Pumps Flashcards
What is a pump?
A machine that moves fluids or semi-fluids by mechanical means
What are the two basic types of pump classifications?
- dynamic
- postive displacement
How do Dynamic Pumps move fluids?
centrifugal force
What causes slip when talking about pumps?
When centrifugal force created by the impeller is the same resistance in the discharge pipe
What type of pump can have slip?
Dynamic
When is a dynamic pump used in terms of volume and pressure?
High volume
Low pressure
What is happening when slipping is occurring in a dynamic pump?
The impeller is spinning in the fluid opposed to creating more pressure
What type of flow delivery can you expect from a dynamic pump?
Smooth and continous
What are the 4 categories of dynamic pumps?
- Radial Flow
- Axial Flow
- Mixed flow
- Peripheral Pumps
How does a positive displacement pump work?
Moves fluid by trapping a fixed volume of liquid in a pumping chamber and forcing it into a discharge pipe
What are the two classifications of a positive displacement pump?
- reciprocating
- rotary
What methods are used to seal a positive displacement pump chamber?
- close tolerance
- combination of packing or membranes and check valves
What type of pump can not slip?
Positive displacement pump
What type of pump can maintain discharge against very high discharge resistance?
Positive displacement pumps
What type of pump requires a relief valve on the discharge pipe?
Positive displacement pump
In a positive displacement pump if viscosity increases what will happen to the flow rate?
It will also increase
Why does flow rate increase with viscosity in positive displacement pumps?
The internal clearances are filled
If viscosity increases in a dynamic pump what will the affect on the flow rate be?
Flow rate will drop
How will varying pressure affect a dynamic pumps flow?
Flow will also vary
How will varying pressure affect a positive displacement pumps flow?
Flow rate will stay constant
What is density when referring to pump terminology?
The mass or weight of a substance per unit of volume
What are the typical units of measurements for density when referring to pumps?
- pounds/cubic foot (lbs/ft3)
- kilograms/cubic metre (kg/m3)
What is specific gravity (S.G) in terms of pumps?
The ratio of the density of a substance in comparison to water
What is pressure in terms of pumps?
Measure of intensity of effort described as force per unit of area
What are the two typical units of measurement of pressure in terms of pumps?
- pounds per square inch (psi)
- newtons per square metre (kpa)
What is 1 psi equal to in kPa?
6.9
What is the formula used to determine pressure?
Pressure = force/area
What is the difference between a gauge reading and an absolute reading?
Gauge uses atmosphere as a reference point where absolute uses zero pressure as a reference point
Which type of pump is typically more efficient?
Positive displacement
Why are positive displacement pumps typically more efficient
They force the liquids out
How will head pressure affect a pumps efficiency?
More head pressure = less efficiency
Do pumps create pressure?
No. They crate flow not pressure
How are pumps measured?
Volume/period of time
How do pumps pull liquids into it?
By creating an area of low pressure
What is head pressure?
The pressure on the discharge pipe of a pump
What does staging pumps do?
Adds pressure
In double acting pumps is the volume the same on each side?
No
Why do double acting pumps not have the same volume on each side?
The rod takes up room
How would you find the pistons area of a pump?
3.14 x r2
Which type of pump is more efficient? dynamic or positive displacement pump
Positive displacement
Why are positive displacement pumps more accurate?
The liquid MUST be pushed out
How does head pressure affect efficiency?
More head pressure = less efficiency
Why does more head pressure cause a decrease in efficiency?
Due to it being another force the pump must overcome. The greater the force the higher the loss
How do liquids get drawn into pumps?
Pumps create a low pressure that pull liquids into it at the intake side
What must a supply tank have to create a low pressure?
A vent
What risks happening if you don’t have a vent on a supply tank but you have a very strong positive displacement pump?
You risk collapsing the supply tank
How are pumps measured?
Volume / period of time
What do pumps create?
Flow
Do pumps create pressure?
No
If you have a slurry substance you are pumping with a positive displacement piston pump using packing as your seal what should you add?
