Crown Boiler MWC Series Specifications download pdf (Page 127)

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units

114

ii) Best efficiency

point

Combined flow of 2x50%

TDBFPs shall be based on

TMCR requirement

and corresponding head.

iii) Emergency point Two turbine driven feed

pumps to be capable of

generating the discharge

pressure corresponding to

steam generator highest

safety valve set pressure at

100% BMCR flow.

Requirement of

emergency point

shall be met by

MDBFP at 50

Hz grid frequency.

iv) Other Capabilities Combined flow of 2x50% TDBFP shall meet the

following:

a) BMCR flow and head corresponding to rated

steam pressure.

b) V.W.O. output, 1% makeup, worst condenser

pressure (MDBFP should meet the

corresponding requirement at 47.5Hz).

v) Rated discharge

flow through

interstage bleed off

for reheater

attemperation

As per 8% of maximum reheat steam flow for

the unit as a minimum.

Note: Discharge flow of main pump not to include any seal flow, warm-up

flow and balance drum leakage flow.

15.3 Design Requirements

15.3.1 Pumps

i) NPSH Margin: The ratio between NPSH (A) and NPSH (R) at 3%

head drop for booster pump and main pump shall be not less than 2.5 at

design point corresponding to lowest level of deaerator and maximum

pressure drop across the suction strainer.

ii) Trip Speed of TD-BFP: 10% above the design speed of the feed pump.

iii) Performance Curve: The characteristic curves of booster pump and

main pump should be continuously rising type with decrease in flow

and shut off head shall be in the range of 115% to 130% of TDH at

design point.

iv) Minimum Recirculation: The minimum flow of the booster pump and

main pump shall not be less than 25% of design flow. ON-OFF or

modulating type minimum recirculation valve with valve body

designed for about 40% of design flow shall be provided.

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Crown Boiler MWC Series Specifications Page 127

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