Endress+Hauser prowirl 77, Руководство по эксплуатации

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Poor or strongly varying flow signal
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Is the fluid to be measured single-phase and homogeneous?
The fluid must be single-phase and homogeneous, and the pipeline always com-
pletely filled to ensure accurate and reliable flow measurement. In many cases the
measuring result may be improved under poor conditions by taking the following
measures:
– For liquids with low gas content in horizontal pipelines, the flowmeter should be
mounted with the head pointing downward or to one side. This improves the
measuring signal as the sensor is positioned away from any gas bubbles.
– For liquids with low solids content, the electronic housing should not be mounted
pointing downward.
– For steam or gas with low liquid content, the electronic housing should not be
mounted pointing downward.
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Do the inlet and outlet sections correspond to the mounting instructions on page 10?
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Are gaskets of the correct internal diameter (not smaller than the pipeline) and
correctly centred?
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Is the static pressure sufficiently large to prevent cavitation at the flowmeter?
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Is the flow within the measuring range of the flowmeter (see “Technical Data”
page 55)?
The start of the measuring range depends on the density and viscosity of the fluid
which in turn are functions of temperature. With gases and steam, density is also a
function of pressure.
•
Are pressure pulsations superimposed on the operating pressure (e.g. due to piston
pumps)? These pulsations may affect vortex shedding if they have a similar fre-
quency to that of the vortex shedding itself.
•
Have the fluid (“Application”) and nominal diameter been set correctly? “Appli-
cation” must be set to “Liquid” for liquids, and set to “Gas/steam” for gases and
steam. The nominal diameter of the flowmeter must agree with the setting “Nominal
diameter”. The settings in these two functions determine the filter settings and can
thus affect the measuring range.
•
Does the K-factor of the instrument agree with the setting in the function “Calibration
factor”?
Maintenance / Calibration
If correctly installed, the meter will operate without maintenance. If installed as a
production quality-relevant (ISO 9000) measurement point, the Prowirl 77 can be
recalibrated by Hauser on accredited calibration rigs, traceable according
to EN 45001, and supplied with an internationally recognized certificate according to
EA (European cooperation for Accreditation of Laboratories).
Prowirl 77 PROFIBUS-PA 7 Trouble-shooting
Hauser 47