GB/T 47578-2026Periodic inspection methods for stationary pressure vessels (English PDF)

8.1 Site Conditions

8.1.1 The user unit shall prepare for and assist in the inspection, including the following.

a) For pressure vessels operating under high or low temperature conditions, slowly cool down or heat up according to the operating procedures until they reach a temperature suitable for inspection. The degree of work;

b) Pressure vessels that can rotate or have movable parts should have their switches locked and be securely fixed during inspection;

c) Disconnect the power supply to the pressure vessel and set up clear safety warning signs;

d) Clean or remove any auxiliary parts or other objects that may affect the inspection, in accordance with the inspection requirements;

e) Erect scaffolding, lightweight ladders, and other facilities that meet the inspection requirements;

f) The surfaces to be inspected should be thoroughly cleaned, especially corroded areas and areas prone to cracking or defects. Exposing the metal body;

g) Surfaces subjected to non-destructive testing shall meet the requirements of NB/T 47013 (all parts);

h) For pressure vessels requiring internal inspection, the internal medium should be drained and thoroughly cleaned, and all liquid and gas contaminants should be isolated using blind flanges. Or the source of steam, and at the same time set up clear isolation signs;

i) Pressure vessels containing flammable, explosive, oxidizing, toxic, or asphyxiating media should undergo purging, neutralization, disinfection, and cleaning before internal inspection. Washing, sampling and analysis should be conducted, and the analysis results should meet the relevant specifications and standards; the sampling and analysis intervals should comply with the user's requirements. Relevant regulations;

j) After opening manholes and inspection holes, remove any flammable, explosive, toxic, or harmful gases and liquids that may remain; if necessary, ventilation should also be provided. Facilities such as ventilation and safety rescue.

8.1.2 The user unit and relevant auxiliary units shall conduct a safety inspection before inspection to confirm that the site conditions meet the safety requirements.

a) Scaffolding, lightweight ladders, and other facilities erected for inspection are safe and secure, and safety railings are installed on scaffolding more than 2 meters above the ground;

b) For pressure vessels requiring internal inspection, closed valves should not be used in place of blind flanges;

9.1.1 Inspection Items

9.1.1.1 Periodic inspection items for metal pressure vessels include macroscopic inspection, wall thickness measurement, surface defect detection, safety accessories, and safety protection devices. The main focus is on instrument inspection, with additional testing as needed, including detection of buried defects, material analysis, inspection of sealing fasteners, strength verification, pressure testing, and leakage testing. Verification, etc.

9.1.1.2 If the design documents specify the periodic inspection items, methods and requirements for pressure vessels, those specifications shall also be followed.

9.1.1.3 Internal inspections should be prioritized for periodic inspections of pressure vessels. For pressure vessels that cannot be internally inspected, reliable testing methods should be used. Techniques (such as endoscopy, acoustic emission, and ultrasonic testing) are used to detect internal defects from the outside. For example, in ultra-high pressure crystal reactors, external inspection methods can be employed. The cylinder can be inspected by external methods, and the bottom bolts can generally be left unopened for inspection; non-removable pressure vessels in solar thermal devices Acoustic emission can be used for external detection.

9.1.1.4 For studs of M36 and above (including M36), macroscopic and surface defect inspection should be used to examine their damage and cracks. Ultrasonic testing should be performed if necessary. Wave testing focuses on inspecting the threads and transition areas for circumferential cracks.

9.1.1.5 The insulation layer is generally inspected macroscopically for damage, detachment, and dampness, indicating a tendency for corrosion or formation of corrosion on the container shell or end caps beneath the insulation layer. If cracks are suspected, the insulation layer should be removed for further inspection, and if necessary, the wall thickness should be measured and surface defects should be detected.

9.1.1.6 For pressure vessels with linings, inspect the lining for damage, corrosion, cracks, and detachment. If such pressure vessels are leaking... The signal indicator hole should be checked for any traces of media leakage. If a lining penetration defect is found, or if there is a potential for leakage... When corrosion defects are found in the pressure vessel body, the lining should be partially or completely removed to investigate the corrosion status and other defects of the body.

9.1.1.7 For pressure vessels with weld overlays, inspect the weld overlays for corrosion, cracks, peeling, detachment, and mechanical damage.

9.1.1.8 Heat exchanger tube bundles can be inspected using methods such as rotating ultrasonic, eddy current, and ultrasonic guided wave testing.

