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This standard is a revision of HG/T 20580-2011 Specification of design base for steel chemical vessels according to the requirements of Plan for the development and revision of the third batch of professional standards in 2017 (GONGXINTINGKE [2017], No.106) issued by the Ministry of Industry and Information Technology. It was prepared by Sinopec Ningbo Engineering Co., Ltd., the chief development organization, jointly with other participating development organizations under the organization of the Equipment Design Professional Committee of CPCEA/National Technology Center of Process Equipment entrusted by the editorial department of the standard - China Petroleum & Chemical Engineering Survey and Design Association (CPCEA).
This standard replaces HG/T 20580-2011 Specification of design base for steel chemical vessels from the implementation date hereof.
During the revision process of this standard, the drafting group, through extensive investigation, careful summarization of practical experience, and consultation of relevant foreign design standards, reviewed and finalized the standard, on the basis of extensive consultation.
This standard consists of 10 clauses and 7 annexes, mainly including general provisions, terms and symbols, basic requirements, design pressure, design temperature, design loads, addition to thickness, design working life, minimum thickness and allowable stresses.
The following main changes have been made with respect to HG/T 20580-2011 Specification of design base for steel chemical vessels:
1. The Clause "Scope" is modified with supplements and renamed as "General provisions";
2. Some terms are added;
3. The subclause “Symbols” is added;
4. The Clause “Basic requirements” is added;
5. Some contents of "Design temperature" are revised;
6. Some contents of "Design working life" are revised;
7. Annex A "Common failure modes of pressure vessels" is added;
8. Annex B "Control values of top deflection" is added;
9. Annex G "High temperature oxidation rate of metallic materials" is added;
10. The original attached figure 1 "National reference wind pressure distribution diagram" is canceled;
11. The original attached figure 2 "National reference snow pressure distribution diagram" is canceled.
Standard for design base of steel chemical vessels
1 General provisions
1.0.1 This standard is developed in order to implement national laws and regulations in the design of steel chemical vessels, reasonably determine the design parameters of vessels, and ensure safety, applicability, economic rationality, advanced technology and quality.
1.0.2 This standard is applicable to the determination of design base of steel chemical vessels.
1.0.3 This standard is not applicable to the determination of design base of pressure vessel chamber in steel rotating or reciprocating chemical mechanical equipment.
1.0.4 In addition to those specified in this standard, the design base of steel chemical vessels shall also be determined in accordance with the requirements of the current relevant standards of the nation.
2 Terms and symbols
2.1 Terms
2.1.1
pressure vessel
closed vessel containing fluid medium under pressure
2.1.2
stationary pressure vessel
pressure vessel installed and used in a fixed location
2.1.3
vessel under internal pressure
vessel whose internal pressure is higher than the external pressure during normal operation
2.1.4
vessel under external pressure
vessel whose external pressure is higher than the internal pressure during normal operation
2.1.5
vacuum vessel
vessel with pressure (absolute pressure) of medium inside less than the ambient atmospheric pressure, namely that working in vacuum state, which is a special vessel under external pressure
2.1.6
atmospheric vessel
vessel directly exposed to ambient atmosphere or having working (gauge) pressure of zero
2.1.7
chamber
relatively independent closed space containing the medium in the vessel
2.1.8
part, component
basic unit parts of pressure vessel, such as shells, covers, flanges, pads and support rings of various shapes
2.1.9
pressure part
parts and components of vessel bearing the pressure load (including internal and external pressure)
2.1.10
non-pressure part
parts and components directly or indirectly connected with the vessel in order to meet the use requirements, without bearing pressure load (or bearing negligible pressure load)
2.1.11
pressure
force acting perpendicularly on the unit area of an object, namely the pressure in physics; it refers to gauge pressure herein, unless otherwise indicated
2.1.12
absolute pressure
pressure measured based on zero pressure in absolute vacuum state, which is expressed by adding the letter “A” or “a” following the pressure unit
2.1.13
gauge pressure
