MX2011004931A - Non-destructive ultrasonic testing transducer. - Google Patents

Abstract

The present invention relates to an Ultrasonic Transducer designed for automated equipment for monitoring hydrocarbon-transporting underground pipelines. The invention comprises a highly sensitive and high resolution ultrasonic transducer which requires a reduced space, thereby improving the transducer response by changing the main elements thereof. The main components are an epoxy resin layer, a coupling layer made of bakelite with a thickness of a 1/4 wavelength for protecting the transducer, a tubular- shaped active element made out of a type PZT 5-type piezocomposite material, a counter-mass material including a bakelite matrix and tungsten particles for enhancing the damping and attenuation capacity thereof, all these elements being housed inside a hollow cylindrical casing and sealed by a stainless steel shutter which is attached to an electrical connector of the microdot 10-32 type, connected to the power supply, and is useful for protecting from corrosive environments, high t emperature and high pressure. The arrangement of both the internal elements and the materials used for the manufacture thereof allows the transducer response to have advantages over existing transducers, e.g., the sensitivity is about 10 times higher when the resolution is maintained at a stable level. This feature makes the transducer suitable for its application in automated equipment for the inspection of oil pipelines where the attenuation of ultrasonic waves produced by fluids is usually very high.

Description

The invention consists of an ultrasonic transducer of high sensitivity, resolution and occupying a small volume, these first two characteristics are necessary for the internal inspection of ducts with fluids of high ultrasonic attenuation. In particular, the transducer can be implemented in automatic equipment for internal inspection of buried hydrocarbon transport ducts where physical space is limited. The innovation lies in perfecting the response of the transducer through changes in the main elements of the transducer (countermass, active element and coupling layer).

FIELD OF THE INVENTION The invention has its application in non-destructive tests, specifically in the inspection by the pulse-echo ultrasound technique. In many occasions the ultrasonic inspections are carried out in media with high attenuation, which forces the transducers to have the sensitivity, resolution and sufficient signal-to-noise ratio, to allow the recording of signals during the inspection. Additionally, automated equipment for the inspection of pipeline lines, known as instrumented devils (in English Pipeline Inspection Gauges) have limitations of physical space, so the transducers must have a size that allows an arrangement of them within the equipment. at mechanical waves with ultrasonic frequencies. The transducers, as part of an equipment, are used in various fields. Its application area depends on the power with which they radiate, the frequency of the wave and the type of emission (pulsed or continuous). In the industry they are used in the analysis of defects in pieces (welding, search for discontinuities or cracks), for the measurement of thickness, level, flow, etc. In medicine they are applied to the visualization of the interior of the human body, measurement of blood flow (Doppler effect), etc. High power and continuous wave transducers are also used in sonars, destruction of kidney stones, nebulizers, aerosol and emulsion formation, cleaners, medical therapy.

Within the petrochemical and metal-mechanic industry there is a wide range of equipment and devices for the inspection of the health of parts and materials by ultrasonic methods, typically using ultrasound transducers for non-destructive testing. Such is the case of the automated equipment for the inspection of pipelines for the transport of hydrocarbons known as "ultrasonic instrumented devils". These equipments are introduced inside the duct, they are driven by the same fluid flow and during their trip they carry out an inspection of the structural integrity of the duct using non-destructive techniques. In the case of ultrasonic instrumented devils, whether for thickness measurement or crack detection, they usually have a large array of transducers. The number of transducers in a device depends on the diameter of the duct to be inspected, since the array of transducers must be such that the periphery of the duct is completely covered. Only in this way can a uniform inspection be ensured in the entire wall of the duct. The volume / size of the transducers plays an important role in the optimal arrangement of the same installed in the inspection equipment. For example, to inspect a 10-inch pipeline Materials are composed of three main elements that are: the coupling layer, the active element, and the countermass. Each of these elements significantly influences the response of the transducers, causing changes in the length and amplitude of the pulses emitted. This translates into changes in the bandwidth, resolution and sensitivity of the transducers, with the latter two (sensitivity and resolution) being one to the detriment of the other. This is explained in the following way, as the damping of a transducer is lighter the mechanical waves of lower energy will be captured by the sameIn other words, the lower the damping, the greater the sensitivity of the transducer. This type of transducer (high sensitivity) usually has long pulse lengths because they lack a damping high enough to quickly brake the oscillation of the active element, this causes signals from two nearby discontinuities to overlap and it is impossible distinguish one from another. On the other hand, the greater the buffering of a transducer, the shorter the pulse lengths, with which the resolution of the pulse increases, however due to the strong damping the low energy mechanical waves will cause low or no oscillation in the active element of the transducer, so they will not be detected, affecting the degree of sensitivity of said transducer. It is therefore important the development of transducers that have a high sensitivity, in this way it can counteract the losses of ultrasonic energy. However, as explained in previous lines, increases in sensitivity are often accompanied by losses in the resolution capacity of the transducers, so that the increase in sensitivity must be achieved with the lowest possible sacrifice of resolution. In addition to this, it must be taken into account that the medium between the transducer and the wall of the pipeline can be from hydrocarbons to any associated product. The hydrocarbons present a great attenuation of the acoustic energy emitted by the transducers. These hydrocarbons may be accompanied by a mixture of sludge, water or debris, to make it impossible to inspect the health of the pipelines.

