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5. Technical data
Sulphur hexafluoride:
Critical temperature:
Critical pressure:
Critical volume:
Critical density:
Maximum values:
Temperature range:
Maximum pressure:
Threshold value for
safety valve:
Theoretical long-term
pressure:
Theoretical rupture
pressure:
Materials:
Test gas:
Hydraulic fluid:
Measuring cell:
Temperature coating:
Recommended
thermal medium:
Determination of volume:
Piston diameter:
Piston surface:
Displaced volume:
Maximum volume:
Scale division for
displacement:
Maximum displacement: 50 mm
Determination of pressure:
Manometer:
Measured quantity:
Indicator:
Manometer diameter:
Connections:
Hole for
temperature sensor:
Connections for
thermal medium:
Connection for
regulating valve:
Gas connection:
General specifications:
Dimensions:
Weight:
318.6 K (45.5°C)
3.76 MPa (37.6 bar)
3
197.4 cm
/mol
0.74 g/mol
10-60°C
6.0 MPa (60 bar)
6.3 MPa (63 bar)
7.0 MPa (70 bar)
>20.0 MPa (200 bar)
Sulphur hexafluoride (SF
Castor oil
Transparent acrylic
Transparent acrylic
mixture of water and anti-
freeze in the ratio 2:1
20.0 mm
2
3.14 cm
× displacement
2
3.14 cm
3
15.7 cm
0.05 mm
Class 1.0 (max. 1% deviation
from full scale value)
Excess pressure
60 bar max.
160 mm
6 mm dia.
7 mm dia.
1/8'' dia.
1/8'' (3.17 mm) dia. (as
supplied)
3
380 x 200 x 400 mm
7 kg approx.
6. Volume calibration
6.1 Preliminary notes:
P
O
Q
R
S
)
A
6
Fig. 1: Cross-section of apparatus with measuring cell (A),
conical seal (B), oil chamber (C), piston (D), cylin-
der (E), heat casing (F), silicone seal (G), end
plate (H), square grommet (I), piston cover (J),
threaded axle (K), gasket (L), manometer connec-
tion (M), guide tube (N), spring (O), sleeve (P), hole
for temperature sensor (Q), circular grommet (R) and
valve plate (S)
One turn of the handwheel winds the piston into/out
of the cylinder by means of a threaded axle. This
leads to a change of volume in the oil chamber (see
Fig. 1). Since oil is practically incompressible and all
the other components other than the conical seal are
almost rigid, a change in volume in the oil chamber
causes the conical seal to deform, thereby creating an
almost equal change in volume ΔV
cell. As a first approximation for ΔV
Δ
=
Δ ⋅
V
A
s
G
A =
where
3.
14
cm
The piston displacement is shown in divisions of
2 mm on the fixed scale. Intermediate values are read
on the vernier scale in divisions of 0.05 mm.
The fixed scale can be moved by loosening the two
knurled screws. The vernier scale can be repositioned
and turned around the threaded axle on loosening
the grub screw (between scale positions 0 9 and 1 0).
6.2 Zero point calibration:
The zero point for the volume scale must be deter-
mined by conducting a calibration.
For this, we take advantage of the fact that in a pres-
sure range of 1-50 bar and in a temperature range of
270-340 K, air acts as a near-ideal gas (the real gas
factor has a deviation of less than 1% from 1). There-
fore, at a constant temperature (e.g. room tempera-
ture) for two piston displacements s
3
N
M
B
C
D
E
F
in the measuring
G
, we can assume:
G
and Δs = displacement of piston.
2
and s
0
L
K
J
I
H
G
(1)
and for
1
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