difference between the internal pressure of the vessel and the ambient atmospheric pressure, which is expressed by adding the letter “G” or “g” following the pressure unit. In the documents on pressure vessel design, unless otherwise specified, the pressure involved refers to the gauge pressure
2.1.14
operating pressure, working pressure
maximum possible pressure on the top of vessel under normal working condition
2.1.15
design pressure
preset maximum pressure on the vessel top, which shall be taken as the basic design load condition together with the corresponding design temperature; it shall not be less than the working pressure
2.1.16
calculation pressure
pressure used to determine the part thickness at the corresponding design temperature, including additional loads such as the static pressure of liquid column
2.1.17
maximum allowable working pressure (MAWP)
maximum allowable working pressure on the vessel top at corresponding specific temperature, which is calculated according to the effective thickness of each pressure part of the vessel and by taking into account all the loads borne by the part, and the minimum value is taken
2.1.18
actuating pressure
set pressure of the safety valve or the design burst pressure of the bursting disc herein
2.1.19
set pressure
preset pressure under which the safety valve starts to open under operating conditions, which is the gauge pressure measured at the valve inlet. Under such pressure, the force opening the valve generated by medium in specified operating conditions is balanced with that keeping the valve disc on the valve seat
2.1.20
design burst pressure
burst pressure value of the bursting disc at the design burst temperature, set according to the working conditions of the vessel and the corresponding safety technical specifications
2.1.21
test pressure
pressure on the vessel top during pressure test or leakage test
2.1.22
operating temperature, working temperature
temperature of contents in the vessel under specified normal working conditions
2.1.23
metal temperature
mean temperature along the metal section of the vessel part during the usage of the vessel
For shell and tube heat exchangers, the metal temperature of shell-side cylinder and the metal temperature of heat exchange tube (i.e. wall temperature) refer to the mean metal temperature along its axial length.
2.1.24
design temperature
metal temperature set for parts when the vessel is under normal working conditions
2.1.25
minimum design metal temperature (MDMT)
minimum metal temperature of each part under various possible conditions expected during the operation of the vessel when such vessel is designed
2.1.26
test temperature
metal temperature of the vessel shell during pressure test or leakage test
2.1.27
ambient temperature
temperature of medium around the location of the vessel
2.1.28
mean monthly minimum temperature
sum of the minimum temperature of each day in the current month divided by the number of days of that month
2.1.29
mean daily minimum temperature
minimum value of daily mean temperature over the years
2.1.30
required thickness
thickness calculated according to the calculation method specified in the standard based on the calculated pressure. If necessary, the thickness required by other loads (see Clause 6) shall also be taken into account. For parts under external pressure, it refers to the minimum thickness that meets the stability requirements
2.1.31
design thickness
sum of required thickness and corrosion allowance
2.1.32
nominal thickness
sum of design thickness and negative deviation of material thickness, rounded up to the thickness under the standard specification of material, generally the thickness marked in the design drawings (that is, the drawing thickness).
2.1.33
effective thickness
thickness obtained by deducting the corrosion allowance and negative deviation of material thickness from the nominal thickness
2.1.34
minimum required fabrication thickness
minimum thickness required to ensure meeting the design requirements after the pressure part is fabricated
2.1.35
thickness of steel material
thickness of raw materials such as steel plates, steel pipes or forgings which the vessel is directly made of
2.1.36
corrosion allowance
addition to make up for thickness reduction caused by corrosion and mechanical wear, so as to meet the design working life of parts
2.1.37
volume
geometric volume of the vessel or its chamber, which is calculated based on the dimensions marked on the design drawings (regardless of manufacturing tolerances) and rounded off. Generally, it is necessary to deduct the volume of internal components permanently connected to the inside of the vessel
For a shell and tube heat exchanger, the geometric volume of the shell side shall be deducted from the volume of its tube bundles, and that of the tube side shall be added with the volumes of all heat exchange tubes.
