Gardner Denver Reavell 5236, Operating & Maintenance Manual

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WIKA data sheet IN 00.18 ∙ 06/2016 Page 3 of 6
In order to avoid the formation of condensation in the case,
WIKA recommends filling the instruments with glycerine.
For contact gauges, the filling can be made with silicone oil,
since silicone oil, unlike glycerine, is not hygroscopic and
therefore prevents a short circuit within the instrument.
If the ambient temperature drops below -20 °C, then we
recommend that the instrument absolutely must be filled with
silicone oil. Even at temperatures down to -50 °C, silicone oil
can still be used due to its low viscosity.
For flammable and/or explosive media, e.g. oxygen, inert
filling liquids must be used.
5. Hermetically sealed instruments and effects associated with them
In order to prevent the intrusion of water into the case, it is
recommended that an ingress protection method is chosen
that reliably inhibits this (see illustrations 1 and 2). The
ingress protection demands that the instrument is hermetical-
ly sealed.
4. Measures against the formation of condensation
Different filling liquids depending on the ambient temperature and the electrical conductivity
Temperature in °C
Influence in %
5.1 Temperature errors for unfilled and filled Bourdon tube pressure gauges
A standard 232.50/30 instrument with a pressure range greater than 25 bar can be made hermetically sealed without any
problems, and manufactured with an ingress protection of IP66. The temperature error that occurs with these instruments is
negligible, since it is so small in relation to the pressure range, that the instrument still will operate within its specified class
accuracy.
Instruments with a scale range of less than 25 bar can likewise be made hermetically sealed, though a temperature error will
then be present (see illustration 4). The temperature errors present are shown in the following graphs.
Temperature errors in hermetically sealed, unfilled Bourdon tube pressure gauges
Adjusted at 20 °C
With vented instruments, the vent valve has to be closed
in order to achieve the specified ingress protection.
This, however, produces a temperature error, which can
affect the measuring result (see illustrations 4, 5 and 6).
Therefore the vent valve has to be opened for a short time
before reading the measured value.
Illustration 4
GARDNER DENVER APP457