Multistage Pump Example

To show the mechanical rotor variations, a six-stage boiler-feed pump with a design capacity of 1250 gpm (284 m3/h), 2200 ft (670 m) total head, and driven by a 1000-hp (746-kW), two-pole motor has been selected. This pump utilizes interstage bushings as support bearings to the rotor. The contribution of these bushings as bearings will probably be less than might be assumed.

FIGURE 5 Synchronous critical speed summary with first three mode shapes of a single-stage overhung pump with heavy coupling of 62 lb (28 kg) and rigid foundation. Rotor weight = 157.4 lb (71.4 kg); rotor length = 30.3 in (77.0 cm); number of stations = 22; number of bearings = 2. (a) Rigid support, modes 1, 2, and 3 respectively: 4279, 15,865, and 64,970 cpm; (b) flexible support, modes 1, 2, and 3 respectively; 3580, 9339, and 35,565 cpm. (lb X 0.454 = kg; lb/in X 175 = N/m)

FIGURE 5 Synchronous critical speed summary with first three mode shapes of a single-stage overhung pump with heavy coupling of 62 lb (28 kg) and rigid foundation. Rotor weight = 157.4 lb (71.4 kg); rotor length = 30.3 in (77.0 cm); number of stations = 22; number of bearings = 2. (a) Rigid support, modes 1, 2, and 3 respectively: 4279, 15,865, and 64,970 cpm; (b) flexible support, modes 1, 2, and 3 respectively; 3580, 9339, and 35,565 cpm. (lb X 0.454 = kg; lb/in X 175 = N/m)

Pressure or seal leakage control bushings contribute rotor support if they are long. The hot feedwater has very low viscosity and little damping. The bearing stiffness will be relative to the eccentricity ratio of the shaft in the bushings. An eccentricity ratio of unity (maximum) implies that the shaft is rubbing directly on its bushing.

The impeller weight is increased by the water trapped in each impeller. Many pump manufacturers improperly list pump undamped critical speeds from dry pump data or calculations. The bushings, labyrinths, and wear rings all contribute to the actual critical speed. Also, bearing housing resonances are more common than expected.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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