Patent Application
20100316328
The present invention refers to methods of measuring the position of equipment in deep wells in onshore and offshore installations. Specifically it is of application on flow control valves, called “choke”.
Some manufacturers have commercially developed fiber optic position transducers based on interferometry or light intensity. Fiso's position transducer falls into this first category, as described in the article, “Fiso's White-Light Fabry-Perot Fiber-Optics Sensors”; Fiso Technologies Inc. The Philtec position transducer, presented in “Philtec Fiber optic Displacements Sensors”, Philtec Inc. 2002, currently uses measurement of light intensity. Other well known devices, that have not reached the commercial stage, are: The transducer on an arm based on interferometry, described by F. Ruan; Y. Zhou; Y. Loy; S. Mei, Ch. Liaw and J. Liu in the article, “A Precision Fiber Optic Displacement Sensor Based on Reciprocal Interferometry”; Optics Communication, No. 176, pp 105-112, 2000, and the transducer based on reflective prisms, describe by Y. Takamatsu; K. Tomota and T. Yamashita in “Fiber-optic Position Sensor; Sensors and Actuators”, No A21-A23, pp 435-437, 1990.
Transducers that are supported by interferometry depend on an opening from which the light exits the fiber and is reflected by some type of mirror. This presents a weakness, since the mirror can be displaced in relation to the fiber, leading to the need to mechanically align the light beam as well as problems related to the cleanliness of the optical surfaces (tip of the fiber and mirror). Moreover, if dealing with transducers that must be located at the end of the fiber, serial multiplexing is not possible.
The high sensitivity to angular misalignment of the fiber optic line in relation to the surface is one disadvantage of transducers based on light intensity that even require a visually homogeneous target surface, with reduced result precision when the surface is less reflective.
On the other hand, some recent articles describe the use of magnetostrictive materials as a base for the construction of position transducers. The effect of magnetostriction, that occurs in the majority of cases with ferro-magnetic materials, is a variation in the length variation of a segment subject to a magnetic field; the magnetostrictive material expands or contracts in response to changes in the strength of the magnetic field in the area where the segment is found. This effect is symmetrical in relation to the applied field, with distortions in only one direction, independent of the magnetic field signal.
Some applications already exist that use these magnetostrictive materials in the construction of devices for measuring magnetic field and torque, for example, but up until now, there are few that are large enough to use as position sensors. Among these are found patents JP10253399-A and U.S. Pat. No. 6,232,769-B1, and those that are described in the articles, “Dynamic behavior of Terfenol-D”, by Koshi Kondo; J. of Alloys and Compounds 258 (1997) 56-60; “On the calibration of position sensor based on magnetic delay lines” by E. Hristoforou, H. Chiriac, M. Neagu, V. Karayannis; Sensors and Actuators, A 59 (1997) 89-93; “A coily magnetostrictive delay line arrangement for sensing applications”, by E. Hristoforou, D. Niarchos, H. Chiriac, M. Neagu; Sensors and Actuators A 91 (2001) 91-94 and “New position sensor based on ultra acoustic standing waves in FeSiB amorphous wires”, by H. Chiriac, C. S. Marinescu; Sensors and Actuators 81 (2000) 174-175. All the cited applications above are based on the principal of acoustic wave propagation through a connecting rod (stem/rod) or waveguide made-with magnetostrictive material. The sensor elements are inductive or optic, and position is determined by measuring the time interval related to the position of the emitting element, a bobbin or a magnetic or an electromagnetic element. All require an electronic circuit next to the location of the measurement and have a dynamic range of between 30 mm to 300 mm.
Similarly, the position measuring device described in U.S. Pat. No. 5,821,743 is a device that includes a magnetostrictive waveguide that extends through a measured field, and a means to produce a signal that shows the position of a magnet. It is endowed with a piezoceramic element.
U.S. Pat. No. 5,394,488, which presents a speed sensor, and the article “A Magnetostrictive sensor interrogated by fiber gratings for DC-current and Temperature discrimination”, by J. Mora, A. Diez, J. L. Cruz, M. V. Andres; IEEE Photonics Tech. Letters 12 (2000) 1680-1682, although they are not referring to the measurement of position, they solve the cited problems in a manner related to the present invention, based on the joint use of magnetostrictive material and Fiber Bragg Grating Sensors.
By including the information from its optic specter, Fiber Bragg Grating Sensors supply an absolute measurement that is easily multiplexed, with applications where traditional sensing systems have shown to be inefficient. The wave length variation values of a Fiber Bragg Grating Sensor are related to variations in temperature and distortions through the equation:
ΔλB/λB−K1ΔT+K2ε (I)
where λB is the value, in meters, of the wavelength reflected by the sensor, ΔT is the temperature variation, in ° C., and represents the distortion suffered by the sensor, in m/m, and K1 and K2 are constants that depend upon the specific assembly.
