Regarding whether a pressure tap is necessary,
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Measure the pressure in the pipelines carrying compressed air and nitrogen. Is it necessary to use a pressure tap? Should the transmitter be installed above the pressure measurement point, or can it be installed more closely to that point? What about the case where the medium is water at a pressure of 1.0 MPa? Are there any effects from environmental factors? As shown in the figure below,
For things like compressed air, it’s fine to install them using direct connectors; adding pressure lead pipes simply serves to place the gauge in a location where it can be easily observed and maintained. Additionally, for pipelines with significant vibration, this approach helps reduce the impact of such vibration on the instrument. If the medium is water, it is best to use a pressure guiding pipe to lead the fluid down; otherwise, air accumulation can easily cause fluctuations.
There’s no need to discuss this; if you can’t do it, you can ask for help.
Whether to use pressure guiding tubes is not a necessary issue; the purposes of using such tubes are mainly as follows: 1. To lead the fluid to a location where it can be easily observed and maintained, facilitating inspections and repairs； 2. The header is too heavy, and the pressure lead is not sufficient to support the weight of the transmitter ； 3. The flow fluctuations of the medium, especially liquid media, cause vibration in the transmitter; severe or prolonged resonance can lead to loosening of the welds at the joints where the pipes meet the pressure transfer tubes ； 4. If the medium temperature is too high or too low, the pressure tap can act as a buffer for temperature, preventing damage to the transmitter. So, if you use pressure tubes with sufficient strength (such as 18*3), transmitters that are not too heavy (like RJA530A or Rosemount 2088) can be used, and short installation lengths pose no problem at all
Generally, pressure measurement is carried out through a pressure conduit; this factor does not need to be considered for gases. For liquids, however, the height difference must be taken into account. If the pressure is high enough, this factor can be ignored
OP, may I ask what the triangle (p/i) in the diagram means? Thank you; there are valves shown in my PID diagram as well. I would appreciate an explanation, thank you
Short installation is possible; the problem is that the typical diagrams in HG’s documentation for hook-up transmitters do not show short installation, with only pressure gauges having typical diagrams for short installation； It’s terrible when you run into someone who insists on following the rules strictly
piping/instrument boundary interface