Anhui Star Control Instrument Co., Ltd.

Anhui Star Control Instrument Co., Ltd.

Pressure gauge type selection instructions

pressure gauge type selection instructions
In order to adapt to the use of different requirements and use environment, use a pressure gauge in the decision as a pressure measuring instrument, must be in strict accordance with the actual production needs, choose the suitable pressure gauge, to ensure that can meet the requirements of production safety, and process control. The selection of pressure gauges should be based on the production requirements of the use process, specific analysis of the specific situation. On the premise of meeting the technological requirements, the following aspects should be considered comprehensively and comprehensively in line with the principle of economy.
1. Selection of types
The selection of instrument type must meet the requirements of process production. For example, whether remote transmission, automatic recording or alarm is required; The nature of the measured medium (such as the temperature of the measured medium size, viscosity, corrosion, smudgy degree, whether the flammable and explosive, etc.) is put forward special requirements for instrument, on-site environmental conditions (such as humidity, temperature, magnetic field intensity, vibration, etc.) for instrument types of requirements, etc. Therefore, the proper selection of instrument type according to the technical requirements is an important prerequisite for the normal operation and safe production of the instrument.
Such as normal pressure gauge of the spring tubes with copper alloy using alloy steel (high voltage), and ammonia pressure gauges spring tube materials are using carbon steel or stainless steel, are not allowed to use copper alloy. Ordinary pressure gauges cannot be used for ammonia pressure measurements because ammonia reacts with copper to explode.
Oxygen pressure gauges can be the same in structure and material as normal pressure gauges, except that oxygen pressure gauges must be oil tight. Oil entering the human oxygen system is explosive. The oxygen pressure gauges used should not use oil as the working medium as the normal pressure gauges do when checking, and the oxygen pressure gauges should strictly avoid contact with oil during storage. If the existing oil pressure gauge must be used to measure the oxygen pressure, it must be cleaned repeatedly with carbon tetrachloride before use.
2. Determination of scope
In order to keep the elastic component can work reliably within the scope of the safety of the elastic deformation, when selecting range, must according to the size of the measured pressure and the pressure change of speed, enough leeway, therefore, the upper limit of pressure gauge should be higher than the process in the production of possible maximum pressure value. According to the "technical regulation of chemical automatic control design", when measuring stable pressure, the maximum working pressure should not exceed 2/3 of the upper limit value. When measuring pulse pressure, the maximum working pressure should not exceed 1/2 of the upper limit value. When measuring high pressure, the maximum working pressure should not exceed 3/5 of the upper limit. The minimum value of the measured pressure shall not be less than 1/3 of the upper limit value of the instrument measurement. Thus, the linear relation between the output and the input of the instrument is guaranteed
The upper and lower limits of the instrument are calculated according to the maximum and minimum values of the measured parameters. When selecting the upper limit of the scale of the instrument, we should select it from the standard series set by the state. According to the national standard GBT 1226-2010 general pressure gauges, the range of pressure gauges is as follows (in MPa) :
pressure gauge:
0 ~ 1 * 10n, 0 ~ 1.6 * 10n,
0 ~ 2.5 times 10n, 0 ~ 4 times 10n,
0 ~ 6 x 10 n
Note: n is a natural integer, positive or negative
Vacuum gauge: -0.1 ~ 0
Pressure vacuum gauge:
-0.1 ~ 0.05, -0.1 ~ 0.15,
-0.1 ~ 0.3, -0.1 ~ 0.5,
-0.1 ~ 0.9, -0.1 ~ 1.5,
0.1 ~ 2.4
3. Selection of accuracy grade
According to the maximum absolute error permitted by the process production and the maximum range of the selected instrument, the maximum reference error allowed by the instrument is calculated, and the accuracy of the instrument is determined in the accuracy level specified by the state. Generally speaking, the more accurate the instrument used, the more accurate and reliable the measurement results. However, the higher the accuracy of the selected instruments, the better, because the more sophisticated instruments are generally more expensive, the more difficult the operation and maintenance.
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