Production • Processing • Handling
the proper operation of LUFMs but are not visible to other types of traditional metering equipment. Tese parameters can not only be used to quantify the liquid flow stream, but can be used to set limits to define if there is an aspect of the flow stream that is abnormal and may impede measurement accuracy. Each of these parameters has a limit that can be programmed into the meter’s software to trigger an alarm condition. Tese alarms can turn on an alarm output to a supervisory system to provide instant notification or they can be monitored via communications by reading the values in the appropriate modbus registers. Te Smith Meter Ultra6
uses a Windows-based
software program Winscreen to interface with the meter.
Tis software can be used to monitor current
data, program the meter, access historical data and run diagnostics on the meter. Fig. 5 shows the Measured Values window
within Winscreen which displays current data read from the meter. Te Measured Values screen shows the current
combined average values of all paths, the current individual path values, a graphic representation of the current axial and transverse flow profiles and a rolling display of flow velocity and velocity of sound (VOS).
Te data shown on the Measured Values screen
can be grouped into two categories, flow profile parameters and signal parameters. Table 1 shows the flow profile parameters for the Smith Meter Ultra6 6-path flow meter. Tese parameters are normally listed as a
percent from normal, for example, a profile symmetry value of 0 per cent means that the flow is equally balanced between the top two planes and the bottom two planes (a symmetrical profile).
Calibration of meters A reference profile can be entered into the database as individual limits for each of these parameters when the meter is calibrated. Whenever the meter is in operation, as long as these parameters are within the programmed limits, the current flow profile matches the reference profile. If the deviation between the current profile
and the reference profile is larger than allowed by the programmed limits, an alarm condition will be triggered. If an alarm condition is present on one of these parameters, it indicates that something has caused a change to the flow profile. Tis change could be caused by many different conditions such as a significant change in fluid
viscosity, a damaged flow conditioner or excessive accumulated debris in the strainer upstream of the meter run.
Fig. 3. The Smith Meter Ultra6 Meter.
Fig. 4. Axial Component V and Transverse Component Vs. Table 1. Flow profile parameters
Profile flatness Describes the amount of flow on the outer paths compared to the center paths. This measure quantifies how parabolic the flow profile is.
Profile symmetry
Swirl flow
Describes the amount of flow on the top planes compared to the bottom planes.
Describes the amount of transversal flow that is rotating in the pipe. (Typical flow profile after a double elbow out of plane.) A positive number means that the swirl flow is clockwise if you look downstream.
Cross flow
Describes the amount of transversal flow that is generating a double swirl pattern with individual vortices in the top and bottom of the pipe. (Typical flow profile after a single bend.) The sign of the number indicates the direction of the cross flow.
Turbulence
The turbulence level describes the stability of the flow measurements on each path. Variation in the measured flow velocity on each path is created by turbulence in the flow. If the level of this variation increases from its normal level it can be a sign that the time detection of the ultrasonic signals is not stable.
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