The presentation discusses about the conservation of energy in pumps and pumping stations as whole in Thermal Power Stations.The pumps efficiency is also discussed in details, how to calculate and the steps to increase efficiency of pumps as well as pumping stations.

1. DIFFERENT TYPES OF PUMPS
ENERGY CONSERVATION RELATED
TO PUMPS USED IN THERMAL
POWER STATIONS
MANOHAR TATWAWADI
30-Jul-19 1total output power solutions

2. CLASIFICATION OF PUMPS
Pumps
Rotodynamic
Centrifugal
Radial
Volute Type
Single or
multi stage
Diffuser Type
Semi Axial
Mixed
Axial Pump
Propeller
Positive
Displacement
Reciprocating
Piston
Plunger
Rotory
Gear
Screw
Sliding Vanes
Rotor
30-Jul-19 2total output power solutions

3. PUMPS IN POWER PLANTS
• High Capacity Pumps: Boiler Feed Pumps,
Condensate Pumps, Cooling water Pumps,
Raw water Pumps, etc.
• Medium Capacity Pumps:- Ash Handling, Coal
Handling, WT Plant, etc.
• Low Capacity Pumps:- Small Lub oil Pumps,
Chemical Dozing Pumps etc,
30-Jul-19 3total output power solutions

4. Boiler Feed Pumps
• General.
• Boiler feed pumps are used to pressurize
water from the deaerating feedwater heater
or deaerating hot process softener and feed it
through any high pressure closed feedwater
heaters to the boiler inlet.
• BFPs discharge from the boiler, superheated
steam in order to maintain proper main steam
temperature to the steam turbine generator.
30-Jul-19 4total output power solutions

5. Boiler Feed Pump Types
• Types of Pumps.
• There are two types of centrifugal multi-stage boiler
feed pumps commonly used in steam power plants
–horizontally split case and
–barrel type with horizontal or vertical
(segmented) split inner case.
• The horizontal split case type are used on boilers
with rated outlet pressures up to 6Mpa.
• Barrel type pumps are used on boilers with rated
outlet pressure in excess of 6MPa.
30-Jul-19 5total output power solutions

6. Pumps Design Criteria
• Pump head will be maximum at zero flow with
continuously decreasing head as flow
increases to insure stable operation of one
pump, or multiple pumps in parallel, at all
loads.
• Pumps will operate quietly at all loads without
internal flashing and operate continuously
with- out overheating or objectionable noises
at minimum recirculation flow.
30-Jul-19 6total output power solutions

7. Pumps Design
• Provision will be made in pump design for
expansion of
(a) Casing and rotor relative to one another.
(b) Casing relative to the base.
(c) Pump rotor relative to the shaft of the
driver.
(d) Inner and outer casing for double casing
pumps.
• All rotating parts will be balanced statically -
and dynamically for all speeds.
30-Jul-19 7total output power solutions

8. Design Criteria ………….
• Each pump will be provided with a pump
warmup system so that when it is used as a
standby it can be hot, ready for quick startup.
• This is done by connecting a small bleed line
and orifice from the common discharge
header to the pump discharge inside of the
stop and check valve.
• Hot water can then flow back through the
pump and open suction valve to the common
suction header, thus keeping the pump at
operating temperature.
30-Jul-19 8total output power solutions

9. Design Criteria………
• Pump will be designed so that it will start
safely from a cold start to full load in 60
seconds in an emergency, although it will
normally be warmed before starting as
described above.
• Pump design will provide axial as well as radial
balance of the rotor at all outputs.
• One end of the pump shaft will be accessible
for portable tachometer measurements.
30-Jul-19 9total output power solutions

10. 30-Jul-19 10total output power solutions

11. 30-Jul-19 11total output power solutions

12. 30-Jul-19 12total output power solutions

13. 30-Jul-19 13total output power solutions

14. Pump Efficiency
• The overall efficiency of a pumping system,
also called the “wire‐to‐water” efficiency, is
the product of the efficiency of the pump
itself, the motor, and the drive system or
method of flow control employed.
• Pumps lose efficiency from turbulence,
friction, and recirculation within the pump.
• Another loss is incurred if the actual operating
condition does not match the pump’s best
efficiency point (BEP).
30-Jul-19 14total output power solutions

15. Pump Efficiency
• The various methods for controlling flow rate decrease
system efficiency.
• Throttling valves to reduce the flow rate increases the
pumping head.
• Flow control valves burn head produced by the pump.
• Recirculation expends power with no useful work, and
• VFDs produce a minor amount of heat.
Of these methods, VFDs are the most flexible and
efficient means to control flow despite the minor heat
loss incurred
– Note that inefficiency in more than one component can
add up quickly, resulting in a very inefficient pumping
system.
30-Jul-19 15total output power solutions