9.1.1.9 Pressure vessel nozzles are primarily inspected macroscopically and their wall thickness measured. When necessary, magnetic particle testing, penetrant testing, and ultrasonic testing can be used to inspect welded joints. Perform non-destructive testing.

9.1.2 Macroscopic Test

9.1.2.1 Macroscopic inspection mainly adopts visual methods, and when necessary, endoscopes, magnifying glasses or other auxiliary instruments and measuring tools are used for inspection. The pressure vessel's body structure, geometry, surface condition (such as cracks, corrosion, leaks, deformation), as well as welds, insulation layers, linings, and weld overlays. Layers, etc.

9.1.2.2 Macroscopic tests generally include the following.

a) Structural inspection, including head type, connection between head and shell, opening location and reinforcement, arrangement and type of longitudinal (circumferential) welds, and supports. The type and arrangement of supports or bearings, and the installation of drainage (drainage, sewage) devices, etc.

b) Geometric dimension inspection, including the difference between the maximum and minimum inner diameters on the same cross-section of the cylinder, the misalignment of longitudinal (circumferential) weld joints, and the angles. Angles, undercut, weld reinforcement, etc. The templates used for measuring edge angles are selected according to the requirements of the product standard.

c) Visual inspection, including nameplates and markings, corrosion on the inner and outer surfaces of the pressure vessel, cracks, leaks, and bulges in the main pressure-bearing components and their welds. Damage caused by packaging, deformation, mechanical contact damage, overheating, weld marks on tools and fixtures, arc burns, subsidence, tilting, or cracking of supports, bases, or foundations; high Inclination of vertical and spherical containers with a diameter-to-diameter ratio greater than 5; expansion holes in supports of multi-supported horizontal containers; discharge (drainage, drainage) (Pollution) devices and leak signal indicator holes. blockage, corrosion, deposits; condition of sealing fasteners and anchor bolts; insulation layer. Damage, detachment, dampness, damage, detachment, corrosion, mechanical damage, etc. of linings and weld overlays.

b) should be performed during the initial periodic inspection. Subsequent periodic inspections should only be performed on pressure vessels subjected to fatigue loads, and with particular emphasis on these vessels. New defects were found in the problematic areas.

9.1.2.3 Unless otherwise specified in this document, the inspection and testing methods for pressure vessels are generally macroscopic inspections.

9.1.3 Wall thickness measurement

9.1.3.1 Wall thickness is generally measured using ultrasonic methods. However, pulsed eddy current and electromagnetic ultrasonic methods may also be used, provided the validity of the inspection is guaranteed. Thickness measurement method.

9.1.3.2 The measurement locations should be representative, with a sufficient number of measurement points. After measurement, a graphical record should be made, and any abnormal thickness measurement points should be marked in detail. Thickness Measurement Points are generally selected from the following locations.

a) Locations where the liquid level frequently fluctuates;

b) Parts susceptible to corrosion and erosion, such as material inlets, flow deflections, and abrupt changes in cross-section;

c) Parts where the wall thickness is reduced during manufacturing and parts that are prone to deformation and wear during use;

d) The nozzle body and the container shell near the nozzle;

e) Suspicious areas discovered during macroscopic inspection.

9.1.3.3 When measuring wall thickness, if delamination defects are found in the base material, additional measuring points should be added or ultrasonic testing should be used to determine the distribution of delamination. The inclination of the material relative to the surface of the base material should be plotted and recorded.

9.1.4 Surface Defect Detection

9.1.4.1 Surface defect detection shall employ the magnetic particle testing, penetrant testing, or array eddy current testing methods as specified in NB/T 47013 (all parts). Iron Surface inspection of pressure vessels made of magnetic materials should preferentially employ magnetic particle testing or array eddy current testing. For pressure vessels made of non-ferromagnetic materials... For surface inspection, penetrant testing or array eddy current testing should be given priority.

9.1.4.2 Low-temperature pressure vessels made of non-alloy steel and low-alloy steel, pressure vessels that are prone to environmental cracking or mechanical damage, and pressure vessels with... Pressure vessels prone to reheat cracking, Cr-Mo steel pressure vessels, and low-alloy steel pressure vessels with a standard lower limit of tensile strength greater than 540 MPa Pressure vessels, pressure vessels designed according to fatigue analysis, and Class III pressure vessels with a design pressure greater than or equal to

1.6 MPa for the first periodic inspection. For containers, the length of surface defect inspection should not be less than 20% of the length of the butt weld.

