Boiler Feedwater Pumps
GerardBHawkins
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71 slides
Oct 16, 2013
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About This Presentation
0 INTRODUCTION / PURPOSE
1 SCOPE
SECTION ONE - INTEGRATING.THE PUMP INTO THE SYSTEM
2 AVAILABILITY CONSIDERATIONS
3 CHOICE OF NUMBER OF PUMPS
4 CHOICE OF PUMP TYPE
4.1 Barske Type
4.2 Peripheral Type
4.3 Multistage Centrifugal Type
4.4 Inlet Booster Pumps
5 DRIVERS
5.1 Steam...
Slide Content
A,
CPT
CATALYST, PROCESS TECHNOLOGY
CONSULTANCY
Engineering Design Guide:
GEHE MAC-1504
Boiler Feedwater Pumps
CPT
CATALYST, PROCESS TECHNOLOGY
CONSULTANCY
Engineering Design Guide:
GEHE MAC-1504
Boiler Feedwater Pumps
AILABILITY CONSIDERATIONS.
HOICE OF NUMBER OF PUMPS
CHOICE OF PUMP TYPE
Peripheral Type
Multistage Centrifugal Type
Inlet Booster Pumps
DRIVERS
Steam Turbine
Electric
HOICE OF NUMBER OF PUMPS
CHOICE OF PUMP TYPE
Peripheral Type
Multistage Centrifugal Type
Inlet Booster Pumps
DRIVERS
Steam Turbine
Electric
TEMPERATURE GRADIENTS IN CASINGS.
INLET STRAINERS AND CASING PIPING CONNECTIONS
10.4 Strainers
10.2 Casing Piping Arrangements
SEAL COOLING
114 ategory 1 Pumy
SECTION TWO - PUMP CONSTRUCTION FEATURES
MINIMUM FLOW THROUGH PUMP
+ Stage Cavitation Dama
INLET STRAINERS AND CASING PIPING CONNECTIONS
10.4 Strainers
10.2 Casing Piping Arrangements
SEAL COOLING
114 ategory 1 Pumy
SECTION TWO - PUMP CONSTRUCTION FEATURES
MINIMUM FLOW THROUGH PUMP
+ Stage Cavitation Dama
ategory 1 Pumps
ategory 2 Pumps
AXIAL HYDRAULIC THRUST BALANCE METHODS
16.1 Opposed Impeller Configuration
CASING
Casing Type
Casing Connections
MATERIALS
DRIVER CONSIDERATIONS
ategory 2 Pumps
AXIAL HYDRAULIC THRUST BALANCE METHODS
16.1 Opposed Impeller Configuration
CASING
Casing Type
Casing Connections
MATERIALS
DRIVER CONSIDERATIONS
CHNICAL COMPARISON SHEETS
FIGURES
TYPICAL CROSS-SECTION OF PUMP IN CATEGORY 1
TYPICAL CROSS-SECTION OF PUMP IN CATEGORY 2 SHOWING
AXIALLY SPLIT CASING
TYPICAL CROSS-SECTION OF PUMP IN CATEGORY 2 SHOWING
BARREL CASING WITH RING TYPE CARTRIDGE
ECTION OF PUMP IN CATEGORY 3 FOR
C APPLICATIONS WITH DRY RUNNING.
CAPABILITIES
DOCUMENTS REFERRED TO IN THIS ENGINEERING DESIGN GUIDE
FIGURES
TYPICAL CROSS-SECTION OF PUMP IN CATEGORY 1
TYPICAL CROSS-SECTION OF PUMP IN CATEGORY 2 SHOWING
AXIALLY SPLIT CASING
TYPICAL CROSS-SECTION OF PUMP IN CATEGORY 2 SHOWING
BARREL CASING WITH RING TYPE CARTRIDGE
ECTION OF PUMP IN CATEGORY 3 FOR
C APPLICATIONS WITH DRY RUNNING.
CAPABILITIES
DOCUMENTS REFERRED TO IN THIS ENGINEERING DESIGN GUIDE
nin Engineering Design €
GBHE-MAC-5101. Pump relabilty is more dificult o obtain as the pressure of
ystem increases. Current practice isto distinguish three categories of the
Category 3 covers a mod
Design Guide
ategory 2, BFW pumps are normally required to have 100% ava
to avoid boiler ‘dry-out’. Then:
A standby pump on autostart for immediate readiness is required,
As a precaution against failure of the electricity supply
requires a steam turbine driver with the steam supply taken either from the
boiler or from a secure source. See Appendix A.
GBHE-MAC-5101. Pump relabilty is more dificult o obtain as the pressure of
ystem increases. Current practice isto distinguish three categories of the
Category 3 covers a mod
Design Guide
ategory 2, BFW pumps are normally required to have 100% ava
to avoid boiler ‘dry-out’. Then:
A standby pump on autostart for immediate readiness is required,
As a precaution against failure of the electricity supply
requires a steam turbine driver with the steam supply taken either from the
boiler or from a secure source. See Appendix A.
No process interruption upon short-term trip of main pump.
Identical piping arrangement, minimizing design" effort
Arrangement 2
Two running 50% duty pumps with one identical standby pump. This
arrangement may be selected in order to:
(a) Reduce the NPSH requirement to avoid the need for inlet booster pumps
Ensure continuity of BFW supplied for process use. This condition
important when delivery lines are long or heat exchangers are included
whic
Increase overall power efficiency when the steaming rate is expected to
be less than 50% of plant rating for long periods, thus allowing operation
with one pump,
Relax constraints ystem control.
Identical piping arrangement, minimizing design" effort
Arrangement 2
Two running 50% duty pumps with one identical standby pump. This
arrangement may be selected in order to:
(a) Reduce the NPSH requirement to avoid the need for inlet booster pumps
Ensure continuity of BFW supplied for process use. This condition
important when delivery lines are long or heat exchangers are included
whic
Increase overall power efficiency when the steaming rate is expected to
be less than 50% of plant rating for long periods, thus allowing operation
with one pump,
Relax constraints ystem control.
ne main pump capac
4 CHOICE OF PUMP TYPE
41 Barske Type
The high-speed one or two stage Barske type pump requires a high NPSH and
may have an unstable Q-H characteristic. Nevertheless, where the steam
demand varies widely, with campaigns of low flow operation, consider the use of
or more such pumps in parallel so that the number of running pumps can be
Adjusted to meet the BFW demand
Peripheral Type
oheral type pump is well suited to BFW service for small capaci
Q-H characteristic is inherently stable and because BFW
ty pure and free from suspended solids to mal ptable this pumy
sensitvily to erosion. Specify this type of pump in preference to reciprocating
pumps.
4 CHOICE OF PUMP TYPE
41 Barske Type
The high-speed one or two stage Barske type pump requires a high NPSH and
may have an unstable Q-H characteristic. Nevertheless, where the steam
demand varies widely, with campaigns of low flow operation, consider the use of
or more such pumps in parallel so that the number of running pumps can be
Adjusted to meet the BFW demand
Peripheral Type
oheral type pump is well suited to BFW service for small capaci
Q-H characteristic is inherently stable and because BFW
ty pure and free from suspended solids to mal ptable this pumy
sensitvily to erosion. Specify this type of pump in preference to reciprocating
pumps.
34 for stif rotors, capable of dry running.
= 186 for conventional roto
A double-entry first stage is the equivalent of 2 single-entry stages for this
ulation.
Where the number of than the number of stages
required to obtain a re enc onsider a vertical shaft pump.
44 Inlet Booster Pumps
These may be needed when the NPSH available is insutficient to meet the NPS
required by the main pump.
The conventional arrangement has the booster directly coupled to a double
electric motor which also drives the geared main pump.
