GB/T 12241-2021 Safety valves—General requirements English
Safety Valves — General Requirements
1 Scope
This standard specifies the terms and definitions, design, production testing, type testing of safety valves, determination of safety valve performance, determination of sizing of safety valves, as well as marking and sealing of safety valves.
This standard is applicable to safety valves having a flow diameter of 4 mm and above which are for use at set pressures of 0.1 MPa and above.
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 1239.2 Cold Coiled Helical Springs Technical Specifications — Part 2: Compressions Spring
GB/T 7306 (all parts) Pipe Threads with 55 Degree Thread Angle Where Pressure-tight Joints are Made on the Threads
GB/T 9124 (all parts) Steel Pipe Flanges
GB/T 12224 General Requirements for Industrial Steel Valves
GB/T 12716 Pipe Threads with the Thread Angle of 60 Degrees Where Pressure-tight Joints are Made on Threads
GB/T 15530.1 Cast Copper Alloy Integral Flanges
GB/T 15530.8 Specifications for Copper Alloy and Composite Flanges
GB/T 17241.6 Integral Cast Iron Flanges
GB/T 17241.7 Specifications for Cast Iron Pipe Flanges
GB/T 23934 Hot Formed Helical Compression Springs — Technical Requirement
GB/T 36588 Safety Devices for Protection against Excessive Pressure — Common Data (GB/T 36588-2018, ISO 4126-7:2013, MOD)
JB/T 2768 Components of Valves — High Pressure Pipes, Fittings and End-to-end Dimensions of Valves
JB/T 2769 Components of Valves — High Pressure Threaded Flanges
3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
3.1
safety valve
valve which automatically, without the assistance of any energy other than that of the fluid concerned, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed to re-close and prevent further flow of fluid after normal pressure conditions of service have been restored
Note: The valve can be characterized either by pop action (rapid opening) or by opening in proportion (not necessarily linear) to the increase in pressure over the set pressure.
3.2
direct loaded safety valve
safety valve in which the loading due to the fluid pressure underneath the valve disc is opposed only by a direct mechanical loading device such as a weight, lever and weight, or spring
3.3
set pressure
predetermined pressure at which a safety valve under operating conditions commences to open
Note: It is the gauge pressure measured at the valve inlet at which the pressure forces tending to open the valve for the specific service conditions are in equilibrium with the forces retaining the valve disc on its seat.
3.4
maximum allowable pressure
PS
maximum pressure for which the protected equipment is designed
Foreword II
1 Scope
2 Normative References
3 Terms and Definitions
4 Symbols and Units
5 Design
5.1 General
5.2 Valve end connections
5.3 Minimum requirements for springs
5.4 Pressure-temperature ratings
6 Production Testing
6.1 Purpose
6.2 General
6.3 Hydrostatic testing
6.4 Pneumatic testing
6.5 Adjustment of set or cold differential test pressure
6.6 Seat leakage test
7 Type Testing
7.1 General
7.2 Tests to determine operating characteristics
7.3 Tests to determine flow characteristics
7.4 Determination of the coefficient of discharge
7.5 Certification of coefficient of discharge
8 Determination of Safety Valve Performance
9 Sizing of Safety Valves
10 Marking and Sealing
10.1 Marking
10.2 Sealing of a safety valve
Bibliography
