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GB/T 18442.6-2019 English PDF (GBT18442.6-2019)

GB/T 18442.6-2019 English PDF (GBT18442.6-2019)

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GB/T 18442.6-2019: Static vacuum insulated cryogenic pressure vessel -- Part 6: Safety device requirements

This part of GB/T 18442 specifies the selection principles and setting requirements of safety accessories, gauges, handling accessories used in static vacuum insulated cryogenic pressure vessels, as well as the calculation of the safety discharge volume of tank, the calculation of the discharge capacity of the overpressure relief device.
GB/T 18442.6-2019
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 23.020.40
J 76
Replacing GB/T 18442.6-2011
Static vacuum insulated cryogenic pressure vessels -
Part 6: Safety protection
ISSUED ON: DECEMBER 31, 2019
IMPLEMENTED ON: DECEMBER 31, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 6
3 Terms and definitions ... 6
4 Safety accessories, instruments and handling accessories ... 6
Appendix A (Normative) Calculation of safe discharge volume of tank and discharge capacity of overpressure relief device ... 18
References ... 31
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, gauges, handling accessories used in static vacuum insulated cryogenic pressure vessels (hereinafter referred to as "cryogenic vessels"), as well as the calculation of the safety discharge volume of tank, the calculation of the discharge capacity of the overpressure relief device.
This part applies to cryogenic vessels that meet the following conditions at the same time:
a) The working pressure of the inner vessel is not less than 0.1 MPa;
b) The geometric volume is not less than 1 m3;
c) The insulation method is vacuum powder insulation, vacuum composite
insulation or high vacuum multilayer insulation;
d) The storage medium is a refrigerated liquefied gas with a standard boiling point not lower than -196 ??C.
This part does not apply to cryogenic vessels in the following ranges:
a) The inner vessel and outer shell materials are non-ferrous or non-metallic; b) Spherical structure;
c) Stacked and insulated;
d) Mobile;
e) Store frozen liquefied gas medium with standard boiling point lower than -196 ??C;
f) The storage medium is a toxic gas according to GB 12268;
g) Special requirements for national defense and military equipment.
2 Normative references
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) are applicable to this standard.
GB/T 150 (all parts) Pressure vessel
GB/T 567.1 Bursting disc safety device - Part 1: Basic requirements
GB/T 567.2 Bursting disc safety device - Part 2: Application, selection and installation
GB/T 567.3 Bursting disc safety device - Part 3: Classification and
installation dimensions
GB/T 567.4 Bursting disc safety device - Part 4: Type test
GB/T 18442.1 Stationary vacuum thermal-insulating cryogenic pressure
vessel - Part 1: Rule
GB/T 18442.3 Stationary vacuum thermal-insulating cryogenic pressure
vessel - Part 3: Design
GB/T 18442.5 Stationary vacuum thermal-insulating cryogenic pressure
vessel - Part 5: Inspection and test
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
The terms and definitions as defined in GB/T 150, GB/T 18442.1, GB/T 18442.3, GB/T 18442.5 apply to this document.
4 Safety accessories, instruments and handling
a) The safety valve shall be installed vertically when installing;
b) A shut-off valve should not be installed between the overpressure relief device and the tank. In order to facilitate the verification, maintenance, replacement of the overpressure relief device, the shut-off valve can be installed between the overpressure relief device. Shut-off valve can only be installed between the overpressure relief device and the tank after
approval by the person in charge of the pressure vessel safety technology of the user unit and taking reliable preventive measures. During the
normal use and operation of the cryogenic vessel, the shut-off valve shall be in a fully open state (lead sealed or locked); meanwhile its structure and diameter shall not affect the safe discharge of the overpressure relief device.
4.2.1.5 The overpressure relief device of the inner vessel shall be clearly and permanently marked; the marking content shall include at least:
a) The operating pressure of the overpressure relief device;
b) Rated exhaust capacity or minimum discharge area;
c) Manufacturing license number and mark;
d) The name or marking trademark of the manufacturer.
