Pay attention to when choosing pressure gauge:
1) determine the range of pressure gauge. When the tested pressure is relatively stable, make 1/3 of the range of the pressure gauge of the commonly used tested pressure position ~ Within the range of 1/2; when the measured pressure changes dramatically, it should be between 1/3 and 1/2 of the measuring range, so as to make the measurement more accurate and extend the service life of the pressure gauge;
2) determine the precision of the instrument according to the maximum error allowed by the production process. Common precision levels are divided into 0. 5,1. 0,1. Level 5,2. 5;
3) Select appropriate type of pressure gauge according to production requirements, medium properties, measurement range, environmental conditions, etc. Other medium pressure gauge cannot be used to measure oxygen pressure.
During installation, in order to make the selection of the pressure measuring point represent the real size of the pressure under measurement, the following points should be paid attention:
1) Choose the straight pipe part of the medium flow under test, not the elbow, fork, dead angle or other places that are easy to form vortex.
2) when measuring the pressure of flowing medium, make the pressure-taking point perpendicular to the flowing direction and clear the burrs of the drill hole.
3) when measuring the liquid pressure, the pressure point should be at the bottom of the liquid so that no gas can be stored in the pressure guide pipe; when measuring the gas pressure, the pressure point should be at the top of the pipe, make sure there is no liquid in the pressure guide pipe.
The pressure guide tube transmits pressure and differential pressure signals. In order to make the signals transmit quickly and accurately, attention should be paid:
1) the pressure guide tube should not be too thin, too long or too thick. Generally, the inner diameter is 6 ~ 10mm, length not more than 50 m;
2) The Pressure Guide pipe should not be laid horizontally, and the inclination between 1:10 and 1:20 should be kept to facilitate the discharge of liquid in the pipe;
3) If the medium under test is easy to condense or freeze, heating pipe must be installed and heat insulation should be added;
4) when measuring the liquid pressure, a collector should be set at the highest position of the pressure guide tube system. If the gas pressure is measured, a water separator should be set at the lowest place. When the medium under test may produce precipitation, a separator should be added in front of the instrument to discharge the precipitation.
Attention should be paid when installing:
1) The position should be easy to install and overhaul;
2) avoid the influence of temperature, keep away from high-temperature heat source or add heat insulating baffle, and do not exceed the highest working temperature specified by the instrument;
3) when the medium is corrosive, protective measures should be taken. If appropriate isolation containers are added, or a protective film is added;
4) when there is vibration, all kinds of spring-type or cushion-type dampers should be installed, or the pressure should be led to the place without vibration;
5) when the side pressure fluctuates frequently and violently (such as the outlet of compressor and pump, etc.), damping device can be used;
6) sealing gasket should be added to the sealing place of the pressure gauge. Less than 0. 6 MPA surface pressure) use colloid asbestos pad or Teflon pad;
In 80 ~ Use asbestos paper or aluminum sheet when the temperature is lower than 450℃ and 5MPa; use annealing copper or lead pad when the temperature and pressure are higher. In addition, the influence of medium should also be considered: for example, the air separation Tower and other pressure gauges which are in direct contact with oxygen, oil must be strictly prohibited, oil-immersed gaskets and organic compound gaskets should not be used, and the degreasing should be strictly prohibited.
The pressure gauge can only be put into use if it is verified to be qualified by the measuring department before use. Regular inspection should be paid attention to and used within the validity period.
