GB/T 12243-2021 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 12243-2021 | English | 365 |
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Spring loaded safety valves
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| GB/T 12243-2005 | English | 85 |
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Spring loaded safety valves
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| GB/T 12243-1989 | English | 279 |
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GB/T 12243-2021: Spring loaded safety valves---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/GBT12243-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 13.240
CCS J 16
Replacing GB/T 12243-2005
Spring loaded safety valve
Issued on. APRIL 30, 2021
Implemented on. NOVEMBER 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 Design... 8
5 Performance... 14
6 Test and inspection... 17
7 Appearance... 21
8 Marks and lead seals... 21
9 Protection and storage... 22
Annex A (normative) Non-destructive testing... 23
Annex B (informative) Another method for calculating the rated displacement of safety
valve... 25
1 Scope
This document specifies the design, performance, test and inspection, appearance, mark
and lead seal, protection, storage and transportation for spring loaded safety valves
(hereinafter referred to as safety valves).
This document is applicable to safety valves for steam with a set pressure of
0.1MPa~42.0MPa, and flow passage diameters greater than or equal to 15mm, as well
as safety valves for gas and liquids with a diameter greater than or equal to 7mm.
This document is applicable to safety valves whose discharge medium temperature is
not lower than -29°C.
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 9440, Malleable iron castings
GB/T 12224, General requirements for industrial steel valves
GB/T 12225, General purpose industrial valves - Specification of copper alloy
castings
GB/T 12227, General purpose industrial valve - Specification of spheroidal graphite
iron castings
GB/T 12228, General purpose industrial valves - Specification of carbon steel
forgings
GB/T 12229, General purpose industrial valves - Specification of spheroidal
graphite iron castings
GB/T 12230, General purpose industrial valves - Specification of stainless-steel
castings
GB/T 12241, Safety valves - General requirements
GB/T 12242, Pressure relief devices - Performance test code
GB/T 23935, Design of cylindrical helical springs
JB/T 2203, Center-to-face dimensions of spring loaded safety valve
JB/T 5263, Specification for steel casting for power station valves
JB/T 6439, Methods of magnetic examination for valves
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 12241 as
well as the followings apply.
3.1 full-lift safety valve
A safety valve that the actual discharge area is the flow channel area.
3.2 low-lift safety valve
A safety valve that the actual discharge area is the curtain area.
3.3 discharge area
The smallest cross-sectional area in the fluid passage when the valve is vented.
3.4 flow-rating pressure
The static pressure at the inlet of the valve when measuring the displacement of the
safety valve.
4 Design
4.1 General
4.1.1 The design of the safety valve shall comply with the provisions of GB/T 12241.
4.1.2 The applicable temperature range of the safety valve shall be determined
according to its structure (such as spring heat insulation and cold insulation), material,
medium working characteristics, and temperature change limit value during discharge.
The safety valve shall work normally within the marked temperature range.
4.1.3 When the safety valve used for compressible gas medium is in the discharge state,
due to the phenomenon of condensation and frost due to temperature drop, the
suitability of its structure and materials shall be fully considered. Prevent jamming and
other phenomena during the action of the disc.
4.2 End connection
The end connection of the safety valve shall be in accordance with the provisions of
GB/T 12241.Safety valves with threaded end connections shall be provided with
wrench flats for easy installation.
4.3 Structural length and verticality limit deviation
The structural length of the safety valve is in accordance with the provisions of JB/T
2203 or the requirements of the order contract. The structural length and the limit
deviation of the verticality of the end face of the inlet and outlet flanges shall be in
accordance with the regulations in Figure 1 and Table 1.
4.4 Valve body
4.4.1 The design of the valve body shall ensure that the safety valve does not undergo
any harmful deformation under the strength test and working conditions and is easy to
manufacture and maintain.
4.4.2 The reaction force when the safety valve discharges shall be considered.
Reinforcement measures need to be taken on the inlet or outlet flange of the valve, such
as. adopting the thickness of the flange adjacent to the higher pressure grade or the
flange adjacent to the nominal size of the larger grade.
4.5 Valve seat and disc
4.5.1 The material of the valve seat and disc shall be shock-resistant and medium-
resistant. Cast iron materials shall not be used.
4.5.2 The sealing secondary material can be the material of the valve seat and the disc
body. It can also be welded with another alloy material, or inlaid with non-metallic
elastic sealing material.
4.5.3 The sealing surface of the valve seat and disc shall be in the form of a plane. When
the tapered sealing surface is used, the angle between the sealing surface and the valve
axis is preferably 45°.
4.6 Spring
4.6.1 The requirements for springs shall not be lower than those specified in GB/T
12241.When 4.6.2~4.6.15 is inconsistent with the requirements stipulated in GB/T
12241, the regulations in 4.6.2~4.6.15 shall be followed.
4.6.2 The slenderness ratio (ratio of free height to middle diameter) of the spring shall
be less than 3.7.
4.7 Material
4.7.1 Valve body material
4.7.2 Valve seat and disc
4.7.2.1 The corrosion resistance of the valve seat and disc body material shall not be
lower than that of the valve body material. Iron materials are not allowed. It shall be
suitable for the discharge condition of the safety valve.
