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I know its happened. but my question is why ? even compressed air bubble have equal pressure on its every side. then why the trapped air in impluse line are cause error in measurement ? why a pressure is applied on one side of impluse is not rached to other / transmiter side. please refer to any website for detailed theory.
The gas bubbles affect the measurement accuracy as the gas is compressible and prevents liquid pressure to be propagated without significant pressure loss. The following typical measures and practices help to eliminate this issue in liquid filled legs:
- For liquid pressure measurement, the proper pressure tapping location should be below the pipe and in a horizontal center line. This avoids the vapor/gas bubbles from getting into the impulse line
- The instrument should be installed below tapping point(s) to avoid gas bubble getting into the instrument body
- Specifying capillary type and the close-coupled pressure transmitters