= 186 for conventional roto
A double-entry first stage is the equivalent of 2 single-entry stages for this
ulation.
Where the number of than the number of stages
required to obtain a re enc onsider a vertical shaft pump.
44 Inlet Booster Pumps
These may be needed when the NPSH available is insutficient to meet the NPS
required by the main pump.
The conventional arrangement has the booster directly coupled to a double
electric motor which also drives the geared main pump.
Ah large non-criical clearances. Consequently the pr
rangement is to have main pumps driven by electric motors or high
nventional turbine
ided with slowrol and quickstart facilities.
tandby turbines of normal construction are held on slowroll to ensure
adiness. For this purpose current practice is to leave the emergency steam
valve open and the inlet autostart valve closed but bypassed by a small
ictor whose oriice adjusted to give the required slowroll
ed. The autostart valve actuator is damped to give a valve stroking time of
nds (for a linear valve characı in order to
ck that the slowrol s
bearings. Small standby turbines having
exemplified by t he Terry turbine, need not slow
A standby pump with steam turbine driver impo: ıdden high demand on the
team supply system upon starting. Such a steam demand can be supplied direct
from the boiler. However, in process plant these turbines are normally supplied
from an intermediate pressure header. Conventional control
th reductions than with increases in steam demand:
preferred driver for the standby pump is an electric motor. Then, current practice
city Arrangement 2 with each main pump having a turbine driver.
rangement is to have main pumps driven by electric motors or high
nventional turbine
ided with slowrol and quickstart facilities.
tandby turbines of normal construction are held on slowroll to ensure
adiness. For this purpose current practice is to leave the emergency steam
valve open and the inlet autostart valve closed but bypassed by a small
ictor whose oriice adjusted to give the required slowroll
ed. The autostart valve actuator is damped to give a valve stroking time of
nds (for a linear valve characı in order to
ck that the slowrol s
bearings. Small standby turbines having
exemplified by t he Terry turbine, need not slow
A standby pump with steam turbine driver impo: ıdden high demand on the
team supply system upon starting. Such a steam demand can be supplied direct
from the boiler. However, in process plant these turbines are normally supplied
from an intermediate pressure header. Conventional control
th reductions than with increases in steam demand:
preferred driver for the standby pump is an electric motor. Then, current practice
city Arrangement 2 with each main pump having a turbine driver.
that remain stationary need special cc
'ould then be provided with an electric motor driven auxiliary oil pump
running to maintain an oil fm over the gear teeth.
Dual Drivers
pump may be coupled to two drivers, each capable of driving the whole set.
‘Such an arrangement gives a cost saving for large pumps when the reliability of
the normal driver is much lower than that of the pump. This
ormal driver is an electric motor connected to an unreliable electric supply
tem and the alternative driver is a steam turbine. Now the failure rate of
ategory 2 pumps is of the order of 0.5/year, consequently this arrangement is
‘ot justifiable for most sites with access to the CEGB grid, when the supply
failure rate is of the order of 0.1/year.
The dual drive arrangement may be used for power recovery
turbine is in continuous operation and the motor can act as an induction
generator exporting surplus energy as electrical power.
'ould then be provided with an electric motor driven auxiliary oil pump
running to maintain an oil fm over the gear teeth.
Dual Drivers
pump may be coupled to two drivers, each capable of driving the whole set.
‘Such an arrangement gives a cost saving for large pumps when the reliability of
the normal driver is much lower than that of the pump. This
ormal driver is an electric motor connected to an unreliable electric supply
tem and the alternative driver is a steam turbine. Now the failure rate of
ategory 2 pumps is of the order of 0.5/year, consequently this arrangement is
‘ot justifiable for most sites with access to the CEGB grid, when the supply
failure rate is of the order of 0.1/year.
The dual drive arrangement may be used for power recovery
turbine is in continuous operation and the motor can act as an induction
generator exporting surplus energy as electrical power.
Category |
culating available -NPSH note that some boilers have only single
lement level control: this demands either a generous NPSH allowance for
ration head or a heavily damped throttle control valve, to cope with
transient boiler upsets.
BFW pumps may require unusually large values of NPSH. As speed or cape
increase, keeping S „constant maintains hydraulic performance but the inte
of local cavitation increases. There is a limiting value of NPSH for a given
material and impeller construction. For typical castings in 13% Cr steels take
culating available -NPSH note that some boilers have only single
lement level control: this demands either a generous NPSH allowance for
ration head or a heavily damped throttle control valve, to cope with
transient boiler upsets.
BFW pumps may require unusually large values of NPSH. As speed or cape
increase, keeping S „constant maintains hydraulic performance but the inte
of local cavitation increases. There is a limiting value of NPSH for a given
material and impeller construction. For typical castings in 13% Cr steels take
2 low io a
0% of the pump minimum flow limit also
increases but no generalized quantitative guidance can be given.
‘Small high-speed Barske pumps require a minimum flow of the order of 60%
BEP flow.
7.2 Minimum Flow Arrangements
Proprietary leak-off val ions of a non-return valve and
a bypass valve are currently limited to Category 1 installations.
Current practice to ensure the minimum flow limit is to employ a simple
ypass through a let-down MULTIPLE restrictor back to the inlet
ass bas been used for process purposes. The
capacity of the pump is then increased to supply both the bypass and the
delivery flows
Largo category 2 pumps may merit a dedicated control system to maintain
minimum flow by opening the bypass valve when the delivery flow falls below the
specified minimum flow. Such a system should be of high integrity.
0% of the pump minimum flow limit also
increases but no generalized quantitative guidance can be given.
‘Small high-speed Barske pumps require a minimum flow of the order of 60%
BEP flow.
7.2 Minimum Flow Arrangements
Proprietary leak-off val ions of a non-return valve and
a bypass valve are currently limited to Category 1 installations.
Current practice to ensure the minimum flow limit is to employ a simple
ypass through a let-down MULTIPLE restrictor back to the inlet
ass bas been used for process purposes. The
capacity of the pump is then increased to supply both the bypass and the
delivery flows
Largo category 2 pumps may merit a dedicated control system to maintain
minimum flow by opening the bypass valve when the delivery flow falls below the
specified minimum flow. Such a system should be of high integrity.
8 TRANSIENT EFFECTS
8.1 _ Reverse Flow upon Trip
Process heat exchangers in the delivery of BFW pumps constitute accumulators
capable of supplying steam which may run the pumps in reverse rotation. Current
practice is to provide a ch pump discharge line and
NOT install reverse rotation locks. For steaming’ exchangers the risk is great
and two non-return valves in series are required at each pump discharge.
82 Flashing
‘Sudden reductions in the speed of turbine driven booster pumy
flashing in the main pump where booster pumps supply BFW through feed
heaters giving water temperatures> 200C at the main pump inlet. The rate of
deliberate speed adjustment should be limited to give a pressure reduction rate
xceeding 3 barimin in the feed heater.
8.1 _ Reverse Flow upon Trip
Process heat exchangers in the delivery of BFW pumps constitute accumulators
capable of supplying steam which may run the pumps in reverse rotation. Current
practice is to provide a ch pump discharge line and
NOT install reverse rotation locks. For steaming’ exchangers the risk is great
and two non-return valves in series are required at each pump discharge.
82 Flashing
‘Sudden reductions in the speed of turbine driven booster pumy
flashing in the main pump where booster pumps supply BFW through feed
heaters giving water temperatures> 200C at the main pump inlet. The rate of
deliberate speed adjustment should be limited to give a pressure reduction rate
xceeding 3 barimin in the feed heater.