4.2.2 Safety discharge volume of inner vessel
4.2.2.1 The discharge capacity of the inner vessel?€?s overpressure relief device shall not be less than the safe discharge volume required by the inner vessel. The calculation method for the safe discharge volume of the inner vessel and the discharge capacity of the overpressure relief device shall be in accordance with the provisions in Appendix A.
4.2.2.2 When calculating the safety discharge volume required for inner packaging, at least the following working conditions and possible combinations shall be considered:
a) The structure of the insulation system is intact and in a normal vacuum state, the outside is the ambient temperature, the temperature of the inner vessel is the saturation temperature of the stored medium under the relief pressure;
b) The structure of the insulation system is intact and in a normal vacuum state, the outside is the ambient temperature, the temperature of the inner vessel is the saturation temperature of the stored medium under the relief pressure, meanwhile the booster system is in a fully open working state; 4.3.1.3 The explosion-proof device shall be able to prevent the blockage of the insulation material. The explosion-proof device shall be located at the top of the enclosure as much as possible.
4.3.1.4 The explosion-proof device of the enclosure may adopt a self-tightening explosion-proof device or a welded bursting disc device. The cover plate of the self-tightening explosion-proof device shall have corresponding protection measures. When using a welded rupture disc device, the connection with the enclosure shall also be welded; there shall be protection measures such as rain and dust.
4.3.2 The discharge area of enclosure explosion-proof device
The discharge area of the enclosure explosion-proof device is generally not less than the product of the geometric volume of the inner vessel (m3) and 340 mm2/m3, but it does not have to exceed 5000 mm2.
4.4 Emergency cut-off device
4.4.1 Requirements for setting of emergency shut-off devices
4.4.1.1 Cryogenic vessels storing flammable and explosive media shall be equipped with emergency shut-off devices as follows, except when it is
confirmed that emergency shut-off devices or other similar emergency shut-off devices that can prevent a large amount of leakage have been installed in the engineering system :
a) An emergency shut-off device shall be installed as close as possible to the tank on the liquid phase inlet and outlet pipelines.
b) The emergency shut-off device generally consists of an emergency shut- off valve, a remote-control system, a fusible alloy plug. The emergency cut-off device shall be flexible in action, reliable in performance, easy to overhaul; meanwhile it shall not be used for other purposes.
c) The emergency shut-off valve shall meet the requirements of GB/T 24918; the valve shall not be made of cast iron or non-metallic materials. The upper stem of the emergency shut-off valve shall not be equipped with a handwheel.
4.4.1.2 In the event of a fire or accidental leakage during filling and draining, the emergency shut-off device shall be able to automatically shut down; meanwhile the device shall be capable of remote control.
4.4.1.3 When the remote-control system adopts a pneumatic control system, the gas used shall adopt an external compressed air source and meet the following requirements:
c) The accuracy level is not less than 2.5;
d) For flammable and explosive media, explosion-proof liquid level
measuring devices shall be used; meanwhile there shall be protective
devices to prevent leakage;
e) It shall be set in a position that is convenient for observation and operation; its maximum allowable safety level shall be clearly marked;
f) The level gauge shall be accompanied by the upper and lower limits of the medium density in the tank, as well as the comparison of the liquid level indicator scale and volume.
4.7 Pressure measuring device
4.7.1 Cryogenic vessels shall be equipped with one or more pressure
measuring devices, such as mechanical pointer pressure gauges (hereinafter referred to as "pressure gauges") or digital pressure display instruments, to display the working pressure in the tank.
4.7.2 The selection and setting of pressure measuring devices shall meet the following requirements:
a) It shall be compatible with the medium in the tank and meet the
requirements of the operating conditions;
b) It shall meet the requirements of the corresponding national standards or industry standards;
c) The pressure gauge shall meet the requirements of JB/T 6804; the dial diameter shall not be less than 100 mm; the accuracy level shall not be less than 1.6; the dial scale?€?s limit value shall be 1.5 times ~ 3.0 times the working pressure;
d) The installation location shall be convenient for operators to observe and clean; it shall avoid the influence of adverse factors such as radiant heat, freezing or vibration;
e) The installation structure shall be firm and reliable, to prevent it from falling off;
f) A needle valve or other shut-off valve shall be installed between the pressure measuring device and the tank. The needle valve or shut-off
valve shall have an opening mark and a locking device; it must not be
connected to the accessories or fittings for other purposes
4.7.3 The verification of the pressure measuring device shall meet the following 4.10 Measuring devices with sensors or electrical control elements
4.10.1 A measuring device with sensors or electrical control components is to meet the real-time measurement of temperature, pressure, liquid level and other parameters in the tank. It uses the corresponding sensors to collect signals and convert to data display, to realize remote transmission function if necessary.
