NB/T 47011-2022Zirconium pressure vessels (English PDF)

Foreword

This document was issued on 4 November 2022 by the National Energy Administration of the PRC and takes effect on 4 May 2023.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 23.020.30, Chinese classification J 74.

It replaces NB/T 47011-2010, which is superseded.

This document has been drafted 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 NB/T 47011-2010, Zirconium pressure vessels. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to NB/T 47011-2010.

a) The scope of application has been revised: the main body of the standard now applies to single layer welded pressure vessels (including tubular shells) whose shells are made entirely of zirconium material (see Clause 1).

b) The indispensable normative references have been adjusted as required by the main body of the document (see Clause 2).

c) Supplementary requirements have been introduced for GB/T 21183 standard zirconium plate used for the fabrication of pressure retaining components (see 5.2.2).

d) Penetrant testing requirements have been introduced for zirconium forgings used for the fabrication of pressure retaining components (see 5.4.3).

e) Penetrant testing requirements have been introduced for zirconium bars used for the fabrication of pressure retaining components (see 5.5.2).

f) Requirements for externally purchased finished zirconium parts and components have been added (see 7.1.1.2).

g) Requirements relating to risk prevention and control during the fabrication of zirconium vessels have been added (see 7.1.5 and 7.1.6).

h) Requirements for the re-inspection of materials have been added (see 7.2.1).

i) The requirements of the welding clauses have been revised and supplemented (see 7.4).

j) The requirements of the heat treatment clauses have been revised and supplemented (see 7.5).

k) The requirements of the clauses on test coupons and test specimens have been revised and supplemented (see 7.6).

l) The requirements of the non-destructive testing clauses have been revised and supplemented (see 7.7).

m) The requirements of the clauses on pressure tests and leak tests have been revised and supplemented (see 7.8).

n) The requirements of the clauses on the hot gas cycling test have been revised and supplemented (see 7.9).

o) The normative annex Zirconium clad plate pressure vessels and zirconium lined pressure vessels has been added (see Annex D).

p) The informative annex Material properties of zirconium for pressure vessels has been revised (see Annex E).

q) The informative annex Welded joint structures of zirconium clad plate vessels and zirconium lined vessels has been revised (see Annex F).

Attention is drawn to the possibility that some of the content of this document may involve patents. The issuing body of this document assumes no responsibility for identifying patents.

This document was proposed by and is under the jurisdiction of the National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China (SAC/TC 262).

Drafting organizations of this document: Hefei General Machinery Research Institute Co., Ltd.; China Special Equipment Inspection and Research Institute; Nanjing Baose Co., Ltd.; Sinopec Engineering Construction Co., Ltd.; CNNC Baoti Zirconium Industry Co., Ltd.; Xi'an You'nai Special Vessel Manufacturing Co., Ltd.; Zhejiang University of Technology; Hefei General Special Material and Equipment Co., Ltd.; China Huanqiu (Wuhuan) Engineering Co., Ltd.; Baoti Group Co., Ltd.; Western Titanium Industry Co., Ltd.

Main drafters of this document: Cui Jun, Chen Zhiwei, Wu Pijie, Li Shengli, Dai Xingwang, Li Xianjun, Sun Wancang, Chen Bingbing, Du Yongqin, Xu Pengcheng, Xu Caifu, Feng Junning, Hu Xukun, Dai Yi.

The successive editions of this document and of the document it replaces are as follows: first issued in 2010 as NB/T 47011-2010; this is the first revision.

1 Scope

NB/T 47011-2022 governs pressure vessels made of zirconium and zirconium alloys, replacing the 2010 edition. Zirconium is the material of last resort for the most aggressive chemical duty - hot concentrated sulphuric, hydrochloric and organic acids, and urea service - where even titanium and high nickel alloys corrode, and it is expensive enough that a vessel is normally built as zirconium clad on steel or as a thin loose liner. Almost every rule follows from the metal's behaviour: it absorbs oxygen, nitrogen and hydrogen readily at temperature and embrittles, it ignites as fine swarf, and it is ruined by contact with iron. The standard sets the permitted grades and their allowable stresses against temperature, together with zirconium-clad plate and the requirements on the bond. It covers general requirements and design conditions, the design of shells, heads, openings, nozzles and flanges, and wall thickness with the corrosion allowance appropriate to the service. Fabrication is treated at length - forming and its temperature limits, cutting, the cleanliness and complete segregation from ferrous tooling, welding procedure and welder qualification with the inert gas shielding and trailing shields required, the control of weld colour as evidence of shielding, heat treatment and weld inspection. Testing, marking and the documentation delivered with the vessel close the document. It applies to the design, manufacture, inspection and acceptance of zirconium pressure vessels in China.

