DE102011017824A1 - Interferometric pressure transducer for oil production industry, has separation membrane chamber that is connected with transducer chamber through hydraulic path at which transfer fluid with specific temperature is filled - Google Patents

Abstract

The transducer has a movable measuring membrane (11) that is made of silicon. A transparent counter portion (12) is arranged facing a metallic support structure (13). A separation membrane chamber is connected with a transducer chamber through a continuous hydraulic path. The distance between the measuring membrane and the separation membrane chamber is set to predetermined range. The transfer fluid with specific temperature and pressure is filled in the separation membrane chamber, the transducer chamber and the hydraulic path.

Description

The present invention relates to a high temperature transducers, especially for temperatures above 125 ° C.

The publication WO 2009/079803 A1 discloses pressure measuring cells with white light interferometric evaluation for high temperature application, wherein the base body and the measuring membrane of these pressure measuring cells have corundum or sapphire. Such pressure measuring cells are intended in particular for use in oil extraction, for example in the monitoring of hot steam extraction in deposits. The principle of interferometric pressure transducers, in particular so-called white light interferometric pressure transducers or interferometric pressure transducers with light of short coherence length is known per se and with regard to the optical basis in a review article of Rao and Jackson (Measuring Science and Technology 7 (1996) 981-999) described.

In Industrial Process Measurement, pressures of various process media must be measured. Pressure sensors with a measuring membrane, which has aluminum oxide, are characterized by a high media resistance, and can be applied directly to a variety of process media. Pressure sensors with a silicon pressure transducer, however, are unsuitable for direct contact with process media in many cases. Therefore, it is common practice not to pressurize the silicon pressure transducers directly with the process medium, but to transmit the pressure to be measured with a pressure transmitter to the silicon pressure transducer, wherein the pressure transmitter comprises a hydraulic path which extends between a metallic separation membrane and the silicon pressure transducer, and wherein the separation membrane can be acted upon by the process medium. The silicon or semiconductor pressure transducers are often mounted on so-called TO sockets, which have a metallic base, which is pressure-tight to integrate in a sensor housing via soldering or welding, details of which are for example in the published patent applications DE 10 2004 006 197 A1 . DE 10 2004 003 413 A1 . DE 10 2004 006 201 A1 . DE 10 2004 006 199 A1 . DE 10 2004 011 203 A1 disclosed.

Apart from the sensitivity to various process media, silicon pressure transducers are only suitable for a limited temperature range, especially when they have doped semiconductor structures as are common in the conventional piezo-resistive pressure transducers. Such silicon pressure transducer can only be used up to about 125 ° C. Therefore, diaphragm seals are often used to thermally decouple the silicon pressure transducer from the process medium at least to the extent that the temperature of the semiconductor pressure transducer does not exceed a critical temperature value of for example 125 ° C, even if the temperature of the process medium is considerably higher. For this purpose, the pressure measuring cell is positioned at a sufficient distance from the process medium in order to reduce the difference between the temperature of the medium and the critical temperature over a temperature gradient that runs along the hydraulic path between the separation membrane and the silicon pressure transducer. Thus, the current high-temperature diaphragm seal on a certain length, which causes a large volume of transmission fluid. However, the volume of the transfer fluid affects the so-called separation diaphragm error on the accuracy of measurement, because the separation membrane is deflected by the volume expansion of the transfer fluid, which leads to a change in pressure in the hydraulic path due to the rigidity of the separation membrane.

Another limit for the use of the diaphragm seal results from the temperature-dependent vapor pressure of the transmission fluid, with which the hydraulic path is affected. When the vapor pressure of the transfer liquid rises above the actual pressure of the process medium and possibly the pressure due to the separation diaphragm error, the transfer liquid begins to outgas, whereby the separation membrane can be plastically deformed in the extreme case.

To prevent this, it must be ensured that the filling liquid contains no components which can develop a critical vapor pressure at high temperatures. For this purpose, a transmission fluid can be conditioned at high temperature under vacuum in the sense that the volatile components evaporate. The hydraulic path should then be filled with the conditioned transfer fluid at high temperature, preferably under vacuum. With a high temperature, the maximum temperature to be expected during operation is meant in this case, in any case the filling temperature should approach this temperature as far as possible. Here again, however, proves the silicon pressure transducer as a limiting factor, since it should not be subjected to temperatures above its critical temperature, for example, 125 ° C.

