MXPA00005748A - Monitoring pipes - Google Patents

Abstract

An apparatus and method are disclosed for monitoring a liquid filled pipe by ultrasonic techniques. It suggests the use, on a vehicle capable of fitting inside the pipe, and of being transported there along by the liquid flowing therewithin, of rings each of several ultrasonic transducers preferably disposed at equidistance circumferentially therearound, the rings being so arranged that one ring of transducers operates in the reflection mode purely radially while two ringsof transducers operate as a pair in a longitudinal refraction mode. The vehicle is associated with power supply means, data gathering means and data storage capability, and a means for measuring the distance travelled along the pipe.

Description

TUBE MONITORING This invention relates to the monitoring of tubes, and refers in particular to the use of ultrasound. It will characterize tubes filled with liquids.

Owners of liquid-filled pipes often want to monitor the condition of these pipes. Uncertainties may include the type of material, internal diameter, and the thickness of the tube, the type of material, and the thickness of the internal coating if present, the presence of corrosion on the inner surface of the tube, the presence of corrosion on the external surface of the tube, damages the coating, the thickness of some deposits of material on the inner surface of the tube or on the pipe if they occur, the presence and magnitude of cracks on the circumference, the presence and magnitude of longitudinal cracks, and the position of accessories such as elbows, dead ends, valves and connections. In view of the high cost of replacing work pipe, and the significant potential damage due to the loss by forced entry into the working pipe, this may be justifiable for the owner to carry out by a regular inspection of the condition of the pipe. working tube from inside the tube using a vehicle transported along the inside of the tube. In some circumstances this is important so as not to damage any deposit on the pipe wall. In these cases the necessary conditions to be evaluated without wall contact.

So-called "intelligent pigs or devils" are often used inside high pressure gas pipes to detect the presence of corrosion and other defects. The old vehicles are devices for magnetic flux leaks. A powerful magnetic field is used to saturate the steel wall, and some defects in the wall of the tube cause anomalies in the magnetic field of the low flow which are subsequently detected by the "pig or devil". This device requires a steel tube without internal lining, without internal device, the demands of close contact with the wall, and require a great energy. So, these failures to find many of the requirements described above. Even in steel tubes, the leakage method for flow fails to detect large longitudinal cracks. The leakage method for flow has been successfully applied in uncoated steel tubes filled with fluid, but the accidental hit before the flow leakage device was used on carefully cleaned tubes from some tank.

To detect longitudinal cracks, other vehicles inside high pressure gas pipes use ultrasonic transducers in the cutting method. The fluid-filled resin wheels are pressed tightly against the wall of the tube, and are used to join ultrasonic shear waves in the wall. The ultrasonic waves in this case refer to the elastic waves in high frequency ranges in hundreds of kilohertz (and even under megahertz). A compression of the wave is analogous to the visible movement transmitted along a stationary line of rail cars when it is hit by a diesel-powered metal locomotive. A cutting wave is analogous to the way a snake handles its forward progress by zigzagging its body. The shear waves induced by the resin-filled wheels of fluid travel around the tube circumferentially, and are detected by the adjacent wheels. In principle this technique can detect longitudinal cracks. This is evident through, that many failures regarding the method to locate the maximum problem of the monitoring condition described above. Fluid-filled wheels are required inside the gas screw because the large impedance of the incompatibility between the gas and the solid results in a total reflection close to the inner surface of the tube if the waves were thrown into the gas. This limitation does not apply in tubes filled with liquid by comprehensive waves. The liquid can provide a good bond between the compressive waves in the liquid and in the solid.

In the oil industry, Ultrasonics have been used in the reflection mode as gauge tools to measure the diameter of the underground depth of the wells. Such wells are usually filled with various types of liquids.

The proposals of the invention for this purpose of Apparatus for the characterization of a tube filled with liquid, which Apparatus contains: 1. A vehicle capable of adapting inside the tube and being transported by the liquid along the tube. 2. The carrier vehicle of rings of several ultrasonic transducers, preferably arranged in a circumferentially equidistant around the ring and the arranged rings such that: 2. 1 A ring of transducers operates in the purely radial reflection mode. 2. 2 Two transducer rings operate as one pair displaced axially from each other. The pair is used in a longitudinal refraction mode. A ring of transducers emits pulses along the tube at the critical angle to the wall such that the wave is refracted as traveling waves within the debris, coating and in the wall of the tube, and the refracted wave is received by the other ring of translators. 2. 3 The emission ring of the transducers of the refraction mode pair also has the ability to receive refracted resonances, this is a refraction / reflection method. 2. 4 A transducer ring is used in a circumferential refraction / reflection mode. Each transducer emits pulsations in a radial plane but at a critical angle circumferentially to the wall such that the wave is refracted as a circumferential wave along the debris, coating and wall of the tube and the transducer receives refractions back along the the same trajectory. 3. The force of the transport vehicle to supply the ultrasonic and associated data collected and stored data. 4. The capacity of the data collected from the transport vehicle to store the ultrasonic information which is captured at regular intervals of distance along the tube.

