Pressure gauge selection, calibration and installation - Solutions - Huaqiang Electronic Network

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The correct selection, calibration and installation are important links to ensure that the pressure gauge plays its due role in the production process. First, the selection of pressure gauges should be selected according to the requirements of use, specific analysis for specific situations. In accordance with the technical conditions proposed in the production process, in accordance with the principle of conservation, the selection of the type, model, range and accuracy level is reasonably carried out. The selection mainly considers three aspects: (1) Determine the meter range according to the magnitude of the measured pressure. For flexible pressure gauges, in order to ensure that the elastic components work reliably within the safe range of elastic deformation, it is necessary to consider that there is sufficient room for selecting the pressure gauge range, generally in the case where the measured pressure is relatively stable, the largest The pressure value should not exceed 3/4 of full scale; in the case of large fluctuations in measured pressure, the maximum pressure value should not exceed 2/3 of full scale. In order to ensure the measurement accuracy, the measured pressure value should not be less than 1/3 of the full range. (2) Determine the accuracy of the instrument according to the maximum measurement error allowed by the production. When selecting, the pressure gauge with low precision and low cost should be selected as much as possible when the production requirements are met. (3) The nature of the measured medium should be considered when selecting. Such as temperature, viscosity, corrosion, dirt, flammable and explosive. Also consider the environmental conditions at the site, such as high temperatures, corrosion, humidity, vibration, etc. In this way, the type and model of the pressure gauge are determined. Second, the check of the pressure gauge The so-called check is to pass the same pressure on the school pressure gauge and the standard pressure gauge, and compare their indication values. The absolute error of the selected standard table should generally be less than 1/3 of the absolute error of the instrument being tested, so its error can be ignored, and the reading of the standard meter is considered to be the value of the real pressure gauge. If the reading error of the instrument to be tested on the standard instrument is not greater than the specified error of the instrument being tested, the instrument is considered qualified. Third, the installation of the pressure gauge 1, the selection of pressure points, the selected pressure point can reflect the real situation of the measured pressure. (1) Select the section of the pipe in which the measured medium flows straight, and do not choose where the pipe turns, forks, dead ends or other places where vortices are easy to form. (2) When measuring the pressure of the flowing medium, the pressure point should be perpendicular to the flow direction to remove the drilling burr. (3) When measuring the liquid pressure, the pressure point should be in the lower part of the pipeline so that no gas is accumulated in the pressure guiding tube. When measuring the gas, the pressure point should be above the pipeline so that no liquid is accumulated in the pressure guiding tube. 2. Laying of pressure guiding pipe (1) The thickness of the pressure guiding pipe is suitable, generally 6 to 10 mm in inner diameter and 3 to 5 m in length. (2) When the measured medium is condensed or frozen, it is necessary to add a heat tracing line. (3) A shut-off valve should be installed between the pressure port and the pressure gauge, and should be close to the pressure tap. 3, the installation of the pressure gauge (1) pressure gauge should be installed in the easy to observe and repair. (2) Installation location should be designed to avoid vibration and high temperature effects. (3) Condensate tube should be installed when measuring steam pressure to prevent high temperature steam from directly contacting the load cell; for corrosive media, it should be equipped with isolation tank filled with neutral medium. In short, for specific situations (such as high temperature, low temperature, corrosion, crystallization, precipitation, viscous medium, etc.), take appropriate protective measures. Sealing gaskets should be installed at the joint of the pressure gauge. Generally, the asbestos paperboard or aluminum sheet is used at a pressure lower than 80 ° C and 2 MPa, and the annealed copper or lead pad is used at a higher temperature and pressure (50 MPa). Also consider the influence of the medium. For example, a pressure gauge for measuring oxygen cannot use a gasket with oil or organic compounds, otherwise it will cause an explosion. It is forbidden to use copper pads when measuring acetylene pressure.