1.1 This document specifies the requirements for the materials, design, fabrication, inspection and acceptance of zirconium pressure vessels. It applies to single layer welded pressure vessels (including tubular shells) whose shells are made entirely of zirconium material.

1.2 This document applies to zirconium pressure vessels with a design pressure not greater than 35 MPa.

1.3 The design temperature range covered by this document is determined by the service temperature permitted for the zirconium material.

1.4 The design and calculation methods given in this document apply to pressure retaining components made entirely of zirconium material. Those parts of a zirconium pressure vessel that are made of non-zirconium materials shall be designed and calculated in accordance with the relevant product standard for the material concerned.

1.5 This document does not apply to the following pressure vessels.

a) Vessels with a design pressure lower than 0.1 MPa and a degree of vacuum lower than 0.02 MPa.

b) Vessels governed by the Regulation on Safety Technology Supervision for Transportable Pressure Vessels.

c) Pressure vessels used in military equipment, nuclear facilities, aerospace craft, railway locomotives, offshore installations and ships, and underground mines.

d) Pressure retaining chambers that form an integral part of, or are a component of, rotating or reciprocating mechanical equipment, such as pump casings, compressor casings, turbine casings, hydraulic cylinders and papermaking rolls.

e) Vessels heated directly by flame.

f) Plate heat exchangers, spiral plate heat exchangers, air cooled heat exchangers and cooling coils.

g) Vessels whose volume (the geometric volume excluding the permanent internals) is less than 0.03 cubic metres, or whose inside diameter (for non-circular cross sections, the largest geometric dimension of the inner boundary of the cross section) is less than 150 mm.

h) Vessels for which a fatigue analysis is carried out.

1.6 Definition of the boundaries of the vessel.

1.6.1 Connections between the vessel and external piping are bounded as follows: a) the end face of the groove of the first circumferential joint for a welded connection; b) the end face of the first threaded joint for a threaded connection; c) the sealing face of the first flange for a flanged connection; d) the first sealing face for a special connector or pipe fitting connection.

1.6.2 The pressure retaining heads, flat covers and their fasteners of nozzles, manholes, handholes and the like.

1.6.3 The connection welds between non-pressure retaining components and pressure retaining components.

1.6.4 Non-pressure retaining components directly attached to the vessel, such as supports and skirts.

1.6.5 The overpressure relief devices of the vessel.

1.7 For vessels or pressure retaining components whose structural dimensions cannot be determined in accordance with this document, the following design methods may be used: a) design by verification test (such as experimental stress analysis or verification hydrostatic test), in compliance with GB/T 150.1; b) comparative empirical design based on comparable structures already in service, in compliance with GB/T 150.1; c) design by stress analysis and assessment methods including the finite element method, in compliance with GB/T 150.1.

2 Normative references

The following documents contain provisions which, through normative reference in this text, constitute indispensable provisions of this document. For dated references, only the edition corresponding to that date applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 150.1 Pressure vessels - Part 1: General requirements.

GB/T 150.2 Pressure vessels - Part 2: Materials.

GB/T 150.3 Pressure vessels - Part 3: Design.

GB/T 150.4 Pressure vessels - Part 4: Fabrication, inspection and testing, and acceptance.

GB/T 151 Heat exchangers.

GB/T 196 General purpose metric screw threads - Basic dimensions.

GB/T 197 General purpose metric screw threads - Tolerances.

GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature.

GB/T 228.2 Metallic materials - Tensile testing - Part 2: Method of test at elevated temperature.

GB/T 232 Metallic materials - Bend test method.

GB/T 241 Metallic tubes - Hydrostatic pressure test method.

GB/T 242 Metallic tubes - Drift expanding test method.

GB/T 1804 General tolerances - Tolerances for linear and angular dimensions without individual tolerance indications.

GB/T 4842 Argon.

GB/T 4844 Pure helium, high purity helium and ultra pure helium.

GB/T 5193 Titanium and titanium alloy processed products - Method for ultrasonic inspection.

GB/T 8769 Zirconium and zirconium alloy bars and wires.

