Installation location of the transmitter
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If the process fluid is a gas, in principle the transmitter should be located above the pressure tap valve. If the process fluid is a liquid or vapor, the transmitter should, in principle, be located below the pressure tap valve. Is the installation location of the transmitter somewhat flexible, so that it isn’t necessary to follow these principles? Are there any specific requirements regarding the installation of differential pressure transmitters?
When the medium under test is a corrosive gas or liquid, it is necessary to install enclosures to protect the diaphragm box and measurement tubes of the differential pressure transmitter from corrosion. The connection port of the capsule to the throttle element is the \"inlet\", while the port to the measurement catheter is the \"outlet\“. When the density of the medium being measured is lower than that of the filling fluid, the capsule should move \"upward in and downward out\"; whereas when the density of the medium being measured is higher than that of the filling fluid, the capsule should move \"downward in and upward out\“.
Take a look at the \"Code for Installation and Acceptance of Automatic Instrumentation Engineering\" GB 50093-2002, which contains detailed regulations.
When measuring the gas pressure inside a pipeline, some transmitters specified by the design institute require to be placed above the pressure sampling point, while others need to be placed below it. Why is that?
If the gas contains no gaseous liquid components, the transmitter is above the pressure tapping point; otherwise, it is below the pressure tapping point
When measuring the pressure of gaseous media, the transmitter should be installed at a higher position than the pressure sampling point; when measuring the pressure of liquids or vapors, the transmitter should be installed at a lower position than the pressure sampling point. This is done to reduce the need for additional devices for venting gas or liquid.
Gas: The transmitter is above the pressure tapping point; liquids are below the pressure tapping point. Sometimes it also depends on whether such conditions exist on site
I agree with what everyone has said: for pure gases without any liquid phase, it is best to use a pressure measurement point at a higher position, such as in the case of dry gas. In situations where there is a liquid phase, such as with steam, it is generally appropriate to use a pressure measurement point at a lower position. (When measuring steam, it is generally accurate to take the measurement only when the condensate fills both the positive and negative pressure chambers.)