions shall be considered:
a) the load borne by the inner vessel at the bracing point during the cooling from the ambient temperature to the working temperature.
b) the reactive force applied to the inner vessel by the pipeline due to thermal expansion or cold contraction of the inner vessel and annular space pipeline, and at least the following three conditions shall be considered:
1) pre-cooling condition: the inner vessel and the outer jacket are in hot state, but the annular space pipeline is in cold state;
2) filling and discharging conditions: the inner vessel and the annular space pipeline are in cold state, but the outer jacket is in hot state;
3) liquid storage condition: the annular space pipeline and the outer jacket are in hot state, but the inner vessel is in cold state.
c) where the annular space is heated and vacuumized during tank fabrication , since the inner vessel and the outer jacket are at different temperatures, the loads at the following joints shall be considered:
1) the thermal stress load of inner vessel at the bracing point;
2) the thermal stress load applied by annular space pipeline to the joint of inner vessel.
6.2.5 During the empty tank transportation, the inertia force load borne by the annular space bracing structure is converted into equivalent static force according to the following requirements, with the maximum mass being the sum of the mass of inner vessel and its accessories:
a) direction of motion: maximum mass multiplied by twice of gravitational acceleration;
b) horizontal direction perpendicular to the direction of motion: maximum mass multiplied by gravitational acceleration;
c) vertically upward: maximum mass multiplied by gravitational acceleration;
d) vertically downward: maximum mass multiplied by twice of gravitational acceleration.
6.3 Design loads of outer jacket
6.3.1 For the pressure load, loads caused by internal pressure or external pressure shall be considered.
6.3.2 The gravity load (the dead weight of tank and accessories such as external pipelines, ladders and platforms) borne by the tank support under normal working conditions and that of contents contained in the inner vessel under normal working conditions or test conditions shall be considered. The supporting counterforce borne by the outer jacket at the joint with the support is equal to the gravity load borne by the support.
6.3.3 For the thermal stress load, the load applied to the outer jacket by the annular space pipeline under the conditions of b) and c) in 6.2.4 shall be considered.
6.3.4 For the inertia force load, at least the loads applied to the outer jacket by the transportation support or lifting lug under the following conditions of a) and b) shall be considered:
a) during empty tank transportation, the inertia force load borne by the cryogenic vessel transportation support is equal to the mass of vessel with empty tank multiplied by the inertia force load coefficients in different directions specified in 6.2.5;
b) during empty tank hoisting, the load coefficient of the inertia force load borne by the lifting lug of tank shall meet the requirements of HG/T 21574;
c) the inertia force borne by the joint between the tank and the transportation support or lifting lug is equal to the supporting counterforce of the transportation support or lifting lug.
6.3.5 Dynamic loads such as wind load, seismic load and snow load shall be considered.
6.3.6 For vertical cryogenic vessels, the load borne by the annular space bracing and the supporting counterforce of the outer jacket at the bracing shall be considered where the tank is in a horizontal position under the fabrication, transportation and hoisting conditions.
6.4 Exemption criteria for fatigue analysis
6.4.1 Fatigue analysis may be exempted where all requirements of any one of 6.4.2, 6.4.3 or 6.4.4 are met. Otherwise, the inner vessel shall be designed for fatigue analysis according to JB 4732.
6.4.2 For inner vessels with number of cycles less than or equal to 106, fatigue analysis may be exempted if the designed cryogenic vessel has comparable shape and load conditions with respect to the cryogenic vessel successfully used, and has been operated for a long enough time and proved by use experience. However, special attention shall be paid to the adverse effects incurred due to the following conditions:
a) the inner vessel is of non-integral structure, such as that the opening is reinforced by reinforcing ring or fillet weld joint is adopted;
b) significant thickness variation is available between adjacent components of the inner vessel;
c) connectors and connecting pipes at the transition area of formed seal head.
6.4.3 Where the inner vessel is made of austenitic stainless steel, the total number of the following cycles shall not exceed 4,000:
a) the expected (design) number of cycles for the full-range pressure cycle including filling and discharging;
b) the expected (design) number of cycles of the working pressure cycle in which the pressure fluctuation range of the inner vessel exceeds 50% of the design pressure;
c) the effective number of metal temperature difference fluctuations between any two adjacent points including pipelines, of which the calculation method meets the relevant requirements of JB 4732;
d) the number of temperature fluctuation cycles of components (including welds) composed of materials with different thermal expansion coefficients in case of (α1-α2)ΔT>0.000 34, wherein, α1 and α2 are the average thermal expansion coefficients of two materials respectively, and ΔT is the temperature fluctuation range during operation.
6.4.4 Where the corresponding exemption conditions for fatigue analysis specified in JB 4732 are met.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Design documents
6 Loads
7 Temperature
8 Pressure
9 Welded joint coefficient
10 Allowable stress
11 Corrosion allowance
12 Tank thickness
13 Filling rate
14 Vacuum insulation performance index
15 Vacuum performance of annular space
16 Pressure test
17 Leakage test
18 Structural design
Annex A (Normative) Risk assessment report
Annex B (Informative) Thermodynamic data of common refrigerated liquefied gases
