Dynamic pumps Flashcards
What are the 2 basic types of pump classifications?
- dynamic
- positive displacement
What type of pump moves fluids by using centrifugal force to spin it outwards over an impeller giving it velocity as the casing guides the fluid out of the pump?
dynamic pump
_______________ pumps are typically used to pump a high volume of fluid at relatively low discharge pressure.
dynamic pumps
As it concerns a dynamic pump, what is slip?
when the centrifugal force created by the impeller is the same as the resistance in the discharge pipe, and the impeller spins in the fluid
What are the 4 categories of dynamic pumps?
- radial flow
- axial flow
- mixed flow
- peripheral pumps
______________ pumps move fluids by trapping a fixed volume of the liquid in a pumping chamber and forcing it into a discharge pipe.
positive displacement pumps
Which type of pump can experience slip: positive displacement or dynamic?
dynamic
Which type of pump produces a fixed flow rate: positive displacement or dynamic?
positive displacement
Which type of pump has a constant flow rate regardless of pressure changes?
A. positive displacement pump
B. dynamic pump
A. positive displacement pump
Which type of pump has a varying flow rate depending on pressure or head?
A. positive displacement pump
B. dynamic pump
B. dynamic pump
Which type of pump will see a flow rate increase if the viscosity of the pumping medium increases?
A. positive displacement pump
B. dynamic pump
A. positive displacement pump
- this happens because the internal clearances are better filled
Which type of pump will see a flow rate drop as viscosity increases?
A. positive displacement pump
B. dynamic pump
B. dynamic pump
Which type of pump has a pulsating delivery?
A. positive displacement pump
B. dynamic pump
A. positive displacement pump
Which type of pump is able to produce very high pressures?
A. positive displacement pump
B. dynamic pump
A. positive displacement pump
Which type of pump would have a smooth continuous delivery?
A. positive displacement pump
B. dynamic pump
B. dynamic pump
Which type of pump is capable of creating lift or suction without a prime?
A. positive displacement pump
B. dynamic pump
A. positive displacement pump
Which type of pump needs to be primed to create a suction lift?
A. positive displacement pump
B. dynamic pump
B. dynamic pump
Which type of pump needs to operate above a minimum speed to create flow?
A. positive displacement pump
B. dynamic pump
B. dynamic pump
Which type of pump does not need a relief valve on the discharge side?
A. positive displacement pump
B. dynamic pump
A. dynamic displacement
_____________ is the mass or weight of a substance per unit of volume.
density
____________ ___________ (2 words) is the ratio of the density of a substance to that of water.
specific gravity
A substance that is lighter than water would have a specific gravity that is ___________ (less/more) than 1.
less
A substance that is heavier than water would have a specific gravity that is ___________ (less/more) than 1.
more
_______________ is a measure of intensity of effort described as force per unit of area.
pressure
1 PSI = _________ kPa
1 PSI = 6.9 kPa
True or false:
pressure = force ÷ area
true
When it comes to pump pressures, what is a gauge reading?
pressure readings that do not include atmospheric pressure
- a pressure reading that uses atmosphere pressure as a reference point
- if a gauge pressure read 20 PSI, it would be written as 20 PSIG
When it comes to pump pressures, what is absolute readings?
gauge pressure + atmospheric pressure
- a pressure reading that uses 0 pressure as a reference point
What is atmospheric pressure?
the weight of the earths atmosphere
What is the atmospheric pressure at sea level?
14.7 psi
In relation to pump pressures, what is PSIG?
gauge pressure
In relation to pump pressures, what is PSIA?
absolute pressure
In what unit of measurement is vacuum pressure frequently expressed?
inches of mercury Hg
___________ ______________ (2 words) is the height in feet of a column of water that is one square foot at the base.
head pressure
One foot head of water has a head pressure of ________ PSI.
0.433 PSI
True or false:
Pressure can be expressed either as force per unit area (PSI) or head pressure (ft).
true
What formula is used to calculate PSI when the height of the column of liquid and the specific gravity are known?
PSI = ft x 0.433 x S.G.
