Baker Hughes Panametrics Sentinel LCT8, User Manual

Page: 106 / 138

5.4 Fluid and pipe problems
If preliminary troubleshooting with the error code messages
and the diagnostic parameters indicates a possible
problem, proceed with this section. Measurement problems
fall into two categories:
•
Fluid problems
• Pipe problems
Read the following sections carefully to determine if the
problem is related to the fluid or the pipe. If the instructions
in this section fail to resolve the problem, contact
Panametrics for assistance.
5.4.1 Fluid problems
Most fluid-related problems result from a failure to observe
the flow meter system installation instructions, as described
in Chapter 2 . Installation on page 5 . Refer to that chapter
to correct any installation problems.
If the physical installation of the system meets the
recommended specifications, it is possible that the fluid
itself may be preventing accurate flow rate measurements.
The fluid being measured must meet the following
requirements:
• The fluid must be homogeneous, single-phase, relatively
clean and flowing steadily.
Although a low level of entrained particles may have little
effect on the operation of the Sentinel LCT8 , excessive
amounts of solid particles will absorb or disperse the
ultrasound signals. This interference with the ultrasound
transmissions through the fluid will cause inaccurate flow
rate measurements. In addition, temperature gradients in
the fluid flow may result in erratic or inaccurate flow rate
readings.
• The fluid must not cavitate near the measurement point.
Fluids with a vapor pressure relatively close to the process
pressure may cavitate near the measurement point.
This causes problems resulting from gas bubbles in the
fluid. Cavitation can usually be controlled through proper
system design.
• The fluid must not excessively attenuate ultrasound
signals.
Some fluids, particularly those that are very viscous,
readily absorb ultrasound energy. In such cases, signal
warning and error messages will appear on the display
screen to indicate that the ultrasonic signal strength is
insufficient for reliable measurements.
• The fluid soundspeed must not vary excessively.
The Sentinel LCT8 will tolerate relatively large changes
in the fluid soundspeed, as may be caused by variations
in fluid composition and/or temperature. However, such
changes must occur slowly. Rapid fluctuations in the fluid
soundspeed, to a value that is considerably different
from that programmed into the Sentinel LCT8 , will result
in erratic or inaccurate flow rate readings. This may
occur when changing batch fluids, though most likely the
Sentinel LCT8 will recover.
NOTE: Refer to Chapter 3 . Programming on page 21 to
make sure the appropriate soundspeed is programmed into
the meter.
5.4.2 Pipe problems
Pipe-related problems may result from improper choice in
meter location or errors in programming. The following may
result in problematic installations:
•
The collection of solid material at one or more transducer
locations.
Accumulated debris at the transducer location(s) will
interfere with transmission of the ultrasound signals.
Choose an installation point for the meter where solid
particles will not settle into the transducer ports. Refer to
Chapter 2 . Installation on page 5 , for more details on
proper installation practices.
• The inner surface of the pipe is not sufficiently clean.
Excessive buildup of scale, rust or debris will change the
inner dimensions of the pipe, which results in inaccuracies
in the calculation of the flow rate from the fluid velocity
measurement.
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