The methods are used inside tubes in a refraction mode to determine tube diameters and to detect the presence of a micro ring in the wall of the tube surrounding the cement. These are also used in the refraction mode to detect the presence of a micro ring in the wall surrounding the cement tube. These also have to be used in both reflection and reflection methods to detect flaws in the tubes. However, in all these cases the material of the wall is assumed to be known so the speed of sound in the material is known, and in none of the above cases is there supposed to be some coating or deposit on the interior surface of the wall. Wall. This invention starts to combine ultrasonic methods in reflection, refraction modes and reflection-refraction in order to identify the materials of the wall of the tube, the coating and some important waste in the interior to use this information for the size of the wall. tube, radius and thickness, the coating and some rubble then to identify and then identify aspects such as cracks, corrosion and an accessories.

In a consequent aspect, the invention provides an Apparatus for the characterization of a plain tube of a liquid, such Apparatus consists of: 1. A vehicle able to fit inside the tube and to be transported by the liquid along the tube. 2. The carrier vehicle of rings of several ultrasonic transducers, preferably arranged circumferentially equidistant around the ring and arranged rings such that: 2. 1 A ring of transducers operates in the purely radial reflection mode. 2. 2 Two transducer rings operate as a pair displaced axially from one another. The pair is used in a longitudinal refraction method. A ring of transducers pulses along the tube at a critical angle to the wall such that the wave is refracted as waves traveling within the debris, coating and wall of the tube, and the refracted wave is received by the other ring "of the transducer. 2. 3 The ring emission of the transducers of the refraction mode pair also has the ability to receive reflected resonances, this is a refraction / reflection mode. 2. 4 A ring of transducers is used in a circumferential refraction / reflection method. Each transducer emits pulsations in a radial plane but the critical angle circumferentially to the wall such that the wave is reflected as a circumferential wave along the debris, the coating and the wall the tube and the transducer receives reflections back along of the same trajectory. 3. The vehicle that carries energy to supply the ultrasonics and associated data collected and data storage. 4. The vehicle that carries a data storage capacity to store the information which is captured at regular intervals along the tube 5. The vehicle optionally carries an umbilical cable that transmits energy and incorporates a data communication link back to the tube inlet to avoid storage of energy and memory required in the table. 6. The vehicle carries a means of measuring the distance traveled along the tube.

In one aspect, consequently, the invention provides an Apparatus for use in the characterization of a tube filled with liquid, such Apparatus contains a vehicle capable of adapting within the tube and being transported by the liquid along the tube, the vehicle it carries rings of several ultrasonic transducers arranged such that during the use of the rings they are co-axial with the tube and spaced along the vehicle, and such that a first ring of transducers operates in the purely radial reflection method while a second and A third ring of transducers operate as a pair displaced axially from one another, the pair must be used in a longitudinal refraction method in which a ring of the torque pulses along the tube generally at a critical angle to the wall - it is say, along directions propagated in a cone in such a way to accommodate expected variations in the critical angle of the tube, coating and mat debris waste - such that the wave is refracted as waves traveling inside the debris, the lining and the wall the tube, and the other ring receives the refracted wave, The emission of the ring of the transducers of the refractive method torque also has the ability to receive reflected resonances, this is a mode of refraction / reflection, and a fourth ring of transducers is used in a circumferential refraction / reflection mode in which each transducer emits pulsations in a radial plane but at the critical circumferential angle To the wall such that the wave is refracted as a circumferential wave along the debris, the lining and wall of the tube and the ring then receives reflections back along the same path, the vehicle also carries methods for Measure the distance traveled along the tube.

