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Regular inspection
For regular inspection, when the pipeline operating conditions do not affect the effectiveness and safety of the inspection, an inspection strategy can also be formulated based on the damage mode and risk level combined with the usage of the pipeline, and the inspection can be implemented under operating conditions.
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Regular inspection
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- Outline
Regular inspection
General requirements
Usually performed during shutdown
When the pipeline operating conditions do not affect the effectiveness and safety of the inspection, an inspection strategy can also be formulated based on the damage mode and risk level combined with the usage of the pipeline, and the inspection can be implemented under operating conditions.
Inspection plan formulation
Reviewed and approved by the technical leader or authorized person
For pipelines with special circumstances, seek opinions from the user unit
Preparation before inspection
Data preparation and review
Design Resources
Qualification certificate
Design and installation instructions
design pattern
Strength calculation book
Installation information
Installation unit qualification certificate
Completion acceptance information
Quality certification documents including pipeline components and pipeline supports
Pipeline installation supervision and inspection certificate
Modification or major repair information
construction plan
Completion information
Supervision and inspection certificate
Use management information
Use registration certificate
Use registration form
Summary table of basic information on pressure pipelines - industrial pipelines
Operation records, start and stop records, records of changes in operating conditions, records of abnormalities during operation and corresponding handling situations
Inspection and inspection data
Safety accessories and instrument calibration and verification data
Annual inspection report within the periodic inspection cycle
Last periodic inspection report
Inspection site preparation
Set up safety guardrails 2 meters above the ground
Reliable isolation, cleaning and replacement when necessary
Slowly cool down and heat up
Cut off the power supply related to the pipeline, set up warning signs, verify that the lighting voltage does not exceed 24V, the cables are well insulated and grounded reliably.
During radiographic inspection, isolate the transilluminated area and set warning signs
Equipment and instrument calibration
Should be within the effective calibration or inspection period
Inspection work safety requirements
Check implementation
Periodic inspection items
Mainly macroscopic inspection, wall thickness measurement and inspection of safety accessories
If necessary, add surface defect detection, buried defect detection, material analysis, pressure strength check, stress analysis, pressure test and leakage test, etc.
Periodic inspection methods and requirements
Macroscopic inspection
Pipe structure inspection
Pipe layout
Hangers
expansion joint
Open hole reinforcement
Emissions settings
Geometric dimension inspection
Pipe weld seam offset amount
undercut
Weld reinforcement
Visual inspection
Pipeline sign
Corrosion, cracks, leaks, bulging, deformation, mechanical contact damage, overheating, and arc burns of pipeline components and their welds
Deformation and cracking of pipe supports
Clogging, corrosion, and sedimentation of discharge (drainage, sewage) devices
Damage and peeling of anti-corrosion layer
Damage, peeling, moisture, and corrosion and cracks under the insulation
During the first periodic inspection, the pipeline structure and geometric dimensions should be inspected. During the second periodic inspection, only pipelines that are subject to fatigue loads, pipelines that have been transformed or major repairs will be inspected for new defects in abnormal parts of the structure and geometric dimensions.
Wall thickness determination
Measuring point position
Susceptible to corrosion and erosion
Wall thickness reduction during manufacturing and molding
Parts prone to deformation, fluid accumulation, and wear during use
Suspicious parts discovered by ultrasonic guided wave testing, electromagnetic testing and other methods
Branch pipe connection parts, etc.
Proportion of random inspections of elbows (elbows), tees and reducers (no less than 3 measuring points on one side of each pipe component and welded joint straight section to be inspected)
GC1≥30%
GC2≥20%
GC3≥10%
If the austenitic stainless steel or medium is non-corrosive or slightly corrosive (0.05mm/year), and there is no abnormal thinning in the wall thickness of the spot-checked parts, the spot-check ratio can be appropriately reduced, but it shall not be less than 50% of the elbow.
When there is an abnormality in the wall thickness, add measuring points nearby to determine the abnormal area. If necessary, increase the proportion of spot checks on the entire pipeline.