16. 30-Jul-19 16total output power solutions

17. 30-Jul-19 17total output power solutions

18. Variation of Absolute Pressure inside A Pump
Flow Path
pabsolute
30-Jul-19 18total output power solutions

19. CAVITATION
• As the liquid flows onto the impeller of the pump it is
accelerated and initially its pressure falls (Bernoulli).
• The pressure subsequently increases as the fluid leaves the
impeller and as the kinetic energy is recovered in the volute
chamber.
• If the pressure of the liquid falls below the vapour pressure,
Pv, the liquid boils, generating vapour bubbles or cavities-
cavitation.
• The bubbles are swept into higher pressure regions by the
liquid flow, where they collapse creating pressure waves and
cause mechanical damage to solid surfaces.
• Moreover, pump discharge head is reduced at flow rates
above the cavitation point.
• Operation under these conditions is not desirable and
damages the equipment.30-Jul-19 19total output power solutions

20. 30-Jul-19 20total output power solutions

21. NPSH
• Net Positive Suction Head required, NPSHr
• NPSH is one of the most widely used and least understood
terms associated with pumps.
• Understanding the significance of NPSH is very much
essential during installation as well as operation of the
pumps.
• Pumps can pump only liquids, not vapors
• Rise in temperature and fall in pressure induces
vaporization
• NPSH as a measure to prevent liquid vaporization
• Net Positive Suction Head (NPSH) is the total head at the
suction flange of the pump less the vapor pressure
converted to fluid column height of the liquid.
30-Jul-19 21total output power solutions

22. NPSH
30-Jul-19 22total output power solutions

23. LOSS OF NPSH
30-Jul-19 23total output power solutions

24. NPSHr is a function of pump design
• NPSH required is a function of the pump design and is
determined based on actual pump test by the vendor.
• As the liquid passes from the pump suction to the eye of the
impeller, the velocity increases and the pressure decreases.
• There are also pressure losses due to shock and turbulence as
the liquid strikes the impeller.
• The centrifugal force of the impeller vanes further increases
the velocity and decreases the pressure of the liquid.
• The NPSH required is the positive head in Meters absolute
required at the pump suction to overcome these pressure
drops in the pump and maintain the majority of the liquid
above its vapor pressure.
• The NPSH is always positive since it is expressed in terms of
absolute fluid column height.
• The term "Net" refers to the actual pressure head at the
pump suction flange and not the static suction head.30-Jul-19 24total output power solutions

25. NPSHr increases as capacity increases
• The NPSH required varies with speed and capacity within any
particular pump.
• The NPSH required increases as the capacity is increasing
because the velocity of the liquid is increasing, and as anytime
the velocity of a liquid goes up, the pressure or head comes
down.
• Pump manufacturer's curves normally provide this
information.
• The NPSH is independent of the fluid density as are all head
terms.
Note: It is to be noted that the net positive suction head
required (NPSHr) number shown on the pump curves is for
fresh water at 20°C and not for the fluid or combinations of
fluids being pumped.
30-Jul-19 25total output power solutions

26. Available NPSH At Site
Kinetic power mvs
2/2
Frictional loss in suction piping







g
V
hHgpp s
fststaticinletsuction
2
2
,min, 
vapoursuctionavailable ppNSPH  min,
30-Jul-19 26total output power solutions

27. Net Positive Suction Head available, NPSHa
• Net Positive Suction Head Available is a function
of the system in which the pump operates.
• It is the excess pressure of the liquid absolute
over its vapor pressure as it arrives at the pump
suction, to be sure that the pump selected does
not cavitate.
• It is calculated based on system or process
conditions
• A limit on Low Pressure feed water heat
regeneration.
• Performance of Deaerator influences NPSHa.
30-Jul-19 27total output power solutions

28. Deaerator Outlet Conditions
30-Jul-19 28total output power solutions

29. NPSHa in a nutshell
• NPSHa = Pressure head + Static head - Vapor pressure head of
your product – Friction head loss in the piping, valves and
fittings.
• “All terms in mwcl absolute”
• In an existing system, the NPSHa can also be approximated by
a gauge on the pump suction using the formula:
NPSHa = hpS - hvpS  hgS + hvS
– hpS = Barometric pressure in mwcl absolute.
hvpS = Vapor pressure of the liquid at maximum pumping
temperature, in mwcl absolute.
hgS = Gauge reading at the pump suction expressed in
mwcl (plus if above atmospheric, minus if below atmospheric)
corrected to the pump centerline.
hvS = Velocity head in the suction pipe at the gauge
connection, expressed in m.
• NPSHa should always be greater than NPSHr.30-Jul-19 29total output power solutions

30. ADVERSE SCENERIO
• Energy consumption is higher than optimum value due
to reduction in efficiency of pumps.
• Operating point of the pump is away from best
efficiency point (b.e.p.).
• Energy is wasted due to increase in head loss in
pumping system e.g. clogging of strainer, encrustation
in column pipes, encrustation in pumping main.
• Selection of uneconomical diameter of sluice valve,
butterfly valve, reflux valve, column pipe, drop pipe
etc. in pumping installations.
• Energy wastage due to operation of electrical
equipments at low voltage and/or low power factor.
30-Jul-19 30total output power solutions

