Endress+Hauser cerabar M PMP 46, Техническая информация

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Design Planning for
the Diaphragm Seal
Diaphragm Seal Filling Fluid
The temperature and pressure of the
process are of critical importance when
selecting the filling fluid for the
diaphragm seal.
,
The suitability of the fluid to meet the
requirements of the medium must also
be considered. For foodstuffs
applications, only physiologically safe
fluids such as vegetable oil or silicone
oil (AK 100) may be used in the
diaphragm seal.
Guidelines for Mounting Capillary
Tubes
The transmitter should generally be
mounted below the tapping point. A
maximum height difference between the
tapping point and transmitter should not
be exceeded. This will otherwise result
in a break in the column of fluid in the
capillary and damage the diaphragm
seal.
•
Minimum bending radius of capillary
tubing: 100 mm (3.94 in).
•
In the case of applications in vacuum,
the instrument should be mounted
below the pressure tapping point.
Smallest Recommended Measuring
Span and Diaphragm Diameter
The effects of temperature cause the
diaphragm seal to expand. This in turn
gives rise to an additional temperature
effect on the zero point. When selecting
the diaphragm seal the following points
are to be observed:
•
The nominal diameter of the
diaphragm seal determines the width
of the diaphragm.
•
Temperature effects vary inversely
with the width of the diaphragm
diameter.
The largest possible width of diaphragm
should be chosen for small measuring
spans and/or capillaries so that
temperature effects remain within the
nominal range of the application.
Temperature Effects
The temperature coefficients of the
diaphragm seals as stated in the
technical data and dimensions (page 21
onwards) apply to silicone oil
(calibrating tempe20°C/+68°F)
and are determined by the process and
ambient temperatures.
For other fluids, the T
K
value is to be
multiplied by the T
K
correction factor.
For instruments with capillary tubing, the
total temperature coefficient T
K
can be
calculated by adding the T
K
of the
Cerabar M to that of the diaphragm
seal, together with the T
K
of the capillary
tubing.
The T
K
of the capillary tubing is
determined by the ambient temperature:
T
K
per meter for silicone oil:
0.5 mbar/10 K.
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Filling fluid
of
diaphragm seal Code Permissible
temperature of
medium at
0.05 bar
≤
p
abs
≤
1 bar
(0.73 psi
≤
p
abs
≤
14.5 psi)
Permissible
temperature of
medium at
p
abs
≥
1 bar
(p
abs
≥
14.5 psi)
Maximum
height
difference
at p
abs
≥
1 bar
(p
abs
≥
14.5 psi)
Minimum
permissible
pressure
at +20°C
(+68°F) Density
[g/cm
3
]
T
K -
Correction
factor
Remarks
Silicone oil
(AK 100) A, J –40…+180°C
(–40…+356°F) –40… +250°C
(–40…+482°F) max. 7 m
(max. 23 ft) 10 mbar
abs
(0.15 psi)
0,96 1 standard, foodstuffs
applications
High-
temperature oil
(paraffin) G,
H, K –10…+200°C
(+14…+392°F) –10… +350°C
(+14…+662°F) max. 7 m
(max. 23 ft) 10 mbar
abs
(0.15 psi)
0.81 0.72
Fluorolube FS-5
1)
N –40…+80°C
(–40…+176°F) –40…+175°C
(–40…+347°F) max. 7 m
(max. 23 ft) 10 mbar
abs
(0.15 psi)
1.87 0.91 inert oil e.g. for oxygen
or chlorine
Glycerine
E — +15…+200°C
(+59…+392°F) max. 4 m
(max. 13.1 ft) 10 mbar
abs
(0.15 psi)
1.26 0.64 foodstuffs applications
Vegetable oil
(Neobee M20)
D, F –10…+120°C
(+14…+392°F) –10…+200°C
(+14…+392°F) max. 7 m
(max. 23 ft) 10 mbar
abs
(0.15 psi)
0.94 1.05 FDA No.:
21CFR172.856
1) Observe operating limits for oxygen service for non-metallic materials.
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