Diverse techniques have been used in the different types of position transducers currently known: capacitive, optical, inductive and fiber optic.
The prevailing technique uses electric induction as the functioning principle. The main advantage of this type of position transducer over the others is its highly resistant quality, since due to the absence of physical contact there is little wear on the sensor element. Its great advantage over the previous ones is its capacity to work under severe conditions with no changes in its performance in humid environments and vibrations. Moreover, they are susceptible to electromagnetic interferences.
The most recent technology uses fiber optic support. There is not one, but several techniques which have in common the use of fiber optics as a light guide used for measurement. Among these techniques are those based on Bragg networks, which, until now, has not yet been applied to position transducers.
A great advantage of fiber optic sensors and transducers, beyond its good performance and simplicity of construction, is the absence of electric signals next to the measurement point, which makes these sensors and transducers totally safe for applications in classified areas.
The purpose of the present invention is to develop a position transducer based on the Bragg Network technology using highly reliable, robust fiber optics for the outflow control valve on the inside of an oil well.
The purpose of this invention is a fiber optic position transducer for uniaxial movements based on the properties of magnetostrictive and that uses Bragg networks as sensing elements.
A fiber optic position measurement system was developed for uniaxial movements based on Fiber Bragg Grating Sensors and the properties of magnetostrictive material. Changes in the relative position between a magnetic field source and a segment of magnetostrictive material, (connected to Fiber Bragg Grating Sensors) cause changes in the size of this segment, which induces alterations in the wave lengths reflected by the Fiber Bragg Grating Sensors. When the spatial dependence of the magnetic field is known, wave lengths reflected by the sensors will be related to the displacement which has occurred. The invention also refers to the process of calibration of the position of the fiber optic position transducer.
For this, a fiber optic position transducer is foreseen that includes the following components:—a magnetic or electromagnetic element;—at least one segment of magnetostrictive material;—Fiber Bragg Grating Sensors;—a rod of material that is impenetrable to magnetic fields;—optical fiber; being that:—said sensors are at least joined and fixed to a segment of magnetostrictive material;—at least one of said segments of magnetostrictive material is fixed to a rod;—and the distortion of the rod relative to the magnetic or electromagnetic element is limited to the direction of the rod's axis.
These and other objects and advantages of this invention, will be more completely understood and appreciated by careful study of the following more detailed description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:
Number I of this figure is the performance of the magnetic or electromagnetic element;
A detailed explanation is given of the fiber optic position transducer with magnetostrictive material and Fiber Bragg Grating Sensors in flow control valves (choke), suitable for use in onshore and offshore installations of deep wells.
It is a position transducer resistant to high pressures and temperatures, with high sensitivity, simple construction, compact, using Fiber Bragg Grating is Sensors (FBG) with magnetostrictive material.
The principle upon which the present invention is based has to do with the relative displacement between a magnetic field source and a segment of magnetostrictive material, which is connected to one or more Fiber Bragg Grating Sensors. Changes in the relative position between a magnetic field source and a segment of magnetostrictive material cause changes in the size of this segment and, for this reason, in the sensor to which it is connected, which induces alterations in the wave lengths reflected by the Fiber Bragg Grating Sensors. Once the spatial dependence of the magnetic field is known, the wave lengths reflected by the sensor are related to the displacement which has occurred.
As the temperature is a factor that can also cause alterations in the wave length of a Fiber Bragg Grating Sensor, the harmonizing device for the present invention is characterized by the use of at least two Fiber Bragg Grating Sensors, to guarantee the necessary compensation for the effect of the temperature.
The other characteristics of the present invention are:
The performance of the sensor can be made of a permanent magnet and/or by the application of a magnetic field.
Preferably, the Fiber Bragg Grating Sensors are made of the same optical fiber. This is advantageous due to its pure simplicity, allowing optical connection elements to be dispensed with, and due to the possibility of measuring other lengths throughout this same fiber.
A graph of the basic configuration of the position transducer in accordance with an example embodiment of the present invention, is shown in
Only as an example, in
The Reading system 6 sends a beam of light through the optical fiber 5. When it reaches sensor 3.1, part of the incident light is reflected in the λ1 wave length of sensor 3.1, while the remaining part of the light is transmitted, arriving at sensor 3.2. When the light falls on sensor 3.2, the same process occurs: part of the incident light is reflected in the λ2 wave length of sensor 3.2, and the remaining part of the light is transmitted, following along the optical fiber 5. The light reflected by each of the sensors (3.1 and 3.2) is recaptured by the reading system 6, where it is analyzed.
One possible configuration for the reading system 6 contains a broadband light source, a coupler and an analysis and detection system. As an alternative, the position transducer in accordance with an example embodiment of the present invention may operate connected to any applicable configuration for the interrogation of Fiber Bragg Grating Sensors.
When a displacement between the magnet 1 and the rod 4 occurs, the reading system 6 will present a different reading of λ2.
