The selection of pressure port position: firstly, make the sampling tube perpendicular to the direction of medium flow, and avoid selecting places where valves, forks, and elbows are prone to forming vortices; Secondly, when there is a protruding object in the pipeline, the pressure tap should be located in front of it; Thirdly, when measuring the pressure of liquids and water vapor, the pressure measuring point should be located on the lower side wall of the horizontal pipeline, so that there is no gas in the pressure pipe and to avoid sediment blocking the sampling pipe mouth in the pipeline; The fourth is the vacuum pressure gauge for measuring liquid and vapor media, which should be installed at the bottom of the instrument panel to prevent liquid or condensate droplets from falling onto other instruments.
The laying of the pressure pipe: The function of the pressure pipe is to transmit pressure signals between the pressure point and the vacuum pressure gauge. The laying should pay attention to the following: firstly, the inner diameter of the pressure pipe is usually taken as 6-10mm, and the length is less than 50mm to reduce measurement errors and avoid the indication delay of the vacuum pressure gauge caused by medium hysteresis; The second is that the horizontal section of the connecting conduit should have a certain slope, maintaining a slope of 1:10-1:20, to facilitate the discharge of condensate or gas inside the pipe. The third is that isolation valves should be installed on the pressure pipeline for use in repairing the vacuum pressure gauge.
Determination of installation height: The installation height should be suitable for workers to observe, level with the general public's line of sight, that is, 1.5m~1.6m. For high pressure, it should be higher than the general human head, that is, about 1.7m~1.8m. When the installation position of the vacuum pressure gauge is significantly perpendicular to the pressure measuring point, the liquid column difference should be corrected. The correction value is equal to the pressure value generated by the liquid column inside the conduit due to the vertical height difference between the instrument and the pressure measuring point. Add this correction value when the instrument is above the pressure measuring point; On the contrary, when the instrument is below the pressure measuring point, this value should be subtracted.
Use sealing gasket: To ensure sealing, a suitable sealing gasket should be selected at the sealing point between the joint of the vacuum pressure gauge and the gauge seat. When the working temperature and pressure are below 80 ℃ and 2MPa, use leather or rubber gaskets; Use asbestos paper or aluminum pad at 80 ℃~45 ℃ and below 5MPa; When the working temperature and pressure are higher, use annealed copper or lead pads.
So that's all for the above about vacuum. I hope it can be helpful for your understanding.
