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GB/T 18442 consists of the following 7 parts under the general title of Static vacuum insulated cryogenic pressure vessels:
——Part 1: General requirements;
——Part 2: Material;
——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 6 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 18442.6-2011 Static vacuum insulated cryogenic pressure vessel - Part 6: Safety device requirements. In addition to editorial changes, the following main technical changes have been made with respect to GB/T 18442.6-2011:
—— general requirements are modified to add explosion-proof requirements for electrical control elements and connection requirements for safety valves, instruments, loading and unloading accessories and pipelines;
—— the setting requirements are modified for the overpressure relief device of the inner vessel, and the typical setting schematic diagram of the overpressure relief device is modified;
—— the design requirements are modified for the overpressure relief device;
—— the installation requirements for the overpressure relief device of the inner vessel, the type of explosion-proof device of the outer jacket and the requirements for its installation location are added;
—— the setting requirements of emergency cut-off valve, grounding resistance value of static conductive grounding device, requirements of liquid level measuring device and pressure measuring device, and requirements of loading and unloading accessories are modified.
—— relevant requirements are added for temperature measuring devices, vacuum degree measuring devices and measuring devices with sensors or electrical control elements;
—— the loading and unloading hose and its related requirements are deleted;
—— in Annex A, requirements are added for the calculation methods of safety relief volume of tanks storing non-flammable and non-explosive contents, and Formula (A.5) is modified.
In this part, the calculation of the safety relief volume of the tank and the discharge capacity of the overpressure relief device refers to ISO 21013-3: 2016 Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and capacity determination.
This part was proposed by and is under the jurisdiction of the National Technical Committee 262 on Boilers and Pressure Vessels of Standardization Administration of China.
The previous editions replaced by this part are as follows:
—— GB/T 18442.6-2011;
—— GB 18442-2001.
Static vacuum insulated cryogenic pressure vessels - Part 6: Safety protection
1 Scope
This part of GB/T 18442 specifies the selection principles and setting requirements of safety accessories, instruments and loading and unloading accessories used in static vacuum insulated cryogenic pressure vessels (hereinafter referred to as "cryogenic vessels"), as well as the calculation of the safety relief volume of tanks and the discharge capacity of overpressure relief devices.
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 0.1 MPa;
b) cryogenic vessel with the geometric volume not less than 1 m3;
c) cryogenic vessel with the insulation mode of vacuum powder insulation, vacuum composite insulation or high vacuum multilayer insulation;
d) cryogenic vessel with storing refrigerated liquefied gas contents with standard boiling point not lower than -196℃.
This standard is not applicable to cryogenic vessels that meet the following conditions:
a) cryogenic vessel with the inner vessel and the outer jacket made of non-ferrous metals or non-metallic materials;
b) cryogenic vessel with spherical structure;
c) cryogenic vessel with stacked insulation;
d) transportable cryogenic vessel;
d) 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 (all parts) Pressure vessels
GB/T 567.1 Bursting disc safety devices - Part 1: Basic requirement
GB/T 567.2 Bursting disc safety devices - Part 2: Application, selection and installation
GB/T 567.3 Bursting disc safety devices - Part 3: Classification and mounting dimensions
GB/T 567.4 Bursting disc safety devices - Part 4: Type test
GB/T 18442.1 Static vacuum insulated cryogenic pressure vessels - Part 1: General requirements
GB/T 18442.3 Static vacuum insulated cryogenic pressure vessels - Part 3: Design
GB/T 18442.5 Static vacuum insulated cryogenic pressure Vessels - Part 5: Inspection and testing
GB/T 24918 Cryogenic emergency shutoff valve
GB/T 29026 Spring loaded safety valve for cryogenic service
JB/T 6804 Shock-resistant pressure gauge
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, GB/T 18442.3, and GB/T 18442.5 apply.