31. AUDIT & MANAGEMENT OF ENERGY
• i) Conduct thorough and in-depth energy
audit covering analysis and evaluation of all
equipment, operations and system
components which have bearings on energy
consumption, and identifying scope for
reduction in energy cost.
• ii) Implement measures for conservation of
energy.
30-Jul-19 31total output power solutions

32. Boiler Feed Pump Efficiency Audit
• Parameters Required
1. BFP Discharge Pressure in Kg/cm2 = P1
2. Feed Flow in TPH = Q
3. BFP Suction Pressure in Kg/cm2 =P2
4. BFP Motor Supply Voltage = V
5. Motor Current = I
6. BFP Motor PF (Cos O) = 0.86
30-Jul-19 32total output power solutions

33. Sl.No. Particular Unit Value
1 FW flow rate at BFP Discharge t/h Reading 330
2 FW pressure at BFP Discharge kgf/cm2 Reading 152
3
Sat. liq. volume at BFP
Discharge m3/kg From steam chart 0.001668
4 FW pressure at BFP Suction kgf/cm2 Reading 7
5 Sat. liq. volume at BFP Suction m3/kg From steam chart 0.001108
6 Power output of BFP kW
{(2x3)-[(4+1.0)x5]}x100 x
(1/3.6) 2242.83
7 Voltage of BFP kV Reading 6.6
8 Current of BFP Amps Reading 295
9 Power factor of BFP No unit Reading 0.86
10 Power input of BFP motor kW SQRT(3)x7x8x9 2900.18
11 Overall efficiency % (6/10)x100 77.33
12 SEC kWh/t (10/1) 8.79
13 Rated BFP power input kW Obtained from TPS 2900
14 Load factor of BFP % (10/13)x100 100.01
15 Pressure gain in BFP kgf/cm2 (2-4) 145
30-Jul-19 33total output power solutions

34. For CW Pumps (Chiller)
• Measured Data
• Pump flow, Q 0.40 m3/ s
• Power absorbed, P 325 kW
• Suction head h1 +1 M
(Tower basin level)
• Delivery head, h2 55 M
• Height of cooling tower 5 M
• Motor efficiency hm 88 %
• Type of drive Direct coupled
• Density of water  996 kg/ m3
30-Jul-19 34total output power solutions

35. Calculations
• Pump efficiency
• Flow delivered by the pump -Q 0.40 m3/s
• Total head, h2 –(+h1), (55-1)- H 54 M
• Hydraulic power – Q X H X  X 9.81/1000
0.40 x 54 x 996 x 9.81/1000 211 kW
• Actual power consumption 325 kW
• Overall system efficiency (211 x 100) / 325 = 65 %
• Pump efficiency 65/0.88 = 74 %
30-Jul-19 35total output power solutions

36. Energy Conservation in Pump Motors
• Properly size to the load for optimum efficiency.
(High efficiency motors offer of 4 - 5% higher
efficiency than standard motors)
• Use energy-efficient motors where economical.
• Use synchronous motors to improve power factor.
• Check alignment.
• Provide proper ventilation (For every 100 C increase
in motor operating temperature over recommended
peak, the motor life is estimated to be halved)
30-Jul-19 36total output power solutions

37. Energy Conservation in Pump Motors
• Check for under-voltage and over-voltage
conditions.
• Balance the three-phase power supply. (An
imbalanced voltage can reduce 3 - 5% in
motor input power)
• Demand efficiency restoration after motor
rewinding. (If rewinding is not done properly,
the efficiency can be reduced by 5 - 8%).
30-Jul-19 37total output power solutions

38. Energy Conservation in Drives
• Use variable-speed drives for large variable loads.
• Use high-efficiency gear sets.
• Use precision alignment.
• Check belt tension regularly.
• Eliminate variable-pitch pulleys.
• Use flat belts as alternatives to v-belts.
• Use synthetic lubricants for large gearboxes.
• Eliminate eddy current couplings.
• Shut them off when not needed.
30-Jul-19 38total output power solutions

39. Energy conservation in Pumps
• Operate pumping near best efficiency point.
• Modify pumping to minimize throttling.
• Adapt to wide load variation with variable
speed drives or sequenced control of smaller
units.
• Stop running both pumps -- add an auto-start
for an on-line spare or add a booster pump in
the problem area.
• Use booster pumps for small loads requiring
higher pressures.
30-Jul-19 39total output power solutions

40. Energy conservation in Pumps
• Increase fluid temperature differentials to
reduce pumping rates.
• Repair seals and packing to minimize water
waste.
• Balance the system to minimize flows and
reduce pump power requirements.
• Use siphon effect to advantage: don't waste
pumping head with a free-fall (gravity) return.
30-Jul-19 40total output power solutions

41. 30-Jul-19 41total output power solutions