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Reference Manual

00809-0200-4801, Rev CA

July 2010

Rosemount 3051S

6-22

L is the impulse line length in meters

r is the radius of the impulse line.

The “C” formula shows the strong influence of air trapped in a liquid filled

impulse line, or an impulse line with air only. Both potential issues indicate the

value of short impulse lines. One installation best practice for DP flow

measurements is the use of the Rosemount 405 series of integrated compact

orifice meters with the 3051S Pressure transmitter. These integrated DP flow

measurement systems provide perhaps the shortest practical impulse line

length possible while significantly reducing overall installation cost and

improved performance. They can be specified as a complete DP flowmeter.

NOTE

The Plugged Impulse Line diagnostic capability in the Rosemount 3051S

OUNDATION fieldbus Pressure Transmitter calculates and detects significant

changes in statistical parameters derived from the input process variable.

These statistical parameters relate to the variability of the noise signals

present in the process variable. It is difficult to predict specifically which noise

sources may be present in a given measurement or control application, the

specific influence of those noise sources on the statistical parameters, and

the expected changes in the noise sources at any time. Therefore, it is not

absolutely warranted or guaranteed that the Plugged Impulse Line Diagnostic

will accurately detect each specific plugged impulse line condition under all

circumstances.

Plugged Impulse Line

(PIL) Functionality

The Advanced Diagnostics Suite provides the Plugged Impulse Line (PIL)

diagnostic, as an easy way to apply Statistical Process Monitoring technology

specifically for detecting plugging in pressure measurement impulse lines.

Similar to SPM, PIL also calculates the mean and standard deviation of the

pressure measurement and generates an alert when the standard deviation

exceeds an upper or lower limit.

Figure 6-19 illustrates a block diagram of the plugged impulse line diagnostic.

Notice that it is very similar to the diagram for SPM shown in Figure 6-3.

However, there are a couple of notable differences with PIL:

• The pressure measurement is fixed as the input

• Statistical values (mean and standard deviation) are not available as

outputs

• The PlantWeb alert generated specifically indicates “Plugged Impulse

Line Detected”

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