Table 1 BFP specifications for 700 MW USC thermal power plant
Purpose Main feed water
Start-up and
Capacity t/h 1200 730
Discharge pressure MPa 38.05 37.26
Rotation speed min−1 6000 6300
Water temperature 188.4 184.1
Drive Steam turbine
Motor drive (with
a fluid coupling)
Output kW 17500 12000
Number of units 2 1
Table 2 Specifications of typical BFPs
of unit
MW t/h MPa min−1 kW % Unit %
500 890 29.67 5500 9999 82 2 4.00
500 1630 30.1 5500 17747 86 1 3.55
600 1000 30.1 5500 11157 83.5 2 3.72
600 1860 33.2 5000 22589 85.3 1 3.76
700 1120 30.6 5500 12711.7 85 2 3.63
1000 1650 30.5 5500 18393.3 86 2 3.68
1050 1700 31.2 6000 19279.5 85.5 2 3.67
Table 3 Measures for increasing the robustness of BFPs
No Degradation Causes Measures for increasing the robustness
Wall thickness reduction of
discharge nozzle
Erosion caused by high velocity and/or uneven flow
Overlaying austenitic stainless steel onto the inner surface
Erosion of high-differential-pressure part of the inner volute
Degraded seal performance of metal touch seal or self compressed gasket associated with increased frequencies of start and stop actions
Using an auxiliary O-ring in combination
Incipient cavitation
Increased duration of low flow operation associated with the adoption of DSS, etc.
Replacing the first stage impeller with new one designed for low flow regarding with inlet
Cracks at the portion to which
auxiliary piping is attached
Impact of pulsation caused by increased duration of low flow operation
Modifying the nozzle stub so that it will be a more rigid structure
Vibration caused by misalignment
Changes in nozzle load associated with increased
frequencies of start and stop actions
Installing an stabilizing device
Increased bearing vibration
Impact of pulsation caused by increased duration of low flow operation
Using a full circular bearing housing
Damaged bearing metal
Wire-wool damage of 13Cr steel shaft caused by foreign particles in lube oil
Overlaying carbon steel to the main shaft journal
Occurring of abruptly changing
Torque locking caused by poor sliding of the gear-coupling tooth surface
Upgrading to a flexible disk coupling
Fretting corrosion on the fitting
portion of the thrust disk
Decreased torque of the shaft-end nut. Loosened fixed disk caused by secular distortion of the disk contact surface
Using a shaft-end nut of a locking sleeve type Using a long hub type thrust disk
Degraded mechanical seal for inter stage bleed off
No maintenance for a long time because it is installed on the suction cover and not required
when the inner-volute rotor disassembly
Discontinuing the use of the bleed off pipe and the mechanical seal as the structure for extraction from the discharge cover