KSB Multitec A SX, Installation & Operating Manual

Page: 35 / 68

6 Commissioning/Start-up/Shutdown
35 of 68
Multitec A SX
Overloading of the motor may generally result in:
▪ an abnormal temperate increase leading to the motor temperature exceeding
the temperature limit of the winding or bearing grease
▪ premature coupling wear
▪
reduced service life of the pump components
▪ irregularities or malfunctions in the system
6.2.3 Flow rate
The minimum flow rates indicated below are for single-pump operation and will
prevent thermal or mechanical overloading of the pump. In case of parallel operation
with pumps of identical or different design, higher flow rates may be required to
guarantee a stable operating behaviour.
Table 10: Flow rate
Size Temperature range (t) Minimum flow rate Maximum flow
rate
100 independent of
temperature
≈ 35 % of Q
opt.
4)
See hydraulic
characteristic
curves.
A temporary minimum flow rate of 25 % of Q
Opt
4)
has been defined. This temporary
flow rate shall be limited to one hour's uninterrupted operation and approx. 200
hours/year.
The calculation formula below can be used to check if an additional heat build-up
could lead to a dangerous temperature increase at the pump surface.
Table 11: Key
Symbol Description Unit
c Specific heat capacity J/kg K
g Gravitational constant m/s²
H Pump head m
T
f
Temperature of the fluid handled °C
T
o
Temperature at the casing surface °C
Pump efficiency at duty point -
Temperature difference °C
6.2.4 Density of the fluid handled
The power input of the pump increases in proportion to the density of the fluid
handled.
CAUTION
Impermissibly high density of the fluid handled
Motor overload!
▷ Observe the information on fluid density indicated in the data sheet.
▷ Make sure the motor has sufficient power reserves.
4)
Best efficiency point