English (GB)
8
6.3 Max. operating pressure
Fig. 7 Pressures in the pump
The inlet pressure + the pump pressure must be
lower than the maximum operating pressure (p)
stated on the pump nameplate. Operation against a
closed discharge valve gives the highest operating
pressure.
6.4 Min. inlet pressure
Pay attention to the minimum inlet pressure to avoid
cavitation. The risk of cavitation is higher in the
following situations:
• The liquid temperature is high.
• The flow rate is considerably higher than the
pump's rated flow rate.
• The pump is operating in an open system with
suction lift.
• The liquid is sucked through long pipes.
• The inlet conditions are poor.
• The operating pressure is low.
6.5 Max. inlet pressure
The inlet pressure + the pump pressure must be
lower than the maximum operating pressure (p)
stated on the pump nameplate. Operation against a
closed discharge valve gives the highest operating
pressure.
6.6 Min. flow rate
The pump must not run against a closed discharge
valve as this will cause an increase in temperature/
formation of steam in the pump. This may cause
shaft damage, impeller erosion, short life of bearings
and damage to stuffing boxes or mechanical shaft
seals due to stress or vibration. The continuous flow
rate must be at least 10 % of the rated flow rate. The
rated flow rate is stated on the pump nameplate.
6.7 Max. flow rate
The maximum flow rate must not be exceeded as
otherwise there is a risk of for instance cavitation and
overload.
The minimum and maximum flow rates can be read
either from the performance curve pages in the
relevant data booklets or from a curve for a specific
pump when selecting it in Grundfos Product Center.
Fig. 8 Example from Grundfos Product Center
showing minimum and maximum flow
rate
TM04 0062 4907
Inlet pressure
Pump pressure
Maximum operating pressure, i.e.
pressure above atmospheric pressure
TM05 2444 5111
Minimum flow rate
Maximum flow rate
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