The patent ES2339626"Perfected Ultrasonic Transducer" mentions a way to control the oscillation of the active element, in search of an adjustment of the resolution and sensitivity of the transducer. In said patent an arrangement is proposed, in which a screw passes through the active element and two metal plates, seeking to adjust the pressure between the three elements (two metal plates and one active element), leaving the active element in the middle of the two plates . In this way as the screw is tightened the pressure between the three elements is increased and consequently the damping of the active element is increased, thus varying the response of the transducer. However, the fact that the active element has a perforation in the center implies that the transducer has a higher electronic noise due to the resonance of the same, which could conceal indications coming from the material inspected.

Additionally, the pipeline lines for the transportation of crude during its operation reach maximum temperatures of 60 ° C and pressures of 1700 psi, as specified in NRF-030-PEMEX-2003, this temperature could seriously affect the ultrasound transducers due to that the Curié temperature (polarization temperature of the piezoelectric element) of many piezoelectric ceramics is close to 50 ° C, so that the piezoelectric element runs the risk of depolarizing, losing its capacity to generate or receive mechanical waves. In addition to this, the high pressures reached in the pipeline for the transport of crude oil can cause the risk of collapsing the ultrasound transducers, since most of the existing ultrasound transducers are designed for application at low pressures.

Transducers for use in automated indoor inspection equipment of buried hydrocarbon transport pipelines must meet four special characteristics: have a small size, have high sensitivity, resist high temperature (approximately 60 ° C), and withstand high pressure (approximately 1700) psi). It is offered, by problem of transducers for automated equipment for the inspection of hydrocarbon transport pipelines, satisfying the requirement of greater sensitivity (approximately 10 times greater than existing transducers), resistance to high pressure and temperature that is required in this application and additionally occupying a small volume.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to an ultrasound transducer for non-destructive testing that can be operated in automated equipment for the inspection of duct lines, which has a novel combination of materials and configuration of the main elements, which allows to increase the response of the transducer without sacrificing resolution. The transducer comprises a tubular configuration of piezocomposite material type PZT-5 embedded in an epoxy resin (also called an active element) that transforms electrical pulses into displacements and generates ultrasonic waves; on each of the poles of the active element (the faces of the tubular configuration) there are welded enameled copper wires in order to conduct the electric current from the connector to the active element. The transducer has a countermass composed of bakelite and tungsten powder in the form of a truncated cylinder that dampens the oscillation of the active element, which is joined to the active element by an epoxy type glue applying a pressure of 120 psi. The union of the active element and the countermass are introduced and fixed inside a hollow cylindrical casing of stainless steel, the active element remaining towards the lower face of the transducer. The free ends of the enameled copper wires are soldered to the microdot connector 10-32 which is fixed to the stainless steel obturator of the transducer. The space between the composite countermass and the obturator is filled with epoxy resin that serves to provide The bakelite coupling layer is attached to the lower face of the active element by means of an epoxy-type adhesive, applying a pressure of 120 psi, and is contained inside the cylindrical stainless steel housing. This coupling layer serves to protect the active element and increase the transmission of acoustic energy. The coupling layer must have a thickness of ¼ wavelength.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows the isometric view of the transducer, in which the connector, the housing, the obturator and the coupling layer can be seen; Figure 2 shows the cross section of the transducer, in which one can see the body of the transducer, the connector, and the main internal elements of the transducer; Figure 3 shows the ultrasound RF signals of 5.0 MHz frequency obtained with the transducer proposed herein; Y Figure 4 shows the ultrasound RF signals of 5.0 MHz frequency obtained with a commercial transducer.

An ultrasound transducer for non-destructive testing that can be operated in automated equipment for the inspection of duct lines is described herein. Figure 1 shows an isometric view of the ultrasound transducer showing a hollow cylindrical stainless steel casing [6] that stores and protects the main elements of the transducer, the lower end of the transducer housing has a thread [ 8] of 3/8 inches in diameter and 32 threads per inch, which serves to attach the same to the inspection shoes of the automatic equipment for internal inspection of ducts, the coupling layer [5] forms the lower face of the transducer, the upper part of the transducer has a stainless steel shutter [7] and in the center of it the electric connector [1] being this a type of 10-32 microdot connector, which is responsible for establishing the electrical connection from the outside of the transducer inside.

