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This standard was proposed by and is under the jurisdiction of the National Technical Committee on Gas Cylinder of Standardization Administration of China (SAC/TC 31).
Pressure relief devices for gas cylinders
1 Scope
This standard specifies the types, structural types, setting principles, selection principles, basic requirements, calculation of minimum flow capacity for safety and certified capacity of pressure relief devices, determination principles of operating pressure or temperature, installation and maintenance, etc.
This standard is applicable to gas cylinders in different structures and for containing various gases.
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 13005 Terminology of gas cylinders
GB/T 16163 Classification of gases filled in cylinder
3 Terms and definitions, symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 13005 and the following apply.
3.1.1
pressure relief device; PRD
general term of pressure relief devices installed on cylinders to make them quickly and automatically exhaust and relieve pressure in unexpected high temperature environment, and to protect their shells from explosion
3.1.2
minimum flow capacity for safety
minimum flow that needs to be discharged in order to make the gas pressure in the cylinder stop rising after reaching the allowable pressure of the cylinder under unexpected high temperature environment
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3.1.3
certified capacity
mass of gas that can be discharged by the devices in unit time under their set discharge conditions
3.2 Symbols
For the purposes of this document, the following symbols apply.
A the minimum relief area of a pressure relief device, mm2;
A0 outside surface of the shell of a gas cylinder, m2;
C the characteristic coefficient of a gas;
K the relief coefficient of a pressure relief device;
k the adiabatic exponent of a gas;
M the molar mass of the medium filled in the cylinder, kg/kmol;
p the relief pressure (absolute pressure), MPa;
Note: For bursting disc devices, it is the design burst pressure; for fusible plug devices, it is the saturated vapor pressure of the medium filled in the cylinder at the operating temperature; for safety relief valves, it is rated relief pressure.
Q the latent heat of vaporization of the medium filled in the cylinder under the relief pressure, kJ/kg;
T the absolute temperature of the medium under the relief pressure, K;
Z the gas compression coefficient of at absolute pressure p and absolute temperature T;
V the water capacity of a cylinder, L;
Wr the certified capacity of a pressure relief device, kg/h;
Ws the minimum flow capacity for safety of a gas cylinder, kg/h.
4 Types and structural types of pressure relief devices
4.1 Fusible plug device
A fusible plug device consists of a fusible plug and its boss. The fusible plug boss is connected with the shell or valve body. When the temperature reaches a preset value, the fusible alloy melts and the gas inside the cylinder will be discharged.
4.2 Bursting disc device
A bursting disc device consists of bursting diaphragm, clamping ring and fasteners (for non-refillable welded steel gas cylinders, the diaphragm may be directly welded at the opening of the shell). When the gas pressure in the cylinder reaches a preset value, the diaphragm will be broken and the gas in the cylinder will be discharged automatically.
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4.3 Safety valve
Safety valve is a type of pressure control device, which is composed of valve seat, disc and spring and can be repeatedly opened and closed. When the gas pressure in the cylinder reaches the preset value, the disc pressed by the spring will leave the valve seat, and the gas in the cylinder will be discharged. When the pressure drops to the preset value, the disc will close again.
4.4 Composite device of bursting disc + fusible plug
It is a pressure relief device composed of bursting disc and fusible plug, which are connected in series. The fusible plug is arranged on the side where the bursting disc will relieve pressure. When the pressure on the bursting disc reaches the preset burst pressure and the ambient temperature reaches the preset value, the composite device will discharge the gas filled to relieve pressure.
4.5 Composite device of bursting disc + safety valve
It is a pressure relief device composed of bursting disc and safety valve, which are connected in series. When the gas pressure in the cylinder reaches the preset value, the bursting disc will burst first; as a result, the gas discharged will make the safety valve open so that the high-pressure gas will be discharged automatically.
5 Setting principle of pressure relief devices for gas cylinders
5.1 The following gas cylinders shall be equipped with pressure relief devices:
a) cylinders for on-board storage of fuel gas for vehicles;
b) gas cylinders for fire extinguishers;
c) gas cylinders for breathing apparatus;
d) dissolved acetylene cylinders;
e) industrial combustible gas cylinders;
f) welded insulated gas cylinders for cryogenic liquefied gas;
g) gas cylinder bundles for liquefied gas;
h) large-volume gas cylinders for tube trailers and tube skid containers
Foreword i
1 Scope
2 Normative references
3 Terms and definitions, symbols
4 Types and structural types of pressure relief devices
5 Setting principle of pressure relief devices for gas cylinders
6 Selection principle of pressure relief device
7 Basic requirements for pressure relief device (PRD)
8 Minimum flow capacity for safety of gas cylinders and certified capacity of pressure relief devices
9 Principles for determining the operating pressure or temperature of pressure relief device
10 Installation and maintenance of pressure relief device
Annex A (Informative) Method for calculating the compression coefficient of high pressure gas
Bibliography
