GB/T 26978-2021 PDF English (GB/T 26978.1-2011: Older version)
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Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of cryogenic liquefied gas
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Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of liquefied nature gases -- Part 1: General
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GB/T 26978-2021: PDF in English (GBT 26978-2021) GB/T 26978-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 75.060
CCS E 24
Replacing GB/T 26978.1-2011, GB/T 26978.2-2011, GB/T 26978.3-2011,
GB/T 26978.4-2011, GB/T 26978.5-2011
Design and Manufacture of Site Built, Vertical, Cylindrical,
Flat-bottomed Steel Tanks for the Storage of Cryogenic
Liquefied Gas
ISSUED ON: DECEMBER 31, 2021
IMPLEMENTED ON: JULY 1, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 4
Introduction ... 9
1 Scope ... 10
2 Normative References ... 10
3 Terms, Definitions, Symbols and Abbreviations ... 13
3.1 Terms and Definitions ... 13
3.2 Symbols ... 18
3.3 Abbreviations ... 22
4 Basic Stipulations and General Rules ... 24
4.1 Types of Storage Tank ... 24
4.2 Overall Design Basis ... 29
4.3 Protection System ... 35
4.4 Actions ... 37
4.5 Inspection and Maintenance ... 39
4.6 Quality Management, Environmental Management and Occupational Health and
Safety Management ... 39
5 Metal Components ... 40
5.1 General Requirements ... 40
5.2 Materials ... 40
5.3 Design ... 44
5.4 Manufacture ... 67
5.5 Welding Process ... 88
5.6 Welding ... 91
5.7 Inspection ... 93
5.8 Air Pressure Lift ... 100
6 Concrete Components ... 101
6.1 Materials ... 101
6.2 Load Combinations ... 102
6.3 Design Requirements ... 102
6.4 Construction Requirements ... 104
6.5 Lining ... 104
7 Thermal Insulation Components ... 105
7.1 Overview ... 105
7.2 Design, Performance, Testing and Selection of Thermal Insulation Materials ... 105
7.3 Thermal Protection - Vapor Barrier... 110
7.4 Design of Adiabatic System ... 111
7.5 Installation of Adiabatic system ... 119
8 Tests, Drying, Replacement and Cooling ... 121
8.1 Hydrostatic Test and Pneumatic Test ... 121
8.2 Drying, Replacement and Cooling ... 126
8.3 Shutdown ... 127
Appendix A (informative) An Example of the Design of Central Reinforcement Ring
... 129
Appendix B (informative) Loads on the Membrane ... 132
Appendix C (informative) Thermal Insulation Materials ... 133
Appendix D (informative) Test Methods for Thermal Insulation Materials ... 135
Appendix E (informative) Acceptance Inspection of Main Thermal Insulation Materials
... 138
E.1 Pressure-bearing Cellular Glass Bricks of the Tank Bottom ... 138
E.2 Expanded Perlite ... 142
E.3 Glass Wool ... 145
E.4 Elastic Felt ... 145
E.5 Asphalt Felt ... 146
Appendix F (informative) Thermal Insulation of the Bottom of Primary Storage Tank -
-- Limit States Theory ... 147
Appendix G (informative) Construction and Installation of Adiabatic System of Storage
Tank ... 149
G.1 Thermal Insulation Installation of Tank Bottom ... 149
G.2 Thermal Insulation Installation of Annular Space ... 149
G.3 Thermal Insulation Installation of Suspended Deck ... 150
G.4 Thermal Insulation Installation of Cryogenic Pipelines in Tank Headspace ... 151
Bibliography ... 152
Design and Manufacture of Site Built, Vertical, Cylindrical,
Flat-bottomed Steel Tanks for the Storage of Cryogenic
Liquefied Gas
1 Scope
This document specifies the general requirements for the design, manufacture and installation
of site built, above-ground vertical cylindrical flat-bottomed steel primary container storage
tanks (including metal components, concrete components and thermal insulation components,
etc.), and describes the procedures and methods for the tests, drying, replacement and cooling
of the storage tanks.