Figure 2 shows a transverse view of the transducer, where the configuration of the main elements is: An active element [4] of tubular configuration of piezocomposite type material PZT-5 with a Curié temperature of 350 ° C, has a natural damping because the piezoelectric material is embedded in an epoxy resin, which transforms the electrical pulses in displacements and generates ultrasonic waves. The piezocomposite material PZT-5 lacks radial modes of vibration, that is, it has only one mode, the mode in the thickness direction. In each of the poles of the active element [4] (the faces of the active element [4] of tubular configuration) there are welded enameled copper wires [2] in order to conduct the electric current from the connector [1] to the active element [4].

A composite countermass [3] of bakelite and tungsten powder. Bakelite material has an acoustic impedance similar to that of the active element (4.65x106 and 14x106 Kg m2 / s respectively). In order to increase the capacity of damping and attenuation of the countermass [31 was added countermass [3] composed. This contramasa [3] influence in the improvement of the response of the ultrasound transducer, obtaining a transducer with a large signal amplitude without sacrificing the resolution significantly. The composite countermass [3] in the form of a truncated cylinder is attached to the active element [4] by means of the lower face which is flat and smooth, by means of an epoxy type glue applying a pressure of 120 psi. The union of the active element [4] and the composite countermass [3] are introduced into a hollow cylindrical stainless steel housing [6], leaving the active element [4] towards the lower face of the hollow cylindrical stainless steel housing [6]. ] of the composite transducer and countermass [3] to the upper face of the hollow cylindrical stainless steel casing [6] of the transducer. The hollow cylindrical stainless steel housing [6] has an external thread [8] of 3/8 inch in diameter and 32 threads per inch to allow adjustment of the transducer to angle shoes, so they can be used for angular beam inspections.

An electric connector [1] microdot 10-32 of smaller volume, hermetic connection and stable connection that decreases the electronic noise, which is fixed to the stainless steel shutter [7]. The power supply of the transducer as well as the signal reception of the ultrasonic echoes is made through the electrical contact between the connector [1] and the active element [4] of the transducer by welding the free ends of the enameled copper wires [2] on each of the faces of the active element [4] and the connector [1].

An epoxy resin layer [9] between the composite countermass [3] and the obturator [7] that gives it greater resistance to external pressure, resisting the high pressure of approximately 1700 psi. The epoxy resin layer [9] serves to fix the stainless steel shutter [7] to the hollow cylindrical stainless steel housing [6].

A bakelite coupling layer [5] with a thickness of ¼ wavelength, this element has an acoustic impedance close to that of the active element [4], which favors the transmission of ultrasonic energy from the piezoelectric element to the materials that are want to inspect. The coupling layer [5] joins the lower face acoustic bottom face of the transducer.

In figure 3 and figure 4 the response of a commercial transducer figure 4 and the transducer proposed here figure 3 can be compared, where the proposed transducer allows an increase 10 times greater in the sensitivity compared to the existing transducers. Another important aspect is that despite the great increase in sensitivity, the pulse length is practically the same compared to similar existing transducers, achieving an increase in sensitivity without sacrificing the resolution of the ultrasound transducer.

Claims (2)

CLAIMS Having described the invention as above, it is considered as a novelty and therefore the content of the following claims is claimed as property:

1. An ultrasound transducer for non-destructive testing used in automated equipment for the inspection of buried hydrocarbon transport pipelines characterized by: A hollow cylindrical stainless steel housing for housing the internal main elements of the transducer, having an upper end and a lower end; A microdot 10-32 electrical connector with a hermetic and stable connection, attached to the stainless steel shutter at the upper end of the transducer, used to seal the transducer and connect to the power supply; A means for electrical communication of enameled copper wires welded to each of the poles of the active element and electric connector microdot 10-32; An active element of tubular configuration of piezocomposite material PZT-5 housed in the hollow cylindrical casing of stainless steel; A countermass composed of bakelite and tungsten powder in the form of a truncated cylinder, joined on its lower face (which is flat and smooth) to the upper face of the active element; A layer of epoxy resin between the composite countermass and the obturator, which fixes the stainless steel obturator to the hollow cylindrical stainless steel housing; Y A bakelite coupling layer with a thickness of ¼ wavelength, attached to the lower face of the active element, contained inside the hollow cylindrical stainless steel housing and forming the acoustic bottom face of the transducer.

2. The ultrasound transducer according to claim 1, characterized in that the upper end has a radial freedom to be screwed into a receptacle in any radial orientation