A lantern ring
What does slurry mean?
Liquid with abrasives combined
If you are pumping slurry’s where should your feed for your lantern ring be from?
An external clean source
What psi does your lantern ring source need to be?
10-15% higher than the substance you are pumping
What is a lantern ring?
A packing ring specifically designed to have fluid flow through it to act as a lubricant and barrier
In a set of packing rings what ring will have the most wear?
The gland follower which is at the front of the packing
If a lantern ring is being used for just sealing purpose where should it be placed in terms of the packing order?
In the middle of the packing
If a lantern ring is being used for flushing where should the ring be placed in terms of the packing set?
At the end
How much should packing glands leak for sealing and lubrication?
40-60 drops per minute
If you want no leakage in a positive displacement piston pump what type of sealing element should you use?
Mechanical seal
When using packing how should the joints be set?
Staggered
(180,90,90)
When cutting packing how should it be cut?
Skiv (diagonal)
What is atmospheric pressure at sea level?
14.7
What is cavitations typically the root cause for cavitation?
Air getting into your pump
Why does cavitation occur?
Air gets into the pump and goes from a low pressure to a high pressure causing it to implode which leads the liquid to suddenly shift eroding the pump.
What does a strainer do in terms of a supply tank?
Prevents air from getting into the pump
If you increase restriction to your input (supply) side of a positive displacement pump what will happen?
Increase in cavitation
Where should a filter be placed in terms of pumps?
After the pump to catch any debris (or limit)
Why should you always try to make piping straight in terms of pumps?
To reduce friction loss and wear
Why can cold oil increase cavitation?
It has a higher viscosity making it easier for it to trap air.
(It’s thicker so air sticks inside it)
How does aeration happen in terms of pumps?
A natural air leak on the low pressure supply side.
What unit are post pump filters typically measured in?
Microns.
What does 1 micron mean?
1 millionth of a meter squared
What is the disadvantage of having a low micron filter (example 1 micron)
Finer filter resulting in more maintenance due to less times between changes
What is the disadvantage of using a higher micron filter (example 10 micron)
Larger area for debris to pass so it can be less effective
What are the 3 typical pumping elements of a reciprocating positive displacement pump?
Piston
Plunger
Diaphragm
What is the difference in flow between a dual acting and single acting pump?
Dual acting is smoother and more consistent
What does the term pump head mean?
The pressure the pump has to overcome to be able to move liquid through the system
What does frictional loss refer to?
The pressure needed to overcome friction as the liquid moves through the piping
What does velocity head refer to?
The force causing the fluid to flow through the chamber which is due to the velocity of the fluid
What is another term for total dynamic head?
Pump head
What is vapour binding?
When the pressure on the suction side of the pump drops below the vapour pressure of the liquid causing vapour to form which can partially or completely stop liquid flow into the pump
What can be the root cause to vapour binding?
Insufficient suction head
High suction lift
Excessive friction head
High liquid temperatures
What does net positive suction head refer to?
Keeping the suction pressure greater than the vapour pressure of the liquid
How is the pumps capacity determined?
Its volume of liquid delivered per unit of time
What are the two most common units to measure a pumps capacity?
Gallons per minute (gpm)
Litres per minute (lpm)
How does a volute pump work?
Rotating impeller discharges fluid into a spiral shaped cavity
What does volute mean
Spiral shaped
What type of pump is this?
Dynamic volute pump
How do diffuser pumps work?
Used in pump casings to create multiple volutes, they are curved vanes which direct the flow of liquid
What type of pump is this?
Dynamic Diffuser pump
How does an axial flow pump work?
An impeller moves on a shaft without changing direction
The impeller has vanes (like a ships propeller) causing a lifting action
What type of pump is this?
Axial flow pump
What are the characteristics of an axial flow pump?
Low suction
Large volume output flow
Low discharge head
What is a mixed flow pump?
Pump that combines axial and radial flow characteristics
What are the characteristics of a mixed flow pump?
Can be mounted vertical or horizontal
Low head
High capacity
What type of pump is this?