In a second aspect the invention provides a method of characterizing a tube filled with fluid with movement, in such a method: 1. The tube characterizes an Apparatus as described above that is transported along the tube by the liquid that is inside the tube. 2. The distance traveled by the Apparatus is measured by one means or another. 3. The pulsations are used in radial reflection, longitudinal refraction, refraction / longitudinal reflection and in refraction / reflection modes at regular intervals of distances along the tube and the received ultrasonic information is stored. 4. The ultrasonic data are processed to determine the materials of the pipe wall, the pipe lining, the rubble accumulated on the inside of the pipe, the radius of the pipe, the thickness of the pipe wall, the lining and the rubble, to detect circumferential and longitudinal cracks, damage to the coating and corrosion of the inside and outside of the tube wall, and to locate accessories such as gaskets, valves and joints.

. The preferred option to display the information as a function of the distance along the tube.

The preferred form of the vehicles is an autonomous device considering sufficient energy on board and memory for the examination of long distances exceeding one kilometer along the tube. The vehicle consists of separating small enough modules to enter the tube by means of suitable accessories. In the water industry there are accessories for the entrance and extraction should be with fire hydrants of which the assembly of the total part can be removed. If the existing entry points are not adequate then the vehicle is inserted and retrieved by tailor-made reduced-pressure live launch methods and recovery stations that are adapted on the tube when they are needed.

The modules connected together mechanically connected and the connection include energy and transmission data between modules. The leader module has some means such as a collapsible floating anchor to ensure supply of the flow of the entrained liquid to produce to send string propulsion of the modules. The modules are designed to be neutrally floating to minimize contact with the wall of the tube. Also as it is neutrally floating, the center of gravity of each of the modules is below the geometrical center of the module. This ensures that the module will remain above the average in the same course and thus reduce the requirements for measuring the vertical alignment. On some modules, such as the ultrasonic modules, this is useful to have gentle springs with light pressing gently against the wall. Centralizing the ultrasonic modules reduces the pressure required to extract the information from the ultrasonic data.

Ultrasonic measurements are made inside the tube at regular intervals and the results are presented as a function of the distance traveled along the tube. This traveled distance can be measured by contact wheel means to the wall but the preferred method uses acoustic means to measure the distance. The vehicle emits an acoustic pulse at regular intervals which detects both at the end of the tube. At launch, the time for the signal to reach the farthest end of the tube, t0 multiplied by the speed of sound in the liquid, vf, the length of the tube L = vf to, During transport, the difference,? T. Between the time of the arrival of the pulse in the final release of the tube and the time of the arrival of the pulse in the recovery of the end of the tube gives the distance,?, Of the vehicle of the end of launch like? = (L + Vf? T). A final unique alternative for this method is to transmit an acoustic signal with an end of the tube and has a transmitter on the vehicle that emits its own acoustic response when it detects the arrival of the first transmitted signal. In the final transmission of the tube, the time between the emission of a signal and the reception of the second return of the first multiplied by the speed of sound in the liquid gives the distance in the vehicle. The transmission and response signals with some reflections of the original transmission signal. If an inert navigation system (INS) is adapted to the vehicle so the distance traveled can be deducted with the INS. Even if such a system is available, the preferred method could also include acoustic means of measuring distance as a data backup.

The combination of ultrasonic transducers is transported axially along the interior of a tube by the vehicle on which they are mounted while they are measured in the radial reflection mode, the axial refraction mode operates at an angle to the wall, in the mode Refraction-axial reflection operates at the angle to the wall and in a refraction-circumferential reflection mode that operates at an angle to the part such that it complements a group that can be used to determine the speed of the ultrasonic waves on the wall of the tube, the internal diameter of the tube, the thickness of the tube, the speed of the ultrasonic waves in some coating if it occurs, the thickness of some internal coating, the presence of corrosion on the internal surface of the tube, the presence of corrosion on the surface external of the tube, the damage to the coating, the thickness of some deposits of material on the inner surface of the tube or coating if it occurs, the presence and extension of circumferential cracks, the presence and extension of longitudinal cracks and the position of accessories such like elbows, dead shots, valves and joints.