This document is applicable to the storage of cryogenic liquefied gas with a temperature range
of 165 C ~ 0 C, including cryogenic refrigerated hydrocarbons, such as: liquefied natural
gas (LNG) and cryogenic liquefied petroleum gas (LPG), etc., whose main components are:
methane, ethane, propane, butane, ethylene and propylene, etc.
This document is applicable to storage tanks whose maximum design pressure is not greater
than 50 kPa.
This document does not apply to storage tanks whose primary container is concrete.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in the text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 150.2-2011 Pressure Vessels - Part 2: Materials
GB/T 150.3 Pressure Vessels - Part 3: Design
GB/T 193 General Purpose Metric Screw Threads - General Plan
GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method
GB/T 709-2019 Dimension, Shape, Weight and Tolerance for Hot-rolled Steel Strip, Plate and
Sheet
GB/T 985.1 Recommended Joint Preparation for Gas Welding, Manual Metal Arc Welding,
Gas-shield Arc Welding and Beam Welding
esi: thickness of each circle of shell plate arranged in sequence, expressed in (mm);
est: thickness of the uppermost shell plate, expressed in (mm);
es,t: calculated thickness of shell plate under the hydraulic test conditions, expressed in (mm);
es,1: thickness of bottom ring shell plate, expressed in (mm);
F: acting force, expressed in (N);
fPLDF: allowable load factor for load-bearing thermally insulating materials prone to creepage;
H: highest design liquid level, expressed in (m);
He: equivalent stable height when the thickness of each circle of shell plate is est, expressed in
(m);
Hh: calculated height between the bottom of shell plate and the maximum design liquid level,
expressed in (m);
Hp: maximum permissible distance between reinforcing supports on the shell with the minimum
thickness, expressed in (m);
Ht: calculated height between the bottom of shell plate and the test liquid level, expressed in
(m);
hs: height of each circle of shell plate, expressed in (m);
K: calculated reinforcement ring coefficient;
k: S-N curve coefficient;
L: single allowable minimum value of compressive strength;
Lr: effective roof length, expressed in (mm);
Ls: effective shell length, expressed in (mm);
la: minimum width between the edge of the irregular plate on the outer ring of the tank bottom
and the inner side of the shell plate, expressed in (mm);
m: average value of all test data of fatigue test;
nj: number of longitudinal welded joints of the shell plate in the first circle;
ns: sample size of the sampling batch;
P: design pressure (for the top open inner tank, the design pressure is 0), expressed in (kPa);
Pe: external load, expressed in (kPa);
Pi: internal pressure, which is the sum of internal air pressure and adiabatic system pressure,
expressed in (kPa);
PLD: allowable load for load-bearing thermally insulating materials prone to creepage,
expressed in (MPa);
Pr: internal pressure minus the weight of the top plate, expressed in (kPa);
Pt: hydrostatic test pressure (for the top open inner tank, the design pressure is 0), expressed in
(kPa);
Q: quality statistics of acceptance sampling inspection;
Qe: quality statistics of compressive strength of the sampling batch;
Qt: quality statistics of thermal conductivity of the sampling batch;
R: characteristic strength value of thermal insulation materials, expressed in (MPa);
Rb: radius of the assembly circle inside the first circle of shell plate, expressed in (mm);
Rel: yield strength of steel or weld metal, whichever is smaller, expressed in (MPa);
Rf: final radius of 9% nickel steel plate, expressed in (mm);
Ri: radius of inner tank, expressed in (mm);
Rl: radius of outer tank, expressed in (m);
Rm: lower limit of the standard tensile strength of steel or weld metal, expressed in (MPa);
Rr: radius of curvature of the tank roof (for conical roof, Rr = R/sin θ), expressed in (m);
R0: initial radius of 9% nickel steel plate (for flat plate, it is infinite), expressed in (mm);
S: standard deviation;
SF: safety factor;
s: standard deviation of sampling batches;
U: single allowable maximum value of thermal conductivity;
Va: design internal negative pressure, expressed in (kPa);
Vw: design wind speed, expressed in (m/s);
𝑋: average value;
𝑋e: average value of compressive strength of the sampling batch;
𝑋t: average value of thermal conductivity of the sampling batch;
