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The use of media in the calibration of general pressure gauges with spring tube
What medium is needed for the spring pressure gauge calibration? When verification should be in accordance with the provisions of the verification regulations, choose the appropriate calibration equipment, but due to the differences in the field work of the instrument, the difference in the working medium is large, will make many people confused, this is discussed.
The verification regulations for jjg52-1999 spring tube general pressure gauges and pressure vacuum gauges are described as follows:
1, the upper limit of measurement is not greater than 0.25MPa pressure gauges, the working medium is clean air or non-toxic, harmless and chemically stable gas.
2, measuring the upper limit (0.25~250) MPa pressure gauges, the working medium is non-corrosive liquid.
3, the upper limit of measurement is (400~1000) MPa pressure gauges, for the medicinal glycerol and ethylene glycol mixture or according to the standard requirements of the use of the working medium.
In accordance with the above provisions, we should strictly according to the range of the meter to select the appropriate pressure medium.
Characteristics of each medium:
1. Common characteristics of clean air and other non-toxic and harmless stable gases
The compression ratio is large, the liquidity is best, especially the air, its zero cost, take less than the characteristics of other media is incomparable.
Suitable for small pressure environment, also can be used as a low pressure pressure cut-off pressure gauge transmission medium.
2. Deionized water
The abundance of water resources determines that it can be easily used as a liquid pressure transmission medium, with a small compression ratio and good fluidity. However, most of the water has ions, which are easy to form scale on the inner wall of the equipment, thus affecting the sealing of the system. Its characteristics of sub-zero solidification also cause it cannot be widely used.
Deionized water is the first medium for high pressure oil cut-off instruments.
3. Other liquids
According to its fluidity, kinematic viscosity and other parameters, select the appropriate pressure medium.
But in practice, out of consideration, may not fully comply with the code requirements, such as working in a gas environment, the range of (0 ~ 1) general pressure gauge of MPa, we can also choose to clean the stable gas such as air, nitrogen as the pressure medium, because it can reflect the actual situation, the characteristics of the air medium stable fast and can't be matched by other liquid medium.
Therefore, the final suggestion is that, according to the actual working situation of the instrument being tested, the verification regulation is the main reference to choose the appropriate transmission medium, the verification equipment should be given priority to the medium model suggested by the manufacturer.