4 Safety accessories, instruments and loading and unloading accessories
4.1 General requirements
4.1.1 The setting of safety accessories, instruments and loading and unloading accessories shall meet the requirements of design documents in addition to TSG 21 and this part.
4.1.2 Safety accessories include overpressure relief device (safety valve, bursting disc device), outer jacket explosion-proof device, emergency cut-off device, static conductive device, etc.
4.1.3 Instruments include pressure measuring device, liquid level measuring device, vacuum degree measuring device, etc.
4.1.4 Loading and unloading accessories include loading and unloading valves, loading and unloading joints, etc.
4.1.5 The selected safety accessories, instruments and loading and unloading accessories shall be suitable for the storage contents.
4.1.6 The manufacturing license and type test of safety accessories and loading and unloading accessories shall meet the requirements of corresponding safety technical specifications.
4.1.7 Safety accessories, instruments and loading and unloading accessories shall meet the requirements of relevant safety technical specifications and product standards, and shall have product quality certificates.
4.1.8 Cryogenic vessels storing flammable and explosive contents shall meet the requirements of relevant standards for explosion-proof design of electrical elements when safety accessories, instruments and loading and unloading accessories with electrical control elements are used.
4.1.9 Before installing, the safety valve and pressure gauge shall be checked and verified, and shall be subjected to lead seal after passing the check and verification.
4.1.10 The connection between safety accessories, instruments and pipelines may be welded, flanged or threaded.
4.1.11 The connection between loading and unloading accessories and pipelines shall be welded or flanged as far as possible.
4.2 Overpressure relief device of inner vessel
4.2.1 Setting requirements for overpressure relief device of inner vessel
4.2.1.1 Inner vessel shall be provided with at least two sets of independent overpressure relief devices. In any case, at least one set of overpressure relief device shall be kept in connection with the inner vessel. In order to meet the requirements of safety relief, each set of overpressure relief device shall be provided with a full lift spring safety valve as the main relief device and a full lift spring safety valve or rupture disk in parallel as the auxiliary relief device. For the inner vessel filled with flammable and explosive contents, safety valve shall be selected as the auxiliary relief device.
4.2.1.2 If the inner vessel is provided with overpressure relief device according to Figure 1 or Figure 2, the following requirements shall be met:
a) the set pressure of the main safety valve shall not be greater than the design pressure of the inner vessel, and the re-seating pressure shall not be less than 0.90 times the set pressure;
b) the operating pressure of the auxiliary relief device shall not be less than the set pressure of the main safety valve and not greater than 1.1 times the design pressure of the inner vessel;
c) the discharge capacity of the main safety valve shall ensure that the pressure of the inner vessel under non-fire conditions does not exceed 1.1 times of its design pressure, and the total discharge capacity of each group of overpressure relief devices shall ensure that the pressure of the inner vessel under fire conditions does not exceed 1.21 times of its design pressure;
d) the discharge capacity of each safety valve or rupture disk device shall meet the safety relief requirements of the inner vessel when considering non-fire conditions, and the discharge capacity of each group of overpressure discharge devices shall meet the safety relief requirements of the inner vessel when considering fire conditions.
Key:
1—— switching valve;
2—— safety valve;
3—— safety valve;
Figure 1 Schematic diagram for combination of safety valves
Key:
1—— switching valve;
2—— safety valve;
3—— bursting disc device;
Figure 2 Schematic diagram for combination of safety valve and bursting disc
4.2.1.3 The design of overpressure relief device of inner vessel shall meet the following requirements:
a) the safety valve shall meet the requirements of GB/T 29026;
b) the bursting disc device shall meet the requirements of GB/T 567.1, GB/T 567.2, GB/T 567.3, and GB/T 567.4;
c) the inlet pipe design of overpressure relief device shall meet the requirements of GB/T 18442.3;
d) when filling with flammable, explosive contents, a relief pipe shall be installed at the outlet of overpressure relief device to discharge the contents to a safe place;
e) the selected bursting disc shall not generate fragments, falling off and sparks during bursting, and reverse arch groove type bursting disc should be adopted;
f) the discharge of gas shall be unblocked, and the gas discharged from pressure relief shall not directly impact the vessel and main stressed structural members;
g) the device can withstand the pressure inside the vessel, possible overpressure and dynamic load including liquid impact force;
h) the outlet shall prevent rainwater and sundries from accumulating and prevent foreign matters from entering;
i) the influence of inlet pressure drop and outlet back pressure of overpressure relief device shall be considered.
