VEGA VEGADIF 65 Chemical seal CSB - Manual (Page 5)

5
3 Planning instructions for isolating systems
Chemical seal CSB • for VEGADIF 65
36133-EN-130417
3 Planning instructions for isolating
systems
3.1 Influence of the components
The following properties of the separating diaphragm determine the
application area of the chemical seal:
•
Diameter
•
Resilience
•
Material
The bigger the diaphragm diameter, the higher the resilience and the
lesser the temperature influence on the measuring result. Note: To
keep this influence in reasonable limits, you should use a chemical
seal with a nominal width ≥ DN 80.
The resilience also depends on the diaphragm strength, the material
as well as a possible coating.
The capillary line influences the temperature coefficient TK
Zero point
, the
permissible ambient temperature and the step response time of an
isolating system through the length and the inner diameter. See also
chapter "Influence of the temperature to the zero point", "Ambient
temperature range" and "Step response time".
In the selection of filling oil, product and ambient temperature as
well as process pressure are of utmost importance. Also take note of
temperatures and pressures during setup and cleaning.
Another criterium is the compatibility of the filling oil to the require-
ments of the medium. In the food processing industry, e.g., only filling
oils that present no health risks are permitted, such as medicinal
white oil. See overview of filling oils in the following chart.
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
Silicone oil
KN17
-40 … +180 °C (-
40 … +356 °F)
-40 … +80 °C (-
40 … +176 °F)
0.96
up to
25 °C
55
up to
25 °C
0.00104 1 Standard
silicone oil
KN2.2
-40 … +200 °C (-
40 … +392 °F)
-40 … +150 °C (-
40 … +302 °F)
0.96
up to
20 °C
55
up to
20 °C
0.00104 1 Standard
High tempera-
ture oil KN 3.1
-10 … +300 °C (-
14 … +572 °F)
-10 … +200 °C
(+14 … +392 °F)
1.07
up to
20 °C
39
up to
20 °C
0.0008 0.77 High temper-
atures
High tempera-
ture oil KN 3.2
-10 … +400 °C
(+14 … +752 °F)
-10 … +200 °C
(+14 … +392 °F)
1.07
up to
20 °C
39
up to
20 °C
0.0008 0.77 High temper-
atures
Separating diaphragm
Capillaries
Chemical seal filling oil