the presentation describes in details about the feed water and condensate heaters used in Thermal Power Stations or elsewhere. The performance parameters of the heaters are also described in details.

1. Feed Water / Condensate
Heaters
Manohar D Tatwawadi
mtatwawadi@gmail.com
9372167165
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2. Introduction
• Feed water / Condensate heaters are used in
Thermal Power Plants for preheating the Feed
water going to the boiler.
• The feed water heaters increase the sensible
heat content of feed water so that the
sensible heat required to be given in the boiler
is reduced.
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3. Purpose
• As the steam required for heating is tapped
from the selected stages of the turbine, there
is reduction in exhaust loss in the turbine
cycle.
• As the feedwater temperature of the feed
water entering the boiler increases, the boiler
fuel input decreases.
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4. Feed water / Condensate Heaters in
TPS
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5. Heaters
• In a Shell & Tube or closed Feed water Heater,
the condensate/Feed water flows through the
tubes and the extracted steam is admitted in
the shell and condenses in the shell.
• The condensed steam in the shell in each of
the feed water heater drains is successively
admitted in the next low shell pressure heater
and finally into the condenser or in
condensate line with the help of a pump.
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6. Pressure Classification
• Heaters Placed between CEP and Deaerator
Feed Tank are LP Heaters. The extraction
steam to these heaters is taken from LP and IP
Turbines
• Heaters placed in the feed line after the Feed
Pump upto the point of Feed inlet to the
Economiser are HP Heaters. The Extraction
steam is generally taken from the HP Turbines.
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9. Heater Design
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11. Heaters Performance Parameters
• The primary parameters used to monitor individual
heater performance are;
• The feedwater temperature rise,
• The terminal temperature difference (TTD) and
• The drain cooler approach (DCA).
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12. Definitions…. Feed Water Temp Rise
• Feedwater Temperature Rise is the difference
between the feedwater outlet temperature
and the feedwater inlet temperature.
• A properly performing heater should meet the
manufacturer’s design specifications, provided
the level controls are up to the task.
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13. Definitions …. TTD
• Terminal Temperature Difference (TTD) is defined as the
saturation temperature of the extraction steam minus the
feedwater outlet temperature.
• It provides feedback on the feedwater heater’s
performance relative to heat transfer.
• An increase in TTD indicates a reduction in heat transfer
while a decrease an improvement.
• Typical ranges for TTD on a high-pressure heater with and
without a desuperheating zone are -3° F to -5° F and 0° F,
respectively.
• The TTD for low-pressure heaters is typically around 5° F.
• Steam tables and an accurate pressure reading are required
to complete this calculation.
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14. Definitations ….. DCA
• Drain Cooler Approach (DCA) is the
temperature difference between the drain
cooler outlet and the feedwater inlet.
• It is a method used to infer feedwater heater
levels.
• An increasing DCA temperature difference
indicates the level is decreasing; whereas, a
decreasing DCA indicates a rise in level. A
typical value for DCA is 10° F.
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15. Heater Design TTD
DCA26/07/2019 total output power solutions 15

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18. Lower Final FW Temperature
• Lower than expected final feedwater temperature occurs
when a feedwater heater is taken out of service due to
unreliable level input to the control system or the level is
too high or low.
• If the condition is a result of high feedwater heater level,
the operator would note a decrease in feedwater heater
temperature rise, a decreasing DCA temperature
difference, and an increasing TTD.
• The inverse is true if feedwater heater levels are too low. In
either of the scenarios risk of damage to hardware
increases; heat transfer is impaired and feedwater to the
economizer is not at the required temperature. The
probable responses and impact to a low final feedwater
temperature are listed below.
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19. Heater / s out of service
• Over-fire boiler to increase temperature.
.. Increase in fuel consumption and emissions.
.. Increase in gas temperature exiting the furnace—
reheat and superheat sprays, premature fatigue
of hardware.
.. Flows through IP and LP stages of turbine increase
10% (HP heater out of service).
.. Flashing—damage to drain cooler section
.. Thermal effects on tubes
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20. Heater level too high
• Emergency drains open to lower level.
.. Loss in efficiency
.. Potential damage to hardware if water enters
extraction tube
.. Potential flashing due to sudden pressure drop
.. Turbine Water Induction Protection (TWIP)
trips unit—lost production, startup and
unscheduled maintenance costs.
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