CN102393266A - Annular array energy transducer for pipeline axial residual stress detection based on critically refracted longitudinal wave method - Google Patents

Abstract

The invention relates to an annular array transducer for detecting axial residual stress of pipelines based on critical refraction longitudinal wave method. The axial residual stress detection of the circumferential array of the annular pipe is realized by using the method of critical refraction longitudinal wave. The inner ring of the fixed soft sleeve is evenly equipped with several plexiglass wedges, which are buckled around the circumference of the annular pipe during work. Certain preload. Each plexiglass wedge is equipped with a number of pairs of piezoelectric transducers, which form an axial 360° evenly distributed one-shot-receive mode, and each transducer and the plexiglass wedge contact section form the first critical angle . The device can realize online detection of circular pipelines with different radii, has the characteristics of high sensitivity and convenient use, and is especially suitable for the detection of some large oil pipelines.

Description

Annular Array Transducer for Pipeline Axial Residual Stress Detection Based on Critical Refraction Longitudinal Wave Method

1. Technical field

The invention relates to an annular array transducer for detecting axial residual stress of pipelines based on critical refraction longitudinal wave method. This device can realize the online detection of circular pipelines, and has the characteristics of high sensitivity, high efficiency and convenient use, etc., and is especially suitable for the detection of some large oil pipelines.

2. Background technology

With the development of the world's petroleum industry, the transportation volume of pipelines is increasing, and the transmission pressure is also increasing, so the requirements for the strength of oil pipelines are also correspondingly increased. The spiral weld is the weak part of the oil pipeline. Due to the constraints in the welding process, the shrinkage effect of local heating and cooling, and the change factors of the metal structure, the oil pipeline will inevitably produce residual stress. After the oil pipeline is put into use, all the spiral welds must be subjected to various operating stresses, residual stresses and superimposed forces generated when the oil pipeline transports the medium. The load-carrying capacity and service performance of the pipeline will decline, especially the low-temperature brittle fracture of the oil pipeline will be greatly affected. At home and abroad, there have been many cases of sudden tearing of oil pipes during hydraulic tests and service periods, which have attracted the attention of relevant experts and engineering technicians. Therefore, it is very necessary to measure the actual residual stress of the oil pipeline to reduce accidents.

The residual stress measured by the traditional X-ray method is the average value of the residual stress within a depth of 10 μm on the surface, and the radiation produced is harmful to the human body. However, both the drilling method and the slicing method to detect residual stress are destructive tests, and the production and pasting of strain gauges is cumbersome, which greatly limits the online detection of large-scale pipeline stress. Therefore, the research has high sensitivity, online and efficient The technique of detecting pipeline stress has important practical significance.

The critical refraction longitudinal wave method measures the stress value through the time-acoustic method, which can measure the average stress value of about one wavelength in the depth of the surface. However, for large and long pipelines, this detection method is too inefficient.

The annular array transducer for pipeline axial residual stress detection based on the critical refraction longitudinal wave method can measure the axial stress values of multiple points along the pipeline circumference at one time, realizing efficient online stress detection.

3. Contents of the invention

The purpose of the present invention is to provide an annular array transducer for detecting the axial residual stress of pipelines based on the critical refraction longitudinal wave method. By adopting a send-and-receive mode of several pairs of transducers (determined according to different pipe radii), the problem of high-efficiency detection of the stress of large circular pipes is solved.

The purpose of the present invention is achieved like this:

By accurately calculating the first critical angle, the contact section of the transducer and the plexiglass wedge is assembled at the first critical angle. Each plexiglass wedge adopts a send-and-receive mode with a small contact area. The two transducers assembled inside strictly ensure that the distance is fixed. Fixed soft case. The top of the soft cover is correspondingly opened with several pairs of circular holes, which is convenient for leading out the transmitting line and the receiving line.

The advantages of the present invention are: adopt a soft cover that plays a fixing role, and several pairs of transducers are evenly distributed along the circumference of the pipeline in the soft cover, and the axial distance of each pair of transducers in the plexiglass wedge is kept fixed. In this way, the axial stress field distribution along the circumferential direction of the annular pipe can be quickly and conveniently measured. Moreover, one end of the fixed soft cover is installed with 3 rows of stress buckles, and the other end is opened with 3 rows of holes at different distances according to the pipe radius, so that the stress buckles can be buckled into the 3 rows of holes at different distances according to the pipes with different radii. To ensure a constant preload, so that all the recesses at the bottom of the plexiglass wedges are in good contact with the pipe.

