Seawater Cooling System Modifications Eliminate Pump to Save 5.5MW in Ultra Mega Power Plant
AFT Impulse™ Case Study
Power Generation | Tata Consulting Engineers
“AFT Impulse was very easy to adopt, creating any number of variations was easy, and the study could be completed in the short given time.”
– C Suresh Ram, Tata Consulting Engineers Limited
PROBLEM
- Poor pump operation in independent, single-pass seawater cooling systems
- The plant owner proposed interconnecting systems to
- Improve operating flexibility
- Reduce energy use
ANALYSIS
- An AFT Impulse model was calibrated to within 2% error from field data
- 12+ scenarios were tested interconnecting systems and confirming adequate flow distribution
SOLUTION
- Determined connecting 4 of 5 units could operate 7 of 8 connected pumps, saving 5.5MW in energy
- Transient pump trip analysis confirmed no need for additional surge equipment
Ready to try AFT Impulse?
FIGURE 1: A comparison of the five independent cooling water systems as drawn and as modeled. Pipelines are up to 2.8 m (9 ft) in diameter and lengths of 1000+ m (3300+ ft).
Problem Explained
C Suresh Ram, Tata Consulting
Engineers, was tasked with assessing
a coal-fired Ultra Mega Power Plant
cooling system to address poor
pump operation while ensuring
any modifications do not introduce
waterhammer or surge concerns.
The plant consists of five units, each
cooled by independent once-through
seawater cooling systems. Each cooling
water system is driven by two parallel
pumps each with a rated capacity of
63,000 m3/hr (277,000 gpm).
The owner proposed interconnecting
the pumps of multiple units to reduce
the number of pumps necessary to meet
design requirements, reducing energy
and improving operational flexibility.
The existing system, as drawn and as
modeled, is found in Figure 1.
Tools & Analysis
Ram’s analysis began in AFT Impulse’s
steady-state solver to calibrate the
model’s pipe roughness to match pressure
and flowrate measurements.
Frictional loss was estimated as the
system lacked pressure measurement
instruments. The calculated frictional
loss was consistently less than the
original design loss, indicating oversized
pumps leading to poor performance. A
comparison between the calibrated model
and observed data is found in Table 1.
The calibrated model was then used to
evaluate cases with various parallel units
connected. It was vital to confirm adequate
flow distribution to each condenser unit,
testing the system with any one of the
connected pumps off in turn. This process
was performed with three, four, and all five
units connected.
Solutions & Benefits
The sensitivity study found only four interconnected units met all
condenser requirements with any seven of the eight connected
pumps, reducing energy requirements by 5.5 MW and improving
pump operation.
However, the proposed changes required the system to be reevaluated for hydraulic transients. The new study was to confirm the adequacy of a previous study’s valve closure behavior and surge protection equipment. Ram’s study evaluated a range of pump trips using built-in Four Quadrant curves, from planned trips of each pump individually to the worst-case sudden power failure to all working pumps.
In all tested cases, the transient pressure extremes remained within
pipe design limits, the system stabilized to adequate final flowrates,
and pumps stayed below manufacturer specifications for maximum
reverse speed. Not only did the interconnected design improve
steady-state operation, Ram’s transient study confirmed no further
surge mitigation was required.
Ram noted AFT Impulse had a short learning curve with flexibility to
evaluate the full range of steady-state and transient requirements;
vital as the project was under tight deadlines.
An enlarged portion of the system highlights the interconnections for evaluation between the various units.
TABLE 1: Pump operating conditions comparison between field data and calibrated model data. Calibration establishes a foundation for further steady state and transient analysis.