ABB 10D1477, Instruction Manual

Page: 40 / 52

Other normal effects of temperature, such as influence upon liquid viscosity and density, the size of
the metering area, and the flux density of the magnetic field, have negligible or no effect upon
metering accuracy.
4.2.1.3 Other Liquid Variables
Within the constraints discussed in 4.2.1.1, other liquid variables such as viscosity, density and liquid
pressure have no direct influence on metering accuracy. Liquid 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 as given in
Specifications Section 1.3.
4.2.2 Metering Characteristics
The metering pipe must be completely filled at all times for accurate results. See Installation Section
2.0 for piping information. The magnetic flowmeter will measure the total amount of material passing
in the liquid stream. The meter will not, for instance, differentiate between the amount of liquid and
the amount of entrained gases or 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 measure-
ments of the concentration of the desired medium must be made and appropriate correction factors
must be applied to the magnetic flowmeter output.
In applications involving variable quantities of uniformly dispersed, nonconductive mixing agents, it
must be ascertained that the higher concentrations of mixant will not drive the average conductivity
of the liquid mixture below the minimum conductivity level for the given installation.
10D1477 MAGNETIC FLOWMETER INSTRUCTION MANUAL
4-5