Dynamic Mixed flow
What is a peripheral pump?
A pump that has liquid entering at the peripheral of the impeller
What type of pump is this?
Peripheral pump
What are the characteristics of a peripheral pump
High pressure
Low volume
Why are barrel casings used
Multi stage pumps for ease of maintenance
What determines a pumps casing?
The liquid that will be pumped
In reference to rotary gear pumps how many teeth need to be carrying the load?
7
How many teeth need to be in contact in a rotary gear pump?
2
What limits the size of gear you can use in a rotary gear pump?
Casing size
How many drivers are in a rotary pump?
One
If you close or reduce the discharge on a rotary pump what will happen
Typically blow a seal normally thus is the drive input seal
What are the 4 main types of rotary pumps?
Gear
Lobe
Screw
Sliding vanes
What are the 3 main types of rotary gear pumps?
Spur
Helical
Herringbone
Where does the liquid flow in a herringbone rotary gear pump?
Axially
What is significantly reduced with herringbone rotary gear pumps?
Thrust
What is the main disadvantage with herringbone gear pumps?
Cost (very expensive)
What is the inlet to outlet ratio with rotary spur gear pumps?
1:1 (same size)
What type of pump always needs to be primed and why?
Dynamic as they have very low negative pressure capabilities without being primed
How can you identify an internal rotary gear pump visually?
Crescent
What are the 3 main typical disadvantages to rotary pumps?
Moderate speed
1 bearing runs in product
Over hung load on shaft bearing
What is more precise with lobe pumps compared to rotary gear pumps?
Timing
How many lobes are typically found in a rotary gear pumps compared? (Per gear)
2-3
What is the benefit to having more lobes?
Smoother delivery
When counting lobes on a rotary gear pumps how many rotors count towards the lobe number?
1
How much can you trim an impeller for a centrifugal pump?
Max 20%
Can you trim a lobe pump?
No
What is trimming in terms of impellers?
Shaving down and impeller
Can lobe pumps have wear tips?
Yes
What is wear tips in terms of pumps?
Wear plates that are mounted to a pumps impeller to bring it back to original clearance
Where is liquid carried in a screw pump?
Between the screw threads
What is a progressive cavity pump?
Single screw pump
Do screw pumps typically require timing gears?
Yes
Where is the thrust bearing typically located on a screw pump?
The input end due to the back pressure of the discharge
What efficiency do screw pumps typically run at?
70%
In a triple screw pumps impeller how many screws are driven?
1
What type of pump has a rotor containing vanes within slots?
Sliding vane pump
Is a sliding vane pump reversible?
No
What causes the vanes to push out on a sliding vane pump?
Centrifugal forces
What type of rotary pump uses multiple pistons
Rotary Piston pump
What causes pistons to draw or discharge liquid in a piston pump?
Swashplate
What would happen if a swashplate were mounted completely vertical (90 degrees)
Nothing the pump would not work
What determines the delivery rate on a piston pump?
The angel of the swashplate
Where is the input and outputs of a radial piston pump?
The centre of the rotor
What causes the pistons to retract in a radial piston pump?
The pump housing
Does discharge increase or decrease if a radial piston pump is more balanced?
Decrease
What is the efficiency of a radial piston pump?
81-95% (extremely efficient)
How can you increase consistency in radial piston pumps?
Reduce the speed
How can you increase discharge rate in a radial piston pump?
Adding springs
How is a double suction impeller hydraulically balanced?
Two shrouds and an inlet on both sides of the impeller
What is the function of an inducer?
Provides sufficient head to help the main impeller
What is pump priming?
Removing air from the pump and suction lines
What type of pumps should typically always be primed?
Dynamic
What is water hammer?
Result of a pressure surge through a piping system when a fluid in motion is forced to change directions or stop abruptly
What direction of vanes do most radial flow impellers use?
Backswept
What is backswept vanes?
When the vane of an impeller tips away from the direction of rotation
What does an open impeller consist of?
Curved vanes connected to a hub
What prevents leakage across vanes in an open impeller?
