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Planning guideBasic hydraulic principlesVibrations and resonanceWhen sewage pumps are installed and connected, various aspectsmust be observed to guarantee smooth operation. Fundamentally,every moving machine part causes vibrations.In the case of submersible motor pumps and monobloc pumps, duringrotation, free centrifugal forces are generated at the circulationfrequency. Also, the hydraulic forces acting on the pump impellerconsiderably contribute to the machine vibrations.In order to avoid malfunctions and damage, the strength of the vibrationsin the operating state may not exceed a certain threshold. Thisis achieved by statically and dynamically balancing the correspondingparts.If the pumps are subject to additional external vibrations due tounfavourable installation and connections, these vibrations aresuperimposed. These vibrations can put high levels of stress on individualcomponents.In order for the pumps to work without disturbances and to have longservice lives, they must be installed according to the generally validrules of technology.Q/H diagramTo be able to get the required information out of the Q/H diagram,the following is to be observed:• In the head (1) you will find information about pump type, frequency,rotation speed, impeller shape and free ball passage.• In the standard program, each pump curve (2) corresponds to oneunit. Every pump curve is labelled with the respective type of unit.• In the configured range, every pump curve (2) corresponds to an impellerdiameter for the respective hydraulics. Every pump curve islabelled with the impeller diameter.• The efficiency pump curves (3) correspond to the overall efficiencyfor the standard program. In the configured program, the degrees ofefficiency correspond to the hydraulic efficiency.• The thin part of the pump curve (4) indicates the range in which thepump may not be operated.• In the configured program, the nominal power for each availablemotor is shown as a dotted power curve (5) in the diagram. Based onthis pump curve, you can see which hydraulics can be combined withwhich motor and with how much power reserve the motor can beoperated. In general, the intersection point of the hydraulics curvewith the power curve must always be to the right of the selected dutypoint. The more distance between the selected duty point and theintersection point of the curves, the more reserve the motor has.(1) Pump curves Wilo-EMU FA 20.78D - 50 Hz - 950 rpmMulti-channel impeller - Free ball passage: 76 mmH[m]30 kW 35 kW 37.5 kW 44 kW 47.5 kW 52 kW 55 kW 65 kW 70 kW 75 kW 90 kW403540%50%60%304270%74%77%52520153Ø 470Ø 4901060%Ø 450Ø 425Ø 4005Ø 38000 100 200 300 400 500 600 700 800 9000 40 80 120 160 200 2 40Abbildung: Q/H-Diagramm aus dem konfiguriertem ProgrammQ[m³/h]Q[l/s]8 Wilo Water Management catalogue – 50 Hz – Drainage and sewage – Waste water transport and dewatering – Edition 2012 – Subject to change without prior notice