164 Questions
What is the primary purpose of compressed air in SCBA used by firefighters?
To provide breathable air
Which of the following is an example of the use of compressed gases in the food industry?
Whipped cream
What is the key difference between liquids and gases in terms of compression?
Gases can be compressed, while liquids cannot
What is the primary focus of the construction and operation of compressors?
Managing pressure, volume, temperature, and velocity
Which type of compressor accelerates the gas using impellers or blades?
Dynamic compressor
What is the principle that explains the relationship between pressure and velocity?
Bernoulli's principle
What is the primary function of dynamic compressors?
To convert low-pressure air into high-pressure air
What type of compressor is commonly used to pump air into bike tires or soccer balls?
Reciprocating compressor
In a single-acting reciprocating compressor, how many compression strokes occur per crankshaft revolution?
One
What prevents the gas from leaking past the piston in a reciprocating compressor?
Piston rings
In a double-acting reciprocating compressor, how many compression strokes occur per crankshaft revolution?
Two
What determines the type of compressor used in an application?
Maximum operating pressure required
What is the purpose of the suction valve in a reciprocating compressor?
To draw air into the cylinder
What is the advantage of using a two-stage compressor over a single-stage compressor?
It can produce a higher pressure of compressed air
In a single-stage compressor with multiple cylinders, what is the pressure of the air leaving the discharge valve?
The same from each cylinder
Why is a two-stage compressor used in applications where the required air pressure is high?
Because it can produce a higher pressure of compressed air
What happens when liquid enters the compressor?
The reed and the beam are forced upwards
What is the purpose of the large port opening in the compressor?
To allow the compressed vapour and trapped liquid to escape
How does the diaphragm valve in Figure 10(c) operate?
The diaphragm flexes upward due to gas pressure
What is the importance of tightness and proper seating of compressor valves?
It prevents hot compressed vapour from flowing back into the compressor
How are leaking compressor valves typically repaired?
By replacing the reeds and discs, and resurfacing the seats
What type of compressor is shown in Figure 11?
Sliding vane compressor
What is the advantage of the sliding vane compressor in terms of starting?
It requires low starting torque
What is the common drive used for sliding vane compressors?
Directly connected electric motor
What is the shape of the impellers in a rotary lobe compressor?
Figure-eight
What is the advantage of rotary compressors in terms of valves?
They do not require inlet and discharge valves
What is the purpose of the intercooler in a reciprocating compressor?
To cool the gas before entering the second stage
What is the main function of the piston rings in a compressor?
To provide a flexible seal to prevent the compressed vapour from escaping
What is the main difference between a one-piece and a two-piece compressor block?
The way the crankcase and cylinders are cast
What is the purpose of the wrist pin in a compressor?
To connect the piston to the connecting rod
What is the advantage of using a two-stage compressor over a single-stage compressor?
It produces a larger volume of compressed air at moderate pressure
What is the purpose of the crankshaft in a reciprocating compressor?
To move the pistons up and down
What is the difference between a flexible reed valve and a non-flexible ring valve?
The way they open and close
What is a characteristic of rotary lobe compressors?
Compact design and oil-free air
What is the purpose of the compressor bearings in a reciprocating compressor?
To reduce friction between moving parts
How do the impellers in a rotary lobe compressor operate?
One is driven directly, and the other maintains relative position
What is a benefit of rotary screw compressors?
Compact design and vibration-free operation
What is the advantage of using a radial cylinder arrangement in a reciprocating compressor?
It provides a more balanced operation of the compressor
What is the purpose of the timing gears in a rotary lobe compressor?
To maintain the relative position of the impellers
What is the purpose of the oil ring in a compressor piston?
To distribute lubricating oil evenly over the cylinder wall
What is a characteristic of scroll compressors?
Tolerance of liquids in gases
What is the principle of operation of dynamic compressors?
Bernoulli's principle
What is the advantage of centrifugal compressors over other types?