4.10.2 The measuring range and accuracy level of the measuring device shall meet the requirements of the design documents.
4.10.3 The installation structure of the measuring device shall be firm and reliable; its connecting wires and conduits shall not interfere with adjacent parts. 4.10.4 When selecting mechanical pointers or digital instruments with electrical control components, it shall select the products that meet the requirements of the protection design standards for electrical components. Among them,
cryogenic vessels filled with flammable and explosive media shall also be the products that comply with the provisions of the standards for design of explosion-proof of electrical components.
4.11 Handling accessories
4.11.1 The valve material shall be compatible with the medium; the valve shall not be made of cast iron or non-metallic materials.
4.11.2 The nominal pressure of the handling valve shall not be lower than the design pressure of the pipeline; its pressure test and air tightness test pressure shall meet the following requirements:
a) The pressure test pressure is 1.5 times the nominal pressure of the valve; b) The air-tightness test pressure is the nominal pressure of the valve; the valve shall pass the air-tightness test under fully open and fully closed working conditions.
4.11.3 The manual valve shall be able to be fully opened and fully closed flexibly under the pressure of the air tightness test of the valve; meanwhile there shall be no abnormal resistance or idling.
4.11.4 The handling joints shall meet the following requirements:
a) It shall meet the requirements of the corresponding product standards or design drawings; there shall be product quality certification documents; b) The surface shall be free of oil, debris, etc.;
c) It shall be able to prevent the wrong loading of the medium;
Appendix A
(Normative)
Calculation of safe discharge volume of tank and discharge capacity of
overpressure relief device
A.1 Calculation of the total heat flow from the hot wall (enclosure) to the cold wall (inner vessel)
A.1.1 Non-fire situations
A.1.1.1 The insulation system (interlayer and insulation material) is intact and in a normal vacuum state, the outside is the ambient temperature, the
temperature of the inner vessel is the saturation temperature of the stored medium under the relief pressure. The calculation method of the heat flow from the hot wall to the cold wall is as follows:
a) In a normal vacuum state, the heat flow rate introduced through the
insulating material is calculated according to formula (A.1):
Where:
Hi,v - In normal vacuum state, the heat flow rate introduced through the insulating material, in watts (W);
Ui,v - Under the normal vacuum state, the total heat transfer coefficient of the interlayer insulation material, in watts per square meter Kelvin
[W/(m2??K)];
??i,v - Under normal vacuum conditions, the average thermal conductivity of the insulating material between the temperature range Ta and Td, in units of watts per meter Kelvin [W/(m??K)];
ti - The nominal thickness of the insulation material, in meters (m);
Ai,m - The arithmetic average of the inner and outer surface areas of the insulation layer, in square meters (m2);
Ta - The highest ambient temperature outside the insulated vessel under non-fire conditions, in Kelvin (K);
in Watt (W);
Hi,l - The heat leakage input through the insulating material when the
interlayer loses its vacuum, in watts (W);
Ui,l - The total heat transfer coefficient of the insulating material under atmospheric pressure and ambient temperature, in watts per square meter Kelvin [W/(m2??K)];
??i,l - The average thermal conductivity between the temperature Ta and Td when the interlayer has lost its vacuum, the insulating material is filled with or adsorbed air or medium gas under atmospheric pressure, in watts per
meter Kelvin (W/(m?? K)];
ti - The nominal thickness of the insulation material, in meters (m);
Ai,m - The arithmetic average of the inner and outer surface areas of the insulation layer, in square meters (m2).
