GB/T 24925-2019 PDF English
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Low temperature valve - Technical specifications
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GB/T 24925-2019: Low temperature valve - Technical specifications---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT24925-2019
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
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
GB/T 12235 Steel globe valves and lift check valve for petroleum,
petrochemical and allied industries
GB/T 12236 Steel swing check valve for petroleum, petrochemical and allied
industries
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.
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.
3.3 Drip plate
The disc set at the bonnet extension to prevent condensate from entering the
insulating layer of the extended bonnet.
3.4 Cold working pressure; CWP
The maximum allowable working pressure of the valve when the medium
temperature is -20 °C~38 °C.
3.5 Internal cooling cycle
The method to make the low temperature medium flow through the inside of the
test valve to reduce the temperature of the test valve.
4 Structural style
The typical structural styles of low temperature valve are shown in Figure 1~Figure 10.
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 welded. The flange
shall comply with the provisions of GB/T 9113 and GB/T 13402.The welded
connection shall comply with the provisions of GB/T 12224, or as required by
the order contract. The structural length of the flange connection and welded
connection valve shall comply with the provisions of GB/T 12221, or as
specified in the order contract.
5.1.9 When using welded structure to design the pressure parts, it shall
consider the welding performance of the material and the reliability of the weld
at low temperature. The form of butt welded joint should be adopted.
5.1.11 Non-metallic seat valves for flammable and explosive media shall have
anti-static structure. The design shall ensure that, the valve, opening-closing
parts, and valve stem have electrical conductivity.
5.2 Performance
5.2.1 The normal temperature performance requirements and tests of the valve
shall comply with the provisions of GB/T 26480.
5.2.2 The low temperature performance test of the valve shall be completed on
a special rig. The test rig shall meet the requirements of JB/T 12003.
5.2.3 When required in the order contract, the flange and stem seal in the valve
shall be tested for fugitiveness. The results shall comply with the requirements
of Table 1.
5.3 Valve
5.3.1 Under the total load of the stress generated by the alternating pressure
and temperature of the medium and the additional stress caused by the pipeline
installation, the valve shall be able to maintain sufficient strength.
5.3.2 The minimum wall thickness of the valve shall not be less than that
specified in GB/T 26640.
5.3.3 The cast flanged end valve shall be integrally cast; no flange shall be
welded.
5.3.4 For the cast welded end valve, the flanged end valve shall not be used to
become the welded end valve after removing the flange.
5.4 Bonnet
5.5 Stem
5.5.1 The diameter of the valve stem shall be determined by calculation. Under
the conditions of meeting the operating strength, it shall also meet the stability
requirements. Its dangerous section shall be set outside the pressure boundary
above the stuffing box.
5.5.2 The surface roughness Ra value of the contact surface between the stem
and the packing shall be no more than 0.4 μm.
5.5.3 The stem shall be able to transmit the necessary operating force to the
valve closing member; be able to withstand the additional stress of the
operating load.
5.9 Operation
5.9.1 Manual operation
5.9.1.1 When the manually-operated valve is operated and subjected to the
performance test under low temperature conditions, the maximum operating
force on the edge of handle or handwheel shall not exceed 360 N. When
equipped with deceleration mechanism and actuator, it shall be adapted to the
requirements of ambient temperature and working conditions.
5.10 Material
5.10.1 According to the working temperature and material properties, select the
valve material. It shall meet the following requirements.
5.13.3 Ultrasonic testing
Forged valve body, bonnet, and stem, etc. shall be subjected to ultrasonic
testing. The inspection result shall not be lower than the requirements of level 2 in JB/T 6903-2008.
5.13.4 Magnetic particle testing
5.13.5 Degreasing treatment
When required in the order contract, the valve shall be degreased.
6 Test methods
6.1 Marking inspection
The contents of the visual examination are as follows.
6.2 Visual quality of steel castings
Visual examination. Compare the drawing in JB/T 7927 with any surface of the
casting. The comparison area of the casting surface shall be the same as the
size of the picture. The comparison result shall meet the requirements of 5.11.
6.3 Dimensional check
6.4 Chemical composition
The material of the main pressure parts shall be analyzed for chemical
composition. Each lot of materials with the same heat number shall be
inspected at least once. The inspection results shall comply with the provisions of 5.10.3.
6.5 Mechanical properties
6.5.1 For each lot of materials of main pressure parts (the same heat number,
the same manufacturing process, and the same heat treatment conditions), the
mechanical properties shall be inspected at least once.
6.5.2 For the test methods and results of mechanical properties, refer to the
corresponding material standards listed in Appendix A. It shall comply with the
provisions of 5.10.3.