An extensive variety of tubes can be examined by the ultrasonic method, including, among other materials, cast iron, ductile iron, steel, polyethylene, PVC, and asbestos cement. The sizes of the tubes that can be examined by an autonomous vehicle in a range of 150 mm nominal and supports up to one meter in diameter. The thickness of the wall of the tube may vary according to the liquid, the pressure in the liquid, the proportion of the anticipated flow, the material of the wall of the tube, the structural support for the tube and its design for life. The typical range of thickness ranges from a few millimeters to a few centimeters. The coatings of the tubes depend on the material of the wall, the tube and the liquid inside and are not always used. Typical materials for the coatings include cement mortar, basalt layers, epoxy layers and various plastics. Whether or not there is any accumulation inside the pipe, or debris, depends on the liquid used and the proportion of the flow involved.In the water industry typical accumulations consist of so-called tuberculous growth of hard material initiated by alga in the wall or deposits In the petroleum industry typical accumulations tend to be a waxy hydrocarbon form.Most often the material of the pipe wall, the coating and some accumulation is not known in advance.In this invention this mode of refraction is measured, in identifying the various materials to determine the speed of sound, the measures of the mode of reflection which allow to determine the radius and the thickness of materials.To encourage the combination of all modes of measurements allows the identification of corrosion, longitudinal cracks, cracks circumferential and adaptations such as valves, joints and joints.

The number of ultrasonic transducers used determines the resolution of the circumference of the measurements. For example, in the reflection mode a ring of eight transducers used inside a 150mm support tube gives a circumferential resolution of 59mm. The same circumference resolution is applied for a pair of transducer rings used in the refraction mode, and for a ring used in the refraction / longitudinal reflection mode and for a ring used in the refraction / circumferential reflection mode. The invention describes the method of carrying out the above measurements, particularly with the ultrasonics in the modes of reflection, refraction and refraction-reflection, while transporting the group of axially measured transducers along the interior of the tube. The speed of the ultrasonic waves in the solid and in the liquid is high. For example, typical sound speeds in the iron and water are 5000m / s and 1500m / s respectively. These are sufficiently high compared to the speed with which the transducer can be translated axially along a tube by an autonomous vehicle, typically of the order of lm / s or less, so that these measurements can be taken to vary continuously with distance along the tube. All measurements are taken on a repeated basis as the transducers are transported along the tube. The ratio of the repetition of measurements compared to the interpretation ratio along the tube to determine the axial resolution of the measurements.

For example, if the proportion of the axial interpretation of the modules supports the ultrasonic transducers of O.lm / s then a repetition rate of ten times per second gave a resolution of 10mm. The ultrasonic transducers for both are of a piezoelectric type that emit and receive such as those marketed by Morgan Matroc Limited of Transducer Products Division, Thornhiil, Southampton, Hampshire S019 7TG. There are typically eight or more equally disposed in a ring around the body of the conveyor module in any transverse plane. Such a ring is used for the measurements of the reflection mode. A pair of axially displaced rings relatively to each other are used for the refraction-refraction-reflection mode measurements along the tube. One more ring is used by the refractive measures circumferentially around the tube.

The specific embodiments of the invention are now described by way of the example with reference to the accompanying drawings 1,2,3,4,5, and 6 in which: 1. Figure 1 is an explanatory sketch concerning Snell's law of refraction. 2. Figure 2 shows a schematic view of a tube with an outside cutting section showing a vehicle inside with four rings of ultrasonic transducers around the periphery. 3. Figure 3 shows a cross section (along its longitudinal length) through a tube with an ultrasonic transducer emitting and radially receiving waves. 4. Figure 4 shows a cross-section through the tube with an ultrasonic transducer tube emitting and radially receiving waves. 5. Figure 5 shows a cross section (along its length) longitudinally through a tube, with an ultrasonic transducer emitting waves at an angle to the longitudinal axis of the tube and a second transducer receiving the refracted waves at a axially displaced position of the emitter. 6. Figure 6 shows a cross section through a tube with an ultrasonic transducer that emits waves at an angle to the tube in the circumferential plane. The waves are reflected by a defect in the tube and then received by the same transducer as the emitted pulse.