GB/T 12337 Steel spherical tanks.

GB/T 12969.1 Titanium and titanium alloy tubes - Method for ultrasonic flaw detection.

GB/T 13747 (all parts) Methods for chemical analysis of zirconium and zirconium alloys.

GB/T 16749 Expansion joints of pressure vessels.

GB/T 21183 Zirconium and zirconium alloy plate, strip and foil.

GB/T 25198 Heads for pressure vessels.

GB/T 26283 Zirconium and zirconium alloy seamless tubes.

GB/T 26314 Zirconium and zirconium alloys - Designations and chemical compositions.

GB/T 30568 Zirconium and zirconium alloy forgings.

HG/T 20592 to 20635 Steel pipe flanges, gaskets and fasteners.

JB/T 4745 Titanium welded vessels.

NB/T 10558 Painting and transport packaging of pressure vessels.

NB/T 11025 Reinforcing pads.

NB/T 47002.3 Clad plates for pressure vessels - Part 3: Titanium-steel clad plate.

NB/T 47013.2 Non-destructive testing of pressure equipment - Part 2: Radiographic testing.

NB/T 47013.3 Non-destructive testing of pressure equipment - Part 3: Ultrasonic testing.

NB/T 47013.5 Non-destructive testing of pressure equipment - Part 5: Penetrant testing.

NB/T 47013.7 Non-destructive testing of pressure equipment - Part 7: Visual testing.

NB/T 47013.8 Non-destructive testing of pressure equipment - Part 8: Leak testing.

NB/T 47014 Welding procedure qualification for pressure equipment.

NB/T 47020 to 47027 Pressure vessel flanges, gaskets and fasteners.

NB/T 47041 Tower vessels.

NB/T 47042 Horizontal vessels.

YS/T 753 Zirconium and zirconium alloy plates for pressure vessels.

YS/T 887 Zirconium and zirconium alloy welding wire.

TSG 21 Supervision regulation on safety technology for stationary pressure vessels.

TSG Z6002 Assessment rules for welding operating personnel of special equipment.

AWS A5.24 Specification for Zirconium and Zirconium-Alloy Welding Electrodes and Rods.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 150.1 and GB/T 151 and the following apply.

3.1 zirconium pressure vessel: a pressure vessel whose shell is made entirely of zirconium material.

3.2 industrial class zirconium: a zirconium material in which the hafnium content is not strictly controlled (a content not greater than 4.5 per cent is acceptable). Examples are the Chinese grades Zr-1, Zr-3 and Zr-5 and the United States grades R60700, R60702 and R60705.

3.3 low oxygen zirconium: a zirconium material with an oxygen content less than or equal to 0.10 per cent, such as the Chinese grade Zr-1 and the United States grade R60700. Low oxygen zirconium plate is commonly used as the cladding layer of a zirconium clad plate and can be clad directly onto carbon steel, low alloy steel and similar base metals.

3.4 interlayer of pure titanium: an interlayer of ordinary industrial grade pure titanium plate (usually 2 mm to 3 mm thick) placed between the zirconium cladding layer and the steel base layer, known as the pure titanium interlayer (sometimes also called the pure titanium transition layer). The three materials together form a zirconium-titanium-steel three layer clad plate. Because no brittle intermetallic compounds form between zirconium and titanium, and because titanium bonds relatively easily to steel, a good cladding quality can be obtained.

3.5 press working: a production method that uses the plastic deformation produced in a metal under the action of an external force to obtain raw material, blanks or finished products having a given shape, dimensions and mechanical properties.

3.6 inserted strip: a metal part placed beneath a strip cover or a lining. It is mostly embedded in a machined groove in the shell of a clad plate vessel or a lined vessel so as to be flush with the adjacent cladding layer or lining.

3.7 strip cover: a corrosion resistant metal part laid over the cladding layer of a clad plate vessel or over the lining of a lined vessel and connected to it by fillet welding.

4 General requirements

4.1 In addition to complying with the provisions of this document, the design, fabrication, inspection and acceptance of vessels shall comply with the requirements of the relevant national laws, regulations, rules and safety technical regulations.

4.2 The design and fabrication of pressure vessels within the scope of the Regulation on Safety Technology Supervision for Stationary Pressure Vessels shall be subject to supervision by the special equipment safety supervision body.

4.3 The design and manufacturing organizations of the vessel shall have a sound quality management system in effective operation.

