VEGA VEGADIF 65 Chemical seal CSB - Manual (Page 6)

6
3 Planning instructions for isolating systems
Chemical seal CSB • for VEGADIF 65
36133-EN-130417
Filling oil Permissible
product temper-
atures
Permissible
product tem-
peratures at
0.05 bar
abs
< p
< 1 bar
abs
Densi-
ty in g/
cm³
Vis-
cosity
in m 2 /
s•10 -6
Expan-
sion
coeffi-
cient 1/K
Cor-
rective
factor
for TK
Application
area
Halocarbon oil
KN21 (BAM
tested)
-40 … +150 °C (-
40 … +302 °F)
-40 … +80 °C (-
40 … +176 °F)
1.968
up to
20 °C
14
up to
20 °C
0.00086 0.83 For oxygen
and chlorine
applications
Med. white oil
KN92 (FDA
approved)
-10 … +250 °C
(+14 … +482 °F)
-10 … +160 °C
(+14 … +320 °F)
0.85
up to
20 °C
5.6
up to
40 °C
0.00065 0.63 suitable for
foodstuffs
The implemented filling oil also influences the TK
zero point
, the permis-
sible ambient temperature and the step response time of a chemical
seal. See also chapter "Influence of the temperature to the zero point"
and "Step response time".
The differential pressure transmitter also influences the temperature
application range, the TK
zero point
and the step response time of the iso-
lating system through the volume of its lateral flanges and its control
volume. 1)
3.2 Influence of temperature changes
The filling oil expands as the temperature increases. The additional
volume presses on the chemical seal. The more rigid the diaphragm,
the more it counteracts a volume change. The additional volume also
adds to the process pressure on the measuring cell and thus shifts
the zero point. The respective temperature coefficient "TK
Process
" is
listed in chapter "Dimensions and weights".
The following diagram shows the temperature coefficient depending
on the capillary length. The process temperature corresponds to the
calibration temperature. The temperature coefficients determined
from the diagram apply to silicone oil and the diaphragm material
316L. For other filling oil, these temperature coefficients have to be
multiplied with the correction factor for the TK of the respective filling
oil.
Differential pressure
transmitter
Influence of the tempera-
ture to the zero point
1) The control volume is the volume that must be shifted in order to utilise the
complete measuring range.