Notes On Liquid Conditions; Erroneous Liquid Parameter Specification; Liquid Compatibility; Aeration - Siemens SITRANS F Operating Instructions Manual

Section 5
1010PFM-3G
follows the slewing of actual flow. It thus provides excellent data without sacrificing the fast response
required for precise flow control. Feel free to experiment with time average damping and slewing
factors to discover which settings optimize the collected data. With SmartSlew enabled, you can
create very smooth output graphs without losing the ability to respond to fast flow transients that may
be undetectable with the fixed time average filter enabled.

5.4.3 NOTES ON LIQUID CONDITIONS

Successful transit-time flow measurement depends on sonic transmit signals traveling through liquid
and arriving at the receive transducer without excessive attenuation. Receive signals can be scattered
by liquids carrying dispersed particulate matter, whether of a solid, non-homogeneous or gaseous
nature. This is especially true if the dispersed material is of different sonic impedance than the base
liquid. Liquids that contain an excess of gas bubbles or mineral solids may prove to be unsatisfactory
transit-time applications. However, these liquids are perfectly suitable for Reflexor flowmetering. Liq-
uids containing dissolved gasses or dissolved organic solids will not cause any problems for transit-
time operation.
Most liquids are excellent sonic conductors, regardless of their electrical or optical properties. Although
highly viscous liquids exhibit a greater degree of sonic attenuation, the 1010 operates perfectly with the
vast majority of these liquids. The Valc % (signal strength) item on the Diagnostic Menu is a good
indicator of this condition. A low value (under 30) indicates a possible low liquid sonic conductivity, or
improper transducer installation.

5.4.4 ERRONEOUS LIQUID PARAMETER SPECIFICATION

The viscosity of the liquid is an important factor. It governs the degree of Reynolds Number compensa-
tion that the flow computer applies to the final rate output. Therefore, flow data errors could result if you
enter an inaccurate viscosity value. The Technical Service Department can provide reliable viscosity
data for most liquids.

5.4.5 LIQUID COMPATIBILITY

Since our clamp-on transducer systems never contact liquid, the issue of liquid compatibility only
applies to entrained gases or mineral solid content that might impair sonic signals. Also, since System
1010P is designed to measure flow using both transit-time and Reflexor techniques, we can safely say
that it will operate most successfully on virtually all liquids.

5.4.6 AERATION

Undissolved gases, having very low sonic impedance, may cause sonic beam scattering. In large
quantities, they can reduce the sonic signal strength. Small bubbles, caused by cavitation, usually
provoke more signal loss than an equal quantity of large gas bubbles. Usually, the problem can be
alleviated by eliminating the cause. Aeration may be caused by a mixing tank, throttling valve cavita-
tion, or air suction upstream of the transducer location.
System 1010P can operate successfully with a larger amount of aeration than any other transit-time
flowmeter. It measures and reports the aeration level as the analog output, Vaer %. This represents the
relative degree of aeration detected within the flow stream. Its computer reports the Vaer level until it
impedes operation and forces a Fault Alarm. The Vaer output accommodates applications requiring an
aeration indicator. The Vaer also appears on the display screen. The aeration percentage can be used
as an alarm relay set-point. You can set the aeration alarm setpoint such that it trips before aeration
reaches a level that impairs flow measurement.
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