46 Questions
What is the main purpose of shaft seals in a compressor?
To prevent or minimize leakage of compressed gases
In what scenario are labyrinth seals typically used?
In air compressors where some leakage is acceptable
How do carbon ring seals differ from labyrinth seals?
Carbon rings are segments held together with a spring
What happens when the carbon ring seal is worn or has broken segments?
The entire seal assembly can be removed from the compressor
Why is there considerable wear on carbon ring seals?
Because of the near zero clearance
How does a liquid film seal work?
By using a thin liquid film between the seal and the rotating shaft
What type of seal is used in hydrocarbon, refrigeration, and fertilizer applications to prevent leakage?
Oil film seal
In what situations are oil-free packing ring seals typically used?
Reciprocating gas compressors where maximum oil leakage containment is critical
What type of bearings are commonly used in compressor crankshafts?
Sleeve/shell bearings
What is the purpose of lubricating oil in a compressor?
To reduce the power loss caused by friction
Which type of dry gas seal is specifically designed for non-hazardous gases at moderate pressure?
Single dry gas seal
What principle prevents compressed gases from leaking to the atmosphere in mechanical seals?
Contact between rotating and stationary surfaces
In which system does compressor lubrication provide a film around piston rings, vanes, and valves?
Splash system
What safety hazard is associated with using oil in high-pressure air or oxygen situations?
Risk of oil contamination in the compressed air
'Grooves machined into the face of the rotating ring' in dry gas seals are primarily intended for which purpose?
'Aerodynamic force creation'
'Oil drains away to an oil sump' in which type of seal design?
Oil film seal
What is the primary purpose of internal lubrication in reciprocating compressors?
Lubricate the cylinder walls and pistons
Why do dynamic compressors like centrifugal and axial flow types not require internal lubrication?
Their design prevents metal-to-metal contact
How is lubricating oil delivered to the rotor shaft bearings in rotary and dynamic compressors?
Via a pressure system pump
Why might some applications in the food processing and medical industries prefer oil-free compressors?
To avoid oil contamination in products
What is the function of intercoolers and aftercoolers in a compressed air system?
Cool the gas between stages of compression
What mechanism is commonly used to provide internal lubrication in reciprocating compressors?
Splash lubrication system
How does a pressure lubricator prevent metal-to-metal contact in sliding vane rotary compressors?
By creating a seal between vanes and casing
Why might multistage compressors be necessary for oil-free compressors to attain the required pressure?
To compensate for reduced efficiency without internal lubrication
What type of cooling systems are typically used in compressed air systems?
Shell and tube heat exchangers
What is the primary advantage of using external lubrication in compressors?
Increased energy efficiency
What is the purpose of passing air through the aftercooler in a compressor system?
To remove heat from the air
Which of the following is NOT mentioned as a potential issue if water vapor is not removed from the compressed air?
Creating a fire hazard due to oil vapor deposits
Why are intercoolers used in a compressor system?
To cool the air during compression
What type of construction is typical for water-cooled intercoolers and aftercoolers?
Shell and tube
Which component is crucial to prevent freezing in instrumentation lines or plug nozzles in controllers and positioners?
Air dryer filled with adsorbents
What is the purpose of using adsorbents like silica gel in an air dryer system?
To attract moisture from the air
Why is it mentioned that adsorbents are very porous in an air dryer system?
To allow for a larger surface area to attract moisture
What is the primary function of an aftercooler separator in a compressor system?
To remove condensed moisture and particles from the air stream
Why does the text suggest passing dehumidified air through a cooling coil after using adsorbents?
To reduce temperature after adsorption process heats up
What safety feature must an aftercooler have if there is a shut-off valve between the aftercooler and the receiver?
Safety valve
What is the purpose of regenerating the adsorbent in air dryers?
To drive the adsorbed moisture off by evaporation
Why are absorbents not commonly used in air dryers?
They are difficult to regenerate
What is the purpose of the two heat exchangers in refrigerated air dryers?
To prevent further condensing of moisture from the dry air
Why are safety valves important in air receivers?
To prevent overpressurization and rupture of piping or equipment
What is recommended to minimize corrosion in air receivers?
Draining the receiver regularly
What can result from an overpressure condition in a compressed gas system?
Rupture of piping or equipment
What is the function of check valves in a compressed air distribution system?
To prevent high-pressure air from blowing back into the compressor
Why should ventilation be done after opening an air receiver for inspection?
To prevent carbon monoxide gas accumulation
What is a common cause of air receiver failure?
Weakening of vessel material due to corrosion
Why should safety valves be located at various points on a compressed gas system?
To prevent rupture of piping or equipment due to excessive pressure
Learn about internal and external lubrication methods for compressors, including the components involved and how oil is delivered to moving parts. Understand the importance of lubrication in maintaining the efficiency and longevity of compressor systems.
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