How Does a Diaphragm Pressure Gauge Work? And How to Use It?

Diaphragm pressure gauge consists of a diaphragm isolator and a general pressure gauge. It is suitable for measuring the pressure of media that are highly corrosive, high temperature, high viscosity, easy to crystallize, easy to solidify, and have solid floating substances, and direct measurement of the media must be avoided. Input general pressure gauge to prevent accumulation of sediment and water-prone occasions. Diaphragm pressure gauges are mainly used in industries such as petrochemicals, alkalis, chemical fibers, printing and dyeing, pharmaceuticals, food, and dairy, to measure the pressure of flowing fluid media during the production process.

Working principle of diaphragm pressure gauge

Diaphragm pressure gauge consists of a diaphragm isolator and a general pressure gauge. The diaphragm seals the diaphragm. When the measured medium pressure P acts on the diaphragm, the diaphragm deforms and compresses the working medium filled in the system, making the working medium form ΔP equivalent to P and perform work. The conduction of liquid causes the free end of the elastic element (spring tube) in the pressure gauge to undergo corresponding elastic deformation and displacement, and then the measured pressure value is displayed according to the working principle of the pressure gauge that matches it.

Temperature characteristics of diaphragm pressure gauge: Because the sealing liquid in the diaphragm pressure gauge system is filled as the medium for transmitting pressure, the temperature and expansion coefficient of the sealing liquid cause the pressure gauge to increase with the temperature rise of the pressure. The size of the temperature influence is related to the expansion coefficient of the sealing body, the stiffness of the diaphragm, and the compression temperature. It is particularly significant for low-range pressure instruments. The temperature error of the pressurized part is generally specified as not more than 0.1%/degree. Therefore, the total temperature influence of the diaphragm pressure gauge is generally the sum of the temperature influence of the common instrument and the temperature influence of the pressurized part of the diaphragm device.

Use of diaphragm pressure gauges

Before using and installing the diaphragm pressure gauge, it is necessary to understand the characteristics of the monitored medium because the diaphragm pressure gauge is designed for special media. When monitoring the pressure of general gases, water, and oil, a general pressure gauge can be selected.

For nitric acid, phosphoric acid, and strong alkaline pressures, stainless steel pressure gauges can be used, but when the monitored medium is highly corrosive, such as hydrochloric acid, wet chlorine, and ferric chloride; high viscosity, such as latex; easy to crystallize, such as salt water; easily solidified, such as hot asphalt; and sewage with solid floaters, the above-mentioned pressure gauges are not acceptable because SUS316 stainless steel tubes will be corroded by hydrochloric acid, and asphalt and sewage floaters will clog the pressure gauge's lead hole, rendering the pressure gauge useless. Because the diaphragm pressure gauge has a diaphragm membrane, it can prevent media with high viscosity, easy crystallization, and easy solidification from flowing into the pressure port, ensuring that the pressure gauge reading can reflect the pressure of the measured medium normally.

When using a diaphragm pressure gauge, the following should be noted:

• The installation position of the diaphragm pressure gauge must correspond to the installation position in the precautions of the pressure gauge manual.

• The pressure gauge should select a suitable interface form, diaphragm material, and gasket material according to the nature of the measured medium. When used in environments with strong mechanical vibrations and large pressure fluctuations, earthquake-resistant pressure gauges are required. When the pressure gauge is put into operation under pressure, the valve should be slowly and evenly opened.