In order to resolve this contradiction, the published patent application DE 10 2004 052 950 A1 a pressure transducer for high temperature applications, comprising a sensor module and a transmission module. The sensor module comprises a sensor body which has a measuring cell chamber in which a pressure measuring cell, in particular a silicon pressure transducer is arranged, wherein the pressure measuring cell is acted upon by a first filled with a pressure transfer fluid hydraulic path with a pressure. The transfer module for transferring pressure to the first hydraulic path comprises a second hydraulic path filled with a transfer fluid extending from a process-side separation membrane via a transfer body to a transfer membrane, the transfer membrane being pressure-tightly secured to the transfer body, and wherein the sensor body is pressure-tightly connected to the transfer body such that the first hydraulic path communicates with the transfer membrane so that the pressure of the second hydraulic path through the transfer membrane is transferable to the first hydraulic path.

The division of the hydraulic path now makes it possible for the second hydraulic path, which in operation is exposed directly to the high temperatures of the process medium, to be filled with the transfer fluid at high temperatures without adversely affecting the pressure measuring cell or the silicon pressure transducer as a result of the filling. The first hydraulic path can then be filled with a transfer fluid at a temperature below the critical temperature.

However, the described division into two parts is on the one hand expensive and on the other hand leads to an increased volume of the transfer fluid, which in itself leads to an increased measurement error due to a stronger deflection of the separation membrane, which complicates the fact that even two separation membranes are present. Nevertheless, in order to achieve a sufficiently low separation membrane error at a given volume of transmission fluid and the associated deflections of the separation membranes and to avoid plastic deformation of the separation membranes tend separation membranes with a large diameter, which in turn leads to increased Matertalaufwand and thus higher costs. It is therefore the object of the present invention to provide a high temperature pressure transducer which overcomes the disadvantages of the prior art.

The object is achieved by the Hochtemperaturdruckmessaufnehmer according to the independent claim. 1

The pressure measuring transducer according to the invention comprises a pressure transducer, a metallic carrier and a hydraulic pressure transmitter, wherein the pressure transducer comprises a pressure-dependent deflectable measuring membrane, which comprises silicon, and an at least partially transparent counter body, wherein the measuring membrane and the counter body to form a measuring chamber between the measuring membrane and the The pressure transducer having at least two substantially parallel to each other and aligned with each other reflecting surfaces, wherein a first reflection surface is disposed on the measuring membrane and a second partially reflecting reflecting surface with respect to the counter body has a substantially pressure-independent position, wherein the first reflection surface through the second reflection surface can be illuminated, wherein the path difference between the light reflected at the first reflection surface Lic ht and the reflected light on the second reflection surface is dependent on the difference between a first pressure acting on an outside of the measuring chamber outside of the measuring membrane and a second pressure prevailing in the measuring chamber, wherein the metallic support carries the pressure transducer and wherein the Counter-body facing the metallic support, wherein extends through the metallic support, a light path whose axis is substantially aligned with the first and the second reflection surface, wherein the pressure averaging agent diaphragm, a separation membrane and a transducer chamber, wherein the separation membrane to form a separation membrane chamber between the pressure center body and the separation membrane with at least one peripheral joint is pressure-tightly secured to a surface of the diaphragm seal body, wherein the separation membrane chamber and the converter chamber communicate with each other via a continuous hydraulic path, wobe i the pressure transducer is positioned by means of the carrier body in the transducer chamber and the transducer chamber is pressure-tightly sealed by means of the carrier body, wherein the distance of the measuring membrane of the separation membrane is not more than 100 mm, in particular not more than 60 mm, and preferably not more than 40 mm wherein the separation membrane chamber, the converter chamber and the hydraulic path between the converter chamber are filled with a transfer liquid which at a temperature of 150 ° C has a vapor pressure of less than 6 mbar, in particular less than 4 mbar and preferably less than 2 mbar, and wherein the transfer liquid has a dynamic toughness of not more than 1.0 Pa · s, particularly not more than 0.7 PaS and preferably not more than 0.5 Pa · s at 20 ° C.

The metallic carrier may in particular comprise a TO socket.

In a development of the invention, the separating membrane has a diameter of not more than 50 mm, preferably not more than 35 mm and particularly preferably not more than 25 mm.

In one development of the invention, the distance of the measuring membrane from the separating membrane is not more than twice, in particular not more than 1.5 times and preferably not more than 1 times the diameter of the measuring membrane.

In a further development of the invention, the converter chamber is formed in the diaphragm seal body or another body.

In one development of the invention, the vapor pressure of the transfer liquid at 200 ° C., in particular at 250 ° C., preferably at 280 ° C., is not more than 6 mbar, in particular not more than 4 mbar and preferably not more than 3 mbar.