PSI = head pressure
ft = height of the column of liquid, in feet
0.433 = the pressure exerted by 1 foot of water
S.G. = specific gravity of the liquid
What formula is used to calculate the height of a column of liquid in feet when head pressure and specific gravity is known?
ft = PSI ÷ (0.433 x S.G.)
ft = height of the column of liquid, in feet
PSI = head pressure
0.433 = pressure exerted by 1 foot of water
S.G. = specific gravity of the liquid
What is the differential pressure of a pump?
the difference between the discharge pressure and the suction pressure of a pump
What formula is used to calculate the power consumption of a pump that has a specific gravity other than 1?
multiply the HP requirements of the pump by the specific gravity
What is the vapour pressure of a liquid?
the pressure at which a liquid turns into a vapour.
What are 2 other terms used to describe vapour pressure?
- boiling point
- flashpoint
True or false:
When speaking about pumps, the vapour pressure and the boiling point of a liquid are considered the same thing.
true
True or false:
A liquid and its vapour can coexist in equilibrium at vapour pressure.
true
What happens to the boiling point of a liquid as the pressure on the liquid increases?
pressure ↑ = boiling point ↑
What happens to vapour pressure of a liquid as temperature rises?
temp ↑ = vapour pressure ↑
True or false:
Atmospheric pressure causes liquid to flow into the pump suction.
true
True or false:
A temperature increase in the liquid or too little pressure at the pump suction can cause the liquid to begin to vaporize.
true
If enough vapour is formed at the suction of a pump, it could completely stop the liquid flow into the pump, and the pump would become:
vapour bound
In a pump, when the pressure of a liquid is reduced to below its vapour pressure, small bubbles appear that move to regions of higher pressure and collapse or implode. What is this called?
cavitation
What effect does cavitation have on a pump components?
it can cause fatigue failure on the surface of the effected parts
What condition can occur in a pump when there is leakage on the suction, drawing air into the pump?
aeration
What are 2 possible problems that can be caused by pump aeration?
- erratic delivery of medium
- loss of prime
This type of pump flow occurs when the particles of the liquid no longer move parallel with the axis of the pipe?
turbulent (non-linear) flow
What 4 things cause turbulent flow?
- bends
- abrupt changes in cross-section
- fittings on the pipe
- velocity that is too high
What does Bernoulli’s Principle state?
that in the absence of friction, when an incompressible liquid moves from one place to another at constant flow rate, the total energy remains constant but the components of energy may change
What is the total head of a closed system?
the total energy
What 2 components makes up the total head of a system?
- head pressure (pressure acting on the liquid)
- velocity head (speed of the liquid)
What effect does the velocity head of the liquid have on head pressure in a closed system?
velocity head ↑ = head pressure ↓
- these changes usually happen due to changes in pipe ∅ or from other restrictions, such as elbows
When it comes to pump systems, what is velocity head?
the speed of liquid through a pipe, expressed as the equivalent height the liquid would have to fall to reach the same speed
What formula is used to calculate velocity head of a pump system?
velocity head (ft) = v² ÷ 2g
v² = the velocity measure in feet per second (fps)
g = the acceleration due to gravity (32.2ft/sec/sec)
As a liquid flows through pipe, some kinetic energy coverts to heat and sound energy. This is called:
friction head
- also known as friction losses
Frictional losses in a pump system are effected by what 3 factors?
- size, type, and condition of the piping
- flow velocity
- viscosity and density of the fluid
___________ ___________ is when the supply liquid is above the centreline of the pump.
suction head
What is the static suction head of a pump system?
the vertical distance from the centre of the suction eye of the pump to the surface of the supply.
When it comes to pump systems, what is a positive suction head?
a situation where the weight of the liquid and the atmospheric pressure are available to push the fluid into the pump, resulting in a pump that is always primed
When it comes to pump systems, what is total suction head?
the static suction head on the pump section line above the pump centreline minus all the friction losses
When it comes to a pump, what is a suction lift arrangement?
where the supply reservoir is located below the pump
When it comes to pump systems, what is the static suction lift?
is the vertical distance from the centre of the suction eye of the pump to the surface of the supply
When it comes to pumps, what is dynamic suction head?
the same as total suction head
Most pump manufacturers rate their max static suction lift at _______ ft.
