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 Pressure limit is commonly the same as the supporting system.
q
Cost, initial and operational, may exceed project funding or
q
negatively affect the project Savings-to-Investment Ratio (SIR).
q Flowmeter
may require installation in a bypass line to avoid magnetic
fields present in an existing pipe configuration.
q Data
are inaccurate less than full-flowing pipe.
5. INSTALLATION. Both configurations of the electromagnetic flowmeter,
full-bore type and insertion type, are discussed.
5.1 Full-Bore Meter Installation. The full-bore electromagnetic flowmeter
inserts into a pipeline between two flanges and is secured with bolts. To
obtain accurate measurements, the following conditions must exist:
The meter is subject to electromagnetic fields and must be shielded
q
from large electric motors, transformers, communications equipment,
and other large electrical devices to avoid electromagnetic
disturbances.
q
The meter must be positioned so that the pipe is full flowing
approaching and exiting the meter.
q
The location of the full-bore electromagnetic flowmeter in the system
is important. Whenever possible, it is preferable to locate the
primary element in a horizontal line. To ensure accurate flow
measurement, the fluid must enter the primary element with a fully
developed velocity profile, free from swirls or vortices. Such a
condition is best achieved by the use of adequate lengths of straight
pipe, both preceding and following the primary element. The minimum
recommended lengths of piping are shown in Figure 6-5. The diagram in
Figure 6-5 that corresponds closest to the piping arrangement for the
meter location should be used to determine the required lengths of
straight pipe on the inlet and outlet. These lengths are necessary to
limit piping configuration errors to less than 0.5%.
5.1.1
Meter Grounding. A grounding system must be provided for the meter and
the fluid. Detailed instructions for grounding systems are usually supplied
by the equipment manufacturer. Some grounding considerations are as
follows:
q For
conductive piping, the third wire ground to the power supply and a
ground tie to the piping flanges is typically all that is required.
For nonconductive or lined piping systems, a protective grounding
q
orifice must be used to provide access to the potential of the liquid
being measured.
6-17
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