3.2 Operating Characteristics
3.2.1 Fluid Variables
3.2.1.1 Fluid Conductivity
The Magnetic Flowmeter described in this manual requires a fluid conductivity of 5 microsiemens
per centimeter, or greater, for operation with the accuracies specified. This minimum fluid conduc-
tivity requirement is also dependent upon the length of the signal transmission cable employed in a
given installation; the longer the cable, the higher the minimum fluid conductivity requirement be-
comes. The precise relationship between minimum allowable fluid conductivity and signal transmis-
sion cable length for all Model 10DX3111 Magnetic Flowmeters is shown in Figure 1-2. Changes
of conductivity above the threshold level for a given installation have no effect upon metering accu-
racy as long as the proper installation and interconnection procedures are observed.
3.2.1.2 Fluid Temperature
Having established the minimum fluid conductivity requirements for a given application, any fluid
which exhibits equal or higher conductivity may be metered without concern for any system com-
pensating adjustments. However, due regard for the effect of the fluid conductivity should be con-
sidered.
Most fluids exhibit a positive temperature coefficient of conductivity. It is possible for certain mar-
ginal fluids to become sufficiently non-conductive at lower temperatures so as to hamper accurate
metering; whereas, the same fluid at higher or normal environmental temperatures may be metered
with optimum results. The possibility of an adverse temperature conductivity characteristic should
be investigated before attempting to meter such a fluid. Fluid or ambient temperatures are also lim-
ited by the meter materials specification.
Other normal effects of temperature, such as influence upon fluid viscosity and density, the size of
the metering area, and the flux density of the magnetic field, have negligible or no effect upon me-
tering accuracy.
3.2.1.3 Other Fluid Variables
Other fluid variables such as viscosity, density and fluid pressure have no direct influence on meter-
ing accuracy. Fluid density has no effect on volumetric flow rate since only the area of the meter
pipe and liquid velocity are required to determine the rate of flow. Viscosity and metering pressure
are restricted to physical limitations alone, such as the leakage pressure of the meter pipe flange
connections.
3.2.2 Metering Characteristics
The metering pipe must be completely filled at all times for accurate results. Where there is possi-
bility of operation with a partially filled horizontal pipeline, it is recommended that the Magnetic
Flowmeter be installed in a vertical section of that pipeline such that fluid flow moves upward.
A vertical installation also offers the advantage of an even distribution of liner wear in the event
that solid abrasives are being carried along in the fluid stream.
The ABB Instrumentation Magnetic Flowmeter will measure the total amount of material passing in
the fluid stream. The meter will not, for instance, differentiate between the amount of liquid and
the amount of entrained gases. Also, in the case of a slurry, it will not differentiate the amount of
liquid from solids. If the liquid to mixant ratio is of importance to process control, then separate
10DX3111 INSTRUCTION MANUAL
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