RU2347136C1 - Method for detecting infield pipeline defects - Google Patents

Abstract

FIELD: construction, pipelines.

SUBSTANCE: invention concerns pipeline transport and can be used for detecting defects in the pipelines used for oil, oil product and formation water delivery and provides increase in volume and quality of monitoring the underground pipelines being in service. The method includes measuring magnetic-field pattern above the pipeline while moving the sensor along the pipeline, detecting potentially dangerous pipeline sections and their location, opening these sections and ultrasonic testing of the sections. Ultrasonic testing is carried out by exciting elastic bending and longitudinal vibrations and at the same time the pipeline is exposed to pulse load by partial isolation of liquid flow on the end of the controlled section. Lower amplitude and reflected signal carrier means that there are some defects.

EFFECT: opportunity of effective field monitoring of the pipeline condition and detection of defects of high, moderate and also low degree of hazard beyond the hole boundary on both sides of the hole.

7 dwg, 2 tbl

Description

The invention relates to pipeline transport and can be used to control and detect defects in pipelines used for pumping oil, oil products, produced water.

A non-contact magnetometric method for diagnosing the technical condition of pipelines is known, based on the recording and analysis of anomalies in the magnetic field strength arising in the concentration zones of longitudinal and transverse stresses, in the zones of plastic deformation, changes in the metal structure in the areas of prefracture and fracture of the metal (RD 102-008-2002. Instructions for diagnosing the technical condition of pipelines by non-contact magnetometric method. M., JSC VNIIST, 2003). The method provides for the detection and registration of defective sections of pipelines and allows you to classify nascent and developing defects according to the degree of danger, but does not guarantee the identification of defects that do not cause a change in the level of stress-strain state of the metal, such as through defects, pitting corrosion lesions.

A known method of acoustic monitoring of pipelines (RF patent No. 2243770, IPC G01N 29/04), according to which pulses of free elastic vibrations are excited in a controlled section of the pipeline, the load is changed sequentially in all local zones of the section, and for each zone two measurements are made at different acoustic loads zone by receiving elastic vibrations with a measurement of their frequency as close as possible to a given local zone. The presence and location of defects is judged by the presence and location of local zones, characterized by an abrupt change in the results in the first and second dimensions. In this case, two different states of the acoustic load of the local zones are created by freezing the liquid inside the pipeline simultaneously over its entire controlled area and its subsequent gradual thawing in series in all local areas of this area. This method cannot be used to control underground pipelines in operation that pump, for example, oil or oil products, because To do this, it would be necessary to stop the operation of the pipeline and release it from the product.

Closest to the proposed invention in terms of essential features is a method for detecting defects in infield pipelines described in RF patent No. 2301941, IPC F17D 5/02. The specified method includes measuring the magnetic field characteristics over the pipeline in the process of moving the sensor along the pipeline, identifying potentially dangerous sections of the pipeline and determining their location. After that, these sites are excavated and visual-measuring control is carried out using ultrasonic or eddy current thickness gauges. This method, however, does not guarantee the identification of through defects, and the use of thickness gauges in pits for visual measuring control of thicknesses allows rejection only by reducing the pipe wall thickness of a more normalized value, and does not detect small defects of longitudinal and transverse orientations, as well as defects caused by corrosion lesions in the form of pitting or sulfide stress corrosion cracking both in the pit and beyond the pit.

The objective of the present invention is to expand the volume and quality control of underground pipelines in operation.

The problem is solved due to the fact that in the method for detecting defects in infield pipelines, which includes measuring the characteristics of the magnetic field over the pipeline during the movement of the sensor along the pipeline, identifying potentially dangerous sections of the pipeline and determining their position on the ground, opening these sections and performing ultrasonic monitoring in them , unlike the prototype, ultrasonic testing is carried out by exciting elastic bending and longitudinal vibrations, and at the same time the pipeline subjected to a pulsed load by partially blocking the fluid flow at the end of the controlled area. The presence of defects is judged by a decrease in the amplitude and carrier frequency of the reflected signals.

