【Mechanical Equipment Technology Edition】Daily Question 20171017: Fault Analysis of Refrigeration Systems
Thread Content
This post was last edited by YORK Industrial Refrigeration on 2017-10-20 at 08:39. Starting from now, in order to enhance communication among users, we have launched the \"One Question per Day\" activity on the Mechanical Equipment Technology forum. We hope everyone will participate actively to progress and improve together! ! ! Rewards: 3 wealth points for active participation, 10-15 wealth points for correct answers. This question is valid for two days; no scoring will be given after that period. Motion sickness! It is presumably a nightmare for every refrigeration compressor; please explain the causes of moisture accumulation in compressors and the damage it causes to them! 1. When the refrigerant fails to absorb heat or does so insufficiently, liquid or wet vapor is drawn into the compressor, a condition known as wet compression. 2. Causes of wet compression: (1) Whether the elevation of the gas-liquid separator in the system is below the standard level (which requires it to be at least 1.2 meters above). (2) The automatic control of the liquid level in the system has failed. (3) Excessive and rapid manual liquid supply (or internal leakage in the throttle valve or it being opened too wide). (4) The intake shut-off valve was opened too quickly. (5) Excessive liquid in the auxiliary equipment, low heat load, and rapid startup loading. (6) Sudden increase in heat load (rapid freezing) or failure to make adjustments promptly after defrosting. 3. Consequences of faulty compressors: In mild cases, there is slight vibration; in more severe cases, oil leakage occurs, and in the most serious situations, the bearings inside the compressor get damaged and the screws wear out. ================================ Premium promotions: Mechanical equipment – Maintenance procedures for York screw compressors http://bbs.hcbbs.com/thread-1806833-1-1.html Mechanical equipment – Upgrading York Quinton control centers http://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment – Major repairs for GEA Grasox screw compressors http://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment – Disassembly and maintenance of British HOWDEN screw compressors http://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment – Disassembly and maintenance of Japanese Maekawa MYCOM screw compressors http://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1786445
1. When the refrigerant fails to absorb heat or does so insufficiently, liquid or wet vapor is drawn into the compressor, a condition known as wet compression. 2. Causes of wet compression: (1) Whether the elevation of the gas-liquid separator in the system is below the standard level (which requires it to be at least 1.2 meters above). (2) The automatic control of the liquid level in the system has failed. (3) Excessive and rapid manual liquid supply (or internal leakage in the throttle valve or it being opened too wide). (4) The intake shut-off valve was opened too quickly. (5) Excessive liquid in the auxiliary equipment, low heat load, and rapid startup loading. (6) Sudden increase in heat load (rapid freezing) or failure to make adjustments promptly after defrosting. 3. Consequences resulting from water entering the compressor (1) Liquid enters the compressor, destroying the lubricating oil film and causing numerous bubbles to form, leading to unstable oil pressure. (2) Oil-free friction during the acceleration of moving parts leads to scuffing, shaft seizure, melting of babbitt main bearing shells, and the failure of those parts. (3) Since the liquid is incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be affected; in particular, the exhaust cover may be lifted by the impact force. The deformation of the safety spring can lead to the piston breaking or the connecting rod being torn apart, as well as damage to the engine block, which may result in catastrophic failures. In severe cases, the cylinder head and gaskets may be damaged, posing a risk to human safety.
What are the reasons for moisture accumulation in the compressor? ① Is the elevation of the gas-liquid separator in the system below the standard (it should be above 1.2m). ②The automatic control of the liquid level in the system has failed. ③Manual liquid supply is too large or too rapid (or the throttle valve has internal leakage or is opened too wide). ④The intake shut-off valve was opened too quickly. ⑤Due to excessive liquid in the auxiliary equipment, the heat load is low, resulting in too rapid startup loading. ⑥Sudden increase in heat load (quick freezing) or failure to make adjustments promptly after defrosting. 3. What are the consequences of moisture entering the compressor? ① Liquid enters the compressor, destroying the lubricating oil film and creating numerous bubbles, resulting in unstable oil pressure. ②Accelerated oil-free friction in moving parts leads to scuffing, shaft seizure, melting of the babbitt main bearing shells, and the destruction of the components. ③Since liquids are incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be damaged; in particular, the exhaust cover may be lifted by the impact force. The deformation of the safety spring can lead to the piston breaking or the connecting rod being torn apart, while collisions with the engine block can result in damage. In severe cases, the cylinder head and gaskets may be damaged, leading to serious accidents that can harm people.