15 ft
True or false:
Total suction lift, also known as dynamic suction lift, is the static suction lift plus all the frictional losses in the suction pipes.
true
What is the static discharge head of a pump system?
the vertical distance from the centre of the suction eye to the surface of the liquid discharge tank
What is total discharge head of a pump system?
the head measured at the discharge nozzle
What is total discharge head also known as?
dynamic discharge head
True or false:
The total discharge head of a pump system is made up of the static discharge head plus the velocity head plus all of the frictional losses in the discharge piping.
true
What is the total static head of a pump system?
the vertical distance from the top of the liquid supply level to the top of the liquid discharge level
With a pump system that has a suction head, how is the total static head calculated?
static discharge head minus static suction head
With a pump system that has a suction lift, how is the total static head calculated?
static discharge head plus static suction lift
Total suction lift is also known as:
dynamic suction lift
What is the total head of a pump system?
the measure of the work the pump does to raise the liquid from the level in the suction tank to the level in the discharge tank for a given flow
What is total head of a pump system also known as?
total dynamic head
True or false:
You must know the total head to choose pump for a particular application.
true
True or false:
Total head is the term most used in industry to describe a pumps head.
true
In what 2 ways can total head of a pump system be expressed?
- total discharge head minus total suction head
- total discharge head plus the total suction lift
What is NPSHa stand for?
net positive suction head available
- sometimes it may be identified as NPSH, but it means the same thing
What is NPSHa of a pump system?
a measure of the head or pressure energy available in the fluid
- the suction head in feet absolute above the vapour pressure of the fluid at the pump section
What formula is used to calculate NPSHa?
NPSHa = PS + PA - VP
PS = suction pressure (gauge pressure)
PA = atmospheric pressure (altitude dependent)
VP = vapour pressure (temperature dependent)
In a pump system, the measure of the head or pressure energy available in the fluid is the:
NPSHa
In a pump system, the amount of head used to overcome friction and increase the velocity of the fluid as it flows from the suction flange through the eye of the impeller and onto the vanes is known as:
the NPSHr
What does NPSHr stand for?
net positive suction head required
The ___________ is a pressure drop of the fluid as it flows into the impeller.
NPSHr
True or false:
The suction pressure drop of a pump increases as the flow of the pump gets larger.
true
True or false:
The suction pressure minus the NPSHr is the lowest pressure in the pump.
true
What happens in a pump if the NPSHr is less than the vapour pressure of the fluid?
cavitation
The NPSHa should be at least _____% greater than the NPSHr.
10%
What happens if the NPSHa is less than 10% greater than the NPSHr?
cavitation
This type of pump has no seal between the suction and discharge sides of the pump.
dynamic pump
Kinetic pumps are the same as:
dynamic pumps
What are the 3 main components of a dynamic pump?
- shaft
- impeller(s)
- casing
The _____________ of a dynamic pump imparts velocity energy into the liquid.
impeller
What are the 2 main influences on the GPM of a dynamic pump?
- impeller eye diameter
- driver RPM
What are the 4 main categories of kinetic pump?
- radial flow centrifugal
- axial flow
- mixed flow
- peripheral
With a radial flow centrifugal pump, what 3 things make up the stationary element of the pump?
- casing
- stuffing box
- bearings
With a radial flow centrifugal pump, what 2 things make up the rotating elements?
- impeller
- shaft
When a centrifugal pump rotates, liquid is drawn into the eye of the impeller. What 2 things can cause this to happen?
- the force created by the weight of the liquid (suction head)
- the pressure differential caused by a partial vacuum created by the movement of the impeller (suction lift)
What does the collector (casing that surrounds the impeller) on a radial flow centrifugal pump do?
slows the liquid to a usable velocity, which allows the energy to be converted from kinetic energy to velocity or pressure energy
What does the impeller do in a radial flow centrifugal pump?
flings the liquid outwards, imparting kinetic energy into the liquid
What are the 2 basic forms of a collector on a radial flow centrifugal pump?