Simplicity of operation and minimal maintenance
What is the function of the diffuser vanes in a centrifugal compressor?
To convert kinetic energy to potential energy
What is the maximum pressure output of a single-stage centrifugal compressor?
300 kPa
What is the purpose of the volute shaped casing in a centrifugal compressor?
To convert velocity into pressure
What is the advantage of centrifugal compressors over positive displacement type?
Simple and rugged construction with low maintenance requirements
What is the purpose of adjustable inlet vanes in a single-stage compressor?
To change the capacity of the unit
What is the characteristic of air driven hand tools?
They are often lighter in weight
What is the advantage of compressed air machinery over steam driven machinery?
Transmission losses are less
What is the purpose of vanes at the eye of the impeller in a centrifugal compressor?
To provide shockless entry to the impeller
What is the characteristic of an axial flow compressor?
The airflow is axial to the compressor shaft
What is the purpose of a multistage compressor?
To increase the pressure ratio
What is the disadvantage of compressed air tools compared to electrically driven tools?
They are usually more expensive
What is the purpose of a compressor system in an industrial setting?
To operate pneumatic control systems
What is the advantage of compressed air machinery over electric machinery in explosive atmospheres?
It can be used safely in explosive atmospheres
What is the purpose of a dryer in a compressed air system?
To remove moisture from the compressed air
Why are oil-free rotary compressors used in some processes?
To prevent mixing oil with the air
What is the purpose of pressure regulators in a compressed air system?
To reduce the pressure of the compressed air
Why are automatic drain valves installed in receivers?
To drain off liquids that collect at the bottom of the receivers
What is the purpose of an air filter in an air compressor system?
To prevent dust and other particles from being carried into the compressor
Why are compressors installed in gas plants?
To boost the pressure of the gas to meet pipeline requirements
What is the purpose of a suction scrubber in a natural gas compressor system?
To remove liquids from the gas stream
What is the advantage of a compressor skid?
It is more cost-effective than constructing a new system on-site
Why are certain applications, like instrument air, required to have dry, clean, and oil-free air?
Because they require specific air quality
What is the concern in compressing natural gas?
Preventing liquids from entering the compressor
What is the function of the high-level float or probe in a scrubber?
To signal the compressor to shut down if the level gets too high
What is the purpose of the intercooler in a compression system?
To remove heat from the gas
What is the purpose of the coalescer or knockout drum in a compression system?
To remove moisture from the gas
What happens if the suction valve or discharge valve of a reciprocating compressor is closed?
The compressor will recirculate the gas
What is the primary function of a compressor in a refrigeration system?
To draw the refrigerant from the evaporator and raise its pressure
What is the advantage of a hermetic compressor?
It does not require shaft sealing
What type of compressor is commonly used in refrigeration systems?
All of the above
What is the purpose of the aftercooler in a compression system?
To remove heat from the gas
What happens to the gas as it moves through the intercooler?
It becomes cooler
What is the purpose of the scrubber in a compression system?
To remove moisture from the gas
What is the primary reason why gases can be compressed?
Because they can be forced into a smaller volume
What is the main difference between positive displacement and dynamic compressors?
The way they accelerate the gas
What is the primary function of the heat variable in compressor management?
To control the temperature of the gas
In which industry is compressed hydrocarbons used for transportation?
Natural gas industry
What is the principle that explains the relationship between pressure and velocity in compressors?
Bernoulli's principle
What is the main application of compressed air in hospitals and ambulances?
Providing breathable air
What is the primary difference between a dynamic compressor and a positive displacement compressor?
The method of compression
What is the purpose of the piston rings in a reciprocating compressor?
To seal the piston and cylinder
What happens when the piston moves downward in a single-acting reciprocating compressor?
The suction valve opens and the discharge valve closes
What is the advantage of a two-stage compressor over a single-stage compressor?