Close axial clearance on either side
What can open impellers have to help reduce thrust?
Balance holes
What type of impeller is this?
Open impeller
What type of impeller has a full shroud only on the back of the impeller?
Semi open
What is the benefits of a semi open impeller?
More efficient
Resistance to bending
What type of impeller has a full shroud on both sides?
Closed imepeller
What is an inducer in terms of impellers?
An axial type impeller fixed to the suction side of the main impeller that provides sufficient head to raise the net positive suction head available to the main impeller
What are the four basic categories to pump casings?
Volute
Double volute
Concentric
Diffuser
How much can an impeller size decrease in a volute casing before affecting the pumps efficiency?
20%
What is a twin/dual volute casing?
Consists of two 180 volutes with dividing rib or splitter separating the second volute from the outer casing
When is a concentric casing used?
When an application requires impellers of different diameters
What is a diffuser casing used for?
Slow down liquid converting the velocity head into pressure head
How does a diffuser casing work?
Uses a series of stationary curved vanes with the space between them expanding to slow down the liquid
How much can you reduce the size of the impeller in a diffuser pump before there is a significant reduction in efficiency?
5-10%
What is a foot valve?
A valve that only allows flow towards the pump so when the pump stops the liquid does not drain back to the supply tank
What are the 3 main types of relief valves?
Ball
Poppet
Discs
How does a relief valve work?
The valve has a spring that needs to be overcome by the pressure in the line. Once the pressure of the fluid can overcome the spring pressure the valve opens allowing the fluid to go back to the supply tank
In a two or three screw pump if the driver is left threaded what would the idlers be?
Right threaded (opposite)
What pumps are foot valves considered unnecessary?
Positive displacement pumps as they are self priming
What is a priming loop?
A U shaped section of pipe where a pump is installed so it is ready for start up when the pump stops
Where can pulsation dampeners be installed?
In either the suction or discharge line.
What are the 3 types of pulsation dampeners?
Non separated
Bladder
Diaphram
If the pumping fluid is oil what should a dampener never be charged with?
Oxygen
What is volumetric efficiency?
Actual volume / theoretical
What’s the difference between a unbalanced and balanced vane pump?
Unbalanced can be variable
Balanced must be fixed flow
Why do most positive displacement pumps require a relief valve?
To protect the pump from excessive pressures
What is absolute pressure?
Gauge pressure plus atmospheric pressure
As pressure is reduced is the boiling point of the liquid decreased?
Yes
When liquid vaporizes in a closed system what happens?
Cavitation can occur
When the pump inlet is above the level of liquid in the supply tank does the pump have a suction head?
No
What source of energy is available to allow liquid to enter a pump with a suction lift?
Atmospheric pressure
What is the component that converts mechanical energy to kinetic energy in the pumping system?
Impeller
What do pumps convert mechanical energy into?
Hydraulic energy
Unless otherwise stated, pump performance curves are based on handling what substance?
Cold water
Friction losses through the pipe is dependent on what?
Type of pipe
Length of pipe
Diameter of pipe
Type of fluid
What directly affects the flow produced by the pump?
The impeller or driving force
The stripper in a regenerative turbine pump is located between what?
The suction and discharge
What are impeller shrouds used for?
To stiffen the impeller vanes
Are wear plates used with open impellers?
Yes
What type of impellers would be used with fibrous slurries?
Open or semi open
Where are balance holes drilled on closed impellers?
The rear shroud on the inside wear ring
What type of impeller has a double curvature vane?
Francis
The paddle wheel impeller is also called what?
High speed impeller
What type of flow do inducers have?
Axial flow
Should pumps handling hot liquids be centreline mounted?
Yes
Why would a rigid coupling be used when mounting a motor to a pump?
To make up for a pump rotor having no separate bearings.
Do a double suction single stage pump have a single suction nozzle?
Yes
Can propeller pumps have over 20 stages?
No
Can a barrel pump be mounted horizontally or vertically?
Either
When does hydraulic slap happen?