4.4.1 Qualifications. a) For the design of pressure vessels within the scope of the Regulation on Safety Technology Supervision for Stationary Pressure Vessels, the design organization shall hold the corresponding special equipment (pressure vessel) design licence, and the manufacturing organization shall have obtained the corresponding special equipment (pressure vessel) design licence. b) For the fabrication of pressure vessels within the scope of that regulation, the manufacturing organization shall hold the corresponding special equipment (pressure vessel) manufacturing licence.

4.4.2.1 Responsibilities of the user or of the organization entrusting the design. The user of the vessel or the organization entrusting the design shall submit the design conditions of the vessel to the design organization in formal written form and is responsible for the correctness and completeness of those design conditions. The design conditions shall contain at least the following items.

a) The main standards and codes on which the design of the vessel is based.

b) Operating parameters (including working pressure, working temperature, liquid level height, nozzle loads and the like).

c) The place where the vessel will be used and its natural conditions (including ambient temperature, seismic fortification intensity, wind load and snow load and the like).

d) The composition and characteristics of the medium.

e) The expected service life.

f) Geometric parameters and nozzle orientations.

g) Other necessary conditions required for the design.

4.4.2.2.1 The design organization is responsible for the correctness and completeness of the design documents.

4.4.2.2.2 The design documents of the vessel shall include at least the strength calculation sheet or stress analysis report, the design drawings, the technical conditions for fabrication and the risk assessment report (where required by the relevant laws and regulations or by the party entrusting the design), and where necessary shall also include the installation, operation and maintenance instructions.

4.4.2.2.3 The general design drawing of a pressure vessel within the scope of the Regulation on Safety Technology Supervision for Stationary Pressure Vessels shall bear the corresponding special equipment (pressure vessel) design seal.

4.4.2.2.4 The risk assessment report issued by the design organization shall comply with the requirements of GB/T 150.1.

4.4.2.2.5 The design organization shall retain the complete set of vessel design documents throughout the design service life of the vessel.

4.4.2.3.1 The manufacturing organization shall fabricate in accordance with the requirements of the design documents. If the original design has to be modified, the written agreement of the original design organization to the modification shall be obtained and a detailed record shall be made of the modified parts.

4.4.2.3.2 Before fabrication of the vessel begins, the manufacturing organization shall prepare a complete quality plan, the content of which shall include at least the fabrication process control points, the inspection items and the acceptance indices for the vessel or for its pressure retaining components.

4.4.2.3.3 During and after the fabrication of the vessel, the inspection department of the manufacturing organization shall carry out the various inspections and tests on the vessel as specified in this document, in the design drawings and in the quality plan, shall issue inspection reports and is responsible for the correctness and completeness of those reports.

4.4.2.3.4 After the vessel has passed inspection, the manufacturing organization shall issue a product quality certificate.

4.4.2.3.5 For every vessel product it manufactures, the manufacturing organization shall retain at least the following technical documents for examination throughout the design service life of the vessel: a) the quality plan; b) the fabrication process drawings or fabrication process cards; c) the product quality certification documents; d) the welding and heat treatment procedure documents of the vessel; e) the records of the inspections and tests which the standard allows the manufacturer to select; f) the records of the checks, inspections and tests made during and after fabrication; g) the original design drawing and the as-built drawing of the vessel.

4.5.1 The design organization (design personnel) of the vessel shall design strictly in accordance with the design conditions supplied by the user or by the organization entrusting the design, shall consider all failure modes that may occur in service and shall propose measures to prevent failure. The calculation of the strength, stiffness and stability of the pressure retaining components of the vessel shall comply with GB/T 150.3 and with the relevant provisions of this document.

4.5.2 Loads. The following loads shall be taken into account in the design: a) internal pressure, external pressure or maximum pressure difference; b) liquid static pressure, which may be neglected when it is less than 5 per cent of the design pressure.

Where necessary, the following loads shall also be taken into account: c) the dead weight of the vessel (including internals and packing) together with the gravity load of the medium contained under normal operating conditions or under pressure test conditions; d) the gravity loads of attached equipment and of insulation material, linings, piping, ladders and platforms; e) wind load, seismic load and snow load; f) the reaction forces of supports, base rings, lugs and other types of supporting members; g) the forces exerted by connected piping and other components; h) the forces caused by temperature gradients or by differential thermal expansion; i) impact loads, including the impact load caused by sudden pressure fluctuation and the reaction force caused by fluid impingement; j) the forces arising during transport or lifting.