If there is a variation in temperature in the area of sensors 3.1 and 3.2, the reading system 6 will present different readings of λ1 and λ2 respectively. The device in accordance with an example embodiment of the present invention is pre-calibrated by temperature, that is, curves that give information on variations of λ1 and λ2 with the temperature are previously know. In this basic configuration of the present invention, pre-calibration is carried out at Sensor 3.2, which is fixed to the segment of magnetostrictive material 2, in such a way that the temperature calibration curve for Sensor 3.2 will already take into account the effect of thermal distortion on the segment of magnetostrictive material 2. Since there should be no temperature gradient in the short distance between Sensors 3.1 and 3.2, when equation (I) is applied successively to sensors 3.1 and 3.2, it allows temperature compensation and the identification of the range of the λ2 portion which is exclusively due to the effect the magnetic field has on the segment of magnetostrictive material 2.
The values that the λ2 wave length takes on as a function of the relative position of rod 4 to magnet 1, with the possible effect of temperature already deducted, provide a calibration curve of the position of the device in accordance with an example embodiment of the present invention, in the basic configuration shown in
The graph of
In the case of all three variants of the basic configuration of the present invention described below, the passage of the light is the same as previously described for the basic configuration of the invention: part of the light emitted by the reading system 6 is reflected by Sensors 3.1 and 3.2 in their respective wave lengths, λ1 and λ2, and then returns to the reading system 6, where it is analyzed.
In the first variant of the basic configuration of the present invention, diagramed in
The distinct distortions caused by the magnetic effect on sensors 3.1 and 3.2 are related by the constant volume of the magnetostrictive material segment 2. As described above, the device in accordance with an example embodiment of the present invention is pre-calibrated by temperature. In this first variant (
A second variant of the basic configuration of device in accordance with an example embodiment of the present invention is presented in
Compared with the basic configuration of the present invention, presented in
This configuration of the present invention, diagramed in
The device, in accordance with an example embodiment of the present invention, is pre-calibrated by temperature, as previously described. In this second variant of the basic configuration of the invention, the pre-calibration is carried out through the two sensors, 3.1 and 3.2, respectively, fixed upon the segments of magnetostrictive materials (2.1 and 2.2), so that the respective calibration curves of these temperature sensors have already taken the effects of the thermal distortion of the respective segments of magnetostrictive material (2.1 and 2.2) into account. With the values of the reflected wave lengths from sensors 3.1 and 3.2, and the information referring to the deformations undergone by each sensor, equation (I) is applied to each one of the sensors. The procedure for calibrating the variant position for this second variant of the device will be described in detail below, together with the description of the third variant of the device in accordance with an example embodiment of the present invention.
A third variant of the basic configuration of the device in accordance with an example embodiment of the present invention is presented in
In this third variant of the basic configuration of the invention, the pre-calibration is based on temperature and is carried out in the same manner as described previously for the second variant, through the two sensors, 3.1 and 3.2, respectively, fixed upon the segments of magnetostrictive materials (2.1 and 2.2), so that the respective calibration curves of these temperature sensors have already taken the effects of the thermal distortion of the respective segments of magnetostrictive material (2.1 and 2.2) into account. With the values of the reflected wave lengths from sensors 3.1 and 3.2, and the information referring to the deformations undergone by each sensor, equation (I) is applied to each one of the sensors.
However, the very complex geometry of magnet 1 also translates into a magnetic field whose spatial dependency is more complex.
In relation to the existing position transducers, the invention presents innumerable advantages propitiated by optical fiber technology: its great simplicity of construction, reduced size and weight, the possibility of making measurements in aggressive environments such as, for example, at high temperatures, and the possibility of taking remote readings, without needing electronic circuits at the point of measurement. Moreover, in contrast with transducers based on electrical induction, the present invention avoids the use of cables and electrical circuits close to the place of measurement. However, in the same manner as those transducers, the present invention is capable of supplying measurements of great precision and trustworthiness, because, due to the is absence of physical contact with the magnetic field source, the sensing element does not wear out.
The device, in accordance with example embodiments of the present invention, offers other advantages due to the use of existing optical fiber transducers: it can easily be multiplexed, it does not present problems with surfaces, whether they are clean or not or have a highly reflective quality, and since the light remains inside the fiber, there is no need to make a mechanical alignment.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| PI 0501790-4 | May 2005 | BR | national |
This application is a continuation of application Ser. No. 12/216,076, filed Jun. 30, 2008, which is a continuation of application Ser. No. 11/434,517, filed May 16, 2006, and is based upon and claims the benefit of, priority of, and incorporates by reference, the contents of Brazilian Patent Application No. PI 0501790-4 filed May 17, 2005.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12216076 | Jun 2008 | US |
| Child | 12654654 | US | |
| Parent | 11434517 | May 2006 | US |
| Child | 12216076 | US |
