-
ROTODYNAMIC PUMPS
-
Rotodynamic Pumps
-
Axial and Mixed flow:Axial and Mixed Flow Pumps are the normal
choice for high-volume, low-pressure pumping duties and
particularly for large-scale primary water supplies, flood control,
irrigation and drainage. Such types are available in a wide range
of sizes and capacities. It is a general characteristic of such
pumps that the power input curve is much flatter than that of a
centrifugal pump, thus input power demand does not vary very much
with the working point. Hydraulic performance, however, differs
appreciably.Rotodynamic Pumps
-
Axial and Mixed flow:Axial flow pumps generate head pressure
through an axial motion developed by a combination of propeller and
internal vane design. The combination induces fluids to travel
strictly along the axial of the pump drive shaft.The mixed flow
pump employs a chamber /impeller /vane design to impart both an
axial and radial motion to fluids traveling downstream. Rotodynamic
PumpsThis powerful motion is created by lifting the fluids with an
impeller, while simultaneously forcing fluids out against the bowl
like impeller chamber.
-
Axial and Mixed flow:The outward movement known as an upper
diffuser section. By combining axial and centrifugal motion, the
mixed flow pump generates greater head pressure to downstream
fluids than is possible with a single motion axial pump.These
differences are noted in the generated comparative H-Q curve.
Rotodynamic Pumps
-
Axial and Mixed flow:Rotodynamic Pumps
-
Axial and Mixed flow:Rotodynamic PumpsIn the case of a mixed
flow pump, the H-Q curve tends to be steep, with the point of
maximum efficiency displaced towards maximum capacity.
-
Axial and Mixed flow:Rotodynamic PumpsThe H-Q curve of an axial
flow pump has substantial falling characteristics although the
actual head obtainable is much lower. Efficiency is higher over a
greater (percentage) range of head than for a centrifugal pump.
-
Axial and Mixed flow:Rotodynamic PumpsGeneral form:Axial and
mixed flow pumps are commonly mounted vertically, directly over a
sump. This is most often the case when the source of water is a
river or reservoir. Fluids enter through a flared suction bell that
has been reinforced by heavy vanes.
-
Axial and Mixed flow:Rotodynamic PumpsGeneral form:The vanes, in
addition to lending support to the suction bell, act to direct the
liquid flow parallel to the drive shaft as it travels upstream.
Once past the suction bell, fluids encounter either an axial
propeller or a mixed flow impeller.
-
Axial and Mixed flow:Rotodynamic PumpsGeneral form:While
differing in design, both are always dynamically balanced,
one-piece castings, mounted on a stainless steel pump shaft.
-
Axial and Mixed flow:Rotodynamic PumpsDriver: The drive shaft
may be encased in a tube or open, with supports properly spaced for
intermediate shaft bearings. Positive drive is provided by a
heavy-duty drive key and thrust collar.A variety of drivers may be
used, however, electric motors and right angle gears are most
common.
-
Axial and Mixed flow:Rotodynamic PumpsDriver: These types of
drivers can be grouped into two categories:1. Hollow shaft drivers
- the pump shaft extends through a tube in the center of the rotor
and is connected to the driver by a clutch assembly at the top of
the driver.
-
Axial and Mixed flow:Rotodynamic PumpsDriver: These types of
drivers can be grouped into two categories:2. Solid shaft drivers -
the rotor shaft is solid and projects below the driver-mounting
base. This type driver requires an adjustable coupling between the
pump and driver.
-
Axial and Mixed flow:Rotodynamic PumpsColumn assembly:The column
assembly is of two basic types, either of which may be used on
close coupled units:
-
Axial and Mixed flow:Rotodynamic PumpsColumn assembly:The column
assembly is of two basic types, either of which may be used on
close coupled units:1. Open line shaft construction utilizes the
liquid being pumped to lubricate the line shaft bearings.
-
Axial and Mixed flow:Rotodynamic PumpsColumn assembly:The column
assembly is of two basic types, either of which may be used on
close coupled units:2. Enclosed line shaft construction has an
enclosing pipe around the line shaft and utilizes oil, grease or
injected liquid to lubricate the line shaft bearings.
-
Axial and Mixed flow:Rotodynamic PumpsColumn assembly:The column
assembly will consist of column pipe, which connects the bowl
assembly to the discharge head and carries the pumped liquid to the
discharge head, the shaft, which connects the bowl assembly to the
discharge head, the head shaft, which connects the line shaft to
the driver.
-
Axial and Mixed flow:Rotodynamic PumpsColumn assembly:Column
pipe may be either threaded or flanged and may contain bearings if
required for the particular unit. Note: Some units will not require
a column assembly, having the bowl assembly connected directly to
the discharge head.Note:
-
Axial and Mixed flow:Rotodynamic PumpsDischarge head
assembly:The column assembly is of two basic types, either of which
may be used on close coupled units:
-
Axial and Mixed flow:Rotodynamic PumpsThe discharge head
supports the driver and bowl assembly as well as supplying a
discharge connection (the underground discharge connection will be
located on one of the column pipe sections below the motor stand).