4.5.3 When determining the design pressure or the calculation pressure, the following shall be taken into account: a) where an overpressure relief device is fitted on the vessel, the design pressure shall be determined in accordance with GB/T 150.1; b) when determining the design pressure of an external pressure vessel, the maximum internal to external pressure difference that may occur under normal working conditions shall be considered; c) when determining the shell thickness of a vacuum vessel, the design pressure shall be taken as for a vessel subject to external pressure; where a safety control device (such as a vacuum relief valve) is fitted, the design pressure shall be taken as the lower of 1.25 times the maximum internal to external pressure difference and 0.1 MPa; where no safety control device is fitted, 0.1 MPa shall be taken; d) for a vessel made up of two or more pressure chambers, such as a jacketed vessel, the design pressure of each pressure chamber shall be determined separately; when determining the calculation pressure of a component common to two chambers, the maximum pressure difference between the adjacent chambers shall be considered.

4.5.4 When determining the design temperature, the following shall be taken into account: a) the design temperature shall not be lower than the highest temperature that the metal of the component may reach in the working condition; for metal temperatures below 0 degrees C the design temperature shall not be higher than the lowest temperature that the metal of the component may reach; b) where the metal temperatures of the various parts of the vessel differ under working conditions, a design temperature may be set separately for each part; c) the metal temperature of a component may be obtained by heat transfer calculation, or measured on a vessel already in service under the same operating conditions, or determined from the temperature of the medium inside the vessel in combination with the external conditions; d) when determining the minimum design metal temperature, full account shall be taken of the influence of the low ambient air temperature on the metal temperature of the vessel shell during operation; the low ambient air temperature condition is the lowest value of the monthly average lowest air temperature over the years (the sum of the lowest air temperatures of each day of the month divided by the number of days in that month).

4.5.5 A vessel having several different operating conditions shall be designed for the most severe condition; where necessary the combination of the different operating conditions shall also be considered, and the pressure and temperature values under each operating condition and under the design condition shall be indicated on the drawing or in the corresponding technical documents.

4.5.6 Thickness additions. The thickness addition C shall be determined by formula (1) as the sum of C1 and C2, where C is the thickness addition in mm, C1 is the negative deviation of the material thickness in mm as given in 4.5.6.1, and C2 is the corrosion allowance in mm as given in 4.5.6.2.

4.5.6.1 Negative deviation of material thickness. The negative deviation of the thickness of plate or tube shall be taken in accordance with the material standard.

4.5.6.2 Corrosion allowance. In order to prevent the thickness of vessel components from being weakened and reduced by corrosion or mechanical wear, a corrosion allowance shall be considered as follows: a) for components subject to corrosion or wear, the corrosion allowance shall be determined from the expected design service life of the vessel and from the corrosion rate (or wear rate) of the medium on the metal material; b) where the different components of the vessel are subject to different degrees of corrosion, different corrosion allowances may be used.

4.5.7 The minimum thickness of the shell after forming, excluding the corrosion allowance, is 2 mm.

4.5.8 The nominal thickness and the minimum formed thickness of the pressure retaining components of the vessel shall normally be indicated on the design drawing.

4.5.9 Category A and category B welded joints of the vessel shell shall be of the butt joint type with full penetration over the whole cross section.

4.5.10 For the expanded joints between zirconium heat exchanger tubes and steel tubesheets (especially austenitic stainless steel tubesheets), the effect of the temperature rise on the expanded joint force shall be taken into account.

4.6.1.1 The basis for determining the allowable stress of zirconium material not used for bolting is given in Table 1 and the allowable stress shall be selected from Table 4. In Table 1 the allowable stress in MPa is the smallest of the following values: Rm divided by 3.0, Rm at design temperature divided by 3.0, Rp0.2 divided by 1.5, and Rp0.2 at design temperature divided by 1.5, where Rm is the specified lower limit of the tensile strength of the zirconium material at room temperature in MPa, Rm at design temperature is the tensile strength of the zirconium material at the design temperature in MPa, Rp0.2 is the specified lower limit of the non-proportional extension strength of the zirconium material at room temperature in MPa, and Rp0.2 at design temperature is the specified non-proportional extension strength of the zirconium material at the design temperature in MPa.

