JP2005114453A - Differential pressure measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential pressure measuring system capable of maintaining a good pressure transmission characteristic without generating bubbles in sealed liquid. <P>SOLUTION: The differential pressure measuring system comprises a differential pressure measuring system body sealed with seal liquid and a seal diaphragm provided in the system body and contacting the measuring fluid, and a hydrogen occlusion film provided in the seal liquid side of the seal diaphragm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

In recent years, an increasing number of plants handle hydrogen gas, such as deep desulfurization equipment for removing sulfur from petroleum products and environmentally friendly fuel cell systems.
The present invention relates to the hydrogen permeation problem of differential pressure measuring devices used in these plants, and specifically relates to the structure of the seal diaphragm of the differential pressure measuring device.

  The present invention relates to a differential pressure measuring device that does not generate bubbles in an enclosed liquid and can maintain good pressure transmission characteristics.

FIG. 4 is a diagram for explaining the configuration of a conventional example that is generally used in the past, and is shown, for example, in Japanese Utility Model Laid-Open No. 60-181642.
FIG. 5 is a detailed explanatory view of the main part of FIG.

  In the figure, reference numeral 1 denotes a main body, which includes a columnar neck portion 1A and a block-shaped pressure receiving portion 1B welded and connected at an outer peripheral edge portion 1C of the neck portion 1A. In this case, the neck portion 1A and the pressure receiving portion 1B are made of stainless steel.

  A high pressure side cover flange 2 and a low pressure side cover flange 3 are fixed to both sides of the main body 1 by welding or the like. A low-pressure fluid introduction port 5 having a low-pressure side pressure PL is provided.

  A pressure measurement chamber 6 is formed in the main body 1, and a center diaphragm 7 and a silicon diaphragm 8 are provided in the pressure measurement chamber 6.

  The center diaphragm 7 and the silicon diaphragm 8 are separately fixed to the wall of the pressure measurement chamber 6. The center diaphragm 7 and the silicon diaphragm 8 divide the pressure measurement chamber 6 into two.

  Back plates 6A and 6B are formed on the wall of the pressure measuring chamber 6 facing the center diaphragm 7. The center diaphragm 7 is welded to the main body 1 at the periphery.

The entire silicon diaphragm 8 is formed from a single crystal silicon substrate.
Impurities such as boron are selectively diffused on one surface of the silicon substrate to form four strain gauges 80, and the other surface is machined and etched to form a concave diaphragm 8 as a whole.

  The four strain gages 80 are configured such that when the silicon diaphragm 8 is bent under the differential pressure ΔP, two are tensioned and two are compressed, and these are connected to the Wheatstone bridge circuit. A change in resistance is detected as a change in the differential pressure ΔP.

The silicon diaphragm 8 divides the neck portion 1 </ b> A into two sensor chambers 81 and 82.
A silicon diaphragm 8 is bonded and fixed to the end surface of the support 9 on the pressure measurement chamber 6 side by a method such as low melting point glass connection.
Pressure introducing chambers 10 and 11 are formed between the main body 1 and the high pressure side cover flange 2 and the low pressure side cover flange 3.

High pressure side and low pressure side seal diaphragms 12 and 13 are provided in the pressure introducing chambers 10 and 11, and a back plate having a shape similar to that of the seal diaphragms 12 and 13 is formed on the wall of the main body 1 facing the seal diaphragms 12 and 13. 10A, 11A are formed.
The seal diaphragms 12 and 13 and the high pressure side and low pressure side backplates 10A and 11A constitute high pressure side and low pressure side seal diaphragm chambers 12A and 13A.

The seal diaphragms 12 and 13 are welded to the pressure receiving portion 1B by seal rings 121 and 131.
In this case, the seal diaphragms 12 and 13 and the seal rings 121 and 131 are made of stainless steel.

  The seal diaphragm chambers 12 </ b> A and 13 </ b> A and the pressure measurement chamber 6 are electrically connected through the communication holes 14 and 15.