When using ultrasonic guided wave, electromagnetic and other methods for detection, you can only check the pipe wall thickness at the abnormal signal points.
Surface defect detection
When cracks are found or suspected, non-destructive testing of the outer surface should be carried out at the corresponding parts.
Austenitic stainless steel pipes with damaged insulation or possible rainwater penetration
When the inspector deems it necessary, inspect the branch pipe fillet welds and other parts
The proportion of spot checks should be no less than 5% of the number of welded joints and no less than 2 at welded joints and stress concentration locations.
carbon steel
Low alloy steel cryogenic pipeline
Cr-Mo steel pipe
Low alloy steel pipes with standard tensile strength lower limit ≥540MPa
Pipelines that bear significant alternating loads for a long time
First periodic inspection of GC1 grade pipeline
Pipes prone to environmental cracking
Use other methods on the outer surface to spot-check the inner surface
The random inspection ratio shall not be less than 10% of the number of butt welded joints
and no less than 2
When cracks are found during inspection, the proportion of surface defect detection should be expanded
Buried defect detection
The pipelines inspected for the first time should undergo ultrasonic or radiographic inspection.
GC1 is 15% and not less than 2
GC2 is calculated at 10% and not less than 2
Perform 100% non-destructive inspection on spot inspection welds at a 2-fold ratio
Temperature and pressure cycle changes
Pipes with large vibration
Heat-resistant steel pipe
Buried defect detection is generally no longer required during re-inspection.
When signs of internal damage are found or defects exceeding the standard were found in the previous inspection, the sampling rate shall not be less than 1 times for buried defects detection.
Specific spot inspection proportions and key locations
If no abnormality is found at GC3 level, ultrasound or radiographic spot checks are generally not required.
If grade 3 or 4 defects are found during spot inspection, the proportion of spot inspections should be increased. The proportion shall be determined through consultation between the inspector and the user based on the pipeline operating parameters and actual conditions.
key parts
Repair or repair welding parts during installation or use
Where cracks on the surface of the weld are found, buried defects need to be detected
The welding seam where the misalignment exceeds the requirements of relevant installation standards
Leakage areas and welded joints near them
Stress concentration locations such as pipe fixing openings during installation
The first or adjacent welding joints at the inlet and outlet of pumps and compressors
Welded joints near damaged parts of supports and hangers
Dissimilar steel welded joints
Welded joints in areas with large deformation of pipelines
Other parts required by the user or deemed necessary by the inspector
If the inspector believes that the random inspection ratio cannot meet the testing needs, he or she can negotiate with the user to determine the random inspection ratio.
material analysis
Chemical analysis, spectral analysis, hardness testing, and metallographic analysis can be used
If the material is unknown, it is generally necessary to find out the type of material and its corresponding brand. Chemical analysis and spectral analysis methods can be used to determine it. This item does not need to be verified during re-inspection.
For pipelines subject to high-temperature creep and material deterioration, representative parts should be selected for hardness testing, and metallographic analysis should be performed if necessary.
Pipes with hardness requirements for welds must undergo weld hardness testing
Compressive strength check
The overall thinning of pipe components exceeds the nominal thickness by 20%
or when the inspector has doubts about the strength of the pipeline
The calibration pressure shall not be lower than the allowable (monitoring) operating pressure of the pipeline
Stress Analysis
There is no strength calculation sheet, and the design wall thickness ≥ design outer diameter/6 or Allowable material stress under design pressure/design temperature＞0.385
With large deformation and deflection
Leakage and damage to the sealing structure caused by stress in the piping system
The compensator is not set or the compensator fails when it is required to be set.
Abnormally damaged supports and hangers
The structure is unreasonable and serious defects have been found
There is serious overall thinning of the wall thickness
Withstand voltage test
If there is any doubt about the safety condition of the pipeline, a pressure test should be carried out
The user unit is responsible for implementation, and the inspection agency is responsible for inspection.
Test pressure, temperature and other parameters are calculated based on the allowed (monitored) usage parameters determined by this periodic inspection.