α: ratio of tensile strength to yield strength Rm/Rel;
αn: horizontal seismic influence coefficient of component n before seismic isolation, which is
calculated through the mode superposition response spectrum method in accordance with the
seismic influence coefficient curve of the site;
αn1: horizontal seismic influence coefficient of component n after seismic isolation;
n: shock absorption coefficient of component n in the horizontal direction, which is the ratio
of the maximum acceleration of component n after seismic isolation to the maximum
acceleration of component n before seismic isolation. The acceleration of the components
before and after seismic isolation shall be calculated through the time-history analysis method
in accordance with the OBE seismic acceleration input, and the parameters of the seismic
isolation support shall be based on the hysteresis curve obtained from the test;
γc: safety factor of cylinder effect;
γF: material partial factor;
γi: safety factor of installation;
γL: safety factor applied to the load;
γM: material strength factor;
γm: safety factor of thermal insulation materials;
γt: a factor, by which, differences may exist between the reference method of testing the thermal
insulation product and its installation method;
ε: strain;
εef: extreme fiber strain, expressed in (%);
ε1: first principal strain;
ε2: second principal strain;
ε3: third principal strain;
η: weld joint coefficient of the weld;
θ: at the roof-shell connection position, the slope angle of the top on the meridian, expressed in
();
ρ: maximum density of the storage medium under operating conditions, expressed in (kg/m3);
c) Inlet and discharge liquids in accordance with the specified flow rate;
d) Control evaporation; under abnormal conditions, the boil-off gas can be discharged
to the flare or atmospheric outlet;
e) Prevent the ingress of air and moisture, except when the vacuum relief valve is in
operation;
f) Evaporation complies with the requirements; the water condensation / frost on the
outer surface of the storage tank is controlled to the minimum extent; frost heaving of
the foundation shall be prevented.
4.2.3 Allowable stress and limit states theory
For the design of steel storage tanks and adiabatic system, the allowable stress theory can be
used, and the limit states theory can also be used.
For the concrete structure design, the limit states theory shall be adopted.
The limit states design shall include:
a) Serviceability limit states (SLS): a certain specified state where a structure or
structural component reaches a certain specified limit or durability performance in
normal use;
b) Ultimate limit states (ULS): a structure or structural component reaches the maximum
bearing capacity and manifests fatigue damage, deformation unsuitable for
continuous bearing, or continuous collapse caused by local damage of the structure.
4.2.4 Seismic design
The structural design under seismic action shall be carried out in accordance with the following
stipulations:
---The primary container shall be designed to withstand the actions of OBE and SSE when
it is filled to the maximum normal operating liquid level;
---If a secondary container is used, it shall be designed in accordance with the capability
of withstanding the actions of OBE and SSE when no liquid is contained in it. In
addition, the secondary container shall also be designed in accordance with the
requirements of being able to contain and store all liquids (maximum normal operating
liquid level) under the action of ALE;
---The membrane of the membrane tank shall be designed to withstand the action of OBE.
Under the action of SSE, membranes may fail, but concrete tanks, including TCP, shall
be able to contain and store liquids.
The seismic response spectrum of OBE and SSE, as well as the response spectrum of horizontal
component and vertical component shall be determined in accordance with the following
stipulations, and shall comply with the relevant stipulations of GB 50011:
a) OBE seismic response spectrum:
It shall be the movement represented by the 5% damped response spectrum with a
probability of exceeding 10% (recurrence interval: 475 a) in the 50 a period.
When the damping value of related structures, structural systems or components is
not equal to 5%, the OBE response spectrum shall be correspondingly adjusted in
accordance with the adjustment coefficient of the seismic influence coefficient curve
of building structures in GB 50011.