Higher pressure output
What is the purpose of the crank end suction valve in a double-acting reciprocating compressor?
To draw air into the cylinder
What is the characteristic of a compressor with multiple cylinders?
Higher volume of compressed air
What is the purpose of the discharge valve in a reciprocating compressor?
To discharge compressed air from the cylinder
Why are centrifugal compressors often used in power plants?
Because they can handle high volumes of air
What is the difference between a single-acting and double-acting reciprocating compressor?
The compression and discharge process
What is the purpose of cooling the gas in a two-stage compressor?
To reduce the temperature and volume of the gas
What is the typical arrangement of cylinders in a single-acting type compressor?
Vertical
What is the advantage of using a two-cylinder compressor over a single-cylinder compressor?
Higher volume of compressed air
What is the purpose of the wrist pin in a compressor piston?
To connect the piston to the connecting rod
What is the function of the crankshaft in a compressor?
To convert the linear motion of the piston into rotary motion
What is the purpose of the intercooler in a compressor?
To reduce the temperature and volume of the gas
What is the advantage of a two-piece compressor block over a one-piece block?
It allows for easier replacement of cylinder liners
What is the purpose of the valve guard in a flexible reed valve?
To restrict the movement of the valve
What is the function of the compressor bearings in a compressor?
To support the crankshaft and allow it to rotate smoothly
What is the purpose of the piston rings in a compressor?
To provide a flexible seal to prevent compressed vapour from escaping
What is the advantage of using a two-stage compressor over a single-stage compressor?
It allows for higher compression ratios
What is the consequence of liquid entering the compressor?
The high pressure at the end of the stroke forces the reed and the beam upwards
What is the purpose of the tightness and proper seating of compressor valves?
To prevent leakage of hot compressed vapour
What is the characteristic of a rotary compressor that makes it less efficient than a reciprocating compressor?
It has a lower compression ratio
What is the function of the flexible coupling in a two-stage sliding vane compressor?
To connect the two compressor shafts
What is the shape of the impellers in a rotary lobe compressor?
Figure-eight
What is the consequence of leaking compressor valves?
The compressor output is reduced
What is the function of the ring in a non-flexible ring valve?
To cover a series of ports
What is the advantage of a rotary compressor in terms of valves?
It does not require inlet or discharge valves
What is the function of the vanes in a sliding vane compressor?
To move out against the casing wall due to centrifugal force
What is the maximum discharge pressure of a sliding vane compressor?
1000 kPa
What is the primary function of the timing gears in a rotary lobe compressor?
To maintain the relative position of the impellers
Which type of compressor is more tolerant of liquids in gases?
Scroll compressor
What is the maximum pressure output of a two-stage rotary lobe compressor?
200 kPa
What is the purpose of the diffuser vanes in a centrifugal compressor?
To convert kinetic energy to potential energy
Which type of compressor uses Bernoulli's principle to compress air?
Dynamic compressor
What is the advantage of a rotary screw compressor over a rotary lobe compressor?
Higher speed range
What is the purpose of the volute shaped casing in a centrifugal compressor?
To further increase the pressure of the air
What is the primary advantage of a rotary lobe compressor?
Compact design and low vibration
What is the characteristic of a single-stage centrifugal compressor?
Single impeller design
What is the primary advantage of a scroll compressor?
Quiet operation
What is the primary function of the diffuser vanes in a single-stage centrifugal compressor?
To change the operating characteristics of the compressor
What is the advantage of using electric motors or reciprocating type internal combustion engines as drivers for centrifugal compressors?
They provide high speeds required for the compressor
What is the primary function of the moving blades in an axial flow compressor?
To increase the velocity of the air
What is the difference between a compressor and a compressor system?
A compressor is a component of a larger system, while a compressor system is a standalone unit
What is the advantage of using compressed air to drive tools and other machinery over the use of electricity or steam?
Compressed air machines cannot be damaged by overloading
What is the primary function of the adjustable inlet vanes in a single-stage compressor?
