Unit2 Pumps and compressors Flashcards
Centrifugal pumps convert rotating mechanical energy into kinetic energy then:
Select one:
a. Discharge the kinetic energy
b. Back to mechanical energy
c. Into potential energy in the form of pressure
d. Into centrifugal force
c. Into potential energy in the form of pressure
Rotary pumps should be started with the discharge valve open because they are \_\_\_\_\_ pumps. Select one: a. Reciprocating b. Double-acting c. Positive displacement d. Regenerative
c. Positive displacement
A inspection of a pump that is in operation should include:
Select one:
a. Ensuring water flows freely from the packing
b. Ensuring water drips from the mechanical seals
c. Checking that the suction and discharge pressures are correct
d. Re-priming the pump.
c. Checking that the suction and discharge pressures are correct
Pump wear rings are installed on an impeller by threading, or: Select one: a. Shrinking b. Welding c. Brazing d. Forging
a. Shrinking
If an electric motor’s rotational speed is too high for a given compressor, what may be done?
Select one:
a. use a variable speed drive
b. use compressor unloading
c. use a speed limiter
d. use reduction gears
d. use reduction gears
If the packing gland of a centrifugal water pump is leaking too much:
Select one:
a. Tighten up the gland until all leakage has been stopped
b. Tighten up the gland but permit a slight amount of leakage
c. Tighten up the gland as far as is possible
d. Throttle the suction valve a little
b. Tighten up the gland but permit a slight amount of leakage
Strainers may be found: Select one: a. On the suction side of a centrifugal pump b. On the discharge side of the pump c. Inside the pump d. On the air vent discharge of the pump
a. On the suction side of a centrifugal pump
A double-acting pump: Select one: a. Has two pistons on the pump end b. Has two pistons on the driver end c. Has two slide valves d. Is a positive displacement pump
d. Is a positive displacement pump
When a reciprocating pump delivers fluid every second stroke of its piston, it is called a \_\_\_\_\_\_\_\_\_\_\_ pump: Select one: a. Positive displacement b. Single acting c. Two-stage d. Double acting
b. Single acting
Before starting a centrifugal pump:
Select one:
a. Blow off the liquid from the housing
b. Close the water to the lantern rings
c. Be sure that the pump is primed with liquid
d. Close the suction and discharge valves
c. Be sure that the pump is primed with liquid
Lantern rings:
Select one:
a. Must be greased regularly
b. Prevent liquid leakage from the pump
c. Provide a seal to prevent air from entering the pump
d. Are mostly used on submerged centrifugal pumps
c. Provide a seal to prevent air from entering the pump
A speed-increasing gear is commonly used on: Select one: a. Rotary lobe compressors b. Screw compressors c. Sliding vane compressors d. Lobe compressors
b. Screw compressors
The compressor that would favour volume over pressure would be the: Select one: a. Rotary lobe b. Screw c. Centrifugal d. Sliding vane
c. Centrifugal
Proper priming and venting of a pump is important, especially if:
Select one:
a. The medium being pumped is high temperature
b. The medium being pumped contains suspended solids
c. A mechanical seal is used
d. The pump has a stuffing box and lantern ring
c. A mechanical seal is used
Compressor unloaders work in three different ways. One of these is: Select one: a. Closing the discharge valve b. Keeping the suction valve open c. Activating the stop and start button d. Activating the variable speed drive
b. Keeping the suction valve open
Compression type packing:
Select one:
a. May be saturated with a lubricating material
b. Reduces the maintenance cost on the pump
c. Protects the shaft from scoring and corrosion
d. Is used with all mechanical seals
a. May be saturated with a lubricating material
A reciprocating air compressor works on the principle of: Select one: a. Pressure reduction b. Centrifugal force c. Volumetric expansion d. Volume reduction
d. Volume reduction
The name given to the category of pumps that use gear teeth, vanes, or lobes to move the fluid being pumped is the \_\_\_\_\_ type. Select one: a. Axial flow b. Radial flow c. Dynamic d. Rotary
d. Rotary
circulating pump, known as a cooling water pump, is usually:
Select one:
a. Connected with some type of heat exchanger system
b. A once-through device
c. A reciprocating pump
d. A small capacity pump
a. Connected with some type of heat exchanger system
The capacity of a centrifugal pump should only be reduced by: Select one: a. Throttling the suction valve b. Closing the suction valve c. Opening the pump casing vent valve d. Throttling the discharge valve
d. Throttling the discharge valve
Most pump troubles occur:
Select one:
a. After about six months of continuous service
b. Due to vapour binding
c. During initial start up
d. Because of inadequate operator training
c. During initial start up
Centrifugal pumps do not develop good suction lift because:
Select one:
a. Atmospheric pressure is usually too low
b. Their internal component clearances are too high
c. The speed is too low
d. They favour pressure rather than volume
b. Their internal component clearances are too high
A volute type pump:
Select one:
a. Is a positive displacement pump
b. Has a spiral casing with an increasing cross sectional area.