Karson tics
hanger
The distribution of water flows through the stationary pump is
indeterminat e natural do led water is
encouraged. Study the detail arrangement of the pump in conjunction with
the manufacturer to identity possible stagnant zones. Extraction of coo!
water from such zones may entall the provision of an ancillary pump for
return to the de-aerator. Select a glandless canned motor pump for this,
duty to avoid problems of air ingress.
Temperature gradients can be prevented by positively isolating the pump
to create a truly stagnant water condition. The pump then has to withstand
‘cold star’ conditions of thermal shock. Both these requirements are
difficult to realize; consequently this scheme should be considered only a
the last resort
hanger
The distribution of water flows through the stationary pump is
indeterminat e natural do led water is
encouraged. Study the detail arrangement of the pump in conjunction with
the manufacturer to identity possible stagnant zones. Extraction of coo!
water from such zones may entall the provision of an ancillary pump for
return to the de-aerator. Select a glandless canned motor pump for this,
duty to avoid problems of air ingress.
Temperature gradients can be prevented by positively isolating the pump
to create a truly stagnant water condition. The pump then has to withstand
‘cold star’ conditions of thermal shock. Both these requirements are
difficult to realize; consequently this scheme should be considered only a
the last resort
Fault rates more be the system, not the pump alone,
nsequently the expected reliability may not be achieved when main and
standby systems share common elements
Pressure drop variations may be excessive; this is particularly true of
balance water lines, which should therefore be generously sized.
NEVER permit bypass lines to be returned to inet lines or their manifold
ing layout arrangements remember that incorrect operation of
counts for a large percen s of damage to BFW pumps.
itis important to avoid accumulation
priming: accordingly the rise in the discharge piping adjacent to the pump should
be continuous and exceed a slope of 1 in 40.
The line connecting the booster pump to the main pump inlet should be provided
nd orifice restrictor directly returning to the supply vessel in
guarantee continuous venting. T! Should not be less than 10% of
the booster pump BEP capacity.
nsequently the expected reliability may not be achieved when main and
standby systems share common elements
Pressure drop variations may be excessive; this is particularly true of
balance water lines, which should therefore be generously sized.
NEVER permit bypass lines to be returned to inet lines or their manifold
ing layout arrangements remember that incorrect operation of
counts for a large percen s of damage to BFW pumps.
itis important to avoid accumulation
priming: accordingly the rise in the discharge piping adjacent to the pump should
be continuous and exceed a slope of 1 in 40.
The line connecting the booster pump to the main pump inlet should be provided
nd orifice restrictor directly returning to the supply vessel in
guarantee continuous venting. T! Should not be less than 10% of
the booster pump BEP capacity.
Dis the sleeve diameter mm
Nis the shaft rotational speed, — 1/s
Heat exchangers should be rated for 300% ofthis flow for each gland and shall
cool the flush water to a temperature not exceeding 650 with cooling water or
ambient air temperature at summer values.
The flush should be BFW. Normally the source is a tapping from the main pump
‘st or 2nd stage discharge. When the source pressure exceeds 25 bar g, a
pressure limiting system should be provided, for example:
— flush tapping
T
to gland +—|
to pump
inlet
Nis the shaft rotational speed, — 1/s
Heat exchangers should be rated for 300% ofthis flow for each gland and shall
cool the flush water to a temperature not exceeding 650 with cooling water or
ambient air temperature at summer values.
The flush should be BFW. Normally the source is a tapping from the main pump
‘st or 2nd stage discharge. When the source pressure exceeds 25 bar g, a
pressure limiting system should be provided, for example:
— flush tapping
T
to gland +—|
to pump
inlet
‘mounted above the seal in order to promote thermosyphon act
pump standstil
The standby BFW pump is normally required to run for a short period after
failure of the cooling water supply. For an orderly nits sufficient
to have an overhead reservoir capable of providing the required flow for
about 10 minutes
‘SECTION TWO PUMP CONSTRUCTION FEATURES
12. MINIMUM FLOW THROUGH PUMP
12.1 Limit Due to First Stage Cavitation Damage
The usable capacity range of a pump narrows as S » increases because flow
recirculation in the larger impeller eye results in increased cavitation damage
potential af flows away from the stage b point
When Sn (NPSH „)"* > 0.8 check manufacturer's offer by comparing available
NPSH against curve of ‘onset cavitation NPSH for the recommended minimum
pump standstil
The standby BFW pump is normally required to run for a short period after
failure of the cooling water supply. For an orderly nits sufficient
to have an overhead reservoir capable of providing the required flow for
about 10 minutes
‘SECTION TWO PUMP CONSTRUCTION FEATURES
12. MINIMUM FLOW THROUGH PUMP
12.1 Limit Due to First Stage Cavitation Damage
The usable capacity range of a pump narrows as S » increases because flow
recirculation in the larger impeller eye results in increased cavitation damage
potential af flows away from the stage b point
When Sn (NPSH „)"* > 0.8 check manufacturer's offer by comparing available
NPSH against curve of ‘onset cavitation NPSH for the recommended minimum
Peripheral and Barske type stages have open impellers which can be fully
machined and which can be used at heads up to 1500 m when manufactured in
timum
ings. Errors occur when using
traditional pattern-making and cs ent classification is
ifforential head h
(a) he 40m
inspecting en
machined and which can be used at heads up to 1500 m when manufactured in
timum
ings. Errors occur when using
traditional pattern-making and cs ent classification is
ifforential head h
(a) he 40m
inspecting en
Impellers should not be balanced by local removal of material from the
disc/shroud surfaces. Such surfaces should run true.
560 m
660 m head need thorough investigation of the design and
techniques. Special impeller materials will be required,
exemplified by 17-4 PH stainless steel
13.2 Labyrinth or Bushing Clearances
‘Small clearances improve the hydraulic efficiency only as measured during the
rks performance test. Such small clearances quickly wear to some equilibrium
the consequent rubbing increases the risks of rotor seizure or induced
disc/shroud surfaces. Such surfaces should run true.
560 m
660 m head need thorough investigation of the design and
techniques. Special impeller materials will be required,
exemplified by 17-4 PH stainless steel
13.2 Labyrinth or Bushing Clearances
‘Small clearances improve the hydraulic efficiency only as measured during the
rks performance test. Such small clearances quickly wear to some equilibrium
the consequent rubbing increases the risks of rotor seizure or induced
Minium
Dianetral
Clearance
-
|
|
but approach the nominal
enterline during operation. Eccentric clearance settings are NOT
e; bearing and casing centerlines should coincide.
Bushing wear-rate can be dramatically increased when the pump is run at
Dianetral
Clearance
-
|
|
but approach the nominal
enterline during operation. Eccentric clearance settings are NOT
e; bearing and casing centerlines should coincide.
Bushing wear-rate can be dramatically increased when the pump is run at
ing engineer s
100% to 140% of the least value found for C.
the diffuser vanes should be followed by hand finishing to produce the rounded
entry profile
Pumps with double volutes should be subject to inspection to verify that both the
radius to the tip and the leading edge profile of each volute cutwater is identical
Then, using the same nomenciature
E >004
R
rs should have an ODD number of vanes to reduce perturbing torques.
100% to 140% of the least value found for C.
the diffuser vanes should be followed by hand finishing to produce the rounded
entry profile
Pumps with double volutes should be subject to inspection to verify that both the
radius to the tip and the leading edge profile of each volute cutwater is identical
Then, using the same nomenciature
E >004
R
rs should have an ODD number of vanes to reduce perturbing torques.