4.6.1.2 The circumferential allowable stress of welded tubes with a longitudinal seam shall be the allowable stress obtained from Table 1 multiplied by the welded joint coefficient (generally 0.85 for a seam welded without filler wire); the longitudinal allowable stress shall still be determined from Table 1.

4.6.2 The basis for determining the allowable stress of zirconium material in the annealed condition used for bolting is given in Table 2 and the allowable stress shall be selected from Table 5. In Table 2 the allowable stress in MPa is the smallest of the following values: Rm divided by 4.0, Rm at design temperature divided by 4.0, Rp0.2 divided by 1.5, and Rp0.2 at design temperature divided by 1.5, with the same meanings of the symbols as in Table 1.

4.6.3 When the design temperature is lower than 20 degrees C, the allowable stress at 20 degrees C shall be taken.

4.6.4 Allowable axial compressive stress. The allowable axial compressive stress of a cylinder or tube shall be taken as the smaller of the allowable stress value of the material at the design temperature (see Clause 5) and the value B obtained by the methods given in items a) and b) of this clause. The value B shall be obtained by the following steps: a) from the outside radius and the effective thickness of the cylinder or tube, calculate the coefficient A by formula (2) as 0.094 times the effective thickness divided by the outside radius, where A is the external pressure strain coefficient, the effective thickness of the cylinder or tube is in mm and the outside radius of the cylinder or tube is in mm; b) select the appropriate external pressure stress coefficient curve chart for the cylinder material (Figure 1 and Figure 2) and obtain the value B from its temperature line; within the elastic range (the straight line portion of the chart or the region to its left) the value B may be calculated by formula (3) as two thirds of the product of A and E, where B is the external pressure stress coefficient in MPa, A is the external pressure strain coefficient and E is the modulus of elasticity of the material at the design temperature in MPa.

4.6.5 When seismic load or wind load is combined with the other loads given in 4.5.2, the design stress of the component is allowed not to exceed 1.2 times the allowable stress, but in that case the design temperature of the zirconium vessel shall not exceed 315 degrees C. Where seismic load and wind load act simultaneously, the provisions of the relevant standards shall be followed; where no relevant standard provision exists, the simultaneous action of seismic load and wind load is generally not considered.

4.7.1 The welded joints of the vessel shall be classified in accordance with GB/T 150.1.

4.7.2 The welded joint coefficient phi shall be determined from the type of welded joint of the pressure retaining component and from the proportion of the length subjected to radiographic or ultrasonic testing, as follows: a) for double welded butt joints and full penetration butt joints equivalent to double welded joints, with 100 per cent radiographic or ultrasonic testing, phi equals 1.0; b) for single welded butt joints (with a backing strip closely fitted to the base metal along the whole length of the weld root), with 100 per cent radiographic or ultrasonic testing, phi equals 0.9; where radiographic or ultrasonic testing cannot be carried out, phi equals 0.65; c) for single welded circumferential butt joints without a backing strip, where radiographic or ultrasonic testing cannot be carried out, phi equals 0.6.

4.8.1.1 Pressure tests include the hydrostatic test, the pneumatic test and the combined gas and liquid pressure test.

4.8.1.2 After fabrication the vessel shall undergo a pressure test; the type of test, the requirements and the test pressure value shall be indicated on the drawing.

4.8.1.3 The pressure test is generally a hydrostatic test. For vessels not suitable for a hydrostatic test, a pneumatic test or a combined gas and liquid pressure test may be used.

4.8.1.4 Where a combined gas and liquid pressure test is used, the test pressure shall be as specified for the pneumatic test.

4.8.1.5 An external pressure vessel shall be pressure tested with internal pressure, and the test pressure shall be as specified in 4.8.2.3.

4.8.1.6 For a multi-chamber vessel made up of two or more pressure chambers, the test pressure of each chamber shall be determined from its own design pressure and each chamber shall be pressure tested separately: a) the stability of the common components under the test pressure shall be checked; b) if the stability requirement cannot be met, a leak check shall be carried out first and, after it has been passed, the pressure test shall be performed; during the pressure test a certain pressure shall be maintained in the adjacent chamber so that at any moment of the whole test process (including pressurizing, holding and depressurizing) the pressure difference between the chambers does not exceed the allowable pressure difference, and this requirement together with the allowable pressure difference value shall be indicated on the drawing; c) where the test pressure of a given chamber has to be increased, the provisions of 4.8.3 shall be satisfied.

