50 Deutsch 5.962-786.0 Rev. 05 (06/13)
Pressure
Line length
Pipe fittings
The following specifications must be observed:
Diameter
As per specifications from the flow chart or the ad-
missible flow velocity.
Wall thickness
In accordance with the stipulated operating pres-
sure and the local regulations.
Material
Ensure resistance against the most aggressive
medium used (e.g. detergent).
HD pipe
Stainless steel 1.4301, welded.
Recommendation: Design for 1.5 times higher
pressure than the actually planned system pres-
sure.
Note
Always carry out HD piping (stainless steel) as weld-
ed joints.
Note
Branch pipes to the extraction points can be de-
signed as DN 15, as pressure losses can be disre-
garded because of the pipe length and the water
volume.
Table 3
Especially in pipe ellbows excessive flow velocities
lead to leakages and breaks.
In case of unnecessarily slow flow velocities, overde-
signed pipes increase the cost of materials and the
installation time.
At 65 to 160 bar the flow velocity should be 3 m/s,
max. 4 m/s (optimum)!
Example 1:
At a flow rate of 1,300 l/h the flow velocity for a DN 10
piping is approx. 4.5 m/s (point 1 in the diagram).
In order to reach the ideal flow velocity for high-pres-
sure pipes of approx. 3-4 m/s, a larger pipe diameter
must be selected.
Otherwise there is a risk of leakages and breaks in
the pipe system! In this case, the diameter is changed
from DN 10 to DN 12. As a result a suitable flow ve-
locity of 3.2 m/s is reached (point 2 in the diagram)
Example 2:
For a flow rate of approx. 7,350 l/h no suitable pipe
size is offered (point 3).
For the optimum flow velocity of 3-4 m/s a pipe diam-
eter between DN 25 and DN 32 would be ideal. Now
it must be evaluated which of the available pipe sizes
is to be selected.
The principle is: A pipe that is dimensioned slightly to
big is more expensive, however, it does not hold the
dangers of an excessive flow velocity and the risks
associated with it! For this reason, the pipe DN 32 is
selected in this example (point 4).
6.4.1 Flow velocity
Nominal
pressure
[bar /
Mpa]
Flow speed
[m/s]
Suction pipe Under-
pressure
0,5...1,2
Supply pressure
pipe
3...6
0,3...0,6
1...2
High-pressure pip-
ing
65...160
6,5...16
3...4
High-pressure hose
line
65...160
6,5...16
5...8
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