To control the amount of air that flows to the impeller
What is the primary function of the fixed blades in an axial flow compressor?
To convert high velocity air to low velocity air
What is the advantage of using centrifugal compressors over positive displacement type compressors?
They have simpler and more rugged construction
What is the primary function of the impeller in a centrifugal compressor?
To increase the velocity of the air
What is the disadvantage of using compressed air tools compared to electrically driven tools?
They are usually more expensive
What is the purpose of a receiver in a compressed air system?
To store compressed air
Why are oil-free rotary compressors used in certain applications?
To prevent mixing oil with the air
What is the purpose of a suction scrubber in a natural gas compressor system?
To remove liquids from the gas stream
What is the advantage of a compressor skid in natural gas compression?
It is compact and more cost-effective
Why is a two-stage compressor used in certain applications?
To obtain higher pressures than a single-stage compressor
What is the purpose of automatic drain valves in receivers?
To drain off liquids that collect at the bottom of the receivers
What is the purpose of a dryer in a compressed air system?
To remove moisture from the compressed air
Why are compressors installed in gas plants?
To boost the pressure of gas from wells to meet pipeline requirements
What is the purpose of a pressure relief valve in a compressor system?
To prevent over-pressurization of the system
Why are filters installed in a compressed air system?
To absorb oil from the air
What is the primary function of the compressor in a refrigeration system?
To draw the refrigerant from the evaporator
What is the purpose of the automatic drain valves in a compression system?
To remove moisture from the compressed gas
What is the characteristic of open type compressor housings?
They are suitable for a variety of drives
What is the purpose of the coalescer or knockout drum in a compression system?
To minimize the moisture entrained in the gas leaving the unit
What is the difference between hermetic and semi-hermetic compressor housings?
Hermetic housings are completely sealed, while semi-hermetic housings are not
What is the purpose of the intercooler in a compression system?
To cool the gas as it moves from the first stage to the second stage
What is the advantage of using a reciprocating compressor in a refrigeration system?
It can operate within a closed loop
What is the purpose of the automatic recirculation or bypass control valve in a compression system?
To continue to circulate gas through the compressor until it can flow out the discharge again
What is the primary function of the compressor in a compression system?
To reduce the volume of the gas
What is the purpose of the aftercooler in a compression system?
To cool the gas after it has been compressed
What is the main purpose of a safety head in a refrigeration system?
To prevent damage to the compressor from liquid refrigerant
What is the primary difference between a serviceable semi-hermetic screw compressor and a hermetic type?
The ability to service the internal mechanisms
What is the mechanism that prevents the safety head from lifting during normal operation?
A heavy spring
What is the consequence of liquid refrigerant entering the cylinder of a reciprocating compressor?
Hydraulic pressure damage
What is the purpose of the spring in the safety head of a compressor?
To hold the valve assembly in place
What is the benefit of the safety head in a refrigeration system?
Prevention of compressor damage from liquid refrigerant
What is the primary purpose of the safety head in a refrigeration compressor?
To prevent damage from hydraulic pressure caused by trapped liquid refrigerant
What is the key difference between hermetic and semi-hermetic compressor designs?
The ability to service internal mechanisms
In a refrigeration system, why is the potential of liquid entering the cylinder of a reciprocating compressor higher?
Because the refrigerant is being converted from a gas to a liquid
What is the purpose of the spring in a safety head?
To hold the valve assembly in place during normal operation
In what type of compressors is the safety head principle often applied?
Reciprocating compressors with ring plate valves
What happens when the pressure in the cylinder of a reciprocating compressor becomes too high due to trapped liquid refrigerant?
The safety head lifts, allowing the liquid to pass into the discharge line
Learn about the different types of compressors, including dynamic compressors and positive displacement compressors, and their applications in various industries. Understand the principles of compression and how they work. Test your knowledge with this quiz!
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