14 ROTOR
14.1. Rotor Dynamics
‘Multistage centrifugal pumps in Categories 1 and 2 normally have operating
speeds above the frst lateral critical speed obtained by assuming the pump run
on air; they rely on the damping provided by the pumped water to suppress
14.1. Rotor Dynamics
‘Multistage centrifugal pumps in Categories 1 and 2 normally have operating
speeds above the frst lateral critical speed obtained by assuming the pump run
on air; they rely on the damping provided by the pumped water to suppress
Frequency is easly measured an
close approximation where:
ight of rotor (excluding coupling spacer) kg
measured deflection of rotor at mi mm
diameter of shaft bushes mm
constant “including g at 9.81 m/s‘) of value
86x 10°
142 Rotor Mechanical Balance
Each rotor element should be individually balanced before assembly on to the
ight of rotor (excluding coupling spacer) kg
measured deflection of rotor at mi mm
diameter of shaft bushes mm
constant “including g at 9.81 m/s‘) of value
86x 10°
142 Rotor Mechanical Balance
Each rotor element should be individually balanced before assembly on to the
I frequencies hi red when running in
margins include the normal variation in speed of induction electric motor
ind an allowance of 0.6" frequency of the moto
Jam turbine governors.
or Assembly
Alignment of the hydraulic channels affects to performance. The centerines of
each impeller exit channel and the diffuser is normally aligned by adjusting the
axial location of individual impellers, However, an over-riding requirement is that
the impeller front shroud surface shall never overlap the surface of the diffuser
channel, despite axial float in the thrust bearing and differential thermal
expansion
margins include the normal variation in speed of induction electric motor
ind an allowance of 0.6" frequency of the moto
Jam turbine governors.
or Assembly
Alignment of the hydraulic channels affects to performance. The centerines of
each impeller exit channel and the diffuser is normally aligned by adjusting the
axial location of individual impellers, However, an over-riding requirement is that
the impeller front shroud surface shall never overlap the surface of the diffuser
channel, despite axial float in the thrust bearing and differential thermal
expansion
the impellers progres:
of impellers.
High speed rotors have the impeller bore machining limits adjusted to retain a
transition ft when rotating at the maximum continuous speed. This requires an
interference fit upon assembl
itis essential that impellers do not swash, Le. when the rotor is assembled and
supported on V-blocks, a dial indicator bearing axially against the machined
impeller shroud surface should show no variation in reading upon rotor rotation.
CATEGORY 2 PUMPS HAVING BARREL CASINGS WITH RING
SECTION CARTRIDGES.
Treat as Category 1 pump with ring section casing but add another criterion for
raightness; viz. that second mode bend should be small, less than 10% of the
first bend, the mean TIR at the 25% and 75% points along the span,
of impellers.
High speed rotors have the impeller bore machining limits adjusted to retain a
transition ft when rotating at the maximum continuous speed. This requires an
interference fit upon assembl
itis essential that impellers do not swash, Le. when the rotor is assembled and
supported on V-blocks, a dial indicator bearing axially against the machined
impeller shroud surface should show no variation in reading upon rotor rotation.
CATEGORY 2 PUMPS HAVING BARREL CASINGS WITH RING
SECTION CARTRIDGES.
Treat as Category 1 pump with ring section casing but add another criterion for
raightness; viz. that second mode bend should be small, less than 10% of the
first bend, the mean TIR at the 25% and 75% points along the span,
152 Soft-Packed Glands
Category 1 pumps normally have soft-packed glands to assist rotor damping and
ability. Check that
(a) Packingis one of the standard metric sizes of 6, 8 5, 15 mm
square section,
Current mí Walkers Fortune 417.
hat sleeves are provided, of 13% chromium steel preferably BS
$ 45 hardened to 240 - 280 VH and ground to a surface finish better than
0.4 MR. Ris essential that the sleeve surface is concentric with the
aft: this should be verified at Ihe time when the rotor is inspected for
straightness.
When the pump inlet ool flush water is
injected through a lantern ring
15.3. Mechanical Seals for Category 1 Pumps
Category 1 pumps normally have soft-packed glands to assist rotor damping and
ability. Check that
(a) Packingis one of the standard metric sizes of 6, 8 5, 15 mm
square section,
Current mí Walkers Fortune 417.
hat sleeves are provided, of 13% chromium steel preferably BS
$ 45 hardened to 240 - 280 VH and ground to a surface finish better than
0.4 MR. Ris essential that the sleeve surface is concentric with the
aft: this should be verified at Ihe time when the rotor is inspected for
straightness.
When the pump inlet ool flush water is
injected through a lantern ring
15.3. Mechanical Seals for Category 1 Pumps
Ethylene Propylene
Carbon with Resin Fill
316 Sratnless 5
For pumps employing a ba
(a) The seal springs are s ct co ion with the pump
balance disc gap brought to zero by jacking the rotor axially
a rotor stop is provided to limit the axial displacement to 1.5 mm,
154 Mechanical Seals for Category 2 Pumps
Specity Borg Warner Mechanical Seal Type D or DRT to material code SH4A
Carbon with Resin Fill
316 Sratnless 5
For pumps employing a ba
(a) The seal springs are s ct co ion with the pump
balance disc gap brought to zero by jacking the rotor axially
a rotor stop is provided to limit the axial displacement to 1.5 mm,
154 Mechanical Seals for Category 2 Pumps
Specity Borg Warner Mechanical Seal Type D or DRT to material code SH4A
Balance Disc
Current practice isto restrict the use of balan y 1 pumps. The
balancing thrust is automatically adjusted by the change of pressure in caviy X
consequent upon axial movement ofthe rotor changing gap “Y.
nding on the
Current practice isto restrict the use of balan y 1 pumps. The
balancing thrust is automatically adjusted by the change of pressure in caviy X
consequent upon axial movement ofthe rotor changing gap “Y.
nding on the
stiffness
indeteralnat
within this + DINAMICO.
zone { STLFPNESS
ow y
Because the action of balancing demands freedom of rotor axial displacement
the first choice of bearing type is either the journal or the cylindrical roller.
16.3. Balance Piston
This is required for Category 2 pumps. A piston does not provide exact balance:
a thrust bearing is required to take the residual thrust. The piston should be
proportioned to ensure that this residual thrust is unidirectional over the normal
indeteralnat
within this + DINAMICO.
zone { STLFPNESS
ow y
Because the action of balancing demands freedom of rotor axial displacement
the first choice of bearing type is either the journal or the cylindrical roller.
16.3. Balance Piston
This is required for Category 2 pumps. A piston does not provide exact balance:
a thrust bearing is required to take the residual thrust. The piston should be
proportioned to ensure that this residual thrust is unidirectional over the normal
a
17.1 Casing Type
CATEGORY1 PUMPS
tion type having one cell per stage, the whole
being held together by through bolis.
Both rotor and casing are assembled progressively cell by cell; consequently
important that all parts are match marked
the fit ofthe impeller on the shaft should be a light driving fit
‘Symmetrical loading by the through bolt is important. This implies that the
extension of each through bolt is measured and brought to the same value.
Torque-spanners are useful only for small pumps where the bolt size is less than
M20. Check that the Manufacturers Manual includes specific instructions on the
sequence and method of tightening the through bolis.
This type of casing is prone to thermal distortion because the through bol
rot in contact with the feedwater and the uniformity of bolt temperature depend
on the quality of the lagging application. Consequently this type should be used
17.1 Casing Type
CATEGORY1 PUMPS
tion type having one cell per stage, the whole
being held together by through bolis.
Both rotor and casing are assembled progressively cell by cell; consequently
important that all parts are match marked
the fit ofthe impeller on the shaft should be a light driving fit
‘Symmetrical loading by the through bolt is important. This implies that the
extension of each through bolt is measured and brought to the same value.