When the refrigerant fails to evaporate by absorbing heat or does so insufficiently, the liquid or wet vapor form of the refrigerant is drawn into the compressor, a condition known as wet compression. For piston machines: (1) The refrigerant enters the compressor, causing a large number of bubbles to form in the lubricating oil, which destroys the oil film on the lubricated surfaces and also leads to unstable oil pressure. (2) Operating the moving parts without proper lubrication leads to scuffing; in severe cases, the shaft bearings and the Babbitt alloy of the main shaft melt. (3) The refrigerant enters the compressor, causing the cylinder liner to cool down rapidly and contract, thereby gripping the piston ； In severe cases, it can damage the cylinder liner, piston, connecting rod, and piston pin. (4) Since liquids are incompressible, the forces acting on the connecting rods and pistons under oscillating conditions far exceed the design values, making damage highly likely ； Since the liquid is incompressible, under flooding conditions, the exhaust valve assembly along with the cover will be lifted by the force of the liquid ； In severe cases, it can cause the safety spring to deform, leading to catastrophic accidents such as the destruction of the engine block and cylinder head, as well as the rupture of gaskets, which can injure people. For screw compressors: moisture accumulation can cause vibration and increased noise, as well as damage to the rotor and bearings due to excessive stress ； Severe water intrusion can also damage equipment and cause accidents.
Reason: 1. Is the elevation of the gas-liquid separator in the system below the standard (it is required to be above 1.2 m)? 2. The automatic control of the liquid level in the system has failed. 3. Excessive and rapid manual liquid supply (or internal leakage in the throttle valve or it being opened too wide). 4. The suction stop valve was opened too quickly. 5. Excessive liquid in the auxiliary equipment results in a low heat load, leading to too rapid loading when the system is started up. 6. Sudden increase in heat load (quick freezing) or failure to make adjustments promptly after defrosting. Harm: 1. When liquid enters the compressor, it destroys the lubricating oil film, causing numerous bubbles to form and resulting in unstable oil pressure. 2. The acceleration of moving parts leads to oil-free friction, resulting in scuffing, shaft seizure, melting of the babbitt main bearing shells, and the failure of the components. 3. Since liquids are incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be affected; in particular, the exhaust cover may be lifted by the impact forces. The deformation of the safety spring can lead to the piston being damaged or the connecting rod breaking as a result of compression against the cylinder wall, which in turn can cause damage to the engine block. In severe cases, the cylinder head and gaskets may be damaged, resulting in serious accidents that can harm people.
When a refrigerant fails to absorb heat or does so insufficiently, causing liquid or wet vapor to be drawn into the compressor, this condition is known as wet compression; reasons for wet compression: (1) whether the elevation of the gas-liquid separator in the system is below the standard value (which requires it to be at least 1.2 meters above the surface)； (2) Failure of the automatic control level in the system ； (3) Excessive and rapid manual liquid supply (or internal leakage in the throttle valve or it being opened too wide) ； (4) The intake shut-off valve was opened too quickly ； (5) Excessive liquid in auxiliary equipment, low heat load, rapid loading upon startup ； (6) Sudden increase in heat load (rapid freezing) or failure to make adjustments promptly after defrosting ； Consequences of water ingress in the compressor: (1) Liquid enters the compressor, destroying the lubricating oil film and creating numerous bubbles, resulting in unstable oil pressure ； (2) Oil-free friction during the acceleration of moving parts leads to scuffing, shaft seizure, melting of babbitt main bearing shells, and the disposal of the components ； (3) Since the liquid is incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be affected; in particular, the exhaust cover may be lifted by the impact force. The deformation of the safety spring can lead to the piston breaking or the connecting rod being torn apart, as well as damage to the engine block, which may result in catastrophic failures. In severe cases, the cylinder head and gaskets may be damaged, posing a risk to human safety.
When a refrigerant fails to absorb heat or does so insufficiently, causing liquid or wet vapor to be drawn into the compressor, this condition is known as wet compression; reasons for wet compression: (1) whether the elevation of the gas-liquid separator in the system is below the standard value (which requires it to be at least 1.2 meters above the surface)； (2) Failure of the automatic control level in the system ； (3) Excessive and rapid manual liquid supply (or internal leakage in the throttle valve or it being opened too wide) ； (4) The intake shut-off valve was opened too quickly ； (5) Excessive liquid in auxiliary equipment, low heat load, rapid loading upon startup ； (6) Sudden increase in heat load (rapid freezing) or failure to make adjustments promptly after defrosting ； Consequences of water ingress in the compressor: (1) Liquid enters the compressor, destroying the lubricating oil film and creating numerous bubbles, resulting in unstable oil pressure ； (2) Oil-free friction during the acceleration of moving parts leads to scuffing, shaft seizure, melting of babbitt main bearing shells, and the disposal of the components ； (3) Since the liquid is incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be affected; in particular, the exhaust cover may be lifted by the impact force. The deformation of the safety spring can lead to the piston breaking or the connecting rod being torn apart, as well as damage to the engine block, which may result in catastrophic failures. In severe cases, the cylinder head and gaskets may be damaged, posing a risk to human safety.
