Emerson 3051S Dokumentacja Pobierz pdf (Strona 101)

Reference Manual

00809-0200-4801, Rev CA

July 2010

6-23

Rosemount 3051S

Figure 6-19. Overview of

Plugged Impulse Line

Diagnostics

PIL also includes some additional features to make it especially suitable for

detecting plugging in pressure measurement impulse lines. PIL has the ability

to:

• Automatically relearn new baseline values if the pressure

measurement changes significantly

• Set the status quality of the pressure measurement to “Uncertain” if a

plugged impulse line is detected

• Check for a minimum process dynamics during the learning process

• Adjust the verification settings

• Set separate learning and detection periods

Figure 6-20 shows a flow chart of the PIL algorithm. Note that this diagram

shows the sequence of PIL steps using the default configuration settings.

Information for adjusting these settings is found in “Configuration of Plugged

Impulse Line Detection” on page 6-25. The specific steps that PIL goes

through are as follows:

1. Learning Phase

PIL begins the Learning Process when the PIL is Enabled, when the

User Command is set to “Relearn”, or when a Mean Change is detected

during the Detection Phase. PIL collects the pressure values for

5-minutes and computes the mean and the standard deviation.

NOTE:

The length of the learning period is user-adjustable, with 5-minutes as the

default value. During the Learning Phase the status is “Learning”.

2. Sufficient Variation?

During the Learning and the Verify modes, the PIL checks that the noise

level (e.g. the standard deviation) is high enough for reliable detection of

plugged impulse lines. If the noise level is too low, the status goes to

“Insufficient Dynamics”, and the PIL stops. PIL will not resume learning

again until a “Relearn” command is given.

3. Verification Phase

PIL collects the pressure values for an additional 5-minutes (or same

length as Learning period) and computes a second mean and standard

deviation. During this phase, the PIL status is “Verifying”

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