In a development of the invention, the counterbody has the second reflection surface.

In one development of the invention, the pressure measuring transducer further comprises a receptacle or a connection for a light guide, for coupling light into the light path and for dissipating light which is reflected by the first and the second reflection surface, the light guide being pressure-tightly separated from the transmission fluid is.

In one development of the invention, the pressure measuring transducer further comprises a reference pressure path which extends through the carrier body and through the counter body into the measuring chamber.

In a development of the invention, the counterbody comprises glass, in particular a borosilicate glass.

In a development of the invention, the pressure transducer has a third reflection surface which has a temperature-dependent and substantially pressure-independent distance to one of the two other reflection surfaces, the temperature-dependent distance being suitable for the interferometric determination of a temperature measurement value.

In a further development of the invention, the third reflection surface is formed by a surface of the opposing body facing away from the measuring chamber.

The invention will now be explained with reference to the embodiment shown in the drawings. It shows:

1 a schematic longitudinal section through an embodiment of a pressure transducer according to the invention on a metallic support; and

2 : A schematic longitudinal section through an embodiment of a pressure measuring transducer according to the invention with the pressure transducer from 1 ,

The in 1 illustrated pressure transducer 10 includes a silicon measuring membrane resting on a mating body 12 , The glass is attached by means of anodic bonding, whereby a measuring chamber is formed between the measuring membrane and the counter body, wherein a pressure-dependent deflection of the measuring membrane has to be made against the pressure in the measuring chamber.

The counterbody 12 is on a metallic carrier 13 , which for example comprises a TO socket, fastened with a pressure-bearing adhesive bond or with brazing or brazing.

Escaping with a reflection surface of the measuring diaphragm 11 extends an axial bore 14 through the carrier body 13 , wherein through the bore extends a light path for operating the pressure transducer. In the hole 14 is a ferrule 15 attached to receive the end portion of a light guide, wherein the ferrule 15 or the end portion of the light guide may optionally contain other optical components such as a so-called Grin lens or a converging lens with at least one convex surface to allow irradiation of the pressure transducer with collimated light.

The irradiation of the pressure transducer through the light guide is carried out as intended with light of short coherence length, for example with white light. The pressure-dependent path difference between the on the measuring chamber side surface of the measuring diaphragm 11 reflected light and at the measuring chamber side surface of the counter body 12 reflected light is to be determined with a Auswerteinterferometer not shown here, to which the reflected light is to be supplied via the light guide.

The relative pressure transducer shown here further comprises a reference pressure path 16 formed by locating aligned eccentric axial bores opening in the metering chamber through the carrier 13 and the opposite body 12 extend. In a relative pressure transducer, the air pressure from the environment of the relative pressure transducer of the measuring chamber is via the reference pressure path 16 fed. In the case of an absolute pressure sensor, on the other hand, the reference pressure path is eliminated and the measuring chamber is evacuated.

By the carrier 13 extends a filling channel 17 via a converter chamber into which the pressure transducer 10 is used, and possibly a hydraulic path including a separation diaphragm chamber of a hydraulic diaphragm seal to be filled with a transfer fluid.

The in 2 illustrated pressure transducer 20 includes the pressure transducer 10 out 1 and a pressure transmitter with a particular metallic diaphragm seal body 21 and a metallic separation membrane 22 resulting in the formation of a separation membrane chamber 23 between the diaphragm seal body 21 and the separation membrane 22 on an end face of the diaphragm seal body 21 is attached pressure-tight with a circumferential weld. From the separating diaphragm chamber extends a bore 24 in a converter chamber 25 as a depression in one of the separation membranes 22 remote end face of the diaphragm seal body 21 is trained.

In the converter chamber 25 is that on the carrier 13 arranged pressure transducer 10 used, with the converter chamber 25 by a circumferential weld between the carrier body 13 and the diaphragm seal body 21 pressure sealed.

For filling the converter chamber and the hydraulic path with a transfer liquid, the pressure transducer is evacuated and heated to a filling temperature which, in the ideal case, corresponds at least to the maximum operating temperature, for example 200 ° C. Then the liquid heated to maximum operating temperature under vacuum is passed through the filling channel 17 introduced into the pressure mediator chamber and the hydraulic path including the separation diaphragm chamber, and the diaphragm seal is provided with a metallic closure 18 sealed pressure-tight. Filling at the maximum operating temperature ensures safe operation of the pressure transducer.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/079803 A1 [0002]
• DE 102004006197 A1 [0003]
• DE 102004003413 A1 [0003]
• DE 102004006201 A1 [0003]
• DE 102004006199 A1 [0003]
• DE 102004011203 A1 [0003]
• DE 102004052950 A1 [0007]