- volute
- diffuser type
With this type of dynamic pump, there is no axial component to the discharge from the impeller, and the liquid exits perpendicular to the pump.
radial flow centrifugal pump
A radial flow pump is used where a reasonable __________ (high/low) discharge head is required.
high
This type of dynamic pump has no radial component to the discharge of the impeller, rather the fluid flows parallel to the shaft, resulting in no change to the pumps flow.
axial flow pumps
This type of dynamic pump can be mounted both vertically and horizontally, but should be mounted below the surface of the liquid due to it not having much suction power.
axial flow pump
An axial flow dynamic pump has relatively 1.__________ discharge head and produce a 2.__________ flow volume.
- low
- high
With what type of dynamic pump are volute casing not practical, and instead diffuser vanes are used behind the impeller?
axial flow pump
This type of dynamic pump develops its discharge by using centrifugal force and the lifting action of the vanes on the liquid.
mixed flow pumps
A mixed flow pump is usually mounted vertically and produces 1._______________ discharge heads and 2.__________ flows.
- moderate
- high
True or false:
A common mixed flow pump is the vertical turbine pump.
true
True or false:
Mixed flow pumps are found only with volute casings.
false;
they can have either a volute or diffuser casings
Which type of dynamic pump uses a concentric casing?
peripheral pumps
What are the 2 types of peripheral pumps?
- high speed pumps
- regenerative turbine pumps (sometimes called peripheral pumps)
Where does the pumping action take place in a peripheral pump?
at the periphery of the pump casing
These types of dynamic pumps operate at extremely high speeds and has the pumping fluid make several rotations within the housing before leaving the housing through a diffuser nozzle.
high speed pumps
High speed dynamic pumps have 1.________ flow and 2.__________ head applications.
- low
- high (up to 12,000ft)
What is the main disadvantage of high speed dynamic pumps?
they require very high NPSHa to prevent the liquid from flashing into vapour
Which types of dynamic pumps have impellers with straight profile vanes?
high speed pumps
The regenerative turbine dynamic pump is used where relatively 1.__________ heads and 2.________ flow rates are required.
- high
- low
In general, regenerative turbine dynamic pumps are limited to heads of 1._______ ft and flow rates of 2._______ GPM.
- 600 ft
- 100 GPM
This type of dynamic pump impeller is generally a solid disc with a double row of straight cut or impulse type buckets cut around its periphery housed in a bulbous casing with close axial clearances.
regenerative turbine pumps
True or false:
Specific gravity is a ratio of the density of a substance to that of water.
true
True or false:
Pumps use more power for heavier fluids.
true
True or false:
Staging is a common way to increase the pressure of a pump.
true
True or false:
Suction head is when the supply level is above the center-line of the pump eye.
true
True or false:
Suction lift is when the supply is below the center-line of the pump eye.
true
True or false:
Total static head is the vertical distance between the surfaces of the supply level to the discharge level.
true
Which type of pump uses a stripper, and is good for low flow and high head applications?
regenerative turbine pump
Identify the following pump from the description of its pumping action:
Liquid enters the pump casing and flows to both sides of the impeller, where it is picked up in the spaces between the impeller vanes and then ejected into the annular chamber of the pump casing, changing from kinetic energy into pressure energy.
regenerative turbine pump
In a regenerative turbine pump, the centrifugal swirling motion of the liquid in the annular casing can happen _______ to ________ times during one revolution depending on the head developed by the pump.