6.6 Normal temperature test
It shall be carried out in accordance with the provisions of GB/T 26480.It shall
meet the requirements of 5.2.1.The chloride ion content of the hydraulic test
medium for stainless steel valves shall not exceed 25 μg/g.
6.7 Low temperature test
6.7.1 Test requirements
The low temperature test shall be carried out after passing the normal
temperature test.
6.7.2 Test conditions
6.7.2.1 Test medium
The test medium is shown in Table 7.
6.7.2.2 Cooling medium
The cooling medium is shown in Table 8 or as specified in the order contract.
6.7.2.5 Test preparation
Before the test, the valve parts shall be degreased and dried. The valve shall
be installed in a clean and dustproof environment. Except for the primer, the
valve shall not be painted.
6.7.3 Test procedure
6.7.3.1 The normal temperature test uses nitrogen or air as the initial detection
test, to ensure that the valve is tested under appropriate conditions.
6.7.3.2 The typical test device of low temperature valve is shown in Figure 13.
Install the valve in the test container; connect all the joints, to ensure that the
valve packing gland is located above the lid of the incubator.
6.7.3.3 Before the valve starts to cool, use 0.2 MPa helium medium to
continuously purge the valve cavity, to replace the air in the valve cavity.
6.7.4 Test procedure of check valve
6.7.4.1 The valve test device is shown in Figure 13.The test device shall be
able to reverse the gas source and the measurement system. According to the
opening direction, the check valve is installed in the test container. All joints are
connected.
6.7.4.2 In accordance with 6.7.3.1, perform the initial system verification test on
the marked flow direction of the check valve.
6.9 Nondestructive testing
6.9.1 Radiographic testing
Radiographic testing is carried out in accordance with the provisions of JB/T
6440-2008 and NB/T 47013.2-2015.The inspection result shall meet the
requirements of 5.13.1.2.
6.9.2 Penetrant testing
Penetrant testing of the overlaying-welding surface is carried out in accordance
with the provisions of GB/T 22652.The others are carried out in accordance
with the provisions of NB/T 47013.5-2015.The inspection result shall meet the
requirements of 5.13.2.
6.9.3 Ultrasonic testing
Valves with a nominal size greater than DN25 are tested in accordance with the
provisions of JB/T 6903-2008.The forged valve body, bonnet, and stem, etc.
are subjected to ultrasonic testing piece by piece. The testing results shall meet
the requirements of 5.13.3.
6.9.4 Magnetic particle testing
6.9.4.1 The parts of ferromagnetic materials such as valve body and bonnet
shall be subjected to magnetic particle testing.
6.9.4.2 The magnetic particle testing method of steel castings is in accordance
with the provisions of JB/T 6439-2008.The magnetic particle testing method of
forgings is in accordance with the provisions of NB/T 47013.4.The inspection
results shall meet the requirements of 5.13.4.2.
6.10 Anti-static test
A new and dry valve shall be subjected to no less than 5 cycles of opening and
closing operation. It shall use a DC power supply not exceeding 12 V for
resistance measurement. The measurement result shall meet the requirements
of 5.1.11.
7 Inspection rules
7.1 Inspection items
7.1.1 The inspection of low temperature valves is divided into exit-factory
inspection and type test.
7.1.2 The inspection items, technical requirements, and test methods shall be
in accordance with Table 10.
7.2 Exit-factory inspection
Valves shall be subjected to exit-factory inspection one by one. Only after
passing the inspection, can it leave the factory.
7.3 Type test
7.3.1 In one of the following situations, the prototype shall be type tested. The
mass production can only be carried out after the test is passed.
7.3.2 When the type test is required by the technical agreement, the type test
shall be conducted by sampling. Samples can be randomly selected from the
products, which pass the inspection, at the end of the production line; or
randomly selected from the finished product warehouse. Or 1 piece is randomly
selected from products, which have been supplied to users but have not been
used and remain in the exit-factory state. During the quality assessment of the
entire series of products, according to the range of this series, 2 or 3 typical
specifications are selected therefrom for testing.
7.3.3 All test items of the type test shall meet the requirements of Table 10.
8 Marking
8.1 It shall be in accordance with the provisions of GB/T 12220.It shall mark
the minimum design temperature on the nameplate.
8.2 The nameplate material shall be austenitic stainless steel.
8.3 Valve marking and identification shall be complete, clear, and correct.
8.4 The valve body shall be cast or printed with permanent medium flow
direction indicating arrow. For valves with pressure relief direction requirements,
the relief direction mark shall be set on the obvious position of the valve.
9 Painting, packaging, transportation, and storage
9.1 Valves in a marine atmospheric environment shall be painted to meet
environmental corrosion requirements or as required by the order contract.
9.2 Packaging, transportation, and storage shall comply with the provisions of
JB/T 7928.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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