c. Reduces the velocity in the discharge nozzle
d. Is a regenerative type pump
b. Has a spiral casing with an increasing cross sectional area.
Single stage reciprocating air compressors have:
Select one:
a. One or more cylinders of equal size
b. Variable speed drivers
c. Several cylinders, each of different sizes
d. Low power requirements
a. One or more cylinders of equal size
What size of packing would you use to repack a pump gland having a stuffing box bore of 8.6 cm and a pump shaft diameter of 6.7 cm? Select one: a. 0.5 cm b. 1.9 cm c. 0.675 cm d. 0.95 cm
d. 0.95 cm
An air compressor may be automatically started and stopped by a pressure switch, which is usually found connected to the: Select one: a. Intercooler b. Aftercooler c. Receiver d. Control panel
c. Receiver
The area around a pump shaft, where packing material is placed to reduce leakage past the shaft, is known as a: Select one: a. Seal box b. Stuffing box c. Seal cage d. Wearing ring
b. Stuffing box
Flexible couplings will compensate for: Select one: a. Overheating of packing b. unavoidable shaft misalignment c. Bearing failure d. Impeller imbalance
b. unavoidable shaft misalignment
Which type of pump produces the greatest suction? Select one: a. A volute centrifugal pump b. A centrifugal pump c. A regenerative pump d. A positive displacement pump
d. A positive displacement pump
Rotary pumps: Select one: a. Are low-pressure pumps b. Must be primed before each use c. Are positive displacement pumps d. Must use mechanical seals
c. Are positive displacement pumps
A slight leakage is desired between the pump shaft and the packing in order to: Select one: a. Prevent the ingress of air b. Prevent wearing of the wear rings c. Lubricate the packing d. Prevent the pump from vapour locking
c. Lubricate the packing
The difference between static suction head and static discharge head is: Select one: a. Total static head b. Static discharge head c. Static suction head d. Dynamic head
a. Total static head
An air receiver used in an air compression system :
Select one:
a. Reduces the energy required to compress air
b. Eliminates pulsation in discharge lines
c. Controls the temperature of the air before it enters the system
d. Eliminates moisture from the air
b. Eliminates pulsation in discharge lines
A mechanical pump seal:
Select one:
a. Will have a substantial amount of leakage
b. Will cause more wear on the shaft than a packing seal
c. can be designed for high pressure service
d. Does not need cooling
c. can be designed for high pressure service
A stuffing box:
Select one:
a. Stops air leaking out of the casing when the pressure is above atmospheric
b. Promotes casing leakage when the pressure is above atmospheric
c. Is filled with packing
d. Is always supplied with a lantern ring
c. Is filled with packing
Intercoolers should be equipped with: Select one: a. Moisture separators b. Safety valves c. Baffles d. Automatic blow downs
b. Safety valves
Pump priming is:
Select one:
a. Done to centrifugal pumps with positive suction head
b. Done with the suction valve open
c. Filling the pump with gas
d. Done with the suction and discharge valve closed
b. Done with the suction valve open
Priming of a centrifugal pump refers to: Select one: a. Removal of liquid from the pump b. Filling the pump casing with liquid and removing the air c. Lifting the pump d. Closing the vent on the pump casing
b. Filling the pump casing with liquid and removing the air
Air receivers must have a: Select one: a. Gauge glass b. Thermometer c. High pressure alarm d. Safety valve
d. Safety valve
Consider a pump that delivers liquid into the base of an overhead storage tank, from a reservoir situated below the pump. The vertical distance from the liquid surface up to the pump center line plus the vertical distance from the pump center line up to the surface of the liquid in the discharge tank is: Select one: a. Static discharge head b. Static suction head c. Total discharge head d. Total static head
d. Total static head
Another name for a lantern ring, used in a pump is: Select one: a. Packing box b. Packing ring c. Rotating seal d. Seal cage
d. Seal cage
Before starting a pump, check
Select one:
a. That the packing is drip free
b. That the area around the pump is cool and dry
c. That the suction and discharge valves are in their proper positions.
d. That the lantern ring turns freely
c. That the suction and discharge valves are in their proper positions.