The damping value in 7.1.6 of GB 51156-2015 shall be used. The damping value used
for the vertical pulse effect shall be the same as that for the horizontal pulse effect.
b) SSE seismic response spectrum:
It shall be the movement represented by the 5% damped response spectrum with a
probability of exceeding 2% (recurrence interval: 2475 a) in the 50 a period.
If the SSE response spectrum with 5% damping cannot be determined, the spectrum
can be taken as twice the value of the OBE response spectrum not greater than 5%
damping.
When the damping value of related structures, structural systems or components is
not equal to 5%, the SSE response spectrum shall be correspondingly adjusted in
accordance with the adjustment coefficient of the seismic influence coefficient curve
of building structures in GB 50011. The damping value shall be determined through
the following method:
1) The damping value in 7.1.6 of GB 51156-2015 shall be used, and damping value
used for the vertical pulse effect shall be the same as that for the horizontal pulse
effect;
2) Soil-structure interaction: in the transfer (sloshing) mode, the damping
coefficient is basically independent of the tank material and soil-structure
interaction, and shall not be greater than 0.5%.
4.2.5 Tightness
A metal lining or polymer coating shall be applied to the inner wall of the outer tank. Where
polymer vapor barriers are used, their liquid-tightness and air-tightness shall be verified.
The liquid-tightness of the prestressed concrete structure shall be determined by the minimum
pressure zone thickness and residual stress in the concrete structure. The calculation of the crack
width of the concrete part shall comply with the stipulations of GB 50010.
The concrete secondary container, where the rigid foundation wall is connected, can be installed
with TCP to prevent uncontrollable cracks in the foundation wall connection or in the
foundation floor when the primary container leaks. TCP covers the entire tank bottom and the
lower part of the wall. TCP can be composed of steel plates (double bottom plate) and thermal
insulation materials (double and full containment tanks) or liquid isolation layers and thermal
insulation materials (membrane tanks).
The height of the vertical part of TCP depends on the temperature distribution, the deformability
of the rigid corners and the height of the construction opening of the secondary container.
4.2.11.2 Membrane tank
TCP shall be made of metal or non-metal materials compatible with the temperature of the
product. Under the action of mechanical load and temperature load, it shall be able to maintain
the structural integrity and liquid-tightness of the storage tank.
The test results independently witnessed and verified by a third-party institution of the
membrane shall be provided, so as to prove the liquid-tightness of all components of TCP under
leakage conditions.
After the TCP of the membrane tank passes the non-destructive testing and acceptance
inspection, it shall have the equivalent liquid-tightness as the metal TCP of the full-containment
tank.
4.2.12 Cofferdams and impounding basins
The single-containment tank shall be provided with cofferdams. The internal volume of the
cofferdam shall be able to contain the entire product stored in the tank.
The impounding basins and cofferdams shall be designed to be permanently liquid-tight. The
materials used shall be able to prevent product leakage. Consideration shall be given to
measures of draining rainwater and firefighting water that is collected in the impounding basins
and cofferdams when no product liquid is spilled.
4.2.13 Lightning
The lightning design shall comply with the stipulations of GB 50057.
4.3 Protection System
4.3.1 Monitoring protection
4.3.1.1 Monitoring system
The design of liquid level, pressure, temperature monitoring and gas supply system in the
storage tank shall comply with the relevant stipulations of GB 51156-2015.
4.3.1.2 Roll-over prevention system
The following measures of preventing roll-over can be taken:
a) Use a density measurement system to monitor the density distribution of the liquid in
the tank. When a certain set value is exceeded, this system shall have an alarm
function. The density measurement system and the liquid level gauge system shall
operate independently of each other;
b) Between the bottom and roof of the storage tank, an intermittent or continuous liquid
circulation system shall be set.
4.3.1.3 Gas detection and fire alarm
Combustible gas and toxic gas detection and alarm systems, and automatic fire alarm systems
shall be installed.
4.3.1.4 Leakage detection system
A leakage detection system shall be set up, and the composition scheme shall be determined in
accordance with the type of the storage tank:
a) Temperature drop;
b) Gas detection;
c) Differential pressure measurement.
