Diaphragm pressure gauge working principle and application

The diaphragm pressure gauge consists of a diaphragm isolator and a general-purpose pressure gauge to form a system of diaphragm gauges. It is suitable for measuring the medium pressure of strong corrosion, high temperature, high viscosity, easy to crystallize, easy to solidify, and solid floats, and must avoid direct measurement of the medium. Into general-purpose pressure gauges and occasions where it is easy to prevent sediment accumulation. Diaphragm pressure gauges are mainly used in petrochemical, alkali, chemical fiber, dyeing, pharmaceutical, food, cheese and other industrial sectors for production process fluid medium pressure.

How Does Diaphragm Type Pressure Gauge Work?

Diaphragm pressure gauge is a pressure gauge composed of a diaphragm isolator and a general-purpose pressure gauge. The spring tube is evacuated by special equipment, filled with flushing liquid, and sealed with a diaphragm. When the measured medium The pressure P acts on the diaphragm, causing it to deform, compressing the working fluid filled in the system, so that the working fluid forms a △P equivalent to P, and works with the aid of work. The conduction of the liquid causes the free end of the elastic element (spring tube) in the pressure instrument to produce a corresponding elastic deformation-displacement, and then displays the measured pressure value according to the working principle of the matched pressure instrument.

Temperature Characteristics of Diaphragm Seal Pressure Gauge

Since the diaphragm pressure gauge system is filled with sealing liquid as the medium for transmitting pressure, due to the temperature body expansion coefficient of the sealing liquid, the indication of the pressure gauge increases with the temperature of the pressure receiving part, and its temperature influence is related to the expansion of the sealing body. coefficient, diaphragm stiffness, and pressure temperature, especially for low-range pressure instruments. Generally, the temperature error of the pressure part is not more than 0.1%/degree, so the total temperature influence of the diaphragm pressure gauge is generally the sum of the temperature influence of the general-purpose instrument and the temperature influence of the pressure part of the diaphragm device.

Applications of Diaphragm Manometer

Before installing the diaphragm pressure gauge, be sure to clarify the characteristics of the medium to be monitored, because the diaphragm pressure gauge is specially designed for special media. When monitoring the pressure of general gas, water and oil, you can choose a general pressure gauge. When monitoring For nitric acid, phosphoric acid, and strong alkali pressure, stainless steel pressure gauges can be used, but when the monitored medium is highly corrosive, such as: hydrochloric acid, wet chlorine, ferric chloride; has a high viscosity, such as: latex; easy to crystallize, such as: Salt water; easy to solidify, such as: hot asphalt; solid floating matter such as: sewage, it is not acceptable to use the above pressure gauge, because the SUS316 stainless steel pipe will be corroded by hydrochloric acid, and the floating matter of asphalt and sewage will also block the pressure guide hole of the pressure gauge , so that the pressure gauge loses its function. Because the diaphragm pressure gauge has a diaphragm, it can prevent the medium with high viscosity, easy crystallization and solidification from flowing into the pressure guiding hole, so as to ensure that the reading of the pressure gauge can normally reflect the pressure of the measured medium.

A few points should be paid attention to in the process of using the diaphragm pressure gauge:

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

2. The pressure gauge should choose the appropriate interface form, diaphragm material, and gasket material according to the nature of the measured medium. It is required to be equipped with an anti-seismic pressure gauge when used in places with strong mechanical vibration and medium pressure fluctuations. When the pressure gauge is put into operation under pressure, the valve should be opened slowly and evenly once.

How to calibrate a diaphragm pressure gauge?

Before installing the diaphragm pressure gauge, you must carefully check the model, diaphragm material, and measuring range, and check whether the diaphragm is damaged; when there is no pressure, the pressure gauge indicates whether it is at zero. It can be used only after passing the inspection.

1. Before calibration, prepare the matching joint according to the model of the diaphragm device of the diaphragm pressure gauge to be calibrated, so as to be used on a general pressure calibration platform. The diaphragm device of the diaphragm pressure gauge is generally of flange type. The size and model of the flanges are prepared to match the pressure joints, and the corresponding flanges and general pressure gauge joints can be found on site for processing. This is also the most direct and convenient way.

2. Pay attention to the process of fixing the diaphragm pressure gauge to be calibrated on the standard calibration table: handle with care, and never damage the diaphragm. When turning the diaphragm pressure gauge to be calibrated with a wrench, the wrench must be stuck on the diaphragm The connection nut of the device, instead of being stuck on the general pressure gauge, because the general pressure gauge and the diaphragm device on the instrument are a sealed system. Do not disassemble or replace other pressure gauges at will, so as to prevent the working fluid filled in the system from leaking out. It will affect the performance or even be scrapped, especially for new students who have just joined the work. Before calibrating the diaphragm pressure gauge, this must be explained clearly.

3. Result processing: During the boosting process, compare it with the standard table, if it is out of tolerance, first check whether there is oil leakage, sealing and other problems, if there is oil leakage or poor sealing, it can only be returned to the factory for processing or scrapped; if it is not the above In this case, you can remove the indicator needle and re-set the indicator needle. Long-term experience is that it is more reasonable to re-set the needle at 1/2 of the range; if it is still out of tolerance, it can only be downgraded for use or scrapped.