JPH10132691A - Diaphragm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to hold two kinds of corrosion resistances with one kind of diaphragm by arranging a hydrogen permeation preventing film in an intermediate layer, and connecting stainless to one face of the preventing film and a nickel-based alloy to the other face to form a diaphragm. SOLUTION: The diaphragm is composed of three layers of stainless 2, a hydrogen permeation preventing film 3, and a nickel-based alloy 4, and the hydrogen permeation preventing film 3 is interposed between the stainless 2 and nickel-based alloy 4 in a sandwich state by a method of rolling, etc. As the stainless 2, SUS316L, etc., is used, and as the hydrogen permeation preventing film 3, aluminum, copper, plantinum, gold, etc., are used, and as the nickel-based alloy 4, a material of Hastelloy is used. For example, when a measurement fluid requires corrosion of the nickel-based alloy 4, it is used by connecting with a flange 5, so that the nickel base system alloy 4 is on a side of coming into contact with the measurement fluid and the stainless 4 is on a side of coming in contact with the flange 5 (on a sealed liquid 6 side).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal diaphragm for sealing a pressure sensor and a measurement fluid when a pressure sensor or the like is used, and more particularly to a metal diaphragm suitable for preventing hydrogen permeation.

[0002]

2. Description of the Related Art A metal diaphragm requires corrosion resistance to a measurement fluid, so that stainless steel (SUS316L),
Use materials such as nickel-based alloys (Hastelloy) and tantalum. However, when stainless steel or a nickel-based alloy is used, hydrogen in the measurement fluid is ionized, and the hydrogen ions permeate the metal diaphragm and enter the sealed liquid side as shown in FIG.
To generate hydrogen gas. The sealed liquid is sealed for the purpose of transmitting pressure to the pressure sensor. When hydrogen gas is generated on the sealed liquid side, the pressure is not accurately transmitted to the pressure sensor, and measurement becomes impossible.

Conventionally, as a method for preventing hydrogen permeation of a metal diaphragm, there is a method using a sandwich-structured diaphragm as described in Japanese Patent Application Laid-Open No. 7-260612 (see FIGS. 3 and 4). That is, the diaphragm is composed of three layers, the surface of the diaphragm is made of corrosion-resistant stainless steel or a nickel-based alloy because it comes into contact with the measurement fluid, and the intermediate layer that is not in contact with the measurement fluid is aluminum, copper, Use platinum, gold, etc.

[0004]

As the material of the diaphragm, a material having corrosion resistance to the measurement fluid must be selected. If the measurement fluid requires corrosion resistance of stainless steel, a diaphragm with a structure in which the hydrogen permeation prevention film of the intermediate layer is sandwiched by stainless steel from both sides is required.If corrosion resistance of a nickel-based alloy is required, hydrogen permeation is required. A diaphragm having a structure in which the blocking film is similarly sandwiched from both sides with a nickel-based alloy is required. Thus, two types of diaphragms are required.

An object of the present invention is to provide a hydrogen permeation preventing diaphragm having two kinds of corrosion resistance of stainless steel and a nickel-based alloy with one kind of diaphragm.

[0006]

In order for one type of diaphragm to have the corrosion resistance of stainless steel or a nickel-based alloy and to have an effect of preventing hydrogen permeation, one of the diaphragms having a three-layer sandwich structure is used to prevent hydrogen permeation. The other layer is made of stainless steel, and the other layer is made of a nickel-based alloy. That is, a hydrogen permeation preventing film is provided on the intermediate layer, and stainless steel is used on one of both surfaces of the diaphragm requiring corrosion resistance, and a nickel-based alloy is used on the other surface.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

The diaphragm is made up of three layers of stainless steel 2, a hydrogen permeation preventing film 3, and a nickel-based alloy 4, and the stainless steel 2 and the nickel-based alloy 4 sandwich the hydrogen permeation preventing film 3. That is, a diaphragm having a structure in which the hydrogen permeation preventing film 3 is sandwiched between the stainless steel 2 and the nickel-based alloy 4 is used. The method of joining to the sandwich includes a method such as rolling. SUS316L is used as the stainless material, and aluminum, copper, platinum, and gold are used as the hydrogen permeation preventing film. However, aluminum is used in terms of cost, and a nickel-based alloy uses Hastelloy.

FIG. 5 shows an example in which such a diaphragm is attached to the flange 5. In this mounting example, when the measurement fluid requires corrosion resistance of stainless steel, the stainless steel 2 is joined to the flange 5 so that the stainless steel 2 is in contact with the measurement fluid and the nickel base alloy 4 is in contact with the flange 5.

FIG. 6 shows a mounting example in which the measurement fluid requires the corrosion resistance of the nickel-based alloy 4. The nickel-based alloy is on the side in contact with the measurement fluid, and the stainless steel 2 is on the side in contact with the flange 5. 5.

That is, FIG. 5 and FIG. 6 are views in which the attachment of the diaphragm is reversed.

FIG. 5 illustrates the operation when measuring a corrosion-resistant fluid made of stainless steel using the hydrogen permeation blocking diaphragm having such a structure. Since the surface of the diaphragm in contact with the measurement fluid is made of stainless steel 2 and has corrosion resistance, the hydrogen permeation preventing film 3 works effectively without being corroded. Even if hydrogen in the measurement fluid is ionized and permeates through stainless steel, the permeation of hydrogen ions is prevented by the hydrogen permeation prevention film 3, and no hydrogen gas is generated in the sealed liquid 6.

In addition, when measuring a fluid having a corrosion resistance of Hastelloy, the measurement fluid operates in the same manner as stainless steel, so that no hydrogen gas is generated.

By using such a three-layered diaphragm, one kind of diaphragm has the corrosion resistance of stainless steel and Hastelloy, and can prevent hydrogen permeation.

[0015]

According to the present invention, two kinds of diaphragms, a stainless steel corrosion resistant diaphragm and a Hastelloy corrosion resistant diaphragm, are required as the hydrogen permeation preventing diaphragm. Only one kind of diaphragm is required due to the sandwiched three-layer structure.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory view of a conventional example.

FIG. 3 is a sectional view showing a conventional example.

FIG. 4 is a sectional view showing a conventional example.

FIG. 5 is an explanatory view of another embodiment of the present invention.

FIG. 6 is an explanatory view of another embodiment of the present invention.

[Explanation of symbols]

2 ... stainless steel, 3 ... hydrogen permeation blocking film, 4 ... nickel-based alloy, 5 ... flange, 6 ... filled liquid.

Claims (3)

[Claims] 1. A diaphragm comprising three layers, wherein different metals are bonded to each layer. 2. The diaphragm according to claim 1, wherein stainless steel is disposed on one of both surfaces of the diaphragm, and a nickel-based alloy is disposed on the other surface. 3. The diaphragm according to claim 1, wherein any one of aluminum, copper, platinum, and gold is arranged in the intermediate layer.