4.8.2.1 The minimum pressure test pressure shall be as specified in 4.8.2.2 and 4.8.2.3 and shall also take into account: a) where a vertical vessel is hydrostatically tested in the horizontal position, the test pressure shall include the liquid static pressure that applies in the vertical position; b) where the liquid static pressure of the medium contained under working conditions is greater than the liquid static pressure of the hydrostatic test, the test pressure shall be increased appropriately.

4.8.2.2 Internal pressure vessels. For the hydrostatic test the test pressure is given by formula (4) as 1.25 times the design pressure multiplied by the ratio of the allowable stress at the test temperature to the allowable stress at the design temperature. For the pneumatic test or the combined gas and liquid pressure test the test pressure is given by formula (5) as 1.10 times the design pressure multiplied by the same stress ratio. Note 1: where the design documents specify a maximum allowable working pressure, the maximum allowable working pressure shall be used in the formulae in place of the design pressure. Note 2: where the main pressure retaining components of the vessel (such as the shell, heads, nozzles, flanges and fasteners) are made of different materials or have different design temperatures, the smallest of the stress ratios of those components shall be used.

4.8.2.3 External pressure vessels. For the hydrostatic test the test pressure is given by formula (6) as 1.25 times the design pressure. For the pneumatic test or the combined gas and liquid pressure test the test pressure is given by formula (7) as 1.10 times the design pressure.

4.8.3 Stress check for the pressure test. Where a test pressure higher than that specified in 4.8.2.2 and 4.8.2.3 is used, the stress level of each pressure retaining component under the test conditions shall be checked before the pressure test; for example, the maximum total membrane stress sigma T of the shell components shall be checked as follows: a) for the hydrostatic test, sigma T shall be less than or equal to 0.9 times Rp0.2 multiplied by the welded joint coefficient; b) for the pneumatic test or the combined gas and liquid pressure test, sigma T shall be less than or equal to 0.8 times Rp0.2 multiplied by the welded joint coefficient, where Rp0.2 is the 0.2 per cent non-proportional extension strength of the shell material at the test temperature in MPa and the welded joint coefficient is that of the cylinder.

4.8.4 For vessels on which the pressure test cannot be carried out as specified above, the design organization shall propose the safety measures to be taken in order to dispense with the pressure test while still ensuring the safe operation of the vessel; these measures shall be approved by the technical officer in charge of the design organization and indicated on the drawing.

4.9.1 Leak tests include the gas tightness test, the ammonia leak test, the halogen leak test and the helium leak test.

4.9.2 Vessels containing media whose toxicity is extremely hazardous or highly hazardous, or which do not permit any slight leakage, shall be leak tested after the pressure test has been passed. Note: the degree of toxicity of the medium shall be determined in accordance with the relevant provisions of the Regulation on Safety Technology Supervision for Stationary Pressure Vessels.

4.9.3 The design organization shall specify the method and the technical requirements of the leak test of the vessel.

4.9.4 Where a leak test is required, the test pressure, the test medium and the corresponding inspection requirements shall be indicated on the drawing and in the design documents.

4.9.5 The test pressure of the gas tightness test is the design pressure.

5 Materials

5.1.1 The zirconium material used in a zirconium pressure vessel shall comply with the provisions of this document; non-zirconium materials used shall comply with the requirements of the corresponding pressure vessel product standard for the material.

5.1.2 Industrial class zirconium shall be selected for zirconium pressure vessels, and its chemical composition, mechanical properties, corrosion resistance, technological properties and physical properties shall meet the fabrication and service requirements. The zirconium grades used for the vessel shall be Zr-1, Zr-3 and Zr-5 of GB/T 26314; the chemical composition of press worked zirconium material and the allowable deviations of the product analysis shall comply with GB/T 26314.

5.1.3 The test methods for zirconium material shall generally comply with the following provisions, and other standard test methods may be used by agreement: a) chemical composition analysis in accordance with GB/T 13747; b) room temperature tensile test in accordance with GB/T 228.1 and elevated temperature tensile test in accordance with GB/T 228.2; c) drift expanding test in accordance with GB/T 242; d) tube pressure test in accordance with GB/T 241; e) bend test in accordance with GB/T 232; f) ultrasonic testing of tube in accordance with GB/T 12969.1, other press worked material by reference to GB/T 5193; g) dimensions and shape measured with measuring instruments of the appropriate accuracy; h) surface quality checked by visual inspection.