2.1.38
reference wind pressure
reference pressure of wind load, which is generally determined using the Bernoulli Equation (see Formula 6.0.1) based on the wind speed and the corresponding air density, in which, the wind speed is the maximum once-in-50-year speed obtained through probability statistics with the observed data of the mean wind speed within 10 min at a height of 10 m above the local open flat ground
2.1.39
reference snow pressure
reference pressure of snow load, which is generally determined based on the maximum once-in-50-year value obtained through probability statistics with the observed data of snow self-weight on the local open flat ground
2.1.40
seismic precautionary intensity
seismic intensity which is approved as the criterion of seismic precaution of an area according to the authority specified by the nation
2.1.41
design basic acceleration of ground motion
design value of seismic acceleration with exceeding probability of 10% during the 50-year design reference period
2.1.42
site
location of engineering groups, having the same response spectrum characteristics, and covering an area equivalent to the factory area, residential area and natural village or a flat area of not less than 1.0 km2
2.1.43
terrain roughness
grade used to describe the distribution of irregular obstacles on the ground when the wind blows over the ground within 2 km before reaching the structure
2.1.44
seismic design
specialized design for a vessel that requires seismic fortification, including seismic calculation and seismic precaution measures
2.1.45
seismic fortification measures
seismic design content excluding seismic action calculation and resistance calculation; it includes basic requirements of seismic design and seismic fortification structure measures
2.1.46
load combination
provisions for the design values of various loads appearing at the same time in order to ensure the reliability of the vessel
2.1.47
design working life
period during which a vessel is designed to be used for its intended purpose
2.2 Symbols
C1——the negative deviation of steel thickness, mm;
C2——the corrosion allowance, mm;
D——the nominal diameter of the steel pipe, mm;
dc2——the annual corrosion rate, mm/a;
S——the nominal wall thickness of steel pipe, mm;
Smin——the minimum wall thickness of steel pipe, mm;
td——the design temperature,℃;
tW——the working temperature,℃;
δ——the required thickness, mm;
δd——the design thickness, mm;
δe——the effective thickness, mm;
δmin——the minimum required fabrication thickness, mm;
δn——the nominal thickness, mm;
δs——the thickness of steel material, mm.
3 Basic requirements
3.0.1 The possible failure modes of the vessel in use shall be considered. See Annex A for common failure modes of pressure vessels.
3.0.2 Chemical vessels in regions with a design basic acceleration of ground motion of 0.05 g and above or a seismic precautionary intensity of 6 or above shall be subjected to seismic design. If the design basic acceleration of ground motion is 0.05 g or the seismic precautionary intensity is 6, seismic action calculation may be omitted for vessels other than Class III pressure vessels specified in the current regulation TSG 21-2016 Supervision regulation on safety technology for stationary pressure vessel, Category III storage tanks specified in the current professional standard AQ 3053 Safety technical code for vertical cylindrical steel welded tank, vertical vessels supported by skirt having a height greater than 80 m and vessels used for firefighting, but these vessels shall meet the requirements of seismic fortification measures.
3.0.3 For chemical vessels subjected to seismic design, after suffering earthquake corresponding to the seismic precautionary intensity of this region, their bodies, supporting members and anchor structures shall not be damaged. The seismic design of chemical vessels may be performed in accordance with the current national standard GB/T 50761 Standard for seismic design of petrochemical steel equipment.
3.0.4 For a pressure vessel equipped with over pressure relief device, the actuating pressure of such device shall not be higher than the design pressure of the pressure vessel. If the pressure vessel has the maximum allowable working pressure (MAWP) indicated in the drawing, the actuating pressure of such device shall not be higher than the MAWP of the pressure vessel.
3.0.5 For a pressure vessel with safety valves, if air tightness test requirements are put forward during design, the MAWP of the vessel shall be indicated by the designer in the design drawings. The MAWP may be determined with the following methods: First, determine the MAWPs of the vessel’s cylinder and covers respectively, and take the smaller as the MAWP of the vessel, and then check other pressure parts with this MAWP.
3.0.6 The tube nozzle on the vessel shall not only be able to withstand the design pressure at the design temperature, but also the external load of external piping. Unless otherwise specified, the external load that the opening nozzle and pipe flange can bear may be determined according to the current professional standard SH/T 3074 Steel pressure vessels in petrochemical industry.
Contents
Foreword i
1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 Basic requirements
4 Design pressure
5 Design temperature
6 Design loads
7 Addition to thickness
7.1 Determination of addition to thickness
7.2 Negative deviation of thickness for steel material
7.3 Corrosion allowance
8 Design working life
9 Minimum thickness
10 Allowable stresses
Annex A (Informative) Common failure modes of pressure vessels
Annex B (Informative) Control values of top deflection
Annex C (Normative) Saturated vapor pressure and boiling point under atmospheric pressure of several common media
Annex D (Informative) Load estimation table of steel platform, straight ladder and tray
Annex E (Informative) Piling density of common packings
Annex F (Normative) Negative deviation of thickness for common steel materials
Annex G (Informative) High temperature oxidation rate of metallic materials
Explanation of wording in this standard
List of quoted standards