Torque-spanners are useful only for small pumps where the bolt size is less than
M20. Check that the Manufacturers Manual includes specific instructions on the
sequence and method of tightening the through bolis.
This type of casing is prone to thermal distortion because the through bol
rot in contact with the feedwater and the uniformity of bolt temperature depend
on the quality of the lagging application. Consequently this type should be used
fo ing section pump:
ling of each ring to the casing
CATEGORY 2 PUMPS - NOMINAL SYSTEM PRESSURE ABOVE 100 BAR
The barrel type casing is required. The cartridge is usually assembled as a ring
section pump but when the limits for rotor dynamics are approached the cartridge
assembly in an axial spit arrangement should be considered.
17.2 Casing Connections
(@) Configuration
Horizontal-split casings have side connections in order to retain the
advantage of removing the upper half casing without disturbing the inlet or
discharge piping,
For ing section and barrel casings, specify top discharge and top or side
inlet connections,
ling of each ring to the casing
CATEGORY 2 PUMPS - NOMINAL SYSTEM PRESSURE ABOVE 100 BAR
The barrel type casing is required. The cartridge is usually assembled as a ring
section pump but when the limits for rotor dynamics are approached the cartridge
assembly in an axial spit arrangement should be considered.
17.2 Casing Connections
(@) Configuration
Horizontal-split casings have side connections in order to retain the
advantage of removing the upper half casing without disturbing the inlet or
discharge piping,
For ing section and barrel casings, specify top discharge and top or side
inlet connections,
that the pump can be removed without disturbing
pit casings are torsionally very weak when the upper hall-casing has
; consequently the applied moments should be zero when the
ociated piping is cold. Note that this condition occurs not only when all
Pumps are shut down but also when companion pump(s) remain in operation.
18 MATERIALS
CATEGORY2 PUMPS
urrent practice is to use the 13% chromium steels because of their good
thermal and mechanical properties and immunity from corrosion by
demineralized feedwater.
Because the feedwater is de-aerated, castings for horizontal-spit casings may
have the Chromium content reduced to the lower limit of 5%. High quality
complex castings have become progressively more dificult to obtain.
Consequently for horizontal-spit casings, the inspection plan and weld repair
chniques should be a
pit casings are torsionally very weak when the upper hall-casing has
; consequently the applied moments should be zero when the
ociated piping is cold. Note that this condition occurs not only when all
Pumps are shut down but also when companion pump(s) remain in operation.
18 MATERIALS
CATEGORY2 PUMPS
urrent practice is to use the 13% chromium steels because of their good
thermal and mechanical properties and immunity from corrosion by
demineralized feedwater.
Because the feedwater is de-aerated, castings for horizontal-spit casings may
have the Chromium content reduced to the lower limit of 5%. High quality
complex castings have become progressively more dificult to obtain.
Consequently for horizontal-spit casings, the inspection plan and weld repair
chniques should be a
When the rubbing sf a 19 wear rings mi
used.
CATEGORY1 PUMPS
The important feature is that steam systems in Category 1 normally do not
nploy demineralized feedwater and the pump inlet temperature is less than 120
Early practice using bronze impellers and ftings has been discontinued because
of erratic deterioration of bronze components and the high thermal expansion of
this material
Individual cells of ring section pumps may be in grey cast iron to BS 1452 Grade
city the end-sections in carbon steel or nodular cast iron for
ures above 16 bar y.
Impellers and diffuser rings may be in grey cast iron to BS 1452 Grade 14 or 17
provided that H < 40 m, except for the firsts h should be in 13/4 CrNi
steel when S ,>0.28,
used.
CATEGORY1 PUMPS
The important feature is that steam systems in Category 1 normally do not
nploy demineralized feedwater and the pump inlet temperature is less than 120
Early practice using bronze impellers and ftings has been discontinued because
of erratic deterioration of bronze components and the high thermal expansion of
this material
Individual cells of ring section pumps may be in grey cast iron to BS 1452 Grade
city the end-sections in carbon steel or nodular cast iron for
ures above 16 bar y.
Impellers and diffuser rings may be in grey cast iron to BS 1452 Grade 14 or 17
provided that H < 40 m, except for the firsts h should be in 13/4 CrNi
steel when S ,>0.28,
yy Generating Board increased the unit
rating oftheir turbo generators from 500 MW to 660 MW, the
of the boiler feed pumps was completely reviewed.
hat the pumps should be made less
sensitive to mechanical fault and capable of surviving disturbec
suction conditions without failure. At the same time they were to be
‘capable of rapid replacement, This paper explains the decision
that the pumps should have only two or three stages, with stiff
shafts. Gland security and light-load protection are discussed.
Boller feed pump design for maximum availablity, by R Weldon,
BSc., C.Eng., Mi Mech.
Describes Sulzer design for 660 MW stations.
Advanced-class boiler feed pumps for 660 MW generators, by
TO Leith, BSc., C.Eng., MI
J R McColl, BS
ML Ryall, BSc,
rating oftheir turbo generators from 500 MW to 660 MW, the
of the boiler feed pumps was completely reviewed.
hat the pumps should be made less
sensitive to mechanical fault and capable of surviving disturbec
suction conditions without failure. At the same time they were to be
‘capable of rapid replacement, This paper explains the decision
that the pumps should have only two or three stages, with stiff
shafts. Gland security and light-load protection are discussed.
Boller feed pump design for maximum availablity, by R Weldon,
BSc., C.Eng., Mi Mech.
Describes Sulzer design for 660 MW stations.
Advanced-class boiler feed pumps for 660 MW generators, by
TO Leith, BSc., C.Eng., MI
J R McColl, BS
ML Ryall, BSc,
at 1600 including me: ents on through bolt temperature
differences and casing distortion,
The single-stage high-speed nuclear f
lech.Eng, and JE C Valentin
ions of existing
Jute-type pipeline pumps. Reliability was the key
consideration. The final selection was a single-stage solid c
and condensate injection seals. The
manufacturing problems are discussed, together with perlorman
tests run on the first machines
Application of the thermodynamic method of measurement for the
{determination of Ihe boiler feed pump efficiency in large electrical
power units of Electricite de France, by J SA Guitton, Ingenieur
Ecole Centrale, and H Procaccia, Ingenieur EEIP
Dynamic hybrid bearing characteristics of annular controled
is, by HF Black, MSc., C Eng, MI Mech E, and D N
differences and casing distortion,
The single-stage high-speed nuclear f
lech.Eng, and JE C Valentin
ions of existing
Jute-type pipeline pumps. Reliability was the key
consideration. The final selection was a single-stage solid c
and condensate injection seals. The
manufacturing problems are discussed, together with perlorman
tests run on the first machines
Application of the thermodynamic method of measurement for the
{determination of Ihe boiler feed pump efficiency in large electrical
power units of Electricite de France, by J SA Guitton, Ingenieur
Ecole Centrale, and H Procaccia, Ingenieur EEIP
Dynamic hybrid bearing characteristics of annular controled
is, by HF Black, MSc., C Eng, MI Mech E, and D N
Paper 11 Feed pumps for modern steam boiler applications, design,
development, and operation, by P S Neporozhni and A K Ki
Design of Modem Boiler Feed Pumps by HH Anderson
Development of high-pressure boiler feed pumps in Britain during
the last decade by G F Arkless. COny on Steam Plant Anciltary
Equipment Proc Inst Mech Eng 1966/7 181 (PL3N) 6.
Analysis of cavitation damage in commercial marin
Pumps. PE Paashaus ASME - SNAME Meeting New York December
1964.