A.1.2 Fire situation
A.1.2.1 This clause specifies the calculation method for the safe discharge volume of cryogenic vessels in a fire condition (similar to an external oil pool fire) in a well-ventilated and open space that catches fire. When cryogenic vessels storing non-flammable and explosive media are subjected to non-pool fire conditions, the designer can determine the calculation method for the safe discharge volume according to factors such as the distance of the fire source, the intensity of the flame, the radiation surface area of the tank, the heat absorption coefficient of the atmosphere and the enclosure, etc. For the calculation of the safe discharge volume of cryogenic vessels under severe fire conditions such as jet fire, partially enclosed or fully enclosed space, etc., the designer shall consider separately.
A.1.2.2 The insulation system of the vacuum insulated vessel is intact or partly intact, but the interlayer vacuum has been lost, the outside is subject to fire or high temperature of 922 K, the total heat flow from the hot wall into the inner vessel is calculated according to formula (A.9):
Where:
H4 - The insulation system of the vacuum insulated vessel is complete, but the interlayer vacuum has been lost, the outside is subject to fire or high temperature of 922 K, the total heat flow from the hot wall into the inner A.2 Calculation of the safe discharge volume (mass flow) of inner vessel A.2.1 When the discharge pressure pd of the overpressure relief device of the inner vessel is less than 40% of the critical pressure of the medium, the safe discharge volume of the inner vessel under the above various conditions is calculated according to formula (A.11):
Where:
Ws,i - When the discharge pressure pd of the overpressure relief device of the inner vessel is less than 40% of the critical pressure of the medium, the safe discharge volume of the inner vessel, in kilogram per hour (kg/h); Hi - The total heat flow transferred from the hot wall to the cold wall, corresponding to i = 1, 2, 3, 4, 5, which is calculated by formula (A.6), formula (A.7), formula (A. 8), formula (A.9), formula (A.10), respectively, in watt (W); q - The latent heat of vaporization of the liquid medium under relief pressure, in kilojoules per kilogram (kJ/kg).
A.2.2 When the gas discharge pressure pd of the overpressure relief device is less than the critical pressure of the medium, but greater than or equal to 40% of the critical pressure, that is, 0.4pcrit ??? pd < pcrit, it is necessary to use the formula (A.11) to correct the calculation formula for the safe discharge volume of the inner vessel, that is, it shall be calculated according to formula (A.12): Where:
W's,i - When the gas discharge pressure pd of the overpressure relief device is less than the critical pressure of the medium, but greater than or equal to 40% of the critical pressure, that is, when 0.4pcrit ??? pd < pcrit, the safe discharge volume of the inner vessel, in kilogram per hour (kg/h);
vg - The specific volume of the saturated gas medium under the relief
pressure, in cubic meters per kilogram (m3/kg);
ve - The specific volume of the saturated liquid medium under relief pressure, in cubic meters per kilogram (m3/kg);
Hi -T total heat flow transferred from the hot wall (jacket) to the cold wall (inner vessel), corresponding to i = 1, 2, 3, 4, 5, which is calculated by Where:
Q. - The standard state air volume flow rate as converted according to the mass flow rate Ws,i of the discharged gas, in cubic meters per hour (m3/h); Ws,i - When the discharge pressure pd of the overpressure relief device of the inner vessel is less than 40% of the critical pressure of the medium, the safe discharge volume of the vacuum insulated pressure vessel under the above various conditions, in kilograms per hour (kg/h);
C - Gas characteristic coefficient, as found from Table A.1 or calculated according to the following formula:
k - Gas insulation index, k = cp/cV;
cp - Gas specific heat capacity at constant pressure under standard
conditions, in kilojoules per kilogram degrees Celsius [kJ/(kg????C)];
cV - The gas specific heat capacity at constant volume under standard
conditions, in kilojoules per kilogram degrees Celsius [kJ/(kg????C)];
Z - Compression coefficient of saturated gas under relief pressure;
T - The gas temperature on the inlet side of the relief device, in Kelvin (K); M - The molar mass of the gas, in kilograms per thousand moles (kg/kmol). A.4 The influence of the length of the gas discharge pipe on the gas
pressure and temperature at the inlet of the overpressure relief device When the length of the gas discharge pipe from the inner vessel to the inlet of the discharge device exceeds 600 mm, it shall consider the pressure drop and heat loss of the gas ...

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