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The Structure Principle and Application of Sealed Diaphragm Pressure Gauge

The diaphragm meter is mainly used for measuring the pressure of fluid media like oil and chemical industry, alkali, chemical fiber, dyeing, pharmaceutical, food and other industrial sectors for the productive process. The sealed diaphragm pressure gauge is fitted for measuring the media that have strong corrosion, high temperature, high viscosity, easy crystallization, easy solidification, and solid floating matter. The places with pressure and other situations where are necessary to avoid measuring media directly going into general pressure gauges and preventing sediment from accumulating  in order to make it easy to clean, should apply a diaphragm of the system which is composed of diaphragm isolator and universal pressure gauge.

When producing the sealed diaphragm pressure gauge, the vacuum chamber of the meter measuring system and the upper cavity of the isolator diaphragm are evacuated and to have them filled with sealing liquid; moreover, the two are assembled together to form a sealed space filled with sealing liquid. The sealing fluid does not change the volume in this space, thereby transmitting the pressure sensed by the isolation diaphragm to the measuring element.

When the thread head, connector and the isolator are loose after losing the airtight sealing liquid space and the diaphragm deformed under pressure, sealing fluid will leak through the screw under pressure, resulting in small shrinkage of sealing liquid loss and confined space volume. Also, it makes the measuring element of meter can not correctly feel stress to pass sealing liquid. When it becomes serious, the diaphragm will cause permanent deformation due to the pressure difference between the two sides, resulting in complete failure of the instrument

The phenomena appearing above are caused by the process when the sealed diaphragm pressure gauge is being installed, used and maintained. The connecting thread between the head, the connector and the isolator are moved; or when the pressure gauge is discharged and sent to check, the meter is removed from the station directly, and then the flange isolator is retained on the work station , so that it causes the instrument to fail. The specific performances include: pointer does not goes to zero; concave of diaphragm deforms; pointer does not indicate pressure or indication error is very large. The structure principle of sealed diaphragm pressure gauge is to use dedicated device to vaccumize the bourdon spring and fill it with liquid, and then to use diaphragm to seal it. When using the sealed diaphragm pressure gauge to measure the pressure, the measured media will function on the diaphragm directly to make the diaphragm deform upward. The pressure of the medium is transferred to the spring tube through the filling liquid in the spring tube, so that the spring tube is deformed. The free end generates displacement, and then the movement is driven by a connecting rod, therefore the pointer indicates the measured pressure value on the dial plate.

The sealed diaphragm pressure gauge is mainly divided as diaphragm and bellow— type. The diaphragm type is most widely used. Generally, what we talk about the sealed diaphragm pressure gauge points to diaphragm type. When the measured medium has strong corrosion(such as hydrochloric acid, wet chlorine, two ferric chloride), has a high viscosity (such as latex), and is easy to crystallize(such as brine)and easy to solidification (such as hot asphalt), and has a solid floating matter (such as sewage), it is not workable to choose other pressure gauges. Even though the stainless pipe will also be corroded by hydrochloric. The dirt in the asphalt and sewage will soon clog the pressure hole of the pressure gauge, which will cause the instrument to be out of use. But the sealed diaphragm pressure gauge can deal with these problems well. People can choose different corrosion resisting diaphragm materials according to different strong corrosive media so as to have a effect of anti corrosion. Because of the diaphragm, it can prevent the media with high viscosity, easy to crystallization and easy to solidification into the pressure hole in order to ensure that the instrument can work properly. Thus, the sealed diaphragm pressure gauge is commonly used for measuring the pressure of fluid media like oil and chemical industry, alkali, chemical fiber, dyeing, pharmaceutical, food and other industrial sectors for the productive process.

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