GB/T 12241-2021 PDF English (GB/T 12241-2005: Older version)

GB/T12241-2021 (GBT12241-2021): PDF in English

GB/T 12241-2021 NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 13.240 J 16 Replacing GB/T 12241-2005 Safety valves - General requirements (ISO 4126-1:2013, Safety devices for protection against excessive pressure - Part 1: Safety valves, MOD) ISSUED ON: MARCH 09, 2021 IMPLEMENTED ON: OCTOBER 01, 2021 Issued by: State Administration for Market Regulation; Standardization Administration of the People's Republic of China. Table of Contents Foreword ... 3  1 Scope ... 6  2 Normative references ... 6  3 Terms and definitions... 7  4 Symbols and units ... 9  5 Design ... 10  5.1 General ... 10  5.2 End connection ... 11  5.3 Minimum requirements for springs ... 12  5.4 Pressure-temperature rated values ... 15  6 Exit-factory tests ... 15  6.1 Purpose ... 15  6.2 General ... 16  6.3 Hydraulic test ... 16  6.4 Air pressure test ... 17  6.5 Adjustment of set pressure or cold differential test pressure ... 18  6.6 Seal test ... 18  7 Type test ... 18  7.1 General ... 18  7.2 Action performance test ... 20  7.3 Discharge capacity performance test ... 21  7.4 Determination of coefficient of discharge ... 23  7.5 Certified coefficient of discharge ... 23  8 Determination of discharge capacity performance of safety valve ... 24  9 Determination of safety valve size ... 24  10 Marks and lead seals ... 24  10.1 Marks ... 24  10.2 Lead seal of safety valve ... 25  Bibliography... 26  Safety valves - General requirements 1 Scope This Standard specifies the terms and definitions of safety valve, design, exit-factory test, type test, determination of safety valve discharge capacity performance, determination of safety valve size, marks and lead seals. This Standard is applicable to the safety valves of which the diameter of the flow is not less than 4mm, and the set pressure is not less than 0.1MPa. 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 an automatic valve that uses the force of its own medium to discharge a certain amount of fluid without any external force, so as to prevent the pressure from exceeding a predetermined safety value NOTE: When the pressure returns to normal, the valve closes and prevents the medium from continuing to flow out. 3.2 direct loaded safety valve safety valves that only rely on direct mechanical loading devices such as weights, lever- weighted hammers or springs to overcome the force generated by the pressure of the medium under the disc 3.3 set pressure the predetermined pressure at which the safety valve begins to open under operating conditions NOTE: This pressure is the gauge pressure measured at the valve inlet. At this pressure, the force resulting from the medium pressure to open the valve under specified operating conditions is balanced by the force that keeps the disc on the valve seat. 3.4 maximum allowable pressure; pS the maximum pressure at which the protected equipment is designed 3.5 over pressure the pressure increments above the set pressure of the safety valve NOTE: It is usually expressed as a percentage of set pressure. 3.6 reseating pressure the inlet static pressure when the valve disc is in contact with the valve seat again after the safety valve is discharged (that is, the lift becomes zero) 3.7 cold differential test pressure through the valve. 5.2 End connection 5.2.1 End connection type The end connection type requirements are listed below: a) Steel flange connection is according to the provisions of GB/T 9124, JB/T 2769. The surface roughness of the sealing surface is according to the regulations of GB/T 9124 and JB/T 2768, respectively. Iron flange connection is according to the provisions of GB/T 17241.6. Surface roughness of the sealing surface is according to the provisions of GB/T 17241.7. Copper flange connection is according to the provisions of GB/T15530.1. Surface roughness of the sealing surface is according to the provisions of GB/T 15530.8. b) The welding end of the butt-welding connection shall be in accordance with the provisions of GB/T 12224. c) The threaded connection is in accordance with the provisions of GB/T 7306 and GB/T 12716. d) Other end connections may also be used by agreement between the manufacturer and the purchaser. 5.2.2 End connection design No matter what type of safety valve end connection is designed, the internal cross- sectional area of the external pipe or pipe joint connected to the valve inlet shall be at least equal to the internal cross-sectional area of the valve inlet connection [see Figure 1a)]. The internal cross-sectional area of the external nozzle at the outlet of the safety valve shall be at least equal to the internal cross-sectional area of the valve outlet but excluding the valves that the outlet is internal thread connection [see Figure 1b)]. If the valve outlet is of the structure shown in Figure 1b), a suitable pipe shall be fitted when carrying out the tests specified in 7.1.4. tested according to the technical requirements of the safety valve manufacturer. The allowable stress shall refer to GB/T 23935 and be determined according to experience. The operating temperature of the spring and its working environment shall be considered. 5.3.1.2 Materials The material for the manufacture of safety valve springs shall meet the requirements of the corresponding material standards and be compatible with its working conditions. 5.3.1.3 Marks Spring marks, including stamping or etching, shall be limited to their void ring. For stock springs, labels or other suitable methods may be used to identify when the above marks are not suitable. 5.3.1.4 Sizes Size requirements are listed below: a) Slenderness ratio: that is, the ratio of the free height to the middle diameter, which shall be less than 5. b) Winding ratio (spring index): that is, the ratio of the middle diameter to the diameter of the steel wire, which shall be in the range of 3 to 12. c) Coil Spacing: the coil pitch shall be uniform. The compression of the spring (deformation under the maximum working load) shall not be greater than 80% of the nominal (calculated) deformation from the free height to the height of the coil when it is tightened. d) End ring: the ends of the support rings at both ends of the spring shall be tightened with the working ring, and the ends shall be ground flat. Both ends of the spring shall have a support plane greater than or equal to 3/4 turn and be perpendicular to the axis. 5.3.1.5 Inspection, test and tolerance Permanent deformation: All springs shall be tested for permanent deformation. That is, measure the original free height of the spring after compressing the spring at least 3 times according to the test load specified by the safety valve manufacturer. Then use the test load to compress the spring at least 3 times. Measure its final free height again. The permanent deformation of the spring shall not exceed 0.5% of its original free height. Each spring shall be subject to at least the following size inspections: a) The load and height at the maximum compression the spring will use, or the spring stiffness within a given range (and within a linear range) of less than 80% of the calculated total deflection; b) Inspection of wire diameter and free height; c) Inspection of end face verticality: Stand the spring on the plate and lean against a square. Measure the maximum deviation between the upper end ring and the square. The inspection method is in accordance with the provisions of GB/T 23934 and GB/T 1239.2; d) Inspection of end face parallelism (when applicable): Make the spring stand on the plate. Measure the height difference between the highest point and the lowest point on the upper end face. When applicable, this measurement shall be repeated with the ends of the spring turned upside down. Tolerance: The dimensional tolerance of the spring shall be determined according to the provisions of GB/T 23934 and GB/T 1239.2 or determined by the valve and spring manufacturer. 5.3.2 Minimum requirements for disc springs 5.3.2.1 General The spring manufacturer shall provide a certificate of quality for the disc spring, to indicate that the disc spring is made of the specified material and has completed the test according to the technical requirements of the safety valve manufacturer. The allowable stress shall be determined by reference to GB/T 1972 and based on experience. The operating temperature of the spring and its working environment shall be considered. Disc spring packs shall be well guided just like the spring disc.......
Source: https://www.ChineseStandard.net/PDF.aspx/GBT12241-2021