Figure 2 shows a schematic view of a tube 32 filled with a liquid -2 with an outside cut section 31 showing in module 33 inside with four rings of ultrasonic transducers around the periphery. A pair of rings consists of a ring 35 for transmitting and a ring 38 for receiving waves of the mode of refraction. The transmission ring 25 also serves to receive waves of the longitudinal refraction / reflection mode. Ring 36 is used for waves of the radial reflection mode. The ring 37 is used for the indas of the circumferential reflection / refraction mode. The vehicle serves to transport the array of transducers along the tube. Module 33 is free of float, drawn along the flow of liquid 2 and typically forms part of a chain of such modules. The other modules have various functions such as supplying power and memory storage. The cross section through the tube 32 shows the wall of the tube 3 and the inner lining 4. The debris on the liner is not shown. Figure 3 shows an axial cross section through a tube with a center line 1 containing the liquid 2 and showing on one side of the center line 1 the wall of the tube 3, the cladding 4, the cladding 4 in the wall of the tube 3, and the tank 5 on the lining 4. An ultrasonic transducer 6 mounted on the module 33 is shown emitting a pulse which is transmitted on the 7 through the liquid and reflected at the interface 8 with the tank 5, on the interphase 9 with the liner 4, on the front face 10 of the wall the tube 3, and on the black face 11 of the wall of the tube. The width of the pulse does not need to extend to any great extent beyond the size of the transducer 6. (The width is shown delimited by the parallel lines 27). These reflections travel back along the same thereof to the transducer 6 in which they are detected. Some of these materials can be multiplied reflections.

The timing of the return of the reflected pulses indicates the thickness of the tank 5, the coating 4, the wall of the tube 3 and the distance of the transducer 6 from the wall. The transducer is at a known distance from the center line 1 of the tube, and thus the radius of the tube is determined while the speed of sound in the solid materials is known. The liquid material must have a consistent known speed of sound.

A defect 18 is shown on the outside of the wall of the tube 3, and a second defect 19 is shown on the inside wall of the tube 3. The timing of the return of reflections of such defects gives a measure of the depth of the defects. They are applied inside the coating.

In Figure 3 the transmitted wave 7 is shown outside of some lateral propagation 27 because it is not necessary to include a significant lateral propagation beyond the width of the emitted transducer 6, although inevitably there must be some diffraction propagation.

In Figure 4 a radial cross section is shown through the same array of the transducer 6 in the reflection mode. Each of the eight transducers 6 are shown resting on a circle around the center line. The transmitted wave 7 is shown to extend over an arc delimited by the thrown lines * 24 determined by the size of the transducer 6. The resulting measurements based on the reflections are an average of received resonance of the surface area bounded by the arc 24 and this arc determines the angular resolution. In Figure 5 there is shown an axial cross section through the wall of the tube 3 with an ultrasonic transducer 12 emitting a wave 14 at an angle to the wall, it shows a reservoir 5 on a coating 4. The wave 14 is refracted inside of the various materials at a critical angle 16, the travels along the materials, and refractions out again at the critical angle 17, and the wave 15 is received at a second transducer 13 axially displaced from the first one 12 of which the Wave was emitted. The critical angle 16 depends on the material, and thus the waves 14 are deliberately propagated in a cone shown by the thrown lines 25 to accommodate expected variations in the angle 16. A circumferential defect 18 is shown, and this could represent a crack, corrosion , or an accessory such as a flange, valve or a union on a branch on one side of the tube. The travel time through the different materials indicate the speed of sound in these materials. The speed of sound in the material identifications the materials of the wall the pipe, the coating and the debris. ' In short, the speed of sound in each material is needed to multiply the transit times of the radial pulses in the reflection mode so that to convert this time within the absolute distance includes the thickness of the debris, the thickness of the coating and the thickness of the tube wall. The transmitted wave 14 is reflected in a defect 18 when the positions of the defect 12 and 13, and the reflected wave is received is the same transducer 12 as the original transmitted pulse. Reflections of defect 18 indicate the presence of such defects.

Figure 6 shows a radial cross section through the tube with a transducer 20 emitting a wave 21 at a critical angle to the wall such that it circumferentially travels the wave around the wall of the tube 3 within the material of the wall. A longitudinal defect reflects the wave back to the emission of the transducer 20, and the timing of the return indicates the position of the defect. To accommodate variations in the critical angle, the wave 21 extends through a cone delimited in Figure 6 by a thrown wave 26.

In the reflection mode, a pulse is emitted by the ultrasonic transducer in a radial direction, normal to the tube wall, and reflections from normal surfaces to the ultrasonic wave course are received, commonly in the same ultrasonic transducer. The normal surfaces to the course of this reflection mode pulse could be inside the surface of some deposit and the interface between deposits, coating, corrosion and the surfaces of the tube wall inside and outside it.

