Pipe inspection. Terms of Reference For holding a closed tender for the selection of a service company for the provision of services for flaw detection and repair of drill pipes for the needs of the branch "Urengoy drilling" Drilling

Basic Methods non-destructive testing:

Magnetic method It is used to inspect products made of ferromagnetic materials, which, under the influence of an external magnetic field, significantly change their magnetic characteristics.

eddy current— based on the analysis of the interaction of an external electromagnetic field with an electromagnetic field of eddy currents induced by an exciting coil in an electrically conductive test object.

Ultrasonic method represents the radiation of pulses of ultrasonic vibrations by transducers. They receive and register signals reflected from the inner and outer surfaces of the pipeline and from the formed defects.

Equipment for flaw detection control pipelines

The main welding quality control methods used in the construction of gas and oil pipelines are visual-measuring, radiographic (works on the principle of radiography and gammagraphy), ultrasonic (manual or automated). The examination is carried out by an x-ray crawler. It is a small electrically operated cart carrying a panoramic X-ray tube and a battery.

The operator controls the movement of the battery using a hand-held remote control. For diagnostics main pipelines usually, flaw detection devices are used, consisting of one or more interconnected modules, each of which performs certain functions, for example, transportation of batteries, equipment of the physical method used, recording equipment, etc.

To move the flaw detection apparatus inside the pipeline, the energy of the fluid medium (oil, gas, condensate, etc.) is usually used. At the same time, rubber (or from another elastic material) rings covering the cross sections of the pipeline between the module bodies and the inner surface of the pipeline.

Thus, they perceive the pressure of the fluid and contribute to the continuous movement of the apparatus through the pipeline. There is an apparatus for magnetic inspection of pipelines made of ferromagnetic materials. The housings of the apparatus modules are rigid cylindrical shells made of non-magnetic material, coaxial with the pipeline and having a diameter approximately two times smaller.

Permanent magnets are installed on these shells along the circumference of their cross sections, which form single magnetic circuits with the pipeline wall in each section by connecting the magnets to the pipeline wall with a plurality of wire or foil elastic metal elements. Also known is an apparatus designed to detect defects such as corrosion pits.

It is equipped with one or more ultrasonic radiation generators with a plane wavefront directed towards the inner wall of the pipeline. Analysis of the delay time of the signal reflected from the wall reveals the presence of corrosion damage on inner surface pipeline. At present, the world's leading companies are working on the creation of flaw detection devices for determining longitudinal cracks and crack-like defects in pipelines.

For example, a new flaw detector "Ultrascan CD" designed primarily to search for longitudinal cracks. It is based on the principle of ultrasonic technology: it uses shear waves generated by the emission of an ultrasonic pulse in a binding medium (oil, water, etc.) at an angle to the surface of the pipeline. However, the classification of defects according to the degree of danger can be performed only after their additional examination in the pits.

For example, the results of flaw detection by Ultrascan make it possible to assess the risk of detected stress-corrosion defects and determine defects that should be opened and examined by local non-destructive methods. Up to now, the registration of information received from flaw detection devices has been carried out, as it were, in the X-ray recording mode, i.e. static pictures of defects are obtained - only their geometric characteristics are measured without revealing the behavior of the latter when the pipeline is loaded.

One of the methods of non-destructive testing of pipelines is that by means of transducers mounted on a piston element (the piston element itself is located in a pipeline in a fluid medium), a signal is emitted. The signals reflected from the inner and outer surfaces are recorded, this procedure is carried out twice at different pressures of the fluid medium in the controlled section of the pipeline, and the presence of defects is judged by the difference in the registered signals. Another well-known method of loading pipelines during their non-destructive testing is the creation of a pressure drop by moving a piston-type device through the pipeline by means of a fluid medium.

Determination of stress in front of cracks in structural elements

One of the most common methods is as follows: the surface is illuminated with coherent radiation up to the full load value. Simultaneously loading the element in stages, two-exposure holograms are recorded at each stage in colliding beams for the surface of the element in the crack tip zone and interference patterns are recorded, the parameters of which are used to calculate the stress in front of the crack.