Answer: When a refrigerant fails to absorb heat or does so insufficiently, causing liquid or wet vapor to be drawn into the compressor, this condition is known as wet compression. Reasons for compressor flooding: ① Is the elevation of the gas-liquid separator in the system below the standard (it should be above 1.2m). ②Automatic level control in the system is malfunctioning. ③ Manual liquid supply is too large or too rapid (or there is a leak in the throttle valve or it is opened too wide). ④The intake shut-off valve was opened too quickly. ⑤Due to excessive liquid in the auxiliary equipment, the heat load is low, resulting in too rapid startup loading. ⑥Sudden increase in heat load (quick freezing) or failure to make adjustments promptly after defrosting. Consequences of moisture entering the compressor: ① Liquid enters the compressor, destroying the lubricating oil film and creating numerous bubbles, resulting in unstable oil pressure. ②Accelerated oil-free friction in moving parts leads to scuffing, shaft seizure, melting of the babbitt main bearing shells, and the destruction of the components. ③Since liquids are incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be damaged; in particular, the exhaust cover may be lifted by the impact force. The deformation of the safety spring can lead to the piston breaking or the connecting rod being torn apart, while collisions with the engine block can result in damage. In severe cases, the cylinder head and gaskets may be damaged, leading to serious accidents that can harm people.
Reason: 1. Is the elevation of the gas-liquid separator in the system below the standard (it is required to be above 1.2 m)? 2. The automatic control of the liquid level in the system has failed. 3. Excessive and rapid manual liquid supply (or internal leakage in the throttle valve or it being opened too wide). 4. The suction stop valve was opened too quickly. 5. Excessive liquid in the auxiliary equipment results in a low heat load, leading to too rapid loading when the system is started up. 6. Sudden increase in heat load (quick freezing) or failure to make adjustments promptly after defrosting. Harm: 1. When liquid enters the compressor, it destroys the lubricating oil film, causing numerous bubbles to form and resulting in unstable oil pressure. 2. The acceleration of moving parts leads to oil-free friction, resulting in scuffing, shaft seizure, melting of the babbitt main bearing shells, and the failure of the components. 3. Since liquids are incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be affected; in particular, the exhaust cover may be lifted by the impact forces. The deformation of the safety spring can lead to the piston being damaged or the connecting rod breaking as a result of compression against the cylinder wall, which in turn can cause damage to the engine block. In severe cases, the cylinder head and gaskets may be damaged, resulting in serious accidents that can harm people.
Reasons for moisture accumulation in the compressor: ① Is the elevation of the gas-liquid separator in the system below the standard (it should be above 1.2 m). ②The automatic control of the liquid level in the system has failed. ③Manual liquid supply is too large or too rapid (or the throttle valve has internal leakage or is opened too wide). ④The intake shut-off valve was opened too quickly. ⑤Due to excessive liquid in the auxiliary equipment, the heat load is low, resulting in too rapid startup loading. ⑥Sudden increase in heat load (quick freezing) or failure to make adjustments promptly after defrosting. Harm of moisture in the compressor ① Liquid enters the compressor, destroying the lubricating oil film and creating numerous bubbles, resulting in unstable oil pressure. ②Accelerated oil-free friction in moving parts leads to scuffing, shaft seizure, melting of the babbitt main bearing shells, and the destruction of the components. ③Since liquids are incompressible, this can cause the piston, piston pin (the screw rotor vibrates and generates noise due to liquid expansion), connecting rod, and cylinder liner to be damaged; in particular, the exhaust cover may be lifted by the impact force. The deformation of the safety spring can lead to the piston breaking or the connecting rod being torn apart, while collisions with the engine block can result in damage. In severe cases, the cylinder head and gaskets may be damaged, leading to serious accidents that can harm people.
Due to the low temperature, Pv/T is a constant value; the pressure is also low, below the saturated vapor pressure, which causes bubbles to burst