  The sealing diaphragm chambers 12A and 13A are filled with filled liquids 101 and 102 such as silicon oil, and the filled liquids 101 and 102 reach the upper and lower surfaces of the silicon diaphragm 8 through the high-pressure side and low-pressure side conduction holes 16 and 17, respectively. Has reached.

  The encapsulated liquids 101 and 102 are divided into two by the center diaphragm 7 and the silicon diaphragm 8, and consideration is given so that the amounts thereof are substantially equal.

In the above configuration, when pressure is applied from the high pressure side, the pressure acting on the high pressure side seal diaphragm 12 is transmitted to the silicon diaphragm 8 by the sealing liquid 101.
On the other hand, when pressure acts from the low pressure side, the pressure acting on the low pressure side seal diaphragm 13 is transmitted to the silicon diaphragm 8 by the sealing liquid 102.

  As a result, the silicon diaphragm 8 is distorted in accordance with the pressure difference between the high-pressure side and the low-pressure side, and the strain amount is electrically taken out by the strain gauge 80, and the differential pressure is measured.

  Here, when the measurement fluid contains hydrogen gas, a part of the hydrogen gas is adsorbed on the surfaces of the seal diaphragms 12 and 13 and is dissolved in the seal diaphragms 12 and 13.

  The dissolved hydrogen diffuses into the seal diaphragms 12 and 13, but since the thickness of the seal diaphragms 12 and 13 is thin, the hydrogen is released to the sealing liquids 101 and 102 to form bubbles.

  When bubbles are formed in the sealing liquids 101 and 102, the pressure transmission characteristic to the sensor 80 is hindered, and the bubbles expand and contract due to a change in ambient temperature, so that the influence of temperature on the pressure transmission characteristic to the sensor 80 is affected. There is a problem of growing.

As a countermeasure, gold plating may be applied to the seal diaphragms 12 and 13 as shown in FIG.
Since gold has a low hydrogen solubility and a slow hydrogen diffusion rate, hydrogen can be prevented from passing through the seal diaphragms 12 and 13. Although FIG. 6 shows an example in which the gold plating 21 is provided on the back side of the seal diaphragms 12 and 13, the front side may be used.

Japanese Utility Model Publication No. 60-181642 (page 2-5, Fig. 1)

  However, in such an apparatus, when the gold plating 21 is applied to a portion where the seal diaphragms 12 and 13 and the pressure receiving portion 1B are in contact with each other, the seal diaphragms 12 and 13 are surrounded by the seal rings 121 and 131 on the pressure receiving portion 1B. Since the parts are welded, the airtightness and the corrosion resistance are lowered, so that the gold plating 21 cannot be applied to the entire surfaces of the seal diaphragms 12 and 13.

  Here, “a” represents hydrogen in the measurement fluid, “b” represents dissolved hydrogen, and “c” represents hydrogen that has permeated the outer periphery of the seal diaphragm.

  For this reason, the part which is not gold-plated 21 remains in the outer peripheral part of the seal diaphragms 12 and 13, and hydrogen permeate | transmits here.

The present invention solves this problem.
The object of the present invention is to prevent hydrogen from permeating through the seal diaphragms 12 and 13, but not to make it completely zero.

Therefore, on the assumption that hydrogen permeates, the problem is solved by providing means for capturing the permeated hydrogen before forming bubbles in the sealing liquids 101 and 102.
That is, the present invention is to provide a differential pressure measuring device that does not generate bubbles in the sealed liquids 101 and 102 and can maintain good pressure transmission characteristics.

In order to achieve such an object, in the present invention, in the differential pressure measuring device according to claim 1,
In a differential pressure measuring device comprising a differential pressure measuring device main body in which a sealing liquid is sealed, and a seal diaphragm provided in the differential pressure measuring device main body and in contact with a measurement fluid,
A differential pressure measuring device including a hydrogen storage film provided on the sealed liquid side of the seal diaphragm is provided.

According to claim 2 of the present invention, in the differential pressure measuring device according to claim 1,
The hydrogen storage film is made of a hydrogen storage alloy.