9.1.4.3 Key inspection areas for surface defects include.

a) Locations of stress concentration, deformation, and areas where cracks are detected during macroscopic inspection;

b) Austenitic stainless steel lining and weld overlay;

c) Welded joints of dissimilar steels, T-joints, and pipe corner joints;

d) Weld repair areas, weld marks on tools and fixtures, and areas damaged by electric arc;

e) The location where defects were found during the last periodic inspection;

f) Other suspected sites.

9.1.4.4 For materials sensitive to welding cracks, pay attention to inspecting for possible delayed cracks.

9.1.4.5 If cracks are found during inspection, the inspector should expand the scope or area of non-destructive testing to detect any other potential cracks. defect.

9.1.4.6 If it is not possible to inspect the inner surface, other effective methods can be used on the outer surface to inspect the inner surface.

9.1.5 Detection of Buried Defects

9.1.5.1 The detection of buried defects shall employ methods such as radiographic testing or ultrasonic testing as specified in NB/T 47013 (all parts). The non-destructive testing methods used shall be... The testing method and sampling ratio shall be determined by the inspectors based on the specific circumstances.

9.1.5.2 Buried defect detection shall be performed under any of the following circumstances.

a) Areas that have been repaired by welding during use;

b) Areas where surface cracks are found on the welded joint during inspection, indicating a need for inspection of buried defects in the welded joint;

c) Welded joints where the misalignment and edge angle exceed the product standard requirements;

d) Locations where welded joints leak during use, and their extended ends;

e) Welded joints and other stress concentration areas of pressure vessels subjected to alternating loads;

f) Locations where buried defects were discovered during the last periodic inspection;

g) Parts required by the user or deemed necessary by the inspectors.

9.1.5.3 When necessary, the acoustic emission testing method of NB/T 47013 (all parts) can be used to determine the activity of the defect.

9.1.5.4 If no abnormalities are observed during use, no further testing is required for parts that have already undergone buried defect detection.

9.1.6 Material Analysis

9.1.6.1 Material analysis. Depending on the specific circumstances, methods such as chemical analysis, spectroscopic analysis, hardness testing, and metallographic analysis may be used.

9.1.6.2 For pressure vessels of unknown material, it is generally necessary to determine the material type of the main pressure-bearing components; for Class III pressure vessels and those with special characteristics... For pressure vessels with special requirements, the material should be determined. For pressure vessels whose material has already been determined using material analysis methods and for which specific treatments have been applied, further investigation is required. The container does not need to be checked repeatedly.

9.1.6.3 Pressure vessels with a tendency for material deterioration should undergo hardness testing, and metallographic analysis should be performed if necessary.

9.1.6.4 For pressure vessels with welded joint hardness requirements, hardness testing shall be performed.

9.1.6.5 Hardness testing and ferrite content determination shall be performed on austenitic stainless steel heads and expansion joints during the first periodic inspection.

9.1.7 Strength Check

9.1.7.1 For corrosion (and erosion) depths exceeding the corrosion allowance, nominal thicknesses unknown, or structural defects (and serious defects already discovered), or For pressure vessels whose strength is questionable by inspectors, a strength check should be performed.

9.1.7.2 Strength verification shall be conducted by an inspection agency or a qualified pressure vessel design unit in accordance with GB/T 150 (all parts), GB/T 151, The standards are GB/T 4732 (all parts) and others.

9.1.7.3 The relevant principles for strength verification are as follows:

a) If the original design has clearly specified the strength design standard, the strength check can be carried out according to that standard;

b) If the original design does not specify the strength design standard on which it is based or does not include strength calculations, it can generally be determined according to the intended use (e.g., petroleum, chemical, metallurgical). Metal, light industry, refrigeration, etc.) or structural type (e.g., spherical tanks, waste heat boilers, glass-lined equipment, heat exchangers, high-pressure vessels, etc.), according to Strength verification was performed according to the relevant standards at the time;

c) For imported products or those designed according to foreign standards, the strength verification should, in principle, still be conducted according to the original design specifications; if the design specifications are unclear... You may refer to the relevant domestic regulations;

d) For pressure vessels with unknown material grades and no special requirements, the strength shall be checked according to the lowest strength value of similar materials;

e) The weld joint coefficient shall be selected based on the actual structural type and inspection results of the weld joint, with reference to the original design specifications;

f) The remaining wall thickness is calculated by subtracting the corrosion amount up to the next inspection date from the measured minimum value, and this is used as the wall thickness for strength verification.

g) The pressure used for verification shall not be less than the allowable (monitoring) operating pressure of the pressure vessel;

h) The wall temperature for strength verification shall be the design temperature or the allowable (monitored) operating temperature; for cryogenic pressure vessels, ambient temperature shall be used.

i) The shell diameter is selected according to the maximum measured value;

j) When performing strength checks on equipment such as towers and spherical tanks, additional loads such as wind loads and seismic loads also need to be considered.