The cooling water for an air compressor should be turned on:
Select one:
a. When the compressor reaches operating temperature
b. After starting the compressor
c. When the operating pressure is reached
d. Before starting the compressor
d. Before starting the compressor
An air compressor auxiliary which will decrease the power requirement is the: Select one: a. Receiver b. Diffuser c. Intercooler d. Aftercooler
c. Intercooler
An advantage of a pump using a mechanical seal is: Select one: a. Lower first cost b. Less maintenance c. Less lubrication d. Ease of repair
b. Less maintenance
Preferably, dynamic pumps should be located \_\_\_\_\_ the liquid source. Select one: a. Directly under b. Above c. At d. Below
d. Below
When a pump discharges into a vessel operating at 300 kPa, the 300 kPa is referred to as: Select one: a. Dynamic head b. Pressure head c. Discharge head d. Friction head
b. Pressure head
A diffuser pump: Select one: a. Does not have a volute b. Does not have to be primed c. Has high suction lift d. is more effective at changing velocity to pressure than a volute pump
d. is more effective at changing velocity to pressure than a volute pump
A centrifugal pump consists of: Select one: a. An impeller surrounded by a casing b. Gears rotating in a housing c. Sliding vanes d. A pulsating disc
a. An impeller surrounded by a casing
Centrifugal pump power requirements are decreased when:
Select one:
a. Discharge pressure is decreased
b. The mass of fluid delivered is decreased
c. The casing pressure drops
d. The discharge velocity is high
b. The mass of fluid delivered is decreased
Positive displacement compressors:
Select one:
a. Cannot deliver pulsation-free air
b. Must have suction and discharge valves
c. Must all use internal lubrication
d. Could be single stage with three cylinders
d. Could be single stage with three cylinders
Centrifugal compressors:
Select one:
a. Are used for high pressure and low flow
b. Could be of the multi-stage type
c. Must have a safety valve on the discharge when steam driven
d. Require inlet and discharge valves
b. Could be of the multi-stage type
Compressed air tools tend to be: Select one: a. Heavier than equivalent electrical tools b. Damaged by overloading c. Hot after prolonged operation d. More expensive than electrical tools
d. More expensive than electrical tools
In order to protect the drive motor, a start-stop air compressor should be equipped with:
Select one:
a. Variable speed control
b. Constant speed control
c. Safety heads
d. A speed-sensitive automatic cylinder unloader
d. A speed-sensitive automatic cylinder unloader
The capacity of a centrifugal pump:
Select one:
a. Varies with discharge pressure
b. Is fixed and can only be altered by changing the impeller
c. Should be varied by suction valve manipulation
d. Can be altered by speed variation only
a. Varies with discharge pressure
Shaft misalignment during operation of a pump can be caused by bearing wear, thermal expansion and: Select one: a. Shaft flexing b. Overloading the pump c. Loss of lubrication d. Improper installation
a. Shaft flexing
To reduce air temperature between stages, \_\_\_\_\_\_\_\_\_\_\_\_ are used. Select one: a. intercoolers b. aftercoolers c. receivers d. air dryers
a. intercoolers
The seal cage on the shaft of a centrifugal pump:
Select one:
a. Holds the shaft packing against the shoulder of the stuffing box
b. Assists in reducing shaft vibration
c. Distributes sealing fluid to the stuffing box
d. Prevents fluid from leaking out of the pump casing
c. Distributes sealing fluid to the stuffing box
Wear rings are usually constructed of: Select one: a. Ceramics or aluminum b. Graphite or bronze c. Bronze or cast iron d. Steel or alloy steel
c. Bronze or cast iron
When starting up a rotary pump you must be sure that the: Select one: a. Discharge valve is closed b. Discharge valve is open c. Pump is filled with air d. Pump suction valve is closed
b. Discharge valve is open
The purpose of shaft sealing on a pump is to:
Select one:
a. Keep air in the pump
b. Keep the packing gland cool
c. Reduce fluids from leaking along the pump shaft
d. Prevent lubricating oil from leaving the pump
c. Reduce fluids from leaking along the pump shaft
Wear rings are usually constructed of: Select one: a. Ceramics or aluminum b. Graphite or bronze c. Bronze or cast iron d. Steel or alloy steel
c. Bronze or cast iron
A pump is capable of suction lift due to:
Select one:
a. Its ability to convert kinetic energy into potential energy
b. The speed at which it operates
c. Its input power
d. Atmospheric pressure
d. Atmospheric pressure
Sliding vane compressors: Select one: a. Use suction and discharge valves b. Are dynamic compressors c. Use cylinder unloading d. Are positive displacement compressors
d. Are positive displacement compressors
Which of the following air compressors gives two compression strokes per crankshaft revolution?