According to claim 3 of the present invention, in the differential pressure measuring device according to claim 2,
The hydrogen storage alloy is formed by sputtering.

According to claim 4 of the present invention, in the differential pressure measuring device according to claim 1,
The hydrogen storage film is made of a resin mixed with a hydrogen storage alloy powder.

According to claim 5 of the present invention, in the differential pressure measuring device according to claim 4,
The resin includes a fluororesin.

According to a sixth aspect of the present invention, in the differential pressure measuring device according to any one of the first to fifth aspects,
The hydrogen storage alloy is an alloy containing nickel titanium.

According to claim 7 of the present invention, in the differential pressure measuring device according to any one of claims 1 to 6,
The hydrogen storage film is provided except for a portion where the seal diaphragm is in contact with the differential pressure measuring device main body.

As described above, according to the first aspect of the present invention, the following effects can be obtained.
Even if hydrogen in the measurement fluid permeates the seal diaphragm, it is captured by the hydrogen storage alloy film formed on one side of the seal diaphragm, and no bubbles are generated in the liquid contained in the pressure receiving part, maintaining good pressure transmission characteristics. A differential pressure measuring device that can be obtained is obtained.

According to claim 2 of the present invention, there are the following effects.
Since the hydrogen storage film is made of a hydrogen storage alloy, a differential pressure measuring device capable of selectively and efficiently absorbing hydrogen can be obtained by employing the hydrogen storage alloy.

According to claim 3 of the present invention, there are the following effects.
The seal diaphragm is a thin metal and is designed to have low stiffness.
By sputtering the hydrogen storage alloy, a uniform and thin micron hydrogen storage film of several microns can be formed on the seal diaphragm, and a differential pressure measurement device that hardly affects the rigidity of the seal diaphragm can be obtained.

According to claim 4 of the present invention, there are the following effects.
Since the hydrogen storage film is made of a resin mixed with a hydrogen storage alloy powder, the surface area of the hydrogen storage film is greatly increased, and the hydrogen absorption performance is improved.
By mixing the powder of the hydrogen storage alloy into the resin and applying and fixing the powder to the surface of the seal diaphragm, a differential pressure measuring device capable of realizing a hydrogen storage film with improved hydrogen absorption performance can be obtained.

According to claim 5 of the present invention, there are the following effects.
Since the resin contains a fluororesin, the fluororesin is chemically stable, does not chemically react with the hydrogen storage alloy, and a differential pressure measuring device capable of stably maintaining hydrogen absorption performance over a long period of time is obtained. It is done.

According to claim 6 of the present invention, there are the following effects.
Since the hydrogen storage alloy is an alloy containing nickel titanium, a hydrogen storage alloy mainly composed of nickel and titanium is readily available and inexpensive, and a differential pressure measuring device capable of realizing a hydrogen storage film at a low price is obtained. .

According to claim 7 of the present invention, there are the following effects.
The hydrogen storage film was provided except for the part where the seal diaphragm was in contact with the differential pressure measuring device main body.
In general, the seal diaphragm is fixed to the differential pressure measuring device main body by welding.
Accordingly, since the hydrogen storage film is not interposed between the seal diaphragm and the differential pressure measuring device main body, a differential pressure measuring device in which the airtightness and the corrosion resistance are not deteriorated can be obtained.

  Therefore, according to the present invention, it is possible to realize a differential pressure measuring device that does not generate bubbles in the sealed liquid and can maintain good pressure transmission characteristics.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating the configuration of the main part of one embodiment of the present invention, and FIG. 2 is a diagram illustrating the operation of FIG.
In the figure, the same symbol structure as in FIG. 4 represents the same function.
Only the differences from FIG. 4 will be described below.

The hydrogen storage film 31 is provided on the sealed liquids 101 and 102 side of the seal diaphragms 12 and 13.
In this case, a nickel titanium-based hydrogen storage alloy film 31 is formed on one surface of the seal diaphragms 12 and 13 in contact with the sealing liquids 101 and 102 by sputtering or the like.