The timing of the signs of the radial reflection mode gives an indication of the radial dimensions of the tube, the thickness of the tube wall, the coating and the deposits of the tube. Assume, for example, that the speed of sound in the liquid is vf and the first reflection pulse is received after tf seconds. Then the distance traveled through the liquid by the transducer in the deepest side of the wall, possibly the debris, and the return to the transducer is the 0.5vftf product. The next reflection of the interface between the debris and the coating. If this reflection is received at time td and the speed of sound in the rubble vd then the thickness of the debris is the product 0.5 (d - t) Vd- The same principle was applied for some number of reflections supplied in such a way that This is possible to distinguish them. Some abnormalities in the timing indicate the presence of several defects.

For example, if the measurements continuously produce the thickness of the wall of the tube as the transducers travel axially along the tube and then at some points there is much reduced time of arrival of the outer face of the tube wall, this indicates that there is at the point of the wall a substantial corrosion. This may be that multiple reflections within some of the materials in the course and more likely on the wall. Such a multiple of reflections results in repeated resonances in the receiver and the server to reinforce the thickness calculation of the material. The time between these resonances multiplied by the speed of sound in the repeated material produces the estimation of the thickness of the material.

The timing information gives the radial distance of the transducer to the first reflection face, such as debris, since then the speed of sound in the liquid is known. However the timing information can not give the dimensions of the materials, debris, coating or tube wall, unless the speed of sound in this material is known exactly. The speed of sound in materials comes from the timing of the pulses transmitted by the pulse of the refraction mode, described below.

In the refraction mode, a pulse is emitted by the ultrasonic transducer at the angle in the wall of the tube known as the angle of incidence. The angle involved is determined by Snell's law which confronts the speed of sound in two media through the sine of the subtended angles for the normal at the interface by the waves in the two materials. In Figure 1 for example, a transmitted wave 7 shows the liquid 2 within the debris 5 at an angle of incidence 30 for the radial normal 34, of the debris within the coating at the angle 29, of the coating within the wall of the pipe at an angle 28. If the speed of sound in the liquid, debris, coating and tube wall is represented by v_ > vd, v_ and vp respectively at the angles 30, 29, 28 are represented by af, a < _, and otj respectively then sin a.f = vt / vp, sin ad = vd / vp, and sin a = Vi / vp.

The wave is refracted inside the tube wall and travels along the wall. The angle of incidence of the wave with the tube resulting in a wave within the wall of the tube traveling parallel to the wall of the tube is referred to as the critical angle by the refraction within the wall of the tube. The critical refractive angle within the coating sh be slightly large and even the critical angle for refraction within the debris sh be slightly large. For the transmission of waves over a small range of angles, all angles are included. At the angles of incidence unless the critical introduction of longitudinal waves within the tube wall is at least efficient. The plane contains the normal for the tube wall and the projected wave can be longitudinal, in which case the direction of the trip through in the solid is circumferential. As the pulse travels along it is continuously refracted out again from the wall, back into the region of the liquid, and some of these refracted transmission waves are detected in a second, receive, ultrasonic transducer. Refracted waves can also find areas of refraction along the wall of the tube, such as cracks, corrosion and junctions, and the reflected waves are detected in the same transducer from which the wave was transmitted. The first arrival in the receiver transducer in the refraction mode is that of the waves transmitted through the wall of the tube since that material has the highest sound velocity, around 500m / s. The length of the courses in the refraction mode was determined by the distance apart from emitting and receiving the transducers and this is prescribed in advance by the geometry. Since then the speed of sound in the liquid can be supposed to be known, the time of the arrival of the first pulse produces the speed of sound in the wall of the tube. Assume the distance of the transducer to the debris is Xf, the thickness of the debris is xd, the thickness of the lining is Xi, the distance between emitting and receiving the transducers is L and the time to receive the pulse is t then we have for the speed of the sound on the wall of 2x, 2xv 2x, tube the expression v = - L - We warn that thing ^ thing thing, xd, xi and the angles üf, ad and ai are unknown until the sound velocities in the materials are determined. By this means the various equations are slightly associated. The coupling is weak because the distances xd and i are small compared to the radial distance Xf. The equations quickly converge if they are solved by an interactive scheme so initially the little unknown are ignored and increasingly refined in each interaction.