Discharge head assembly:
-
Axial and Mixed flow:Rotodynamic PumpsA shaft sealing
arrangement is located in the discharge head to seal the shaft
where it leaves the liquid chamber. The shaft seal will usually be
either a packing box or mechanical seal assembly.Discharge head
assembly:
-
Axial and Mixed flow:Rotodynamic PumpsBowl assemblies:The bowl
assembly consists of impellers rigidly mounted on the bowl shaft,
which rotate and impart energy to the fluid. The bowls (or
diffusers) contain the fluid at increased pressure and direct it
vertically to the next stage and eventually to the column pipe.
-
Axial and Mixed flow:Rotodynamic PumpsBowl assemblies:The
suction bell or case directs the fluid into the first stage
impeller. Bearings are located in the suction bell, discharge case,
and between each impeller.Impeller
-
Axial and Mixed flow:Rotodynamic PumpsBowl assemblies:The
rotating element is mounted in an individual housing, which is
usually replaceable and situated just above the section bell, close
to the pump inlet. The housing may be bronze, stainless steel or
any other material similar to the impeller.Why ?Impeller
-
Axial and Mixed flow:Rotodynamic PumpsBowl assemblies:The same
resistance to shock.The same thermal extension.Why ?To keep a
clearance between impeller and casing as designed (performance of
the pump).Impeller
-
Axial and Mixed flow:Rotodynamic PumpsBowl assemblies:After
emerging from the housing, fluids travel past an upper diffuser
chamber and out through the guide case. The guide case, consisting
of a column pipe and discharge elbow is of welded steel plate or
cast iron.
-
Axial and Mixed flow:Rotodynamic PumpsBowl assemblies:Sections
are flanged or bolted together. A registered fit is used to
maintain proper alignment on all mated parts.
-
Axial and Mixed flow:Rotodynamic PumpsPullout options, which
make for easier maintenance and inspection, are a common feature of
these pumps, the best designs permit removal of the entire bowl
assembly (including all rotating parts, diffuser, impeller housing
and suction bell) through the outer shell, without disturbing
either the discharge or floor plate connections.Pullout
options:
-
Channel impeller pumps:Rotodynamic PumpsA channel impeller pump
employs an impeller with turbine-type blades mounted on the
periphery running in an annular channel (or channels) surrounding
the periphery of the wheel.In practice, only two main subtypes
emerge, known generally as the peripheral pump and side channel
pump respectively.
-
Rotodynamic PumpsThe main difference is in the form and
positioning of the channels:Channel impeller pumps:The peripheral
pump has a double-sided channel in which the liquid circulates,
this channel being located partly in the cylindrical part of the
casing and partly in the side plates. The side-channel pump has two
channels cut in the side plates only, adjacent to each side of the
impeller blades.
-
Rotodynamic PumpsCharacteristics are quite different, eg the
side-channel pump is self-priming and can develop a much higher
head, although its efficiency is lower. Hence, the two are distinct
types.Channel impeller pumps:The peripheral pump is also known as a
regenerative pump.
-
Rotodynamic PumpsH-QEfficiencyBHPHEAD,BHP &
Efficiency100%Peripheral CapacityChannel impeller pumps:
-
Rotodynamic PumpsH-QEfficiencyBHPHEAD,BHP &
Efficiency100%Side-channel CapacityChannel impeller pumps:
-
Rotodynamic PumpsH-QEfficiencyBHPHEAD,BHP &
Efficiency100%Side-channel CapacityH-QEfficiencyBHPHEAD,BHP &
Efficiency100%Peripheral CapacityChannel impeller pumps:
-
Rotodynamic PumpsCentrifugalRegenerativeAxial flowAxial
flowCapacityHEADRegenerative pumps have a substantially straight
and sleep H-Q curve. Pressure developed tends to rise sharply with
decreasing capacity making this type unsuitable for discharge
regulation by throttling. Power output falls with increasing
capacity. Channel impeller pumps:
-
Rotodynamic Pumps
-
Turbine pumps (Regenerative):Rotodynamic PumpsTurbine pumps
obtain their name from the many vanes machined into the periphery
of the rotating impeller. Heads over 900 feet are readily developed
in a two-stage pump.
-
Turbine pumps (Regenerative):Rotodynamic PumpsThe impeller,
which has very tight axial clearance and uses pump channel rings,
displays minimal recirculation losses. The channel rings provide a
circular channel around the blades of the impeller from the inlet
to the outlet.
-
Turbine pumps (Regenerative):Rotodynamic PumpsLiquid entering
the channel from the inlet is picked up immediately by the vanes on
both sides of the impeller and pumped through the channel by the
shearing action. The process is repeated over and over with each
pass imparting more energy until the liquid is discharged .
Centrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal PumpCentrifugal
PumpCentrifugal PumpCentrifugal PumpCentrifugal Pump