  Since the seal diaphragms 12 and 13 are fixed to the pressure receiving portion 1B by welding, in this case, the hydrogen storage alloy film 31 is not formed on the outer peripheral portions of the seal diaphragms 12 and 13.

The thickness of the seal diaphragms 12 and 13 is 50 to 100 microns, whereas the thickness of the hydrogen storage alloy film 31 is 1 to 3 microns.
The seal diaphragms 12 and 13 having the hydrogen storage alloy film 31 on one side are welded to the pressure receiving portion 1B together with the seal rings 121 and 131.

  Since the hydrogen storage alloy film 31 is not formed on the outer peripheral portions of the seal diaphragms 12 and 13, welding is not affected.

In the above configuration, hydrogen molecules contained in the measurement fluid are adsorbed on the surfaces of the seal diaphragms 12 and 13, dissociate into two hydrogen atoms and dissolve.
H2 → 2H

Hydrogen atoms diffuse into the inside of the seal diaphragms 12 and 13, and when they reach the other end, they encounter the hydrogen storage alloy film 31 and are absorbed.
The absorbed hydrogen remains absorbed by the hydrogen storage alloy film 31 and is not released to the sealing liquids 101 and 102 side.

  The hydrogen storage alloy film 31 is not formed on the outer periphery of the seal diaphragms 12 and 13, but hydrogen that has entered from other than the outer periphery of the seal diaphragms 12 and 13 is captured by the hydrogen storage alloy film 31. Comparing the central part, the hydrogen concentration is lower in the central part.

Most of the hydrogen that has entered from the outer peripheral portions of the seal diaphragms 12 and 13 moves to the central portion according to the difference in hydrogen concentration, and is eventually captured by the hydrogen storage alloy film 31.
In FIG. 2, d indicates hydrogen moving from the outer peripheral portion to the central portion.
Part of the hydrogen that has entered from the outer peripheral portion permeates the sealing liquids 101 and 102, but is absorbed in contact with the hydrogen storage alloy film 31 in the sealing liquids 101 and 102.

  In this way, most of the hydrogen that has passed through the seal diaphragms 12 and 13 is absorbed by the hydrogen storage alloy film 31, and bubbles are not formed in the sealed liquids 101 and 102, which adversely affects the pressure transmission characteristics. There is no.

The pressure can be accurately transmitted to the differential pressure sensor 80.
Thin seal diaphragms 12 and 13 have low rigidity and good pressure transmission characteristics.
By forming the hydrogen storage alloy film 31, the plate thickness increases, but the effect is small because it is about several percent.

  As a result, even if hydrogen in the measurement fluid permeates the seal diaphragms 12 and 13, it is captured by the hydrogen storage alloy film 31 formed on one side of the seal diaphragms 12 and 13, and in the sealed liquids 101 and 102 of the pressure receiving portion 1B. In this way, a differential pressure measuring device capable of maintaining good pressure transmission characteristics without generating bubbles is obtained.

  Since the hydrogen storage film 31 is made of a hydrogen storage alloy, a differential pressure measuring device capable of selectively and efficiently absorbing hydrogen can be obtained by employing a hydrogen storage alloy.

The seal diaphragms 12 and 13 are thin metals and are designed to have low rigidity.
A uniform and thin hydrogen storage film of several microns can be formed on the seal diaphragms 12 and 13 by sputtering the hydrogen storage alloy 31, and the differential pressure hardly affects the rigidity of the seal diaphragms 12 and 13. A measuring device is obtained.

  Since the hydrogen storage alloy 31 is an alloy containing nickel titanium, a hydrogen storage alloy mainly composed of nickel and titanium is readily available and inexpensive, and a differential pressure measuring device capable of realizing the hydrogen storage film 31 at a low price is provided. can get.

The hydrogen storage film 31 was provided except for the part where the seal diaphragms 12 and 13 were in contact with the differential pressure measuring device main body.
Generally, the seal diaphragms 12 and 13 are fixed to the differential pressure measuring device main body by welding.
Therefore, since the hydrogen storage film is not interposed between the seal diaphragms 12 and 13 and the differential pressure measuring device main body, a differential pressure measuring device in which the airtightness and the corrosion resistance are not deteriorated can be obtained.

