GB/T 26978-2021Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of cryogenic liquefied gas (English PDF)

3.1 Terms and Definitions

The following terms and definitions are applicable to this document.

3.2 Symbols

The following symbols are applicable to this document.

3.3 Abbreviations

The following abbreviations are applicable to this document.

4.1 Types of Storage Tank

4.1.1 Single-containment tank

There is only one self-supporting steel storage tank for the storage of cryogenic liquids, which can consist of a single-walled or double-walled structure with the insulation layer, and with liquid-tightness and air-tightness.

4.2 Overall Design Basis

4.2.1 General stipulations

The technical specification document of the storage tank design shall determine the following contents.

a) Scope of work, including testing, drying, replacement and cooling, etc.;

4.2.2 Performance requirements

The storage tank design shall satisfy the following requirements.

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.

4.2.4 Seismic design

The structural design under seismic action shall be carried out in accordance with the following stipulations.

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.

4.4 Actions

4.4.1 General rules

Permanent actions, variable actions and occasional actions shall be included.

4.4.2 Permanent actions

Permanent actions include self-weight and prestressed local effect of concrete, steel and thermal insulation components, pipelines, fittings, auxiliary equipment and fixed equipment.

See GB 50010 for the method of determining the prestressed local effect.

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

5.1 General Requirements

The metal components of the cryogenic liquefied gas storage tanks shall be designed in accordance with the type of storage tanks, the storage medium and operating conditions, etc.

5.2 Materials

5.2.1 Temperature

The following factors shall be considered when determining the design temperature of metal components.

5.3 Design

5.3.3 Steel outer container

5.3.3.1 Single-containment tank, double-containment tank and full-containment tank

5.3.3.2 Membrane tank

The steel components on the roof of the membrane tank shall comply with the stipulations of 5.3.3.1.3.

5.3.4 Suspended deck

The suspended deck and its supporting structure shall be designed in accordance with the minimum design temperature conditions.

5.5 Welding Process

5.5.1 General rules

All welding, including repair welding and positioned welding, shall be subject to the welding procedure qualification in accordance with the stipulations of NB/T 47014. On this basis, the welding procedure specification (WPS) and welding procedure qualification report (PQR) can be formulated.

5.6 Welding

5.6.1 Positioned welded joints and temporary welded joints

The positioned welded joints and temporary welded joints shall be completed by qualified welders.

5.7 Inspection

5.7.1 Qualifications of non-destructive testing (NDE) personnel

The non-destructive testing personnel shall pass the examination and obtain corresponding qualifications, which shall comply with the stipulations of TSG Z8001.

5.8 Air Pressure Lift

5.8.1 General Requirements

Before air pressure lift, safety protection facilities shall be configured.

Before construction, confirm that the following procedures are completed and qualified.

5.8.2 Air pressure lifting system

The air pressure lifting system shall include fan system, equilibrium system, sealing system and monitoring system.

The fan system shall satisfy the air volume and pressure required for the steady rise of the steel vault and be equipped with the function of air volume adjustment. In addition, a backup fan shall be provided.

5.8.3 Process control

Before construction, it shall be checked that the construction preparations comply with the requirements for the lifting.

During the lifting of the steel vault, it shall maintain an equilibrium state, and the horizontal deviation should be controlled within 200 mm.

6.2 Load Combinations

6.2.1 General rules

The designed load combinations shall comply with the requirements of 4.4. The partial factor method and limit states theory shall be adopted to ensure the reliability of concrete components.

The load design value, load effect and geometric parameters shall comply with the stipulations of GB 50010.

6.2.2 Partial factors and load combinations of various loads

The permanent load, variable load, seismic action and accidental load of the storage tank shall comply with the stipulations of GB 51156-2015.

The horizontal and vertical seismic actions shall be simultaneously combined, and the partial factors of other seismic actions shall comply with the stipulations of GB 51156-2015.

In addition to satisfying the requirements of 4.4, the partial load factors under the occasional action are shown in Table 27.

6.3 Design Requirements

6.3.1 Prestress

The design of the prestressing system shall comply with the stipulations of GB 50010 and JGJ 369.

For prestressed concrete tank shell, horizontal prestress and vertical prestress shall be applied to it, and the form of oblique prestress can also be adopted.

The maximum prestressed tension should be 75% of the yield strength of the prestressed steel strand, and shall not exceed 80% of the yield strength of the prestressed steel strand.

6.3.2 Shell design

The seismic fortification classification of the prestressed concrete outer tank shall be Class B.

The concrete of the prestressed concrete outer tank shall adopt concrete of low-temperature environment, and shall comply with the stipulations of GB 51081.

6.5 Lining

6.5.1 General rules

A steel lining shall be installed on the inner surface of the concrete, so as to ensure the liquid-tightness of the concrete outer tank.

7.1 Overview

The main functions of thermal insulation components in the cryogenic liquefied gas storage tanks include.

7.2.1 General requirements

Appropriate adiabatic system and thermal insulation materials shall be selected based on the following contents.

7.2.3 Evaluation of material performance

7.2.4.1 General requirements

The performance characteristics of thermal insulation materials shall be demonstrated through the following aspects.

7.3 Thermal Protection - Vapor Barrier

7.3.1 General requirements

Since the adiabatic system is not a self-supporting component of the storage tank, it consists of thermal insulation materials, thermal insulation layer and fixation system, which shall be fixed, placed and filled between components or supported by other components (concrete and steel structures).

7.3.2 Protective structure formed by outer tank

When the outer tank provides protection and support for the thermal insulation materials, the air-tightness of the outer tank shall be ensured.

7.4 Design of Adiabatic System

7.4.5 Thermal insulation of tank shell (external)

7.4.5.1 Structural design

The structural design shall consider the following points.

7.5 Installation of Adiabatic system

7.5.1 General requirements

The installation of the adiabatic system of the storage tank shall comply with the following requirements.

7.5.2 Construction of storage tank adiabatic system

The construction, installation and acceptance inspection of the cryogenic liquefied gas storage tanks should satisfy the requirements of SY/T 7349. See Appendix G for the specific construction and installation requirements of the storage tank adiabatic system.

7.5.3 Damage protection

The thermal insulation materials shall be protected from damage by the following factors.

8.1 Hydrostatic Test and Pneumatic Test

8.1.1 Hydrostatic test

8.1.1.1 General stipulations

The storage tanks shall be subject to a hydrostatic test. Through the hydrostatic test, the following shall be proved.

8.1.1.3 Additional requirements

The following additional requirements shall be satisfied.

8.2 Drying, Replacement and Cooling

8.2.1 Procedures

Procedures for drying, replacement and cooling of the storage tanks shall be formulated. The replacement and cooling shall be continuously performed and contingency plans shall be included in the procedures should any stage be interrupted.

8.2.3 Replacement

Before the cryogenic liquefied gas is injected into the storage tank, inert gas shall be used to as a replacement. Nitrogen can be adopted.

8.2.4 Cooling

The cooling of the primary container shall be controlled to prevent relatively large temperature differences during the cooling process. The temperature of the inner tank or membrane steel shall be monitored to keep it within the allowable range.

8.3 Shutdown

Necessary measures shall be taken to ensure that the storage tank can be safely shut down.

Operating procedures shall be formulated in accordance with the possible shutdown conditions.

In case of a shutdown of the storage tank, the shutdown procedures shall be formulated.