Emerson Rosemount 3051CF Series Reference Manual page 131

Reference Manual
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Figure 7-8: Basics of Plugged Impulse Line
A. Clog
Testing at Emerson
impulse lines. Plugging effectively disconnects the transmitter from the process, changing
the noise pattern received by the transmitter. As the diagnostic detects changes in noise
patterns, and there are multiple sources of noise in a given process, many factors can
come into play. These factors play a large role in determining the success of diagnosing a
plugged impulse line. This section of the product manual will acquaint you with the basics
of the plugged impulse lines and the PLD diagnostic, the positive and negative factors for
successful plugged line detection, and the do's and don'ts of installing pressure
transmitters and configuring and operating the PLD diagnostic.
7.6.2 Plugged impulse line physics
The physics of plugged impulse line detection begins with the fluctuations or noise
present in most pressure and differential pressure (DP) signals. In the case of DP flow
measurements, the flowing fluid produces these fluctuations, which are a function of the
geometric and physical properties of the system. The pump or control system can also
produce the noise. This is also true for pressure measurements in flow applications,
although the noise produced by the flow is generally less in relation to the average
pressure value. Pressure level measurements may have noise if the tank or vessel has a
source of agitation. The noise signatures do not change as long as the system is
unchanged. In addition, small changes in the average value of the flow rate or pressure do
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Advanced pressure diagnostics
July 2020
131