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Questions and Answers
What is the main benefit of constructing the compressor to operate in oil?
What is the main benefit of constructing the compressor to operate in oil?
- It simplifies the lubricating problem. (correct)
- It increases the compressor's horsepower capacity.
- It allows for easier assembly of the unit.
- It enhances the compressor's energy efficiency.
How does the suction vapor travel to the intake tube in this compressor design?
How does the suction vapor travel to the intake tube in this compressor design?
- It flows through holes in the motor rotor. (correct)
- It is forced through a filter before entering the tube.
- It enters through the bottom of the shell.
- It passes directly from the compressor to the tube.
What effect does centrifugal force have on the separation of oil and liquid refrigerant?
What effect does centrifugal force have on the separation of oil and liquid refrigerant?
- It aids in separating oil and liquid refrigerant. (correct)
- It eliminates refrigerant vapor pressure.
- It mixes oil more thoroughly with the refrigerant.
- It accelerates the mixture into the compressor.
Where is oil picked up from to lubricate the main bearings in the compressor?
Where is oil picked up from to lubricate the main bearings in the compressor?
What is a characteristic feature of hermetically sealed compressors?
What is a characteristic feature of hermetically sealed compressors?
What is one precaution that should be taken when assembling a hermetic compressor?
What is one precaution that should be taken when assembling a hermetic compressor?
What range of horsepower capacities do reciprocating compressors typically cover?
What range of horsepower capacities do reciprocating compressors typically cover?
What helps in the lubrication process within the bearings of the compressor?
What helps in the lubrication process within the bearings of the compressor?
What is the significance of viscosity in lubricating oils for refrigeration compressors?
What is the significance of viscosity in lubricating oils for refrigeration compressors?
Which property is NOT necessary for lubricating oil used in refrigeration compressors?
Which property is NOT necessary for lubricating oil used in refrigeration compressors?
During pump operation in hermetic compressors, what role does the oil play?
During pump operation in hermetic compressors, what role does the oil play?
What characteristic is crucial for the miscibility of refrigeration oil with refrigerants?
What characteristic is crucial for the miscibility of refrigeration oil with refrigerants?
Which of the following is a common method of lubrication in compressors?
Which of the following is a common method of lubrication in compressors?
Why is low flash point important for lubrication oils in refrigeration systems?
Why is low flash point important for lubrication oils in refrigeration systems?
Which property aids in maintaining the flow of oil in the compressor crankcase?
Which property aids in maintaining the flow of oil in the compressor crankcase?
What property of lubricating oil is measured in Saybolt Universal Seconds (SSU)?
What property of lubricating oil is measured in Saybolt Universal Seconds (SSU)?
Selecting refrigerant oil requires consideration of which specific need of the refrigeration system?
Selecting refrigerant oil requires consideration of which specific need of the refrigeration system?
Which of the following refers to the lowest temperature at which oil can still flow?
Which of the following refers to the lowest temperature at which oil can still flow?
What is a crucial requirement for the chemical stability of refrigeration oil?
What is a crucial requirement for the chemical stability of refrigeration oil?
What defines the miscibility of a refrigeration oil?
What defines the miscibility of a refrigeration oil?
Which lubrication method uses a pump to force oil into the system?
Which lubrication method uses a pump to force oil into the system?
In which lubrication method does the crank case act as a sump for lubricating oil?
In which lubrication method does the crank case act as a sump for lubricating oil?
What is the limit for the organic acidity in lubricating oils?
What is the limit for the organic acidity in lubricating oils?
What is the key property of oil that determines its ability to resist electrical flow?
What is the key property of oil that determines its ability to resist electrical flow?
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Study Notes
Compressor Leak Testing and Charging
- Recharge pipe and suction pipe must be hermetically sealed.
- Leak testing conducted on hermetic sealed compressors is essential prior to charging.
- Charging pipe connected with high-pressure gauge should indicate 17.0 kg/cm² for gas charging.
- Oil must be added for lubrication before operating the compressor.
Objectives of Lubrication
- Understand the process of oil addition for compressor lubrication.
- Gain knowledge on properties of lubricating oil.
- Learn different methods of lubrication.
Importance of Lubrication
- Lubrication involves maintaining a film of oil to reduce friction between moving parts.
- Oil film is essential to dissipate heat generated during compressor operation.
Properties of Refrigerant Oil
- Viscosity: Must align with manufacturer’s specifications for optimal performance (measured in Saybolt Universal Seconds, SSU).
- Low Acidity: Should maintain acidity levels below 0.05 to avoid corrosiveness.
- Low Flash Point: Oil must not ignite under operating temperature and pressure conditions.
- Low Pour Point: Indicates the lowest temperature at which oil remains fluid.
- Good Dielectric Strength: Oil must resist electrical flow to ensure safety.
- Chemical Stability: Should maintain compatibility with refrigerants and materials in the system.
- Miscibility: Oil must mix well with the refrigerant for effective operation.
Methods of Lubrication
- Splash Lubrication:
- Utilizes oil splashed onto surfaces from the crankcase, suitable for compressors up to 10 kW capacity.
- Crankshaft and connecting rods act as a means to lubricate via oil pooling.
- Forced Feed Lubrication:
- Employs a pump to circulate oil under pressure, returning it to the crankcase via gravity.
- Preferred for high-capacity compressors; ensures consistent lubrication under varying conditions.
Functionality of Hermetic Sealed Compressors
- Reciprocating compressors available from 1/8 HP to 15 HP capacity.
- Constructed to eliminate the need for shaft seals as motor and compressor share a common shaft within a welded steel shell.
- Precautions in assembly:
- Use new gaskets for an airtight seal.
- Align marks for proper fitting and sealing during assembly.
Operational Mechanism
- Compressor designed with suction intake positioned to allow vapor to travel through motor rotor holes before entering the shell.
- Centrifugal force aids in separating oil and liquid refrigerant from vapor, preventing valve damage.
- Oil is pumped from the crankshaft to the main bearings, enriching lubrication across critical components.
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