9.1.7.4 For those that cannot be verified by conventional methods, stress analysis or experimental stress testing may be used for verification.

9.1.9 Pressure Resistance Test

9.1.9.1 During periodic inspections, if the user or inspection agency has doubts about the safety status of the pressure vessel, a pressure resistance test shall be conducted.

9.1.9.2 The test parameters, preparation work, safety protection, test medium, test procedure, and acceptance requirements for the pressure resistance test shall be in accordance with the design standard. Relevant regulations shall be followed. Test parameters such as test pressure and temperature shall be calculated based on the permissible (monitoring) usage parameters determined in this periodic inspection.

9.1.9.3 The pressure resistance test shall be carried out by the user and the inspection agency shall be responsible for the inspection.

9.1.10 Leakage Test

9.1.10.1 For pressure vessels that are specified in the design drawings to undergo a leakage test, a leakage test shall be conducted.

9.1.10.2 Leakage tests include airtightness tests and leak detection tests for ammonia, halogens, and helium. The selection of test methods shall be based on the pressure vessel design drawings. The requirements must be followed.

9.1.10.3 The airtightness test pressure is the allowable (monitored) operating pressure determined in this periodic inspection. Preparation, safety precautions, and test temperature are all included. The degree, test medium, test process, and qualification requirements shall be implemented in accordance with the relevant provisions of the design standard.

9.1.10.4 If a pneumatic test is required for this periodic inspection, the airtightness test may be combined with the pneumatic test.

9.1.10.5 For pressure vessels in large-scale complete sets of equipment, a system sealing test can be used instead of an airtightness test. When the pressure vessel user adopts... When a system sealing test is used in place of an airtightness test, the user should submit the system sealing test report to the testing organization, which may not be required to conduct the test. A separate leak test report will be issued.

9.1.10.6 Leak tests for ammonia, halogens, and helium shall be conducted in accordance with the requirements of the design drawings or relevant test standards.

9.1.10.7 The leakage test shall be carried out by the user and the inspection agency shall be responsible for the inspection.

9.1.11 Compatible with usage evaluation

9.1.11.1 For pressure vessels that have reached the end of their service life, or pressure vessels whose periodic inspections reveal serious defects that may lead to their cessation of use, [further details are needed]. The user unit should handle the defects. If the defects cannot be eliminated in a timely manner due to on-site conditions, the user unit may entrust a qualified inspection agency to conduct a proper inspection. Based on user reviews.

9.1.11.2 The pressure vessel user shall submit an application to a qualified inspection agency for a conformity assessment, and simultaneously submit the documents to be assessed. The basic information of the pressure vessel shall be provided in writing (including electronic documents) to the registration authority.

9.1.11.3 The evaluation of the suitability for use of pressure vessels shall be carried out in accordance with the requirements of TSG21 and GB/T 19624, GB/T 35013, etc.

9.1.11.4 The inspection agency responsible for the periodic inspection of pressure vessels shall, based on the conclusions of the conformity evaluation report and the inspection results of other inspection items, The inspection report shall be issued to determine the safety status level, permissible operating parameters, and the next inspection date of the pressure vessel.

9.1.11.5 The user unit shall submit the conclusion of the pressure vessel's compliance evaluation to the registration authority for record-keeping, and strictly adhere to the inspection report. It is required to control the operating parameters of pressure vessels, implement monitoring and prevention measures, and strengthen annual inspections.

9.1.12 Risk-based testing

9.1.12.1 Pressure vessel users applying for risk-based inspection shall conduct a safety management evaluation in accordance with the requirements of TSG21.

9.1.12.2 The testing organization undertaking RBI shall be approved and obtain risk-based testing qualifications; personnel engaged in RBI shall have obtained corresponding qualifications. Training to familiarize oneself with relevant national standards for RBI and specialized analytical software.

9.1.12.3 The pressure vessel user shall submit a written application for RBI to the inspection agency and submit all relevant documents proving that it has passed the safety management evaluation. The RBI inspection agency shall review the received application materials and inform the registration authority.

9.1.12.4 The inspection organization undertaking RBI shall assess the risk of the equipment and pressure vessel based on the equipment condition, damage mode, management situation, etc., and in accordance with... According to the risk tolerance...