2 to 50 times
True or false:
With a regenerative turbine pump, the less times that the liquid re-enters and is discharged from the impeller, the higher the head is.
false;
the more times it re-enters and is discharged by the impeller, the higher the head is
With a regenerative turbine pump, what is a stripper?
a barrier on the casing that separates the suction and discharge sides of the pump
What needs to happen for a regenerative pump impeller to be able to handle all fluid present, including any entrained air or vapour?
there must be sufficient liquid to seal the clearance between the impeller and the stripper
Regenerative turbine pumps have _________ (high/low) NPSH requirements.
low
What type of pump represents about 75% of all centrifugal pumps?
single stage end suction pumps
In this type of single stage end suction pump arrangement, the combined suction and volute casing remains attached the piping, while the pump assembly can be unbolted from the volute and removed for repair.
back pullout or vertical or radial split design
What is the major disadvantage of single stage end suction pumps with a radial split design?
they require realignment each time the pump is re-installed
True or false:
The impeller in a single stage end suction pump may have balance holes and pump out vanes to counteract axial thrust and leakage.
true
Why is a foot mount pump (bolted to a baseplate) undesirable for high temperature liquids?
the thermal expansion of the pump could cause the shaft to rise and upset alignment
What type of pump mounting is preferred when dealing with high temperature pumping mediums?
centreline or pedestal mounting
What is the advantage to mounting a single stage end suction pump vertically?
saves on floor space
What are 2 common vertical single stage end suction pump orientations?
- in-line mounting
- base elbow mounting
What is the main disadvantage to mounting a single stage end suction pump vertically?
the additional cost incurred due to the increased thrust loads
What is a vertical column pit pump?
a vertical pump that is submerged in the liquid they are pumping
With what type of substance would a cantilever shaft vertical column pump be used?
abrasive services
What is the main advantage of a vertical column pit pump?
the pump can be installed at a lower level, increase the NPSHa
This type of pump has the impeller directly attached to the motor shaft and is encases in a waterproof casing.
submersible pump
- With single stage double suction pumps, where are the flanged suction and discharge nozzles located?
- Why is this?
- in the bottom half of the housing
- to allow for the top half to be easily removed for inspection and maintenance
With a single stage double suction pump, how are axial forces in the pump controlled?
mostly due to the opposing forces of the impeller
- that being said, this is rarely totally eliminated, and bearing should have some capacity to resist axial loads
In multi-stage horizontal pumps, several impellers are mounted in series, each surrounded by its own volute and diffuser. What is this called.
a stage
In a multi-stage pump, how is each stage connected to the next?
the discharge from one stage is connected to the next, increasing the pressure
A multi-stage horizontal pump can create heads up to 1.__________ ft. and flows up to 2.__________ GPM.
- 5000 ft.
- 2500 GPM
In a single casing axial split horizontal pump, what are galleries or crossover piping used for?
to mitigate axial thrust by directing the liquid to opposite sides of successive impellers
- Why must the adjacent stages of a multi-stage pump be isolated from each other?
- What is used to prevent the above?
- they will be at different pressures, so if not properly isolated leakage will occur from the higher pressure stage to the lower pressure stage
- with a diaphragm or (inter)stage piece
A _______________ casing is a casing with a series of vanes surrounding the impeller which accepts the discharge of liquid from the impeller.
diffuser
Single casing radial split pumps overcome what limitation of single casing axial split horizontal pumps by the nature of their design?
external and internal inter-stage leaks due to high pressures
What are the 2 main limitations of single casing radial split pumps when compared to a single casing axial split horizontal pump?
- high axial thrust = casings face in the same direction (can be balanced out with a balancing drum)
- more difficult an time consuming overhaul
- What disadvantage of single casing pumps does a multi-stage barrel pump overcome?
- How is this achieved?
- potential leaks to atmosphere
- by installing a multi-stage pump inside a one-piece outer casing that has radial split ends (or a barrel)
A multi-stage barrel pump is also called a double casing pump or an ultra-high pressure multi-stage pump, can create pressures up to 1.__________ PSI and capacities up to 2.__________ GPM.
- 6500 PSI
- 20,000 GPM
What type of pump would be used to deliver water into a pressurized system?
a double casing pump
This type of suction pump can be mounted horizontally with a radially split end suction volute casing or vertically with a radial split bottom suction volute casting, and is used for moderate heads and flows.
single stage mixed flow pumps
This type of pump is frequently called a propeller pump.
singe stage axial flow pumps
A single stage axial flow pump handles 1.________ volumes at 2.________ heads.