When a check valve closes too quickly
Pumps are primed by bleeding them through where?
The air vent
When should Dynamic pump wear rings should be replaced
When the clearance has increased to 3 times the initial clearance
Can water hammer be eliminated by the use of pulsation dampeners?
Yes
A dial indicator button touching the end of the shaft is used to measure what?
Shaft end float
When blinding piping prior to pump removal where should blinds be placed?
Downstream of the suction valve
Upstream of the discharge valve
Before installing a dynamic pump what is the first thing you should check?
That the rotor turns freely by hand
Do double acting piston pumps discharge an equal amount of liquid on all strokes?
No
What type of piston pumps discharge can run dry?
Diaphragm pump
Do rotary pumps or reciprocating pumps produce a smoother flow?
Rotary
What vane pump uses an oval rotor
External vane pump
What can variable discharge rotary pumps be?
Vanes and pistons
What type of housing does a balanced vane pump use?
Elliptical housing
Is another name for a single cylinder double acting plunger pump a duplex pump?
No
Can plunger pumps have both fixed or adjustable strokes?
Yes
Does a multiples pump have every plunger delivering liquids simultaneously?
No
Is a flexible tube pump a peristaltic pump?
Yes
Does a flexible vane pump require a relief valve?
No
Does an external circumferential piston pumps discharge require timing gears?
Yes
What type of pump has a divider between the discharge and inlet ports?
Flexible liner pump
What type of screw pump has a peristaltic action?
Single rotor
What type of check valve would not be suitable for high pressure?
Flap
What type of check valve is least suitable for liquids containing solids?
Wing guided disc
When a relief valve on a rotary pumps discharge opens where does the product go?
Returned to suction
Are relief valves necessary when handling viscous liquids?
Yes
What does it mean when an emergency pump with a stuffing box that is leaking a small amount of liquid through the packing?
Packing is adjusted correctly
What happens if the discharge valve shuts during operation of a centrifugal pump?
Pump slip increases to a maximum
How is stroke increased on an axial pump?
Increase the swashplate angle
Which pump has the ability through construction to compensate for wear?
Vane pump
In terms of operation how are hydraulic pumps classified?
Positive displacement
Which of the following is a non positive displacement pump?
- gear
- centrifugal
- vane
-piston
Centrifugal
In which type of pump would you find a crescent shape?
Internal gear
What classification are gear vane and piston pumps?
Positive displacement
What is the purpose of a volute in a pump?
Increase pressure
What portion of a square meter represents a micron?
1/ 1,000, 000
How much pressure is present at sea level?
14.7
Why are wear rings installed in a pump?
Reduce impeller/ case wear
What style of pump has a suction opening larger than the discharge?
Centrifugal
What does a monometer measure?
Pressure
Where would you place a strainer in a pumping operation?
Pump suction
At the inlet side of a pump where does the energy which pushes liquid into the pump come from?
Atmosphere
Why should you inspect a damaged pump you are about to replace?
Root cause
What defines a vacuum void with in fluid?
Cavitation
What pressure must a pump over come to move liquid through the system?
Head pressure
Under what condition will cavitation occurs in a pump?
Plugged or blocked inlet
What will happen if the discharge of any positive displacement pump closed while the pumps still under load?
Pump components will break
What function does a pump create in a system?
Flow
Why are suction lines on a pump usually larger than discharge lines?
Reduce friction to water flow
Pumps may be single or multiple stage what advantage do multi stage have?
Higher pressures
What is the purpose of a foot valve on a pump suction?
Maintain liquid in the line for priming
What pump has the pumping action moving liquid only 90 degrees to the shaft?
Radial
What style of pump delivers a precise amount of fluid?
- gear
- vane
- centrifugal
- metering
Metering
Before working in a pump what must you complete?
Lockout
Fluid entering a centrifugal pump is rotated by what?
Impeller
What 3 types of gears are common in gear pumps?
Spur
Helical
Herringbone
What is the minimum number of gears for dealing in a gear pump?
2
What pump style is best suited for explosive atmospheres?
Diaphragm