FIG. 3 is a diagram illustrating the configuration of the main part of another embodiment of the present invention.
In this embodiment, the hydrogen storage film 41 is made of a resin 43 mixed with a powder 42 of a hydrogen storage alloy.
In this case, the hydrogen storage alloy powder 42 is a nickel titanium alloy.
In this case, the resin 43 is made of a fluororesin.

  In this embodiment, instead of sputtering the hydrogen storage alloy film, a fluorine-based resin 43 mixed with the hydrogen storage alloy powder 42 is spray-coated on one side of the seal diaphragms 12 and 13 and then baked to form a fluorine coating film. 41 was used.

  The film thickness of the fluorine coating 41 is about 15 microns, which is thicker than the sputtering film. However, since the rigidity of the fluorine resin 43 is lower than that of the hydrogen storage alloy, the fluorine resin coating film 41 adversely affects the pressure transmission characteristics of the seal diaphragms 12 and 13. Will not give.

As a result, the hydrogen storage film 41 is made of the resin 43 mixed with the powder 42 of the hydrogen storage alloy. Therefore, by making the hydrogen storage alloy into a powder, its surface area is dramatically increased and the hydrogen absorption performance is improved.
By mixing the hydrogen storage alloy powder 42 into the resin 43 and applying and fixing it to the surfaces of the seal diaphragms 12 and 13, a differential pressure measuring device capable of realizing the hydrogen storage film 41 with improved hydrogen absorption performance is obtained. It is done.

  Since the resin 43 contains a fluororesin, the fluororesin is chemically stable, does not chemically react with the hydrogen storage alloy 42, and can maintain the hydrogen absorption performance stably over a long period of time. Is obtained.

  In the above-described embodiment, the example in which the pressure receiving portion 1B is provided with the seal diaphragms 12 and 13 has been described. However, the present invention can also be applied to a seal diaphragm of a so-called differential pressure transmitter with a diaphragm seal. is there.

It is principal part structure explanatory drawing of one Example of this invention. It is operation | movement explanatory drawing of FIG. It is principal part structure description of the other Example of this invention. It is structure explanatory drawing of the prior art example generally used conventionally. It is principal part detailed explanatory drawing of FIG. It is composition explanatory drawing of the other conventional example generally used conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body body 8 Silicon diaphragm 80 Strain gage 9 Support body 10A High pressure side back plate 11A Low pressure side back plate 12 High pressure side seal diaphragm 12A High pressure side seal diaphragm chamber 13 Low pressure side seal diaphragm 13A Low pressure side seal diaphragm chamber 16 High-pressure side conduction hole 17 Low-pressure side conduction hole 21 Gold plating 31 Hydrogen storage alloy film 41 Hydrogen storage film 42 Hydrogen storage alloy powder 43 Fluorine resin

Claims (7)

A differential pressure measuring device main body in which the sealing liquid is sealed;
In the differential pressure measurement device comprising a seal diaphragm provided in the differential pressure measurement device main body and in contact with the measurement fluid,
A differential pressure measuring device comprising a hydrogen storage film provided on the sealed liquid side of the seal diaphragm. The differential pressure measuring device according to claim 1, wherein the hydrogen storage film is made of a hydrogen storage alloy. The differential pressure measuring device according to claim 2, wherein the hydrogen storage alloy is formed by sputtering. The differential pressure measuring device according to claim 1, wherein the hydrogen storage film is made of a resin mixed with a powder of a hydrogen storage alloy. The differential pressure measuring device according to claim 4, wherein the resin includes a fluororesin. The differential pressure measuring device according to any one of claims 1 to 5, wherein the hydrogen storage alloy is an alloy containing nickel titanium. The hydrogen storage film is provided except for a portion where the seal diaphragm is in contact with the differential pressure measuring device main body,
The differential pressure measuring device according to any one of claims 1 to 6, wherein:

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