Hazard assessment of defects detected during in-line inspection

Each defect is characterized by two specific parameters: relative depth (d/t, where d is the maximum depth of the defect, t is the thickness of the pipeline wall) and length L in the longitudinal direction of the pipeline. As a result of the calculation, for each defect, the degree of danger is determined, according to which the defect is classified into three categories: “dangerous”, “non-dangerous” and “inadmissible”.

For "non-dangerous" defects, given that they constitute the absolute majority, an additional subcategory "potentially dangerous" is introduced. For the surveyed area, a curve is constructed that characterizes the danger boundary of corrosion defects such as corrosion pits and spots. As a criterion for the danger of a defect, the condition for the destruction of the pipeline for this defect is taken at the value of the breaking pressure at the level of the minimum test pressure according to SNiP III-42.80.

Thus, all defects lying on the curve have the same degree of danger; for them, the defect hazard coefficient is K = 1. A higher accuracy in assessing the danger of defects detected using in-line flaw detection projectiles can be provided by changing the modes of movement and retrieval of information in order to obtain dynamic characteristics of detected defects, i.e. their behavior under pipeline loading.

To do this, a flaw detection projectile is passed through the pipeline with step-by-step stops or slowdown, while in each investigated zone, various values ​​of the fluid parameters, for example, pressure, speed, temperature, are repeatedly recorded. Based on these data, the values ​​of changes in the nominal parameters of the pipeline state (PST) are determined, as well as the information is repeatedly recorded and the maximum values ​​of the PST are found as the sum of the nominal PST and the values ​​of changes in the maximum local PST, extrapolated from the values ​​of the corresponding, for example, operating parameters of the fluid medium, and compared the obtained maximum values ​​of PST with acceptable values.

Thus, the values ​​of changes in the nominal stresses (strains) are determined as the values ​​of changes in the nominal SST, and methods, for example, holographic interferometry, which allow recording two-exposure holograms of the pipeline zones under study, are used as onboard methods. Using the interferograms of changes in the normal components of the displacement vectors of the inner surface of the pipeline restored from these holograms, the values ​​of changes in the bending components of stresses (strains) at the crack tips are determined and then the maximum values ​​of stresses (strains) near the defects are found as the sum of the nominal values ​​and the values ​​of changes in the maximum local bending components of stresses ( strains) extrapolated from the values ​​corresponding to them, for example, the operating parameters of the fluid, and compare the obtained maximum values ​​of the SST with the allowable values. The proposed method evaluates not only the presence of defects that are acceptable and unacceptable by control requirements, but also their danger, taking into account the current operational loads.

This is extremely important for justifying the safety of pipelines.

A lot depends on the quality and reliability of pipelines today. These are the productivity of work at enterprises, and the uninterrupted supply of water through the water supply system, and the safe operation of heating mains. In addition, the quality of pipes is very important in oil production and other operations that require the use of pipes. We will talk about the cases in which flaw detection is necessary and how it is carried out in this article.

When is defectoscopy needed?

The main purpose of flaw detection is to check the integrity of pipes without destroying their structure. Such studies are necessary before putting the pipeline into operation, especially if the system will operate under significant pressure, or at high temperatures. In addition, such a study must be carried out periodically even after the pipeline is put into operation - this will help determine the condition of the pipes, detect corrosion, and make repairs in time to prevent a rupture.

In addition to checking the pipes themselves, flaw detection of welds is also important. As a rule, in pressurized systems, these are the most vulnerable points. Several non-destructive testing methods are used to check the quality of welds and the integrity of pipes.

Methods of flaw detection

Often, ultrasonic testing is used to check the thickness of pipe walls and the quality of welds. Such a study allows you to identify possible defects without taking the pipeline out of service, which is convenient, since most systems require continuous operation. The use of the ultrasonic method makes it possible to detect a large number of damages, including defects in welds, internal corrosion of pipes, etc.

The eddy current testing method makes it possible to detect microcracks in pipes at their bends even at high surface temperatures. This method of control also does not require the shutdown of the pipeline.

Capillary flaw detection can also be used to determine surface defects in pipes.

Pipelines throughout the entire period of operation are exposed to the negative effects of aggressive environments. Defects obtained during production can lead to the rapid development of corrosion, cracking and other damage. Therefore, quality control of pipelines is very important. Timely identified and eliminated defects can prevent serious problems in the future.