Similarly, subsequently arrivals through the lining and debris produce the speed of sound in these materials. The partial reflection of the signs of the longitudinal refractive mode indicates the presence of a defect such as a circumferential crack while the total reflection of the signs of the longitudinal refractive mode signs indicates the presence of an accessory such as a flange. The partial reflection of the signs of the circumferential refraction mode indicate the presence of a defect such as a longitudinal crack. As the transducers are transported axially along the tube, the transducers of the reflection mode temporarily receive a distorted signal as an accessory such as a flange pass. Consequently both signs of the modes of reflection and refraction can detect corrosion, cracks and adaptations. The comparison of events detected by the signs of the reflection mode and the signs of the refraction mode serve to distinguish cracks by corrosion and various types of adaptations, especially as the repeated use of the transducers allows a process knowledge to be carried out therefore, the quantitative form of the reflections is used to distinguish between different characteristics such as cracks, corrosion and adaptations.

It is stated in relation to this date, method known to the applicant, to carry - practice the aforementioned invention is the result of the manufacture of the objects to which the Having described the invention, c claims as property the contents of the invention.

Claims (10)

1. An apparatus for use in the characterization of a tube filled with li, characterized in that it contains a vehicle capable of adapting inside the tube and being transported by the li along the tube, the vehicle transports rings of several ultrasonic transducers arranged such that during use the rings are co-axial with the tube and spaced along the vehicle, and such that: a first ring of transducers operates in the purely radial reflection mode while a second and a third ring of transducers operate as a pair displaced axially from each other, the pair is used in a longitudinal refraction mode in which a ring of the pair pulses along the tube generally at the critical angle to the wall -that is, along directions extended in a cone in a manner to accommodate expected variations in the critical angle of the tube, coating and debris materials that the wave is refracted as waves traveling inside the debris, the lining and the wall of the tube, and the other ring receives the refracted wave, The emission ring of the transducers of the refracted mode pair also has the ability to receive reflected echoes, this is a d refraction / reflection mode, and a ring of the transducers is used in a d refraction / circumferential reflection mode in which each transducer emits a pulse in a radial plane but at the critical angle circumferentially to the parent such that the wave is refracted as a circumferential wave along the rubble, the lining and the wall of the tube and the ring then receives reflections back along the same course, the vehicle also carries means to measure the distance traveled along the tube.

2. An apparatus as claimed in claim 1 characterized in that there are 8 or more transducers equally arranged in each ring.

3. An apparatus as claimed in any one of the preceding claims, characterized in that the vehicle carries a data storage medium in which the ultrasonic information is stored which in the operation is captured at regular intervals d distance along the tube, together with the means of energy supply by the transducer and the collection of associated data and data storage.

4. An apparatus as claimed in any of the preceding claims, characterized in that the vehicle consists of a plurality of enough small connected modules separated to enter the tube by means of a suitable accessory.

5. An apparatus / co or claimed in any of the preceding claims, characterized in that the vehicle transports a collapsible floating anchor to ensure that in use. The flow of the li provides sufficient drag to produce a propulsion of sending the vehicle.

6. Apparatus as claimed in any of the preceding claims, characterized in that the vehicle is neutrally floating, and has its center of gravity below the geometric center of the vehicle.

7. An apparatus as claimed in any of the preceding claims, characterized in that the vehicle has a spacer means which is used to centralize the vehicle within the tube.

8. An apparatus as claimed in claim 7, characterized in that the spacer means is a plurality of springs laterally extended by the vehicle, such springs are used to press gently against the wall of the tube so as to centralize the vehicle.

9. An apparatus as claimed in any of the preceding claims, characterized in that the means of measuring the distance of the vehicle are acoustic means, which uses to involve measurements the travel time of the acoustic pulses along the tube

10. A method of characterizing a tube filled with a li, characterized oorque: A characterizing apparatus as claimed in any of the preceding claims is placed inside the tube, and the li is caused to flow along the tube, thus transporting the apparatus along. the distance traveled by the apparatus is measured; The ultrasur pulses at regular intervals of distance s along the tube are emitted in radial reflection, in longitudinal refraction, in refraction / longitudinal reflection and in m of refraction / circumferential reflection; and the ultrasonic information received in processed suitably to provide the required characterization. PIPE MONITORING SUMMARY OF THE INVENTION An apparatus and a method for the monitoring of tubes filled with liquids by ultrasound techniques are described. This suggests the use in a vehicle capable of adapting within the tube, and of being transported along by the flow of the liquid therein, of rings which are ultrasonic transducers, preferably disposed at a circumferentially equidistant around this, the rings that it has been arranged that one of the transducer rings operates in the purely radial reflection mode while two transducer rings operate in a purely longitudinal refraction mode. The vehicle is associated with the means of supplying the energy, the means of collecting associated data and the storage capacity of data, and a means for measuring the distance traveled along the tube.