GB/T 12243-2021 Spring loaded safety valves
This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document replaces GB/T 12243-2005 Spring loaded safety valves. In addition to a number of editorial changes, the following main technical changes have been made with respect to GB/T 12243-2005:
a) The range of safety valves applicable to different flow diameters is modified and the range of temperature applicable to safety valves during discharge is added (see Clause 1 of this document; Clause 1 of Edition 2005);
b) Terms and definitions of full-lift safety valve, low-lift safety valve, discharge area and flow-rating pressure are added (see Clause 3 of this document; Clause 3 of Edition 2005);
c) The requirements for lifting mechanism are modified (see 4.1.6 of this document; 4.1.5 of Edition 2005);
d) The requirements for face-to-face dimension of safety valves are added (see 4.3);
e) The requirements for flanges at the inlet and outlet ends are added (see 4.4.2 and 4.4.3);
f) The range of spring index is modified (see 4.6.4 of this document; 4.6.3 of Edition 2005);
g) The requirements for permanent deformation test of springs are modified (see 4.6.8 of this document; 4.6.7 of Edition 2005);
h) The requirements for the deviation of spring rate are modified (see 4.6.9 of this document; 4.6.8 of Edition 2005);
i) The requirements for materials of valve body are modified (see 4.7.1 of this document; 4.7.1 of Edition 2005);
j) The requirements for non-destructive testing are added (see 4.8 of this document);
k) The requirements for discharge pressure are deleted, while the requirements for overpressure are added (see 5.2 of this document; 5.2 of Edition 2005);
l) The requirements for lift are modified (see 5.4 of this document; 5.4 of Edition 2005);
m) The requirements for leakage rate of safety valves with metal sealing face are modified (see 5.6.3.2 of this document; 5.6.3.2 of Edition 2005);
n) An alternative method for calculating the certified capacity of safety valves is added (see 5.7);
o) Items of spring, materials, non-destructive testing and appearance inspection are added (see 6.1);
p) Precision requirements are modified (see 6.2.2 of this document; 6.2.2 of Edition 2005);
q) The test method for gas tightness of safety valves with open bonnet is added (see 6.4.3.2);
r) The protection, storage and transportation requirements are added (see Clause 9).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This standard was proposed by the China Machinery Industry Federation.
This standard is under the jurisdiction of National Technical Committee 503 on Pressure Relief Devices of Standardization Administration of China (SAC/TC 503).
The previous editions of this document and the documents replaced by this document are as follows:
——It was first issued as GB/T 12243-1989 in 1989, and first revised in 2005;
——This is the second revision.
Spring loaded safety valves
1 Scope
This document specifies the design, performance, tests and inspections, appearance, marking and lead sealing, and protection, storage and transportation of spring loaded safety valves (hereinafter referred to as “safety valves”).
This document is applicable to steam, gas and liquid safety valves with set pressure of 0.1 MPa ~ 42.0 MPa, of which the flow diameter shall be ≥ 15mm for steam safety valves and shall be ≥ 7 mm for gas and liquid safety valves.
This document is applicable to safety valves with medium temperature not lower than -29℃ during discharge.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions 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 carbon steel castings
GB/T 12230 General purpose industrial valves - Specification of stainless steel castings
GB/T 12241 Safety valves - General requirements
GB/T 12242 Performance test code - Pressure relief devices
GB/T 23935 Design of cylindrical helical springs
JB/T 2203 Center-to-face dimensions of spring loaded safety valves
JB/T 5263 Specification for steel casting for power station valves
JB/T 6439 Methods of magnetic examination for valves
JB/T 6440-2008 Methods of radiographic examination for steel castings valves
JB/T 6902 Methods for liquid penetrant examination of valves
JB/T 7367 Magnetic particle inspection for helical compression springs
NB/T 47013.2-2015 Nondestructive testing of pressure equipments - Part 2: Radiographic testing
NB/T 47013.3-2015 Nondestructive testing of pressure equipments - Part 3: Ultrasonic testing
NB/T 47013.5-2015 Nondestructive testing of pressure equipments - Part 5: Penetrant testing
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 12241 and the following apply.
3.1
full-lift safety valve
safety valve with actual discharge area as flow area
3.2
low-lift safety valve
safety valve with actual discharge area as curtain area
3.3
discharge area
minimum sectional area of fluid flow path during valve discharge
Note: The minimum sectional area determines the flow through the valve.
3.4
flow-rating pressure
static pressure at valve inlet when measuring the discharge capacity of the safety valve
Note: Static pressure is the absolute pressure of the sum of the set pressure and the overpressure of the safety valve.
4 Design
4.1 General
4.1.1 The safety valves shall be designed in accordance with GB/T 12241.
4.1.2 The applicable temperature range of safety valves shall be determined according to their construction (such as heat insulation and cold insulation of springs), materials, operating characteristics of medium, and the limit of temperature change during discharge. Safety valves shall operate normally within their temperature range indicated.
4.1.3 Since phenomena such as condensation and frosting will occur on safety valves for compressible gas media during discharge due to temperature drop, the suitability of constructions and materials of such valves shall be fully considered so as to avoid jamming and other phenomena during the action of the disc.
4.1.4 The construction shall be designed and manufactured to prevent the discharged medium from directly eroding the spring. As for safety valves with the temperature of their working medium above 235 ℃, it is necessary to consider reducing the influence of medium temperature on springs.
4.1.5 The mechanism for adjusting spring compression shall be provided with a locking device to avoid looseness.
4.1.6 Steam safety valves and safety valves for high-temperature water boilers shall be provided with lifting mechanisms so that when the medium pressure is greater than 75% of the set pressure, the disc can be lifted by the lifting mechanism, and when the water temperature is greater than 93 ℃, such lifting mechanism shall not be used directly to lift the disc. The lifting mechanism shall not affect the action of the safety valve in any way.
4.1.7 Safety valves for toxic and combustible media shall be closed type.
4.1.8 For safety valves with superimposed back pressure or higher built-up back pressure, a back pressure balancing mechanism shall be considered according to the change and size of their back pressure.
4.2 End connection
The end connection of safety valves shall be in accordance with GB/T 12241; safety valves to be connected at threaded end shall be provided with wrench face to facilitate installation.
4.3 Limit deviations of face-to-face dimensions and perpendicularity
The face-to-face dimensions of the safety valve shall be in accordance with JB/T 2203 or the requirements of the order contract, and the limit deviations of face-to-face dimensions and of perpendicularity of flange end faces at inlet and outlet shall meet those specified in Figure 1 and Table 1.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Design
4.1 General
4.2 End connection
4.3 Limit deviations of face-to-face dimensions and perpendicularity
4.4 Valve body
4.5 Seat and disc
4.6 Spring
4.7 Materials
4.8 Non-destructive testing
5 Performance
5.1 Deviation of set pressure
5.2 Overpressure
5.3 Blowdown
5.4 Lift
5.5 Mechanical properties
5.6 Tightness
5.7 Discharge capacity
6 Tests and inspections
6.1 Test and inspection items
6.2 General requirements
6.3 Test media
6.4 Test methods
7 Appearance
8 Marking and lead sealing
9 Protection, storage and transportation
Annex A (Normative) Non-destructive testing
Annex B (Informative) An alternative method for calculating the certified capacity of safety valves