Cited non-patent literature

• Rao and Jackson (Measuring Science and Technology 7 (1996) 981-999) [0002]

Claims (11)

A pressure transducer comprising: a pressure transducer ( 10 ); a metallic carrier ( 13 ); and a hydraulic diaphragm seal ( 20 ); the pressure transducer ( 10 ) a pressure-dependent deflectable measuring diaphragm ( 11 ), which comprises silicon, and an at least partially transparent counter body ( 12 ), wherein the measuring membrane and the counterpart body to form a measuring chamber between the measuring diaphragm ( 11 ) and the counterbody ( 12 ) are connected to each other pressure-tight; the pressure transducer ( 10 ) has at least two substantially parallel to each other and mutually aligned reflecting surfaces, wherein a first reflection surface is arranged on the measuring membrane and a second partially reflecting reflection surface with respect to the counter body has a substantially pressure-independent position, wherein the first reflection surface is illuminated through the second reflection surface, wherein the path difference between the light reflected at the first reflection surface and the light reflected at the second reflection surface depends on the difference between a first pressure, which acts on an outer side of the measuring membrane facing away from the measuring chamber, and a second pressure, which prevails in the measuring chamber, wherein the metallic carrier ( 13 ) the pressure transducer ( 10 ) and wherein the counter body ( 12 ) facing the metallic support, wherein a light path (through the metallic support ( 15 ) whose axis is substantially aligned with the first and the second reflection surface, wherein the pressure transmitter ( 20 ) a diaphragm seal body ( 21 ), a separating membrane ( 22 ) and a converter chamber ( 25 ), wherein the separation membrane to form a separation membrane chamber ( 23 ) between the pressure medium body and the separation membrane with at least one circumferential joint pressure-tight on a surface of the diaphragm seal body ( 21 ), wherein the separation membrane chamber ( 22 ) and the converter chamber ( 25 ) via a continuous hydraulic path ( 24 ) communicate with each other, the pressure transducer ( 10 ) by means of the carrier body ( 13 ) in the converter chamber ( 25 ) is positioned, and the transducer chamber is pressure-tightly closed by means of the carrier body, wherein the distance of the measuring diaphragm ( 11 ) from the separation membrane ( 22 ) is not more than 100 mm, in particular not more than 60 mm, and preferably not more than 40 mm, wherein the separation membrane chamber, the converter chamber and the hydraulic path between the converter chamber are filled with a transfer liquid at a temperature of 150 ° C a Vapor pressure of less than 6 mbar, in particular less than 4 mbar and preferably less than 2 mbar, and wherein the transfer liquid at 20 ° C has a dynamic toughness of less than 0.8 Pa · s, in particular less than 0.5 Pa · s having. Pressure measuring transducer according to claim 1, wherein the separation membrane has a diameter of not more than 50 mm, preferably not more than 35 mm and particularly preferably not more than 25 mm. Pressure measuring transducer according to one of claims 1 to 2, wherein the distance of the measuring membrane from the separating membrane is not more than twice, in particular not more than 1.5 times and preferably not more than 1 times the diameter of the measuring membrane. Pressure measuring transducer according to one of claims 1 to 3, wherein the transducer chamber is formed in the diaphragm seal body. Pressure measuring transducer according to one of claims 1 to 4, wherein the vapor pressure of the transfer liquid at 200 ° C, preferably at 250 ° C, preferably at 280 ° C not more than 6 mbar, in particular not more than 4 mbar and preferably not more than 3 mbar. Pressure measuring transducer according to one of claims 1 to 5, wherein the counter body has the second reflection surface. A pressure transducer according to any one of the preceding claims, further comprising a receptacle or port for a light pipe, for coupling light into the light path and for dissipating light reflected from the first and second reflection surfaces, the light guide being pressure tightly separated from the transmission fluid is Pressure measuring transducer according to one of the preceding claims, further comprising a reference pressure path which extends through the carrier body and through the counter body into the measuring chamber. Pressure measuring transducer according to one of the preceding claims, wherein the counter body comprises glass. Pressure measuring transducer according to one of the preceding claims, wherein the pressure transducer has a third reflection surface, which has a temperature-dependent and substantially pressure-independent distance to one of the other two reflection surfaces, wherein the Temperature-dependent distance for interferometric determination of a temperature reading is suitable. Pressure measuring transducer according to claim 10, wherein the third reflection surface is formed by a surface of the counter body facing away from the measuring chamber.

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