This paper refers to the "bulging” of impeller shrouds upon "hammering
when operating on free suction control
sepumpen. Hin
development, and operation, by P S Neporozhni and A K Ki
Design of Modem Boiler Feed Pumps by HH Anderson
Development of high-pressure boiler feed pumps in Britain during
the last decade by G F Arkless. COny on Steam Plant Anciltary
Equipment Proc Inst Mech Eng 1966/7 181 (PL3N) 6.
Analysis of cavitation damage in commercial marin
Pumps. PE Paashaus ASME - SNAME Meeting New York December
1964.
This paper refers to the "bulging” of impeller shrouds upon "hammering
when operating on free suction control
sepumpen. Hin
g der zula
selspeisepumpen.
Energie 18 (1966), No l, pp 16/18.
Rahlwes, H : Untersuchung zur Klarung Speispumpen bei
Gleitdruckentgasung. No 108, pp 61/67. von Zulaufstorungen an
Mit VGB (Feb 1967),
Stonner, A : Ein Beitrag zur Schaden
Hochdruckkesselspeisepumpen. Energ
These 4 papers discuss flashing within pump casings and init lines.
aper 7D describes effects of leaking stop valves on standby pumps.
Leakage and Hybrid Bearing Properties of Serrated Seals in
Centritugal Pumps. H F Black & E A Cochrane, Sixth International
Conferennce on Fluid Sealing 1973, 65, pp
W Schumacher
selspeisepumpen.
Energie 18 (1966), No l, pp 16/18.
Rahlwes, H : Untersuchung zur Klarung Speispumpen bei
Gleitdruckentgasung. No 108, pp 61/67. von Zulaufstorungen an
Mit VGB (Feb 1967),
Stonner, A : Ein Beitrag zur Schaden
Hochdruckkesselspeisepumpen. Energ
These 4 papers discuss flashing within pump casings and init lines.
aper 7D describes effects of leaking stop valves on standby pumps.
Leakage and Hybrid Bearing Properties of Serrated Seals in
Centritugal Pumps. H F Black & E A Cochrane, Sixth International
Conferennce on Fluid Sealing 1973, 65, pp
W Schumacher
team turbine driven high-speed main pump, with a 50% capacit
arting/standby pump having electric motor drive, appeared about 1955. A
ation ofthis arrangement used a main pump driven through a hydraulic
upling and gearbox from the turbo alternator set.
2 EXTRACT FROM ANSVASME BPV - Vil, 1977 EDITION
cs F Should be available at the boiler at flow rates
and pressures which are adequate to take care of any emergen:
C5403 A spare feedwater pump or injector, in addition to the feedwater
equipment required by PG-61.1, Section |, is preferable. Where
feedwater pumps are electrically driven and there is no fully
independent auxiliary source of electric supply, there shall be
maintained, ready for team-driven feed pumps or injectors
of sufficient capacity to safeguard stoker-fred boilers in case of
failure of electric power. This recommendation also applies to
bo her methods if furnaces contain large amounts of
refractory or are arranged to accumulate slag in the bottom,
Nor
arting/standby pump having electric motor drive, appeared about 1955. A
ation ofthis arrangement used a main pump driven through a hydraulic
upling and gearbox from the turbo alternator set.
2 EXTRACT FROM ANSVASME BPV - Vil, 1977 EDITION
cs F Should be available at the boiler at flow rates
and pressures which are adequate to take care of any emergen:
C5403 A spare feedwater pump or injector, in addition to the feedwater
equipment required by PG-61.1, Section |, is preferable. Where
feedwater pumps are electrically driven and there is no fully
independent auxiliary source of electric supply, there shall be
maintained, ready for team-driven feed pumps or injectors
of sufficient capacity to safeguard stoker-fred boilers in case of
failure of electric power. This recommendation also applies to
bo her methods if furnaces contain large amounts of
refractory or are arranged to accumulate slag in the bottom,
Nor
a the pumpis |
ready for or in operation.
EXTRACT FROM PG-61 (GENERAL REQUIREMENTS FEEDWATER
SUPPLY)
Except as provided for in PG-61.2 and PG-61.4, boilers having more than
500 sq.ft. (47 m?) of water heating surface shall have at least two means
of feeding water. Except as provided for in PG-61.3, PG-61.4 and PG:
5, each source of feeding shall be capable of supplying water to the
boiler at a pressure of 3% higher than the highest setting of any
valve on the boiler. For boilers that are fired with solid fuel not in
suspension, and for boilers whose setting or heat source can continue to
upply sufficient heat to cause damage to the boiler if the feed
interrupted, one such means of feeding shall be steam operated.
Except as provided for in PG-61, a boller fred by gaseous, liquid o
fuel in suspension may be equipped with a single means of feeding
provided means are furnished for the shutting off of its heat input prior to
the water level reaching the lowest permissible level established by PG-
60.
ready for or in operation.
EXTRACT FROM PG-61 (GENERAL REQUIREMENTS FEEDWATER
SUPPLY)
Except as provided for in PG-61.2 and PG-61.4, boilers having more than
500 sq.ft. (47 m?) of water heating surface shall have at least two means
of feeding water. Except as provided for in PG-61.3, PG-61.4 and PG:
5, each source of feeding shall be capable of supplying water to the
boiler at a pressure of 3% higher than the highest setting of any
valve on the boiler. For boilers that are fired with solid fuel not in
suspension, and for boilers whose setting or heat source can continue to
upply sufficient heat to cause damage to the boiler if the feed
interrupted, one such means of feeding shall be steam operated.
Except as provided for in PG-61, a boller fred by gaseous, liquid o
fuel in suspension may be equipped with a single means of feeding
provided means are furnished for the shutting off of its heat input prior to
the water level reaching the lowest permissible level established by PG-
60.
a
blowdown losses. Ifthe blowdown losses etc. are greater than
continuous output of all oilers fed by the
hen the boilers are not equipped with automatic feedwater
| or the total steam output of the boiler plant does not excet
1.25 times the maximum continuous output ofall boilers fed by a
‘common feedwater system if the boilers are equipped with
tomatic feedwater control and the total steam output of the plants
Ihe maximum continuous output of al boilers fed by the
system where the pumps are driven direct from the prime mover.
The total quantity of feedwater required is the sum of the quanti
required for the maximum continuous output ofall boilers fed by the
n. According to German Standard Specification DIN 2901, the
maximum continuous output is 25% above the normal and ‘boilers
fed by the system’ include not’ only those in regular use but also
stand-by boilers, unless they have been certfied as permanently
out of service. The factor of 1.25 includes a 5% allowance for
blowdown losses. Ifthe blowdown losses etc. are greater than
continuous output of all oilers fed by the
hen the boilers are not equipped with automatic feedwater
| or the total steam output of the boiler plant does not excet
1.25 times the maximum continuous output ofall boilers fed by a
‘common feedwater system if the boilers are equipped with
tomatic feedwater control and the total steam output of the plants
Ihe maximum continuous output of al boilers fed by the
system where the pumps are driven direct from the prime mover.
The total quantity of feedwater required is the sum of the quanti
required for the maximum continuous output ofall boilers fed by the
n. According to German Standard Specification DIN 2901, the
maximum continuous output is 25% above the normal and ‘boilers
fed by the system’ include not’ only those in regular use but also
stand-by boilers, unless they have been certfied as permanently
out of service. The factor of 1.25 includes a 5% allowance for
‘one actual
supply 11 ne to the prime mover is required irrespective of whether the
drive is by steam or electricity.
The feed pumps must be so connected to the source of power (whether purely
tric or dual steam and electric) that, in the event of failure of one of the
urces, the pumps which can still be retained in service are capable of
Feed pumps which ha ich can
be switched to an alternative pc pp are included in those regarded as
/llable for service.
The table gives various arrangements which are permissible with steam and
€ drivers or combinations of both.
