JP2001289725A - Pressure sensor for chemical-resistant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a pressure sensor for chemical-resistant, so that leakage phenomenon of a chemical resulting from deterioration of resistant-resistant material composing the pressure sensor can be detected early, and that such a hazard can be perceived beforehand. SOLUTION: This chemical-resistant pressure sensor 1 includes a pressure detection element 4 on which the pressure of the chemical is applied, a body 2 for storing the pressure detection element, and sealing structures 21, 22 for sealing the interval between the pressure detection element and the body, and also includes leakage detection means 23, 24, 25, 26 capable of indicating the degree of the leakage of the chemical leaking out through the sealing structures, and viewing the extent of leakage from the outside of the body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, and more particularly to a pressure sensor of a chemical resistant liquid for use in, for example, a chemical liquid container and a chemical liquid pipe.

[0002]

2. Description of the Related Art Conventionally, a main body of a chemical-resistant liquid pressure sensor for use in a chemical liquid container and a pipe for a chemical liquid is formed of a chemical-resistant substance such as PTFE or PFA, and a pressure detecting portion is similarly formed. Is formed as a diaphragm type pressure sensing element using a chemical-resistant material such as ceramic. The diaphragm type pressure sensing element of this pressure sensing unit is composed of a convex (tongue) shaped seal made of a fluororesin or the like as a close seal, and an O-ring formed on the outer periphery of the diaphragm as a close seal by a fluororubber. The structure of the seal is configured to ensure the safety of leakage to the chemical solution.

[0003] However, even if such a chemical resistant substance such as a fluororesin is exposed to a chemical for a long period of time,
The chemical liquid gradually permeates the seal structure inside the pressure sensor, and eventually the chemical liquid leaks out of the pressure sensor. Such a phenomenon may lead to a very serious accident when the chemical is a particularly dangerous chemical, for example, a strongly acidic or strongly alkaline solution.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to detect a leakage of a chemical solution accompanying deterioration of a chemical-resistant substance constituting a pressure sensor at an early stage and to detect such a risk in advance. And to improve the pressure sensor of the chemical resistant liquid.

[0005]

A pressure sensor for chemical resistant liquid according to the present invention seals a pressure detecting element to which the pressure of the chemical liquid acts, a main body accommodating the pressure detecting element, and a space between the pressure detecting element and the main body. And a leak detecting means for indicating the degree of leakage of the chemical solution leaking through the seal structure and allowing the degree of leakage to be visually recognized from outside the main body.

The leak detecting means includes a minute leak detecting port communicating with the outside of the main body so as to guide leakage of the chemical through the seal structure, an opening to the outside of the main body, a chemical reaction mat for discoloring the chemical, and a chemical liquid. And a lid member for holding the reaction mat and closing the opening.

[0007]

FIG. 1 shows the overall structure of a pressure sensor 1 according to the present invention, and also shows a simplified electric system for processing a pressure detection signal detected by the pressure sensor 1. FIG.

The main body 2 of the pressure sensor 1 is made of a chemical resistant substance P
The main body 2 is provided with a support member 3 made of a fluororesin such as TFE or PFA. The support member 3 is fixed to the inner wall of the main body 2. The support member 3 has, on one side thereof, a pressure detecting unit which is formed of ceramic or the like of a chemical resistant substance and receives a pressure of a chemical in a chemical container or a chemical pipe (not shown) and converts the pressure into an electric signal. The other side supports a diaphragm type pressure sensing element 4, and the other side supports a detection circuit 5 that receives an electric signal indicating the pressure of a chemical solution acting on the pressure sensing element 4 and outputs a pressure detection signal. The detection circuit 5 displays a pressure sensor 1, that is, a power supply 8 for supplying power to the detection circuit 5, and a pressure detection signal from the detection circuit 5 via a connector 6 and a lead 7 provided on the top of the main body 2. To a display 9 (shown as a resistor 9 ′). The lead 7 includes a ground lead for shielding the main body 2.

In the pressure sensor 1 configured as described above, the pressure of the chemical in the chemical container or the chemical pipe acts on the pressure detecting element 4 via the chemical in the cylindrical portion 10 communicating with the chemical. Then, the pressure detecting element 4 converts the detected pressure into an electric signal.

