GB/T 24925-2019 English PDF (GBT24925-2019)

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GB/T 24925-2019: Low temperature valve -- Technical specifications
GB/T 24925-2019
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 23.060.99
J 16
Replacing GB/T 24925-2010
Low temperature valve - Technical specifications
ISSUED ON: OCTOBER 18, 2019
IMPLEMENTED ON: MAY 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 4 
1 Scope ... 7 
2 Normative references ... 7 
3 Terms and definitions ... 9 
4 Structural style ... 10 
5 Technical requirements ... 19 
5.1 General requirements ... 19 
5.2 Performance ... 20 
5.3 Valve ... 21 
5.4 Bonnet ... 22 
5.5 Stem ... 25 
5.6 Opening-closing parts and valve seats ... 26 
5.7 Packing and stuffing box ... 26 
5.8 Medium flange seal ... 26 
5.9 Operation ... 27 
5.10 Material ... 27 
5.11 Visual quality of steel castings ... 28 
5.12 Defect treatment ... 28 
5.13 Nondestructive testing ... 28 
6 Test methods ... 30 
6.1 Marking inspection ... 30 
6.2 Visual quality of steel castings ... 30 
6.3 Dimensional check ... 30 
6.4 Chemical composition ... 30 
6.5 Mechanical properties ... 30 
6.6 Normal temperature test ... 31 
6.7 Low temperature test ... 31 
6.8 Low temperature cycle life test ... 35 
6.9 Nondestructive testing ... 35 
6.10 Anti-static test ... 36 
7 Inspection rules ... 36 
7.1 Inspection items ... 36 
7.2 Exit-factory inspection ... 36 
7.3 Type test ... 36 
8 Marking ... 37 
9 Painting, packaging, transportation, and storage ... 38 
Appendix A (Informative) Table of recommended materials for low temperature
valve ... 39 
Appendix B (Informative) Schematic diagram of internal cooling cycle ... 41 
Foreword
This Standard is drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 24925-2010 "Cryogenic valve technical
specifications". Compared with GB/T 24925-2010, in addition to editorial
changes, the main technical changes are as follows:
- ADD the terms cryogenic treatment, drip plate, CWP, internal cooling cycle,
cold box; modify the term "neck elongation" to "bonnet extension" (see
Clause 3; Clause 3 of the 2010 edition).
- In Clause 4, add axial flow check valve, top-mounted fixed ball valve, top-
mounted floating ball valve, top-mounted eccentric butterfly valve; modify
"low temperature worm geared butterfly valve" to "eccentric butterfly valve"
(see Clause 4; Clause 4 of the 2010 edition).
- In 5.1, add the requirements of the valve's pressure-temperature rating,
valve connection type, drip plate, structural length, minimum diameter of
valve seat, valve installation direction, and pressure relief method
identification, etc. (see 5.1; 5.1 of the 2010 edition).
- ADD "Performance"; modify the leakage rate of the sealing test; ADD the
fugitive test of the medium flange and the valve stem, and the low
temperature cycle life test, etc. (see 5.1; Table 2 of the 2010 edition).
- ADD the minimum wall thickness of the valve body and flange requirements
(see 5.1.4 and 5.3.2; 5.2 of the 2010 edition).
- ADD the requirements for minimum elongation of bonnet extension
(including the elongation of bonnet extension of low temperature valve for
cold box and non-cold box), thermal insulation layer, and drip plate (see
5.4.1 and 5.4.5; 5.3 of the 2010 edition).
- ADD stem torque requirements, anti-blowout structure requirements;
modify requirements for dangerous section setting (see 5.5; 5.4 of the 2010
edition).
- Modify "Valve clack" to "Opening-closing parts (valve clack, valve plate, ball)
and valve seats", where the requirements for ball valves and butterfly
valves are added (see 5.6; 5.5 of the 2010 edition).
- Modify "Stuffing box" to "Packing and stuffing box"; ADD requirements for
packing and stuffing box structure (see 5.7; 5.6 of the 2010 edition).
- ADD requirements for medium flange seal (see 5.8).
Low temperature valve - Technical specifications
1 Scope
This Standard specifies the structural style, technical requirements, test
methods, inspection rules, marking, painting, packaging, transportation, and
storage of low temperature valve (hereinafter referred to as "valve").
This Standard is applicable to flange, wafer and welding-connected low
temperature gate valves, globe valves, check valves, ball valves, and butterfly
valves with nominal pressure PN16~PN400, nominal size DN15~DN1200;
pressure class Class150~Class2500, nominal size NPS1/2~NPS48, medium
temperature -196 °C~-29 °C.
Other low temperature valves may refer to it for use.
2 Normative references
The following documents are indispensable for the application of this document.
For the dated references, only the editions with the dates indicated are
applicable to this document. For the undated references, the latest edition
(including all the amendments) are applicable to this document.
GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method
GB/T 9113 Integral steel pipe flanges
GB/T 12220 Industrial valves - Marking
GB/T 12221 Metal valves - Face to face, end to end, center to face and
center to end dimensions
GB/T 12222 Multi-turn valve actuator attachments
GB/T 12223 Part-turn valve actuator attachments
GB/T 12224 General requirements for industrial steel valves
GB/T 12225 General purpose industrial valves - Specification of copper alloy
castings
GB/T 12234 Bolted bonnet steel gate valves for petroleum and natural gas
industries
JB/T 8527 Metallic sealing butterfly valve
JB/T 12003 Specification for valve cryogenic test rig
JB/T 12622 Liquified natural gas valves - Performance testing
NB/T 47009 Alloy steel forgings for low temperature pressure equipment
NB/T 47010 Stainless and heat-resisting steel forgings for pressure
equipment
NB/T 47013.2-2015 Nondestructive testing of pressure equipment - Part 2:
Radiographic testing
NB/T 47013.4 Nondestructive testing of pressure equipment - Part 4:
Magnetic particle testing
NB/T 47013.5-2015 Nondestructive testing of pressure equipment - Part 5:
Penetrant testing
NB/T 47014 Welding procedure qualification for pressure equipment
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Bonnet extension
The part from the uppermost end of the bonnet support to the bottom of the
bonnet stuffing box.
The part from the top of lower bushing to the bottom of stuffing box of the bonnet
of the lift stem valve.
The part from the top of the lower bonnet bearing of the quarter-turn valve to
the bottom of the stuffing box.
3.2
Cryogenic treatment
The treatment process in which the parts are immersed in liquid nitrogen for
cooling, and when the temperature of the parts is stable at -196 °C, the heat is
kept for 2 h~4 h according to the thickness of the parts, and then taken out of
the box to naturally return to room temperature.
5 Technical requirements
5.1 General requirements
5.1.1 In addition to meeting the requirements of this Standard, the valve shall
also comply with the corresponding valve product standards, such as GB/T
12234, GB/T 12235, GB/T 12236, GB/T 12237, GB/T 21387, JB/T 8527, JB/T
7746.
5.1.2 The pressure-temperature rating of the valve shall comply with the
provisions of GB/T 12224 and JB/T 7746.
5.1.3 According to the contract requirements, the valve shall be provided with a
drip plate.
5.1.4 The end connection of the valve can be flanged or welde...