S = Steam driven E = Motor driven
Output of the individual pumps in % of the maximum continuous load
supply 11 ne to the prime mover is required irrespective of whether the
drive is by steam or electricity.
The feed pumps must be so connected to the source of power (whether purely
tric or dual steam and electric) that, in the event of failure of one of the
urces, the pumps which can still be retained in service are capable of
Feed pumps which ha ich can
be switched to an alternative pc pp are included in those regarded as
/llable for service.
The table gives various arrangements which are permissible with steam and
€ drivers or combinations of both.
S = Steam driven E = Motor driven
Output of the individual pumps in % of the maximum continuous load
1
| Number of Punps
Joy STEAM OR ONLY ELECTRICAL,
CHANGE-OVER TO DIFFERENT SUPPLY
{Mate plane 1x 125
[Stand-by plane Lx 125
|PARTLY STEAM AND PARTLY ELECTRICAL DRIVE WITH PRO
CHANGE-OVER TO A DIFFERENT SOURCE OP ELECTRICITY
541.7
Mata plant aesi2s | ı
Lx ES 261.7
Stand-by plant 1x 2125 241.7
Malo plant 2x 841.7
| “7
Stand-by plant 1x 841.7
PARTLY STEAM AND PARTLY ELECTRICAL DRIVE WITHOUT PROVISION
FOR CHANGE-OVER TO A DIFFERENT SOURCE OF ELECTRICITY
laca plant 5125 | Lx 5125
1
Stand-by plant
|Main plant
Stand-by plant
| Number of Punps
Joy STEAM OR ONLY ELECTRICAL,
CHANGE-OVER TO DIFFERENT SUPPLY
{Mate plane 1x 125
[Stand-by plane Lx 125
|PARTLY STEAM AND PARTLY ELECTRICAL DRIVE WITH PRO
CHANGE-OVER TO A DIFFERENT SOURCE OP ELECTRICITY
541.7
Mata plant aesi2s | ı
Lx ES 261.7
Stand-by plant 1x 2125 241.7
Malo plant 2x 841.7
| “7
Stand-by plant 1x 841.7
PARTLY STEAM AND PARTLY ELECTRICAL DRIVE WITHOUT PROVISION
FOR CHANGE-OVER TO A DIFFERENT SOURCE OF ELECTRICITY
laca plant 5125 | Lx 5125
1
Stand-by plant
|Main plant
Stand-by plant
B.2 CALCULATION OF RATED DIFFERENTIAL HEAD H
The density of water depends on both pressure and temperatı
Now the temperature rise AT through each stage of a pum
given by
differential head across the stage metre
specific heat of vater 63
percentage hydraulic effictency 1
The density change due to this temperature rise, together with the change
ter, is then used to calculate the differential
The density of water depends on both pressure and temperatı
Now the temperature rise AT through each stage of a pum
given by
differential head across the stage metre
specific heat of vater 63
percentage hydraulic effictency 1
The density change due to this temperature rise, together with the change
ter, is then used to calculate the differential
> oan fi 230
total head across pump
Atscharge pressure bar abe
1nlet pressure bar abs
water density at inlet pressure
and temperature kg/litre
APPENDIX C
DEFINITION OF PUMP CATEGORY
The development of BFW pumps has been matched to ad
steam conditions of power salons Stages in is historcal dev
been distinguished by features
pressure of the steam s)
[rss
Stem pressure bar abs.
Note that the pump casing pressure rating is higher than this nominal pressure.
These categories group together construction elements of current horizontal
multi rfugal pumps whose duties are akin to the duties of former power
st ropriate stage of development.
total head across pump
Atscharge pressure bar abe
1nlet pressure bar abs
water density at inlet pressure
and temperature kg/litre
APPENDIX C
DEFINITION OF PUMP CATEGORY
The development of BFW pumps has been matched to ad
steam conditions of power salons Stages in is historcal dev
been distinguished by features
pressure of the steam s)
[rss
Stem pressure bar abs.
Note that the pump casing pressure rating is higher than this nominal pressure.
These categories group together construction elements of current horizontal
multi rfugal pumps whose duties are akin to the duties of former power
st ropriate stage of development.
Head/lupeller — meti
Ro of stages
Speed rs
Inlet BFH temp.
Jiparoutte axial
ability to run dry
| nes
[rypicel Application
section
600
0 to 150
to 250
ring section,
limited to 7
stages and 60 bar
horizontally split.
Limited to 100 bar
barrel type with
ring section cart
ridge above 80 bar
ethanol Plants
no Company
experience
Ro of stages
Speed rs
Inlet BFH temp.
Jiparoutte axial
ability to run dry
| nes
[rypicel Application
section
600
0 to 150
to 250
ring section,
limited to 7
stages and 60 bar
horizontally split.
Limited to 100 bar
barrel type with
ring section cart
ridge above 80 bar
ethanol Plants
no Company
experience
Nomenclature
H Enthalpy kukg
M MassKg
Q FlowKgisec
Suffixes
cold well
water into deaerator
water out of deaerator
heater
pump inlet
For normal running conditions a heat balance gives:
= Qi, + Qu
H Enthalpy kukg
M MassKg
Q FlowKgisec
Suffixes
cold well
water into deaerator
water out of deaerator
heater
pump inlet
For normal running conditions a heat balance gives:
= Qi, + Qu
inlet line, unstable low can occur with complete failure
to pump forward
If the flow through the pump is maintained, Q is constant
When the steam to the deaerator is tumed off, Q,- 0 at time t
here H is the enthalpy in the deaerator at time t
to pump forward
If the flow through the pump is maintained, Q is constant
When the steam to the deaerator is tumed off, Q,- 0 at time t
here H is the enthalpy in the deaerator at time t
My dh 0 (M
a
dg = HI)
ape
‘Similarly it both steam an:! feed heating are stopped at the same time the
enthalpy in the deaerator becomes:
a
dg = HI)
ape
‘Similarly it both steam an:! feed heating are stopped at the same time the
enthalpy in the deaerator becomes:
On systems with a large transient decay it is necessary to optimize the
head during transient conditions by examining the inlet pipe to the pump
Decreasing the diameter increases the velocity in the pipe and so increases the
ction losses. On the other hand the water volume in the inlet pipe itself is
and as the transient decay is directly proportional to the inventory the
transient loss is reduced.
To optimize a
systems sensitive to transients.
Reference: ‘Analysis of Feedwater Pump Si ure Decay under
Instant Turbine Load Rejection’ - by G S Liao and P Leung
(Journal of Engineering for Power, April 197
head during transient conditions by examining the inlet pipe to the pump
Decreasing the diameter increases the velocity in the pipe and so increases the
ction losses. On the other hand the water volume in the inlet pipe itself is
and as the transient decay is directly proportional to the inventory the
transient loss is reduced.
To optimize a
systems sensitive to transients.