Pipeline flaw detection is a common quality control method that makes it possible to detect defects with 100% certainty. It is used to check

• gas pipelines;
• heating networks;
• oil pipelines;
• water disposal and water supply systems.

The company "Micro" carries out qualified flaw detection of pipelines. Our staff consists of certified experts with vast experience. The company has everything necessary equipment for flaw detection.

Methods of flaw detection

The most common and popular methods of flaw detection of pipelines include:

1. Magnetic powder testing. The essence of the technique is based on the fixation of stray magnetic fields that appear above the defects. By their nature, you can determine the size, location and depth of damage. Ferromagnetic mixtures and powders are used in magnetic particle testing. They are able to detect surface and internal cracks, delaminations, sunsets and other defects that are not deep.
2. Radiographic flaw detection. The technique is based on the ability of X-ray radiation to penetrate through the metal and be fixed on the surface of a special film. Rays penetrating damage leave a mark on it. Radiographic studies can detect lack of penetration, cracks, pores, foreign bodies and undercuts.
3. Acoustic emission control of pipeline quality. This type of study is based on the fixation and analysis of sound waves that appear due to the growth of cracks and deformations of the object being evaluated. Acoustic emission flaw detection makes it possible to detect even developing defects.
4. Ultrasonic flaw detection. This quality control technique relies on the ability of ultrasonic waves to reflect off various surfaces. This makes it possible to identify internal and implicit external defects. Ultrasonic flaw detection is characterized by high accuracy and efficiency of execution.
5. capillary research. This method of flaw detection is based on capillary penetration of indicator liquids into the material and fixing the results. During capillary quality control, through and surface defects, their extent and location are detected. The results of the study are very clear.
6. Magnetometric diagnostics. Based on measurements of the magnetic permeability of the pipe walls. The technique makes it possible to detect a decrease in their thickness that occurs under the influence of corrosion and during long-term operation. Such studies are carried out to prevent accidents.

This is not a complete list of studies conducted for quality control purposes. Methods of flaw detection are selected in each case individually. They can also be combined with each other. This allows you to get the most reliable results.

A defect is any non-compliance with regulated standards. The main reason for the appearance of defects is the deviation of the operating parameter from the standard value, justified by the tolerance.

In-line flaw detector provides:

detection of defects with dimensions equal to or exceeding the specified minimum resolution parameters of the in-line flaw detector;

· movement along horizontal, inclined and vertical sections of process gas pipelines of CS and BCS in the range of conditional diameters (Dy) from 500 to 1400 mm;

moving through oily areas, including vertically located areas;

passing through bends, tees, half-bends, taps;

· fixation in vertical and inclined sections of process gas pipelines of CS and BCS to perform control of welds;

· loading of CS and BCS process gas into the pipeline through the opened check valve with a diameter of 720 mm (1020 mm) or manhole with a hole diameter of 400 mm or more;

· work in the temperature range from minus 10 °С to +50 °С;

· distance of movement from the place of loading not less than 250 m;

· application in explosive zone of class B-1.

Defects in pipeline structures are divided into:

pipe defects;

defects in welded joints;

Insulation defects.

There are the following pipe defects:

metallurgical - defects in sheets and strips from which pipes are made, i.e. various types of delamination, rolling film, rolled scale, transverse thickness variation, non-metallic inclusions, etc.

technological - associated with the imperfection of pipe manufacturing technology, which can be conditionally divided into welding defects and surface defects (hardening during expansion, displacement or angularity of edges, pipe ovality)

construction - due to the imperfection of the technology of construction and installation works, violations of technological and design solutions for transportation, installation, welding, insulation and laying works (scratches, scuffs, dents on the pipe surface).

Causes of pipe defects

· the existing technology of metal rolling, the technology of continuous casting of steel at individual metallurgical plants is one of the reasons for the manufacture of low-quality pipes. There are frequent cases of destruction due to delamination of the metal.

· on the pipe factories input control raw materials are imperfect or completely absent. This leads to raw material defects becoming pipe defects.