FIG. 2 is a partially enlarged view of the pressure sensor shown in FIG. 1, and includes a seal structure between the main body 2 of the pressure sensor 1 and the diaphragm type pressure detecting element 4 and a seal structure via the seal structure. FIG. 7 shows a leak detecting means for indicating a degree of leakage of the chemical solution leaking out.

As shown in FIG. 1, especially FIG.
(Tongue) -shaped seal 21 which is processed as a close-fitting seal with a fluororesin or the like between the bottom portion 20 and the pressure sensing element 4.
And an O-ring 22 formed on the outer periphery thereof as a close seal with a fluorine-based rubber to form a double seal structure. In the vicinity of the double seal, specifically, between the convex (tongue) -shaped seal 21 and the O-ring 22, a minute leak detection port 23 communicating with the outside of the main body 2 so as to guide leakage of the chemical solution. And an opening 2 to the outside of the main body 2
4 is a sponge-like chemical reaction mat 25 impregnated with a litmus dye or other reactive paint, which reacts with the chemical.
And a lid member 26 for holding the chemical reaction mat 25 and closing the opening (window) 24 is provided. The cover member 26 is formed of a substantially transparent thin plate of acrylic resin or the like so that the color change reaction of the chemical reaction mat 25 due to the chemical can be visually recognized from the outside of the main body 2. Such a leak detection port 23, an opening 24, a chemical reaction mat 2
5 and the cover member 26 constitute a leak detecting means for indicating the degree of leakage of the chemical solution as a whole.

The structure of a double seal between the bottom portion 20 of the main body 2 and the pressure sensing element 4, specifically, the pressure sensing element 4, the convex seal 21, or the O-ring 22 is deteriorated by a chemical solution. If a chemical solution penetrates directly between them, or if the evaporated gas of the chemical solution leaks, such a leaked substance will
It passes through the leak detection port 23 and reaches the chemical reaction mat 25. Thus, the chemical reaction mat 25 undergoes a color change reaction due to the properties of the chemical, for example, acidity or alkalinity. This discolored state can be visually recognized from the outside of the main body 2 via the substantially transparent lid member 26.

[0013]

According to the present invention, the pressure sensor for chemical resistant liquid is provided with a chemical liquid leak detecting means capable of visually confirming the leakage of the chemical liquid due to the deterioration inside the pressure sensor. The degree can be determined at an early stage by the degree of discoloration of the chemical reaction mat included in the leak detection means, and the degree of discoloration of such a chemical reaction mat can be determined based on the timing of replacement of the pressure sensor or its parts and the degree of danger. Can be used as a criterion for the determination.

[Brief description of the drawings]

FIG. 1 shows an overall structure of a pressure sensor of the present invention, and shows a simplified electric system for processing a pressure detection signal detected by the pressure sensor.

FIG. 2 is a partially enlarged view of the pressure sensor shown in FIG. 1 and shows a seal structure between a main body and a diaphragm type pressure sensing element and a chemical solution leaking through the seal structure. Fig. 4 shows a leak detecting means for indicating the degree of leakage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Main body 3 Support member 4 Pressure detection element 5 Detection circuit 6 Connector part 7 Lead 8 Power supply 9 Display 9 'Resistance 10 Cylindrical part 20 Bottom part 21 Convex (tongue) seal 22 O-ring 23 Leakage detection port 24 Opening 25 Chemical reaction mat 26 Lid member

Claims (4)

[Claims] 1. A pressure detecting element on which a pressure of a chemical solution acts,
In a chemical-resistant liquid pressure sensor including a main body accommodating the pressure detection element and a seal structure for sealing between the pressure detection element and the main body, a degree of leakage of the chemical liquid leaking through the seal structure is indicated. A pressure sensor provided with a leak detecting means for visually confirming the degree of the leak from outside the main body. 2. A leak detecting means communicating with the outside of the main body so as to guide leakage of the chemical solution through the seal structure, an opening to the outside of the main body, and a color change reaction to the chemical solution. 2. The pressure sensor according to claim 1, comprising a chemical reaction mat, and a lid member that holds the chemical reaction mat and closes the opening. 3. The pressure sensor according to claim 2, wherein the chemical reaction mat is a sponge-like member in which an acidic or alkaline solution is impregnated with a litmus dye exhibiting a color change reaction. 4. The pressure sensor according to claim 2, wherein said lid member is formed of a substantially transparent acrylic resin.