Precautions for selecting and using pressure gauges

The selection of pressure gauges should be based on the specific situation and meet the technical requirements of the process. At the same time, cost issues should also be considered. We recommend that the following aspects should be considered when selecting instruments:

(1) The physical and chemical properties of the medium being measured, such as temperature, viscosity, degree of dirtiness, corrosiveness, flammability, explosiveness, and crystallization.

(2) The requirements of the production process for pressure measurement, such as the measured pressure range, accuracy, and whether remote transmission, recording, or upper and lower limit alarms are required.

(3) On-site environmental conditions, such as high temperature, corrosion, humidity, vibration, electromagnetic fields, etc.

In addition, for elastic pressure gauges, in order to ensure that the elastic element works reliably within the safe range of elastic deformation and to prevent the elastic element from being damaged by pressure, which affects the service life of the instrument, the range selection of the pressure gauge must leave enough room. Generally, when the measured pressure is relatively stable, the maximum working pressure should not exceed 3/4 of the full scale of the instrument. When the measured pressure fluctuates greatly, the maximum working pressure should not exceed 2/3 of the full scale of the instrument. In order to ensure the measurement accuracy, the minimum value of the measured pressure should not be less than 1/3 of the full scale.

2. Use of pressure gauge

In order to ensure the accuracy of pressure measurement, the following points must be noted when using the pressure gauge:

(1) Selection of measuring points The selected measuring points should represent the actual situation of the measured pressure. The measuring points should be selected in the straight pipe section, far away from the local resistance. It is best not to extend the pressure pipe into the measured object but should be flush with the process pipeline. The inner diameter of the pressure pipe is generally 6~10mm, and the length should not be greater than 50mm, otherwise it will cause transmission lag. In order to prevent the pressure pipe from being blocked, the pressure point is generally selected on the horizontal pipe. When measuring liquid pressure, the pressure point should be at the bottom of the pipe so that no liquid accumulates in the pressure pipe; if the liquid on the north side is easy to condense or freeze, pipeline insulation equipment must be installed.

(2) When installing to measure steam pressure, a condenser or condenser should be installed to condense the steam measured in the pressure pipe. When the measured fluid is corrosive or easy to crystallize, an isolation liquid and an isolator should be used to avoid damaging the measuring element of the pressure measuring instrument. The isolation liquid should be selected from liquids with high boiling points, low freezing points, and stable physical and chemical properties. The pressure gauge should be installed as far away from heat transfer and vibration as possible to avoid their influence. A shut-off valve should be installed near the pressure port for use when repairing the pressure gauge.

(3) During maintenance and use, cleaning should be carried out regularly to keep the pressure pipe and pressure gauge clean.