4. Description of drawings

Figure 1 Cross-sectional view of piezoelectric transducer and plexiglass wedge assembly

1-Circular pipe 2-Plexiglass wedge 3-Piezoelectric transducer (transmission)

4-lead hole 5-fixing screw 6-fixing soft cover 7-piezoelectric transducer (receiving)

Figure 2 The three-dimensional view of the fixed soft cover

Figure 3 Three-dimensional diagram of transducer and plexiglass wedge assembly

Figure 4 Three-dimensional diagram of array transducer working

5. Specific implementation

The specific embodiment of the present invention is described in detail below:

As shown in Figure 4, the annular array transducer mainly includes several parts such as a fixed soft cover, a piezoelectric transducer, a plexiglass wedge, a transmission line, and a screw. A fixed soft sleeve is used, and the inner ring of the soft sleeve has several stepped grooves. Several plexiglass wedges that have been assembled with transducers according to the first critical angle are assembled into the stepped grooves of the soft sleeve through screws. Then wrap the entire soft sleeve around the annular pipe, and buckle the fixed soft sleeve on the outer wall of the pipe with a locking buckle, so that several pairs of transducers can correspond one by one along the circumference, and each plexiglass wedge can be well contact with the outer wall of the pipe.

As shown in the three-dimensional diagram of the fixed soft cover in Figure 2, there is a screw at one end of the fixed soft cover to rivet a lock buckle, and the head of the lock buckle leads to 3 rows of parallel detents, which can be wound around the fixed axis of the lock buckle head Rotate; the other end of the fixed soft sleeve corresponds to a series of 3 rows of holes, so that according to different pipe radii, add a certain pre-tightening force to insert the 3 rows of bayonet pins into different 3 rows of holes, and the fixed soft sleeve is very fast. Well, cling to the outer wall of the pipe.

1. During the actual measurement, due to the influence of the surface finish and roughness of the pipe, the pipe will be slightly deformed, which will cause poor coupling in the deformed area, resulting in a large error in the acoustic time measurement. As shown in Figure 3, in the propagation direction of the ultrasonic sound beam, a square concave surface is processed at the bottom of the plexiglass wedge, so that the radius of curvature of the concave surface is close to the radius of curvature of the circular pipe, and the area of the concave surface is slightly larger than the area of the sound beam projected on the bottom surface. The contact area between the wedge and the plate can be reduced without affecting the energy of the ultrasonic sound beam, and the error caused by the deformation of the plate can be reduced.

2. The transducer is matched with the Φ8.5 steel sleeve threaded hole on the plexiglass wedge, as shown in Figure 3. The angle between the axis of the transducer and the concave surface at the bottom of the plexiglass wedge is calculated based on the first critical angle.

3. Each plexiglass wedge is assembled to the soft cover and fixed by two M3 screws, as shown in Figure 1. In order to prevent axial and circumferential movement, after the soft sleeve is wrapped around the annular pipe for one week, it is buckled with an appropriate pre-tightening force through 3 rows of stress buckles, so that the concave surface under each plexiglass wedge can pass the couplant and the pipe well. combined.

4. There are 2 grooves on the outer ring of the fixed soft sleeve, and several round holes are punched in each groove, which are opposite to the wiring heads of several transducers, so that the signal wires can be drawn out easily, as shown in Figure 2.

Claims (9)

1. annular array transducer that detects based on the pipeline axial unrelieved stress of critical refraction longitudinal wave method.This device mainly comprises several sections such as fixing soft cover, piezoelectric transducer, organic glass voussoir, transmission line, screw.

2. critical refraction longitudinal wave method according to claim 1 detects the annular array structure of unrelieved stress, it is characterized in that having some to piezoelectric transducer, and is installed to become 360 ° on the circulating line and be uniformly distributed with, and relative transducer is along circumferential centre distance 59mm.

3. fixing soft cover according to claim 1; It is characterized in that every organic glass voussoir that all can assemble a band transducer at a distance of 60mm both sides when open and flat; There is the threaded hole of 2 M3 at every place in order to fixing organic glass wedge piece, and there is 1 circular hole at top, every place in order to draw the signal wire of transducer.

4. fixing soft cover according to claim 3, its material have the characteristic of anticorrosion, anti-cracking, and have certain rigid, and characteristics such as little are wanted in plastic yield.

5. fixing soft cover according to claim 3, an end are equipped with 3 row's tight locking buttons, and the other end is opened 3 rounds of different distance series according to pipeline radius difference.

6. tight locking button according to claim 5, the head of this tight locking button are drawn the parallel bayonet lock of 3 rows, can rotate around the stationary shaft of tight locking button head, and that its material has is antirust, anticorrosion, rigidity is strong, density is light characteristics.

7. critical refraction longitudinal wave method according to claim 1 detects the annular array structure of unrelieved stress, and each transducer all becomes first critical angle with the tangent plane of the concave surface of organic glass voussoir.

8. according to the said organic glass voussoir of claim 3, there is the threaded hole of M3 to be used for fixing on its side and the top and puts soft, there is cavity inside with sealing glycerine, realizes the coupling between transducer and the organic glass.

9. annular array transducer architecture according to claim 1, the edge that can the detect circulating line apace axial stress of the some points of circle (logarithm that depends on transducer) that circumferentially distributes.

Images