4.2.1.4 The installation of overpressure relief device of inner vessel shall meet the following requirements:
a) the safety valve shall be vertically installed;
b) shut-off valve should not be installed between overpressure relief device and tank. In order to facilitate the verification, maintenance and replacement of the overpressure relief device, the shut-off valve may only be installed between the overpressure relief device and the tank after the approval of the person in charge of safety technology of the pressure vessel of the user unit and the adoption of reliable preventive measures. During the normal use and operation of cryogenic vessels, the shut-off valve shall be fully opened (sealed with lead or locked), and its structure and size shall not affect the safe release of overpressure relief device.
4.2.1.5 The overpressure relief device of inner vessel shall be clearly and permanently marked, and the marked content shall at least include:
a) operating pressure of overpressure relief device;
b) rated discharge capacity or minimum relief area;
c) manufacturing license No. and marking;
d) manufacturer name or trademark.
4.2.2 Safety relief volume of inner vessel
4.2.2.1 The discharge capacity of the overpressure relief device of the inner vessel shall not be less than the safety relief volume required by the inner vessel. The calculation method for the safety relief volume required by the inner vessel and the discharge capacity of the overpressure relief device shall be as specified in Annex A.
4.2.2.2 When calculating the safety relief volume required by the inner vessel, at least the following conditions and possible combinations shall be considered:
a) the thermal insulation system is intact and in a normal vacuum state under the ambient temperature, and the temperature of the inner vessel is the saturation temperature of the stored contents under the relief pressure;
b) the insulation system is intact and in a normal vacuum state under the ambient temperature, the temperature of the inner vessel is the saturation temperature of the stored contents under the relief pressure, and the pressurization system is in a fully open working state;
c) the insulation system is intact, with the annular space not in a vacuum state, under the ambient temperature and the temperature of the inner vessel is the saturation temperature of the stored contents under the relief pressure.
d) the thermal insulation system of the cryogenic vessel is intact or partially intact, with the annular space not in a vacuum state, and is exposed to fire or high temperature of 922 K or above;
e) the thermal insulation system structure of the cryogenic vessel is completely damaged, and the jacket is exposed to fire or high temperature of 922 K or above;
f) the flow capacity of other valves in the pipeline connecting the high pressure source and the inner vessel;
g) effect of recycling of possible combinations of pumps;
h) filling the storage tank at the working temperature with flash gas with liquid at the maximum possible flow rate.
4.2.2.3 Design personnel shall identify various possible conditions according to actual conditions, including the conditions listed in items a) to h) of 4.2.2.2 and possible combination conditions.
4.2.2.4 Annex A does not specify the calculation method for conditions of items f), g) and h) in 4.2.2.2. The design personnel shall identify whether these conditions exist according to actual conditions. If these conditions exist, the maximum possible impact of these
conditions shall be fully estimated according to the method of thermodynamic basic theory.
4.2.2.5 The discharge capacity of the overpressure relief device of the inner vessel shall meet the safety relief requirements if several conditions of items a) to d), f), g), and h) in 4.2.2.2 may occur simultaneously, but the possibility of occurrence of extreme conditions of item e) in 4.2.2.2 shall also be fully studied.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Safety accessories, instruments and loading and unloading accessories
Annex A (Normative) Calculation of safety relief volume of tank and capacity of overpressure relief device
Bibliography