In the manufacture of pipes, it is necessary to subject the metal to loads under which it operates beyond the yield point. This leads to hardening, micro-delamination, tears and other hidden defects. Due to the short duration of subsequent factory tests of pipes (20 ... 30 s), many hidden defects are not detected and “trigger” already during the operation of the MT.

· Insufficiently controlled by plants and the geometric shape of the pipes. So, on pipes with a diameter of 500 ... 800 mm, the offset of the edges reaches 3 mm (at the norm for spiral-seam pipes 0.75 ... 1.2 mm), ovality - 2%

mechanical impacts during loading and unloading, transport and installation operations lead to the appearance of dents, scratches, scratches, scuffs on the pipes

Defects occur when cleaning pipelines with cutter scrapers plastic deformation local sections of the pipe surface - risks, undercuts, etc. These stress concentrators are potential centers for the development of corrosion-fatigue cracks. Cleaning pipelines with wire brushes eliminates damage to pipes in the form of undercuts, but under certain processing conditions, it leads to deformations of the metal surface, which reduces its corrosion resistance.

Corrosion damage to pipes (external - in places where the integrity of the insulation is broken, and internal - in places where water accumulates)

The following methods can be applied to carry out the ITD of the Pokhvistnevo-Samara pipeline and other means:

television visual and measuring method of control to detect surface defects on the inner surface of pipes, such as a violation of the continuity of the metal of the pipe and pipe joints (cracks, delaminations, hairline, captivity, flaws, lack of penetration, etc.) with the measurement of their geometric dimensions];

· method of magnetic control for detecting defects such as discontinuity of metal and pipe joints on the inner and outer surfaces of pipes, as well as inside the walls of pipes.

Magnetic flaw detectors

The method of magnetic flaw detection is promising for the inspection of underground gas pipelines. Magnetic flaw detectors allow, at low operating costs, to detect corrosion damage to the pipe walls at large distances, but it must be borne in mind that they are insensitive to cracks, although they can detect fairly large cracks, nevertheless, a device using ultrasound or eddy currents should be used to detect them. .

The method of magnetic flaw detection of metals is based neither on the detection and registration of stray fields that arise in the places of defects during the magnetization of controlled products. In this case, magnetic lines of force propagate in the metal of the pipe wall without changing direction, if there are no defects in it. If there are defects in the pipe walls, the magnetic field lines deviate, and a stray field arises, the magnitude of this field depends on the size and configuration of the defect at a certain value of the pipe wall magnetization.

Magnetic flaw detectors are used to detect defects in circumferential welds (lack of fusion, lack of fusion, undercuts), pitting corrosion;

Longitudinal and transverse magnetization flaw detectors have a high resolution that reaches the efficiency of ultrasonic technology and even exceeds it in terms of defect detection reliability.

On the considered MG, two types of magnetic flaw detectors are used, launching them one after the other.

1. Magnetic flaw detector for detecting longitudinal cracks in main gas pipelines.

Transverse magnetization is carried out using electromagnets, permanent magnets or solenoids. With longitudinal magnetization, the field is directed along the longitudinal axis weld or details. Transverse magnetization is used to detect longitudinal welding defects.

2. Magnetic flaw detector for detecting transverse cracks in main gas pipelines.

Longitudinal magnetization is carried out using electromagnets, permanent magnets or solenoids. With longitudinal magnetization, the field is directed along the longitudinal axis of the weld or part. Longitudinal magnetization is used to detect transverse welding defects.

The choice of in-line flaw detectors and their instrumentation is determined by the tasks of technical diagnostics, technological, design and geometric parameters of the pipeline system, the capabilities of Operating and Specialized organizations, the requirements for technical specifications the means used to ensure the reliability of identifying the necessary parameters of defects.

Preparation of the gas pipeline for the passage of the in-line device

The design of the linear part of the Pokhvistnevo-Samara gas pipeline provides the possibility of in-line diagnostics, including:

* chambers for launching and receiving inline devices;

* constant inner diameter and equal bore linear fittings without components and parts protruding into the gas pipeline, as well as welding beads, backing rings;

* grids on the gas pipeline jumper, excluding in-line devices from entering the branches;

* signaling devices, marker devices that register the passage of inline devices installed at the start-up, reception and intermediate points on the gas pipeline.