4.3.1.5 Adiabatic space monitoring system
The adiabatic space of the membrane tank is isolated from the membrane, and an adiabatic
space monitoring system shall be installed. The system shall satisfy the following requirements:
a) By analyzing the replacement gas components, detect the boil-off gas of the product;
b) By filling inert gas into the adiabatic gas-phase space, it is ensured that the
concentration of the boil-off gas is maintained below 30% of the lower flammable
limit during normal operation;
c) Control the pressure differential between the adiabatic space and the membrane, so as
to prevent membrane damage, and the system shall be designed to be “fail safe”.
4.3.2 Safety valve and fire protection design
4.3.2.1 Safety valve design
The design of the pressure safety valve and vacuum safety valve of the storage tank shall
comply with the stipulations of GB 51156-2015.
4.3.2.2 Fire protection design
The design basic wind pressure of the storage tank should be taken in accordance with
the wind pressure of the 100 a recurrence interval in GB 50009.
e) Snow load
The design snow load of the storage tank should be taken in accordance with the 100
a recurrence interval in GB 50009.
f) Adiabatic system pressure
The design of both the primary and secondary containers shall take into account the
pressure exerted by the adiabatic system (expanded perlite powder).
g) Internal design pressure
The design range should be 1.0 kPa ~ 29 kPa, which shall be determined in
combination with process design parameters.
h) Settlement load
The design of the storage tank and its foundation shall take into account the maximum
total settlement and uneven settlement of the foundation that may occur within the
design service life.
i) Pipe connection load
It shall be determined in accordance with the pipe materials and displacement
requirements.
j) Construction load
It shall comply with the stipulations of GB 50009.
k) Hydrostatic and pneumatic tests
It shall comply with the stipulations of Chapter 8.
l) Thermal effects
All possible thermal effects during construction, testing, cooling, normal or abnormal
operation and pre-cooling shall be considered.
4.4.4 Occasional actions
4.4.4.1 Leakage of primary container
For storage tanks with secondary container, the secondary container shall be designed in
accordance with the condition of containing and storing the maximum amount of liquid in the
primary container. It shall be assumed that the secondary container is gradually filled. In
addition to the leakage of a large amount of product, the consequences of the leakage of a small
amount of product to “cold spots” shall also be assessed.
4.4.4.2 Leakage of pipe connectors
Consideration shall be given to possible leakage from pipe flanges and valves, and their effect
on the roof or shell, assuming the gasket is damaged.
The design shall consider that the area of possible leakage is in contact with the stored liquid
or protect the area by collecting / discharging the product.
4.4.4.3 Safe shutdown earthquake (SSE)
The storage tank shall be designed to withstand SSE ground motion.
4.4.4.4 Aftershock level earthquake (ALE)
ALE is the aftershock after the safe shutdown earthquake. An earthquake of this magnitude will
not destroy the integrity of the system when it acts again. In accordance with the stipulations of
7.1.4 in GB 51156-2015, the ALE response spectrum acceleration value shall be 50% of the
SSE response spectrum acceleration value. After the SSE action, leakage accidents may occur
in the primary container, but the secondary container or the surrounding impounding system
shall be kept intact, and during aftershocks, the liquid product in the storage tank shall be able
to be contained.
4.4.4.5 External fires and explosions
Loads shall be determined through the hazard analysis of external fires and explosions.
4.4.5 Action combination
The permanent actions and variable actions listed above shall be combined in accordance with
the stipulations of GB 50009 and GB 51006. Under any single load condition, the combination
of permanent and variable actions shall only be combined with an occasional action.
4.5 Inspection and Maintenance
The key matters that need to be paid attention to shall be clarified, and the corresponding
inspection and maintenance procedures of storage tanks shall be compiled.
4.6 Quality Management, Environmental Management and Occupational Health
and Safety Management
A quality management system integrating storage tank design, material procurement,
construction and testing shall be established.
A health, safety and environmental plan with the same overall goals shall be formulated for the
design, construction and trial operation of the storage tank. This plan shall include
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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