- large volumes
- low heads
The most common applications for this type of pump is handling sewage, removing water from rivers or lakes for industrial uses, and any applications that require large masses of liquids to be moved.
single stage axial flow pumps
As it pertains to vertical single stage radial flow pumps, what is a pullout design?
a design that allows the impeller, diffuser, and shaft to be removed from the top without disturbing the column piping
True or false:
Propeller pumps with axial vanes and modified propeller pumps with mixed flow vanes, for higher heads, are intended for a maximum of 2 or 3 stages.
true
This type of pump was originally developed for pumping water from wells.
vertical turbine pump
The diffusers in vertical turbine pumps have multiple vanes which have what 3 functions?
- convert velocity energy to pressure energy
- direct fluid into the next impeller
- balance the shaft and impellers from radial thrust loads
With vertical turbine pumps, what holds the impellers in place on the shaft?
split tapered bushings called collets
What are 3 advantages of enclosed impellers on pumps?
- greatest efficiency
- highest capacity
- replacing the wear rings can restore excessive clearances back to normal
What are the 2 types of pump data sheets?
- specification sheets
- pump performance and configuration data
This type of pump data sheet provides important information regarding the installation, function, and maintenance of the pump.
specification data sheet
Why are pump performance curves provided in feet of head?
because specific gravity does not affect the head of the pump since head is created by the conversion of kinetic energy into pressure energy
What effect does it have on the flow and head of a pump when pumping a fluid with a viscosity higher than water?
viscosity ↑ = flow ↓ and head ↓
What is the efficiency of a pump?
hydraulic output : input horsepower
What is the BEP of a pump curve?
BEP = best efficiency point
this is the point where the flow rate and total head developed coincide with maximum efficiency
What is the system curve of a pump?
the total operating head for a given capacity found by adding an estimation of friction losses to the vertical distance from the supply tank to the discharge thank
What 3 things are the frictional losses of a pump system dependent upon?
- length, diameter, type, and age of the pipe
- number and type of fittings
- type of fluid flowing through it
What is a drooping of the pump curve?
a reduction in both head and flow of the pumps curve due to wear
When operated at a constant speed, what effect does the diameter of the impeller have on the capacity of a pump?
capacity varies directly with impeller diameter
When operated at a constant speed, what effect does the diameter of the impeller have on the head of a pump?
head varies with the square of the diameter
When operating at a constant speed, what effect does the diameter of the impeller have on the BHP of a pump?
BHP varies with the cube of the diameter
What effect does changing the speed of a pump have on the capacity of the pump?
capacity varies directly with the speed
What effect does changing the speed of a pump have on the head of the pump?
head varies with the square of the speed
What effect does changing the speed of the pump have on the BHP of the pump?
BHP varies with the cube of the speed
How can the BHP requirements of a pump that is pumping a liquid with a specific gravity other than 1 be determined?
BHP x S.G
This will give you the new HP requirements
With a vertical single stage end suction pump, if both the pump and the driver have separate shafts, each with their own radial and thrust bearings, what type of coupling would be used to join them?
a flexible coupling
With a vertical single stage end suction pump, if the pump rotor is supported by the drivers bearings, what type of coupling would be used?
a rigid coupling
True or false:
A close-coupled pump has the impeller mounted directly on the motor shaft.
True
Which type of impeller has the lowest specific speed?
Radial-flow
Which type of impeller will handle the highest flows?
Axial-flow
Impeller shrouds are used to:
Stiffen the impeller vanes
Which type of impeller has blades cut into its rim?
Regenerative turbine
True or false:
Balance holes are drilled through the rear shroud on the inside of the wear rings.
True
Which type of impeller has a double curvature vane?
Francis vane impeller
What is laminar flow?
Smooth flow
This pump characteristic is is expressed as the equivalent height that a liquid would have to fall to acquire the speed produced by the pump.
Velocity head
True or false:
On pump nameplates, the larger number (i.e. 3 x 6 x 9), the larger number is always the suction nozzle diameter.
True