The pipeline and units for launching and receiving treatment devices are equipped with signaling devices installed on line cranes and recording the passage of treatment devices.

In the general case, the main works on in-line diagnostics include (in the order of their execution sequence):

* preparation of the gas pipeline for the passage of the in-line device;

* reeving of the in-line device into the launch chamber;

* the passage of an in-line device under the pressure of the transported gas with a record of information about technical condition gas pipeline in the device memory;

* acceptance of the inline device in the receiving chamber;

* decoding of the received information.

To start the in-line device, a launch and reception chamber is installed according to the plan. The launch chamber was installed at 115.6 km of the Pokhvistnevo-Samara GP. Were held hot work, according to the plan for the organization and safe conduct of repair (hot) work, as well as the following schemes:

Posting scheme

Gas bleeding scheme

Scheme of carrying out hot work

Scheme of the displacement of the gas-air mixture

· Scheme of filling the gas pipeline section.

This site is equipped shutoff valves in the form of 2 taps on the main line with piping and candles, ensuring timely bleeding of gas and shutting off gas access to the gas pipeline section where hot work is carried out. The jumper connecting the MG threads is closed for the entire duration of the hot work for safety reasons. The installation of the launch chamber was carried out in several stages. At the first stage, gas access to the work site was limited by bleed. Then technical holes were made, followed by the elimination of part of the pipe. During the installation of the chamber, air remained in the pipeline, which was forced out by blowing through one candle.

The flaw detector receiving chamber was installed on the gas pipeline branch to the GDS-16 in accordance with the plan for the organization and safe conduct of repair (hot) work, as well as the schemes.

The assembly, adjustment and calibration of flaw detectors for passing through the examined section of the pipeline was carried out under stationary conditions.

Flaw detectors were delivered to the launch site with precautions. The pre-start functional check of the flaw detectors was performed immediately before the reeving into the scraper launch chamber.

During the passage of the projectile were strictly prohibited:

moving vehicles through the pipeline;

· Presence at the launching and receiving sites, linear cranes and installation sites of markers of persons not involved in the work to ensure the passage of projectiles;

use of open fire, smoking, exit to the protected zone of the pipeline for vehicles with internal combustion engines;

Performing work in the security zone that is not related to a pass.

Select by manufacturer

Not selected Computed radiography DUERR NDT / DÜRR NDT AKS Synthesis NDT Proceq SA SPC Kropus Constanta Center MET Bosello High Technology SaluTron® Messtechnik GmbH ZIO "POLARIS" NPP Prompribor ELITEST Promtest Bruker TOCHPRIBOR FUTURE-TECH CORP. OXFORD Instruments Amcro Newcom-NDT Sonotron NDT YXLON International Array Corporation Raycraft General Electric Vidar systems corporation Arsenal NK LLC Echo Graphic NPP Mashproekt

Pipe flaw detection

11.10.2016

Pipe flaw detection is one of the sub-categories of non-destructive ultrasonic testing, along with base metal and weld flaw detection. This method flaw detection is one of the most demanded services for monitoring oil and gas pipelines in many industries: chemical, oil and gas, fuel, electric power, etc.

During long-term operation, as well as in production, pipelines are exposed to internal and external influences, during which various defects can accumulate (corrosion damage, fatigue cracks, metal integrity violations, non-metallic inclusions, sunsets, captivity, shells, etc.). It is very important to timely detect such defects before the failure of the pipeline. Even more important is the ability to perform diagnostics without shutting down or taking the system out of service. That is why non-destructive testing methods are used for pipe flaw detection, including magnetic (magnetic anisotropy, metal magnetic memory, magnetic permeability), acoustic (pulsed ultrasonic, Lamb waves, phase, acoustic emission), electrical and optical (visual - endoscopic, laser, holographic ).

Such methods are used to detect various defects: leakage, stress state control, quality control and condition of welded joints, leakage control and other parameters responsible for the operational reliability of pipelines.

Among the methods for flaw detection of pipelines, one can single out thickness measurement of the pipe body and ultrasonic examination of the body and ends of the pipe to detect defects in the longitudinal and transverse orientation.