Reference: ‘Analysis of Feedwater Pump Si ure Decay under
Instant Turbine Load Rejection’ - by G S Liao and P Leung
(Journal of Engineering for Power, April 197
c) pump inlet lines
Temperatures and total heat s:
normal deaerator
hot well
water from feed heater
180%
Hy = 760 k3/kg
25%
Hy = 100 k3/kg
160%
Hy = 630 w/kg
loss ofall heating steam, the deaerator pressure will decay as follows
ng Formula 5)
$
2220 - 14608 = 8.830
Temperatures and total heat s:
normal deaerator
hot well
water from feed heater
180%
Hy = 760 k3/kg
25%
Hy = 100 k3/kg
160%
Hy = 630 w/kg
loss ofall heating steam, the deaerator pressure will decay as follows
ng Formula 5)
$
2220 - 14608 = 8.830
otal loss in available NPSH is 9.7 m am oc
seconds after the steam has turned off,
This compares to the value of 10 meters estimated by using Formula 7.
seconds after the steam has turned off,
This compares to the value of 10 meters estimated by using Formula 7.
capacity
(a) de-aerator 1,200 seconds
() feed beater - 7°90 second
(e) pump inlet Unes - 10 second
temperatures and total heats:
(a) mrmal de-serator 133%
Hy = 560
Cb) hot well 25°
= 100
(e) water from feed heater 120%
1 = 500
A fault only affects the steam heat to the deaerator. It does not affect the feed
heat. The enthalpy in the de aerator wil change slowly and the transient head
loss is negligible
APPENDIX E
NOTES ON PROPRIETARY LEAK-OFF VALVES
This type of valve combines the functions of a non-return valve
bypass “Typical arrangements of the Schrosc
are shown in Figures E.| and E.2 respectively.
(a) de-aerator 1,200 seconds
() feed beater - 7°90 second
(e) pump inlet Unes - 10 second
temperatures and total heats:
(a) mrmal de-serator 133%
Hy = 560
Cb) hot well 25°
= 100
(e) water from feed heater 120%
1 = 500
A fault only affects the steam heat to the deaerator. It does not affect the feed
heat. The enthalpy in the de aerator wil change slowly and the transient head
loss is negligible
APPENDIX E
NOTES ON PROPRIETARY LEAK-OFF VALVES
This type of valve combines the functions of a non-return valve
bypass “Typical arrangements of the Schrosc
are shown in Figures E.| and E.2 respectively.
kickback duty.
Current practice is to empl 3 only for Category 1 installations.
For Category 2 installations, adequate ‘demand reliability’
‘current practice is to rmanent bypass or a
modulated bypass valve,
Current practice is to empl 3 only for Category 1 installations.
For Category 2 installations, adequate ‘demand reliability’
‘current practice is to rmanent bypass or a
modulated bypass valve,
laterial Specification
High duty impellers are normally cast in 13/4 Cr Ni steel, typically ASTM A
487 CAG NM.
Dimensional Tolerances and Surface Finish
High duty impellers are normally cast in 13/4 Cr Ni steel, typically ASTM A
487 CAG NM.
Dimensional Tolerances and Surface Finish
Setting-up locations for machining
Swash
The front surface of each intervane passage shall ie within + 0.01 b of th
plane B which passes through the mean position of these surf
perpendicular to the rotation axis.
Concentricity
The datum shall be the circle A through the transition from front shroud to
ne root.
The asymmetrical deviation of the surface from the datum circle shall not
exceed 0.1% of the circle diameter.
Uniformity relations
Swash
The front surface of each intervane passage shall ie within + 0.01 b of th
plane B which passes through the mean position of these surf
perpendicular to the rotation axis.
Concentricity
The datum shall be the circle A through the transition from front shroud to
ne root.
The asymmetrical deviation of the surface from the datum circle shall not
exceed 0.1% of the circle diameter.
Uniformity relations
Notwithstanding that individual toleran tisfied, the
distribution of variations shall be determined by check-balancing the
impeller after preliminary machining. The balance quality shall not be
worse than G.20 grade of BS 5265 before material removal for balancing
Machining allowance and finish
Preliminary machining shall leave all dimensions oversize by 1 to 4 mm
and give a surface finish not worse than 16/ um R in order to obtain
satisfactory balance and dye penetrant tests.
Any final machining shall give a surface finish better than 3.2 um R, on
wetted surfaces.
Quality Control Points
Test sam
distribution of variations shall be determined by check-balancing the
impeller after preliminary machining. The balance quality shall not be
worse than G.20 grade of BS 5265 before material removal for balancing
Machining allowance and finish
Preliminary machining shall leave all dimensions oversize by 1 to 4 mm
and give a surface finish not worse than 16/ um R in order to obtain
satisfactory balance and dye penetrant tests.
Any final machining shall give a surface finish better than 3.2 um R, on
wetted surfaces.
Quality Control Points
Test sam
ANC.6A
PE.IO
ANC.SB
APPENDIX G
AREA RATIO METHOD
Anderson conceived the parameter of the area ratio Y to relate the flow
Conditions at the pump impeller outlet to those at the casing volute throat, where:
flow area at impeller outlet
flow area at volute throat
Worster showed that the Q-H-E performance characteristics of a centrifugal
pump are chiefly determined by Y and not by the impeller blade angle.
PE.IO
ANC.SB
APPENDIX G
AREA RATIO METHOD
Anderson conceived the parameter of the area ratio Y to relate the flow
Conditions at the pump impeller outlet to those at the casing volute throat, where:
flow area at impeller outlet
flow area at volute throat
Worster showed that the Q-H-E performance characteristics of a centrifugal
pump are chiefly determined by Y and not by the impeller blade angle.
The throat area A Is the sum of the two corresponding areas for a double volute
or the sum of the outlet areas between diffuser vanes defined as for the impeller.
Intrinsic assumptions are that:
High efficiency pumps are being sought for clean liquids of low viscosity
so that vane incidence angles and shapes are properly matched to the
npellers have the optimum number of vane
where Bis the vane angle to the tangent, in radians.
Impeller inlet dimensions are not distorted to obtain the exceptionally lo
NPSH capability corresponding to pump operation at suction specific
speed (S,) values above 0.4.
‘Commercial and manufacturing considera It in low specific
or the sum of the outlet areas between diffuser vanes defined as for the impeller.
Intrinsic assumptions are that:
High efficiency pumps are being sought for clean liquids of low viscosity
so that vane incidence angles and shapes are properly matched to the
npellers have the optimum number of vane
where Bis the vane angle to the tangent, in radians.
Impeller inlet dimensions are not distorted to obtain the exceptionally lo
NPSH capability corresponding to pump operation at suction specific
speed (S,) values above 0.4.
‘Commercial and manufacturing considera It in low specific
| centnfugal pump. À
Design by the Area Ratio Method E W Thorne. BPMA Sixth Tech Cont.
Paper C2 1979
Design by the Area Ratio Method E W Thorne. BPMA Sixth Tech Cont.
Paper C2 1979
DIN 50049 Materials Testing (referred to in Appendix F Note 3.5).
BRITISH STANDARDS
s 970 Specification for Wrought Steels for Mechanical
Engineering Purposes (referred to in Clause 15.
Specification for Grey
‘Austenitic Cast Iron (referred to in
ISO Limits and Fits (referred to in Clause 13.2).
Mechanical Balancing of Rotating Bodies (referred to in
Clause 14.2 and Appendix F Note 2.3)
GBHE ENGINEERING SPECIFICATION
GBHE-MAC-18-06A Bearing Arrangements for Machines (referred
to in Clause 14.1).
BRITISH STANDARDS
s 970 Specification for Wrought Steels for Mechanical
Engineering Purposes (referred to in Clause 15.
Specification for Grey
‘Austenitic Cast Iron (referred to in
ISO Limits and Fits (referred to in Clause 13.2).
Mechanical Balancing of Rotating Bodies (referred to in
Clause 14.2 and Appendix F Note 2.3)
GBHE ENGINEERING SPECIFICATION
GBHE-MAC-18-06A Bearing Arrangements for Machines (referred
to in Clause 14.1).
GBH ENTERPRISES, LTD
VULCAN Catalyst Process
Technology Consultancy
Sales and Service
Gerard B. Hawkins
Managing Director, C.E.0.
Skype: GBHEnterprises
VULCAN Catalyst Process
Technology Consultancy
Sales and Service
Gerard B. Hawkins
Managing Director, C.E.0.
Skype: GBHEnterprises
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