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12 Maintenance
Two measures are recommended: cleaning and zero point adjustment.
Cleaning
The density transducer should be cleaned when, for example, liquids tending to sedimentation are
measured. The easiest method is to increase the flow velocity through the density transducer to the
maximum permissible value for some minutes to flush away sediments and solids. If this measure does
not prove successful, the density transducer should be cleaned with a special detergent if flushing
connections are provided. In this case the corrosion resistance of the wetted parts of the density
transducer must be observed.
Zero point adjustment
Abrasion, sedimentation or corrosion may shift the zero point of the density transducer. The zero point
shift can be established by a comparison measurement and rectified by an on-site adjustment (see
sections 9 and 13.1).
13 Error detection/troubleshooting
Periodical checks of the density transducer facilitate error detection and may provide information about
possible error sources.
These checks can normally be limited to a comparison between the measured value and a reference
measurement, using either lab equipment or a density transducer as a master.
For this purpose it is essential that the test equipment is of sufficient reliability and accuracy (e.g. test
equipment approved by the Weights and Measurement Authorities) to ensure correct results. During the
test, the conditions must be comparable to the actual operating conditions; if necessary, the temperature
coefficient of the liquid must be taken into consideration.
If the measured value does not match the result of the reference measurement, the following measures
should be taken:
- Check the evaluation electronis (transmitter):
electrical connection, power supply, cabling to the transducer.
- Ensure that the data of the calibration log or the
service list and the programmed parameters of the evaluation electronics are identical.
- Inspect the density transducer for damage
(temper colors on the transducer housing caused by high temperature and other
mechanical defects such as damaged transmitter housing, damaged gaskets or terminals).
- Look for disturbances from process side (e.g. empty product lines or gas bubbles).
A seriously damaged density transducer should be dismounted and returned to the service department of
Bopp & Reuther Messtechnik (see section 15).
Otherwise, additional inspections should be performed. In general, there are three types of error sources:
- errors/defects caused by the liquid
- errors/defects caused by the transmitter
- errors/defects caused by the density transducer
We reserve all rights of ownership and exploitation in respect of these
documents, including industrial property rights. These documents may only
be used with our express consent in writing, and only to the extent permitted
in any such consent. The documents may not be duplicated or made
available to third parties. In case of violation of the aforementioned
provisions, we reserve all rights.
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