Pressure

TP-1 DATA ANALYSIS 
Data collected by the TP-1 is stored in the Microsoft Database and can be analyzed using standard database procedures, however users find the most convenient method to review data is by graphing it using Pipetech’s “QAnalyze” proprietary software program. The program is specifically designed to aid pipeline operators in assessing the recorded pressures within a pipe.

Immediately upon loading new data into QAnalyze, the user will be offered the option of graphing that data. An example of the QAnalyze graph is shown in the figure below, which shows about 50 hours of data.

Twenty six hours of pressure recording

Twenty six hours of pressure recording

Normal background pressures are depicted in blue, while the transient events are in red. The user may then “click-and-drag” to zoom in on data of greater interest.

Zooming in on 3 hours of data

Zooming in on 3 hours of data

Three hours of data is graphed above. Note an apparent waterhammer recurrence interval of about 30 minutes. This is characteristic of the cycling of a sewage lift pump station that lifts from a surge tank based on upper and lower water pressure limit switches in that tank.

Zooming in on 10 minutes of data

Zooming in on 10 minutes of data

The user might desire to see one of these waterhammer events in closer detail. The graph above depicts ten minutes of data from the previous graph. The single event is shown to be a series of reflected pressure waves.

Thirteen seconds of data

Thirteen seconds of data

One minute of data shows the initial excitation wave, and a reflected wave with a period of about 13 seconds.

Returning to the initial graph, the user might select one particularly strong event that occurred near the beginning of this monitoring period for a closer review.

Six minutes of data, depicting a waterhammer event

Six minutes of data, depicting a waterhammer event

A very severe waterhammer event occurred during the 6 minutes shown above. Normal operating pressure is about 5 psi, then it reaches a full vacuum of -14.7. The pressure oscillates in and out of the negative range for about 10 seconds, following which it rises to about 265 psi.

Five seconds of data including the waterhammer event

Five seconds of data including the waterhammer event

The graph above depicts 3 seconds of time showing the waterhammer event in greater detail. The pressure is seen to rise from a full vacuum to 260 psi, then fall to zero psi in a time span of 0.052 seconds, approximately one twentieth of a second. The TP-1 Transient Pressure Monitoring System data sample rate during this event is 0.01 seconds (or 100 Hz). This would not be accurately captured at a slower data sample rate.

A complete description of the QAnalyze software program capabilities is provided in the TP-1 Installation Manual provided with the TP-1 system.