5.1.4 Zirconium materials not listed in this document and zirconium materials of foreign grades shall comply with the provisions of the Regulation on Safety Technology Supervision for Stationary Pressure Vessels.

5.1.5 Press worked zirconium material used for vessels (including plate, seamless and welded tube, seamless and welded tube for heat exchangers and condensers, forgings and bars) shall be in the annealed condition, and the surface condition shall be polished, pickled or sand blasted.

5.2.1 Zirconium plate, strip and foil shall comply with YS/T 753, GB/T 21183 and the provisions of this document, and each sheet shall be sampled for a room temperature tensile test.

5.2.2 Where GB/T 21183 zirconium plate is selected for the fabrication of pressure retaining components, the supplementary tests and inspections of Table 3 shall be carried out.

Table 3, sheet by sheet transverse sampling room temperature tensile test, grade Zr-1: Rm greater than or equal to 380 MPa, Rp0.2 greater than or equal to 305 MPa, elongation A50 greater than or equal to 20 per cent.

Table 3, sheet by sheet transverse sampling room temperature tensile test, grade Zr-3: Rm greater than or equal to 380 MPa, Rp0.2 greater than or equal to 205 MPa, elongation A50 greater than or equal to 16 per cent.

Table 3, sheet by sheet transverse sampling room temperature tensile test, grade Zr-5: Rm greater than or equal to 550 MPa, Rp0.2 greater than or equal to 380 MPa, elongation A50 greater than or equal to 16 per cent.

Table 3, sheet by sheet longitudinal and transverse sampling bend test, grades Zr-1 and Zr-3: face and root bending on both sides, bend radius greater than or equal to 5 times the thickness, bend angle 105 degrees with no cracking; remark: this test is carried out on plate of thickness less than or equal to 4.8 mm.

Table 3, sheet by sheet longitudinal and transverse sampling bend test, grade Zr-5: face and root bending on both sides, bend radius greater than or equal to 3 times the thickness, bend angle 105 degrees with no cracking; remark: this test is carried out on plate of thickness less than or equal to 4.8 mm.

Table 3, sheet by sheet ultrasonic testing, grades Zr-1, Zr-3 and Zr-5: for thickness greater than 6.0 mm up to 25.5 mm the requirements of level A1 of GB/T 5193 apply; for thickness greater than 25.5 mm up to 60.0 mm the requirements of level A of GB/T 5193 apply; remark: this testing is not carried out on plate of thickness less than or equal to 6.0 mm.

5.2.3 For zirconium plate on which a corrosion resistance test is required, the test method and the acceptance indices shall be stated when the material is ordered.

5.2.4 The allowable stress of zirconium plate shall be selected from Table 4.

5.3.1 Zirconium tube shall comply with GB/T 26283 and the provisions of this document.

5.3.2 Zirconium tube used for the heat exchanger tubes of heat exchangers shall be subjected to the drift expanding test specified in GB/T 26283, and its outside diameter and wall thickness deviations shall comply with the requirements of GB/T 26283 for tube for general industrial heat exchangers.

5.3.3 For zirconium tube used for purposes other than heat exchanger tubes, the outside diameter and wall thickness deviations shall comply with the requirements of GB/T 26283 for tube for general industrial piping.

5.3.4 Zirconium tube used for the fabrication of pressure retaining components shall be subjected, tube by tube, to ultrasonic testing and to a pressure test in accordance with GB/T 26283.

5.3.5 For zirconium tube on which a corrosion resistance test is required, the test method and the acceptance indices shall be stated when the material is ordered.

5.3.6 The allowable stress of zirconium tube shall be selected from Table 4.

5.4.1 Zirconium forgings shall comply with GB/T 30568 and with the provisions of this document, with Zr-3 corresponding to R60702 and Zr-5 corresponding to R60705.

5.4.2 Disc shaped and annular zirconium forgings shall be sampled for two tangential test specimens per piece for the room temperature tensile test, which shall be passed.

5.4.3 Zirconium forgings used for the fabrication of pressure retaining components shall be subjected, piece by piece, to 100 per cent surface testing in accordance with NB/T 47013.5, level I being acceptable; whether ultrasonic testing is carried out shall be determined by the design organization according to the service requirements.

5.4.4 For zirconium forgings on which a corrosion resistance test is required, the test method and the acceptance indices shall be stated when the material is ordered.

5.4.5 The allowable stress of zirconium forgings shall be selected from Table 4.