4.7.2.2 Safety valve seats for steam and saturated water with nominal pressure greater
than or equal to 10MPa and operating temperature greater than 370°C shall be forged
or rolled materials.
4.7.3 Guide sleeve
The material of the guide sleeve shall have good wear resistance and corrosion
resistance. It shall be suitable for the discharge condition of the safety valve.
4.7.4 Spring
The material of the spring shall be selected according to GB/T 23935 and meet the
requirements of the corresponding standards.
4.8 Non-destructive testing
The non-destructive testing of safety valves shall be in accordance with the provisions
in Annex A.
5 Performance
5.1 Set pressure deviation
The set pressure deviation of the safety valve shall be in accordance with the provisions
in Table 4 and Table 5.
5.2 Excess pressure
The excess pressure of the safety valve shall be in accordance with the provisions in Table 6.
5.3 Opening-closing pressure difference
5.3.1 The opening-closing pressure difference of safety valve for steam shall be in
accordance with the provisions in Table 7.The opening-closing pressure difference of
the safety valve for the steam power boiler with the set pressure greater than 0.4MPa
can be determined separately according to the requirements of the order contract.
5.3.2 The opening-closing pressure difference of safety valve for gas shall be in
accordance with the provisions in Table 8.
5.3.3 The opening-closing pressure difference of safety valve for liquid shall be in
accordance with the provisions in Table 9.
5.4 Opening height
The opening height of the full-lift safety valve is greater than or equal to 1/4 of the
diameter of the flow channel. The opening height of the low-lift safety valve is greater
than or equal to 1/40 of the diameter of the flow channel and less than 1/4 of the
diameter of the flow channel.
5.5 Mechanical properties
During the opening and reseating process of the safety valve, there shall be no
frequency jump and no jamming. When the discharge pressure is reached, it shall be
stable without flutter.
5.6 Sealing
5.6.1 The sealing test pressure shall be in accordance with the provisions in Table 10.
5.6.2 The sealing test medium shall comply with the provisions in Table 11.
5.6.3 Sealing requirements
5.6.3.1 When carrying out the sealing test of the safety valve for steam, check the outlet
port of the valve visually or by listening to the sound. If no leakage is found, the sealing
is considered qualified.
5.7 Displacement
The displacement and size of the safety valve shall be determined according to the
provisions of GB/T 12241.For safety valves for steam and gas whose displacement
coefficients have not been measured, calculations can be made with reference to the
provisions in Annex B.
6 Test and inspection
6.1 Test and inspection items
6.1.1 The inspection items of the safety valve are divided into exit-factory inspection
and type test. Test items according to the provisions of Table 14.
6.1.2 Safety valves shall be inspected one by one before leaving the factory. The
products can leave the factory after passing the inspection. The exit-factory inspection
shall comply with the provisions in Table 14.
6.1.3 Newly designed products or design changes (design modifications that affect fluid
passages, opening heights, and safety valve action characteristics) shall be subject to
the type test.
6.2 General requirements
6.2.1 The exit-factory test shall be carried out before painting.
6.2.2 Test equipment, instruments and test procedures shall comply with the provisions
of GB/T 12241 and GB/T 12242.The accuracy of the pressure gauge during the shell
strength test shall not be lower than level 1.6.
6.2.3 The safety requirements during the test shall comply with the provisions of GB/T
12241.
6.2.4 The set pressure test before leaving the factory shall be carried out according to
6.3 Test medium
During the type test, for the safety valve that is used for steam, the test medium is steam.
For safety valves for gas, the test medium is air or nitrogen. For safety valves for liquid,
the test medium is water.
The set pressure of the safety valve for steam and the safety valve for liquid before
leaving the factory and the medium used for the sealing test are allowed to be replaced
by air or nitrogen.
6.4 Test methods
6.4.1 Shell body strength
The shell body strength test complies with the provisions of GB/T 12241.There shall
be no leakage and structural damage during the test.
6.4.3 Gas sealing test
7 Appearance
After passing the test and before leaving the factory, the appearance of the safety valve
shall be visually inspected. At least the following requirements shall be met.
8 Marks and lead seals
8.1 The nameplate of the safety valve or the outer surface of the safety valve shall at
least have the following marking information.
8.2 The lead seal of the safety valve shall comply with the provisions of GB/T 12241.
9 Protection and storage
9.1 Before the safety valve leaves the factory, all external surfaces except the flange
surface shall be painted with paint (except for corrosion-resistant materials). The flange
faces shall be oil-sealed to prevent corrosion.
9.2 Threaded holes shall be plugged with protective plugs. Temporary plugs shall be
clearly distinguishable from permanent metal plugs.
9.3 To prevent damage to the flange surface during shipment and to prevent the entry
of foreign debris, the inlet and outlet flanges of the safety valve shall be protected by
plugging covers.
9.4 The safety valve shall be sealed and packaged. During transportation and storage,
it shall always be kept upright and not shaken. It is strictly forbidden to push down and
carry.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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