TECHNICAL DESCRIPTION
ULTRAFLOW® 54 DN150-300
Kamstrup A/S
·
Technical description
·
5512-876_M1_GB_12.2020
18
7.1
Guidelines for dimensioning ULTRAFLOW® 54
In connection with installations, it has proved practical to work with a static pressure at the flow sensor outlet according
to
. This minimises the risk of measuring errors as a result of cavitation or air in the water.
Nominal flow q
p
Recommended
min. static pressure
Max. flow q
s
Recommended
min. static pressure
[m³/h]
[bar]
[m³/h]
[bar]
150
1
300
2
250
1.5
500
2.5
400 (DN150)
1.5
800
2.5
400
1
800
2
600
1.5
1200
2.5
1000
1.5
2000
2.5
Table 9. Recommended minimum static pressure at flow sensor outlet.
It is not necessarily cavitation in the sensor itself, but also bubbles from cavitating pumps and regulating valves mounted
before the sensor. It can take some time until such bubbles have been dissolved in the water. Furthermore, water can
include air which is dissolved in the water. The amount of air which can be dissolved in water depends on pressure and
temperature. This means that air bubbles can be formed due to a decrease in pressure, e.g. caused by a velocity rise in a
pipe contraction or in the sensor. The risk of these factors affecting accuracy is reduced by maintaining a suitable pressure
in the system.
In relation to the recommended static pressure, the steam pressure at the current temperature must also be considered.
The recommended static pressure applies to temperatures up to approx. 80
o
C.
The steam pressure is the pressure where steam and liquid are in equilibrium at the current temperature (boiling point
at a given pressure). At low temperature and high pressure, water is in the liquid phase. At high temperature and low
pressure, water is in the steam phase. The blue curve (the steam pressure curve) in
equilibrium of the liquid and steam phases. This means that the static pressure in water must be increased at a given
temperature to avoid the steam phase that is shown in the lower right corner of the graph in