The technical result achieved by the implementation of this invention is that the combination of the proposed actions makes it possible to detect defects of various nature not only in the pit itself, but also beyond its boundary at a considerable distance, since the propagation of excited elastic bending and longitudinal vibrations goes through the pipe in different sides for a length of several hundred meters for pipes in excellent condition to several meters for pipes in poor condition, which is many times greater than the length of a standard pit, is 4 meters (RD 39-132-94). In this case, the impulse load, carried out by partially blocking the fluid flow at the end of the controlled area, helps to reveal minor defects and obtain additional information about the state of the controlled area. In general, this allows to increase both the volume and quality of the pipeline control, using the existing pit for this.

The invention can be illustrated by the following specific example.

An infield pipeline for pumping oil with a length of 10,000 kilometers, diameter 159x6 from Art. 20, PVCL insulation coating, working pressure of 3 MPa, temperature 10 ° C, category 1 was monitored. First, potentially dangerous sections of the pipeline were identified by measuring magnetic field characteristics over the pipeline using a non-contact complex of magnetometric diagnostics KMD-01 (Russia), which included blocks of induction and flux-gage magnetometers and a data collection unit. The location of the identified potentially dangerous site was determined on the ground and its autopsy was carried out. Further, ultrasound testing was performed on this site using the Wave-maker system from Guided Ultrasonics (Great Britain).

Figure 1 presents a General view of the monitored area in pit No. 1, Figure 2 shows a general diagram of the scan of this section with the valve fully open, Figure 3 shows the diagram of scanning the section at a distance of 10.5-12.0 m in the positive direction from the place of installation of the sensors, where there is an accumulation of several local defects of a high degree of danger, figure 4 presents a scan diagram with a local defect of a high degree of danger. The results of the inspection of the pipeline section in pit No. 1 with the classification of defects according to the degree of danger are presented in Table 1. Analysis of the presented control results shows that defects of a high and medium degree of danger were detected in this section on one side and the other from the pit at a distance of up to 30 m. The presence of minor defects was not detected.

Figure 5 shows a General view of the test section in pit No. 2, Figure 6 shows a general diagram of the scan of this section when it was pulsed by closing the valve at the end of the section 1/2 section of the pipeline, Figure 7 shows a diagram local defect. Table 2 shows the control results in pit No. 2. As can be seen from the data presented, no significant defects were detected in this area, but with the shutter closing 1/2 the pipe cross section at a distance of 8.14 m from the installation site of the sensors, a low-risk defect was found, which is a local spot of developing corrosion. In the standard search mode, this defect was not detected.

Thus, the proposed method for detecting defects in infield pipelines allows in field conditions to quickly monitor their condition and identify defects not only of high and medium, but also of a small degree of danger beyond the boundary of the pit on both sides.

Table 1 Defect Location (m) Defect class Notes + F1 0.85 - Entrance to the ground + F2 3.32 tall Entrance to the ground + F3 4.07 tall Medium hazard defect + F4 9.86 average Local defect of medium high degree of danger + F5 10.66 tall The accumulation of local defects of a high degree of danger + F6 11.13 tall + F7 11.92 tall + F8 12.72 average Extensive medium hazard corrosion stain + F9 13.59 tall High hazard defect -F1 -0.57 - Entrance to the ground -F2 -1.47 tall Spot of defects with elements of a high degree of danger -F3 -2.63 tall High defect local defect -F4 -7.44 tall High defect local defect

table 2 Defect Location (m) Defect class Notes -F1 -0.62 - Entrance to the ground -F2 -1.41 - Turn -F3 -8.14 small Low hazard defect

Claims (1)

A method for detecting defects in infield pipelines, including measuring the magnetic field characteristics over the pipeline during the movement of the sensor along the pipeline, identifying potentially dangerous sections of the pipeline and determining their location on the ground, opening these sections and performing ultrasonic testing in them, characterized in that the ultrasonic testing is carried out, exciting elastic bending and longitudinal vibrations in a controlled section of the pipeline, and at the same time subject it to an impulse oh load by partial overlap of fluid flow at the end of the controlled section, and the presence of defects is judged by the decrease of the amplitude of the carrier frequency and the reflected signals.

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