Select one:
a. Two-stage two cylinder double-acting compressor
b. A two-stroke compressor
c. Single cylinder double acting compressor
d. Two cylinder single stage double acting compressor
c. Single cylinder double acting compressor
A volute type pump:
Select one:
a. Is a positive displacement pump
b. Has a spiral casing with an increasing cross sectional area.
c. Reduces the velocity in the discharge nozzle
d. Is a regenerative type pump
b. Has a spiral casing with an increasing cross sectional area.
A reciprocating air compressor works on the principle of: Select one: a. Pressure reduction b. Centrifugal force c. Volumetric expansion d. Volume reduction
d. Volume reduction
Wear rings in centrifugal pumps: Select one: a. Are non-replaceable. b. Are installed on impellers c. Compensate for misalignment of the impeller d. Are only found on high pressure pumps
b. Are installed on impellers
Positive displacement compressors:
Select one:
a. Cannot deliver pulsation-free air
b. Must have suction and discharge valves
c. Must all use internal lubrication
d. Could be single stage with three cylinders
d. Could be single stage with three cylinders
Another name for a lantern ring, used in a pump is: Select one: a. Packing box b. Packing ring c. Rotating seal d. Seal cage
d. Seal cage
An advantage of a pump using a mechanical seal is: Select one: a. Lower first cost b. Less maintenance c. Less lubrication d. Ease of repair
b. Less maintenance
Mechanical seals:
Select one:
a. Allow the pump to be run dry
b. Are used where leakage is must be reduced to a minimum
c. Replace seal cages
d. Withstand shaft misalignment and vibration better than packing
b. Are used where leakage is must be reduced to a minimum
Air receivers must have a: Select one: a. Gauge glass b. Thermometer c. High pressure alarm d. Safety valve
d. Safety valve
A diffuser pump: Select one: a. Does not have a volute b. Does not have to be primed c. Has high suction lift d. is more effective at changing velocity to pressure than a volute pump
d. is more effective at changing velocity to pressure than a volute pump
A rotary pump: Select one: a. Is silent in operation b. Has severe discharge pulsations c. Should be equipped with a relief valve d. Is a dynamic pump
c. Should be equipped with a relief valve
If a stuffing box is to prevent the ingress of air, it is equipped with: Select one: a. A vacuum breaker b. A lantern ring c. A bushing d. A thrust collar
b. A lantern ring
Rotary pumps: Select one: a. Are low-pressure pumps b. Must be primed before each use c. Are positive displacement pumps d. Must use mechanical seals
c. Are positive displacement pumps
New pump packing should be installed: Select one: a. Tight enough to stop leakage b. Loose enough to allow leakage for lubrication c. Every shut down d. Every time prior to start up
b. Loose enough to allow leakage for lubrication
It is generally accurate to say that:
Select one:
a. 9.8 kPa pressure results from every metre of water depth or height
b. A water height or depth of 10.34 metre results in 1 kPa
c. 10.21 kPa will result from 1 metre of static water head
d. 1 kPa will result from a water head of 9.8 m
a. 9.8 kPa pressure results from every metre of water depth or height
In a centrifugal compressor the kinetic energy is converted to potential energy in the: Select one: a. Volute, diffuser or both b. Diffuser only c. Compressor cavity d. Volute only
a. Volute, diffuser or both
