JPH04256809A - Area type flowmeter - Google Patents

Abstract

PURPOSE:To prevent the occurrence of errors in precision of the measurement of a flow rates caused by attachment of bubbles to the liquid contact part of an area type flowmeter wherein the liquid contact part is formed of fluoride resin, increase in instability of buoyancy of a float, and narrowing of a flow path. CONSTITUTION:An etching agent, e.g. Tetraetch (trade name), which imparts hydrophilic property is applied on the inner wall of a tapered pipe 1 and the surface of a float 3 of an area type flowmeter. The surface of a liquid contact part becomes easy to get wet with water and becomes hard to attract bubbles.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an area flowmeter, and more particularly to an area flowmeter that measures fluid flow rate by detecting the position of a float within a tapered pipe.

0002

2. Description of the Related Art Conventionally, this type of area type flow meter has been described, for example, in Japanese Utility Model Application Publication No. 2-77632. In order to measure the flow rate of fluid flowing inside a pipe, an area flowmeter uses a transparent tapered pipe 1 that extends upward, set vertically as shown in the figure, and flows fluid 2 from below the tapered pipe 1. This utilizes the principle that the float 3 in the float 1 moves up and down depending on the flow rate.

On the other hand, in the field of manufacturing semiconductors and other electronic products, highly corrosive chemicals such as hydrofluoric acid and hydrochloric acid are used. To measure the flow rate of such chemicals, an area type flow meter is used in which a liquid contacting part such as a float 3 is formed of a fluororesin such as polytetrafluoroethylene (PTFE). Although fluororesin has good physical properties in terms of chemical resistance, it has a hydrophobic surface and is difficult to wet with water.

0004

[Problem to be Solved by the Invention] In the conventional area type flowmeter as described above, the surface of the liquid contact part is made of a hydrophobic fluororesin, so when aqueous chemicals, etc. are flowed, air bubbles are generated in the liquid contact part. is attached. For example, if air bubbles 4 adhere to the float 3 as shown in the figure, the buoyancy of the float 3 will increase indefinitely, the flow path will become narrower, and this will cause a large error in the accuracy of flow rate measurement.

The present invention has been made to solve the above-mentioned problems, and its object is to provide an area type flowmeter that can prevent air bubbles from adhering to the liquid contact portion made of fluororesin.

[0006]

[Means for Solving the Problems] The area type flowmeter according to the present invention is one in which a surface treatment is applied to a liquid-contacting part such as a float using a fluororesin etching agent to make it hydrophilic.

[0007]

[Operation] In this invention, since the surface of the liquid contacting part has hydrophilicity, adhesion of air bubbles is prevented.

[0008]

[Embodiment] An embodiment of the present invention will be described below. An example of an etching agent that imparts hydrophilicity to the surface of a float made of fluororesin is Tetra Etch (trade name of Junkosha Co., Ltd.). When this etching agent is applied to the surface of the float, fluorine atoms are removed from the fluororesin surface, forming hydroxyl groups (-OH) and carbonyl groups (-C=O).
, is substituted with an electrically polar hydrophilic group such as a carboxyl group (-COOH). As a result, the surface of the float made of fluororesin becomes easily wetted by water, making it difficult for air bubbles to adhere to it.

In addition, as a secondary effect, the color tone of the fluororesin surface changes from white or milky white to brownish brown due to surface treatment, so in flowmeters that read the float position visually, the visibility of the float is reduced. improves.

[0010] In the above embodiment, the case where surface treatment is applied to the float has been explained, but the same effect can be obtained by etching not only the float but also other liquid contact parts made of fluororesin, such as the inner wall of the tapered pipe. .

[0011]

Effects of the Invention As is clear from the above description, according to the present invention, the wetted part made of fluororesin is etched to give it hydrophilicity, thereby making the wetted part hydrophilic and preventing air bubbles. The measurement accuracy can be improved by preventing the adhesion of

0012

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part of a conventional area type flowmeter.

[Explanation of symbols]

1 Tapered pipe 3 Float

Claims (1)

[Claims] [Claim 1] An area type flowmeter that detects the flow rate based on the position of a float in a tapered pipe through which a fluid to be measured flows, characterized in that a wetted part made of a fluororesin is etched to give it hydrophilicity. Area flowmeter.