60 Hz
Submersible borehole pumps
112
Flow Velocity v Past the UMA Submersible Motor
Depending on the general installation arrangement (i.e. depending, for example, on the ratio of outside motor diameter to inside
well or shroud diameter, etc.) a distinction must be made between the following cases ...
a) v = 0 m/s ... this applies, for example, when the pump set is installed in a deep well below the well screen / filter,
in a pump sump, tank or other reservoir, etc.
Caution: At v = 0 m/s, UMA 250D motors can only be operated at reduced rated power.
b) v ≥ 0.2 m/s ... this describes with adequate accuracy the case when the pump set is, for example, installed in a deep well above
the well screen / filter, etc. In borderline cases (for ex. if the inside well diameter is very large compared with the
outside motor diameter) the diagram below can be used to double-check the data.
c) v ≥ 0.5 m/s ... In this case it must always be checked, using the diagram below, whether the installation dimensions
(i.e. the ratio of outside motor diameter to inside well diameter) are adequate to ensure a minimum flow velocity
past the motor of v ≥ 0.5 m/s. If not, use a special cooling shroud.
How to read the diagram:
The requirement for a “flow velocity past the motor of v ≥ 0.2 or 0.5 m/s” is met, if the point of intersection of the capacity Q and
the inside well or shroud diameter DN is located on or to the right of the curve applicable to the submersible motor used.
0
200
400
600
800
1000
1200
1400
0 100 200 300 400 500 600 700 800 900
UMA 300D
UMA 250D
UMA 200D
UMA 150D
DN 100
Max. permissible well diameter for compliance with
required f low velocity past the motor
Q[m#/h]
V>=0.2m/s
V>=0.5m/s
DN 100V ≥ 0.1
∅
[mm]
Example:
Given: UPA 300 - 65/4 + UMA 250D 160/21 and v ≥ 0.5 m/s.
Found: For Q = 250 m
3
/h (¶ Q
opt
) the following applies: ⇒ DN ≤ 700 mm.
This means that the requirement for v ≥ 0.5 m/s is met, if the pump set is, for example, installed in a well or cooling shroud of
DN ≤ 700 mm or ≤ 28 inches.
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