Leak test
Pipelines that transport extremely hazardous or highly hazardous media, or are designed to not allow trace leakage, must undergo leakage tests.
For example, air tightness test and ammonia, halogen and helium leak detection test
The user unit is responsible for implementation, and the inspection agency is responsible for confirmation.
Safety accessories and instrument calibration
Is the safety valve within the verification period?
Is the bursting disc device replaced on schedule?
Is the emergency shut-off valve intact?
Is the pressure gauge within the verification period?
Defects and problem solving
Defects should be dealt with
Safety status is designated as Level 4
The discovery of serious defects may lead to discontinuation of use
Defect handling method
Use repair methods to eliminate defects
Conduct fitness-for-use evaluation
Risk-based inspection (RBI)
Risk-based inspection application conditions
Pipeline users that apply for risk-based inspection of large-scale complete installations shall undergo a safety management evaluation of the pipeline user unit by the superior authority or a third-party agency.
Have a complete management system and high management level
Establish and improve emergency plans to deal with various emergencies and conduct regular drills
The pipelines are operating well and can be inspected and maintained in accordance with relevant requirements.
The production equipment and its important equipment information are complete and complete
Stable process operation
The production equipment adopts a digital distributed control system and has reliable safety interlock protection devices.
The third-party organization is a national social organization that is professional, non-profit and has no interest in the applicant unit or inspection agency.
Risk-based inspection implementation
Inspection agencies need to be approved by the National Bureau to obtain risk-based inspection qualifications. Inspection personnel should undergo corresponding training and be familiar with relevant standards and special analysis software.
The user submits a written application and submits safety management evaluation materials. The inspection agency reviews the materials and informs the user registration authority.
The inspection agency conducts risk assessments in accordance with the "Specifications" and relevant technical standards based on pipeline operation conditions, damage patterns, risk acceptability, etc., proposes inspection strategies (including time, content, methods), and issues inspection reports
The user unit formulates an inspection plan according to the inspection strategy, and the inspection agency formulates a specific inspection plan and implements the inspection.
For pipelines whose risks are above the acceptable level during device operation, online inspection and other methods should be used to reduce their risks.
The user should submit the risk-based inspection conclusions to the user registration authority for record, implement various measures to ensure safe operation, and assume the main responsibility for safe use.
Special requirements for periodic inspection of power pipelines
Test items
Carbon steel, low alloy heat-resistant steel power pipes
If the working temperature is ≥450℃ and the operating time is ≥60,000 hours, it must be
Hardness test
Metallographic examination
Working temperature ≥450℃, operating time ≥200,000 hours
According to the metallographic and hardness test results
If necessary, cut the pipe and conduct material evaluation according to relevant standards.
400℃≤working temperature＜450℃, after 80,000 hours of operation
Randomly check the hardness and metallographic structure according to the operating status of the pipeline.
The time and proportion of the next spot inspection will be determined based on the inspection results.
Power piping with creep measurement points installed
Check whether creep measurement records comply with relevant standard requirements
Power pipelines that have been in operation for more than 200,000 hours were found to be
Metallographic structure spheroidization and creep damage
Or the material aging grade, creep strain, and creep rate exceed the requirements of relevant standards.
Should be processed or replaced promptly
9%~12%Cr series steel power pipes
Regular inspections should carry out hardness and metallographic inspections.
Defect handling
The pipe section should be replaced if one of the following conditions occurs:
There are macro cracks and obvious bulges on the outer surface of the pipe
The pipeline has been significantly thinned, and strength verification calculations have been carried out. Safe operation cannot be guaranteed until the next overhaul.
The pipeline is obviously swollen and cannot be guaranteed to run until the next overhaul.
The depth of pipeline corrosion points is greater than 30% of the wall thickness
The pipe material structure is aging or the creep damage level exceeds the relevant standards.
Creep cracks or fatigue cracks have occurred
Periodic inspection report
The inspectors shall conduct inspections based on actual inspection conditions and inspection results.
Assess the safety status level of pipelines in accordance with the provisions of these rules
Issue inspection report
Explicit allowed (monitored) operating parameters and next periodic inspection date