[Mechanical Equipment Technology Edition] Daily Question 201801011: Common Faults in Refrigeration Systems (5.3)
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This post was last edited by YORK Industrial Refrigeration on 2018-1-13 at 10:45. Starting from now, in order to enhance communication among users, a 【Daily Question】 campaign has been launched 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 score will be assigned after that period. What do you think are the necessary conditions for a screw compressor to maintain stable performance? (Analysis can be focused on the compressor itself; there is no need to consider the system.) 1. First, the oil supply must be sufficient (in terms of quality), and the quality of the oil must be guaranteed (through proper maintenance and oil changes). 2. The axial and radial clearances of the compressor screws must be kept within the designed ranges! (Bearing condition assurance) ============================== Premium products: Mobile equipment – Maintenance procedures for York screw compressors https://bbs.hcbbs.com/thread-1806833-1-1.html Mobile equipment – Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Mobile equipment – Major repairs for GEA Grasox screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Mobile equipment – Disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Mobile equipment – Disassembly and maintenance of Japanese Maekawa MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
The influence of factors such as spindle speed, exhaust pressure, and ambient temperature on compressor performance.
This post was last edited by “The Moon in My Hometown is Round” on January 11, 2018, at 12:41. What do you believe are the necessary conditions for ensuring stable performance of screw compressors? (You may analyze this from the perspective of the compressor itself; there’s no need to consider the entire system.) Good alignment, appropriate gaps, and no stress in the pipelines.
Spindle speed, exhaust pressure, and ambient temperature, etc
The influence of factors such as spindle speed, exhaust pressure, and ambient temperature on compressor performance.
Compressor, manufacturing quality of various components, assembly quality of the compressor,
During the trial operation and running-in phase of screw compressors, this process is essential for mechanical products; the consequences of lacking such a running-in phase or of an inadequate running-in process are significant. Such as: cylinder scoring, abnormal leakage from piston rings, severe leakage in the stuffing box, and other such faults ； Screw air compressors may produce abnormal noises, have elevated temperatures, excessive vibration, and even fail to operate properly; damage to the star wheel in single-screw air compressors occurs from time to time. Eliminate it through running in. Possible faults that can occur during the operation of a screw compressor: 1. Fault symptom: High exhaust temperature of the unit (above 100°C). · The lubricating oil level in the unit is too low (it should be visible through the oil sight glass, but not more than half full) ； · The oil cooler is dirty; a special cleaning agent must be used to remove the oil deposits ； · The oil filter element is clogged and needs to be replaced ； · Thermostatic valve failure (faulty component); clean or replace it ； · Fan motor failure ； · Cooling fan damaged ； · The exhaust duct is not unobstructed, or the exhaust resistance (back pressure) is high ； · The ambient temperature exceeds the specified range (38°C or 46°C) ； · Temperature sensor failure ； · Is the pressure gauge faulty (relay-controlled unit)? 2. Fault symptoms: High fuel consumption by the unit or high oil content in the compressed air. · There is too much lubricating oil; the correct level should be checked when the unit is under load, at which point the oil level should not exceed half of the tank ； · Oil return line blocked ； · The installation of the return oil pipe (distance from the bottom of the oil separation element) does not meet the requirements ； · The exhaust pressure is too low while the unit is operating ； · Oil separation core is broken ； · The partition inside the separation cylinder is damaged ； · There is oil leakage in the engine unit ； · The lubricant has deteriorated or been used beyond its expiration date. 3. Fault symptom: Low pressure in the unit · Actual gas consumption is greater than the gas output of the unit ； · Vent valve failure (fails to close under load) ； · The intake valve is faulty and cannot open fully ； · The minimum pressure valve is stuck; it needs to be cleaned, readjusted, or replaced with a new one ； · There is a leak in the user’s pipeline network ； · The pressure switch setting is too low (relay-controlled unit) ； · Pressure sensor failure ； · Gauge failure (relay-controlled unit) ； · Pressure switch failure (relay-controlled unit) ； · The input hose of the pressure sensor or gauge is leaking. 4. Fault symptom: Excessively high exhaust pressure of the unit · Faulty intake valve, which requires cleaning or replacement ； · The pressure switch setting is too high (relay-controlled unit) ； · Pressure sensor failure ； · Gauge failure (relay-controlled unit) ； · Pressure switch failure (relay-controlled unit). 5. Fault symptom: High current in the unit · Too low voltage ； · The connection is loose; check for any signs of heating or burning ； · The unit pressure exceeds the rated pressure ； · The oil separation core is clogged and needs to be replaced ； · Contactor failure ； · Host failure (the belt can be removed to manually turn the shaft a few times for inspection) ； · The main motor is faulty (the belt can be removed to manually turn the motor a few times for inspection), and the motor’s starting current should also be measured. 6. Fault symptom: The unit cannot start. · Fuse is damaged ； · The temperature switch is broken ； · Check whether the main motor or the main unit is stuck, as well as whether the motor is rotating in reverse ； · The main motor thermal relay has tripped and needs to be reset ； · The fan motor thermal relay has tripped and needs to be reset ； · The transformer is broken ； · Fault not resolved (PLC-controlled unit) ； · PLC controller failure. 7. Fault symptoms: High current or tripping when the unit starts · Problem with the user’s circuit breaker ； · The input voltage is too low ； · The star-delta conversion interval is too short (it should be 10–12 seconds) ； · Intake valve failure (excessive opening or sticking) ； · The connection is loose; check for any signs of overheating ； · Host failure (the belt can be removed to manually turn the shaft a few times for inspection) ； · The main motor is faulty (the belt can be removed to manually turn the motor a few times for inspection), and the starting current should be measured again after restarting the machine. 8. Fault symptom: Fan motor overload · Deformed fan ； · Fan motor failure ； · Fault (aging) of the fan motor thermal relay; it needs to be readjusted or replaced with a new one ； · Loose connection ； · Cooler clogged ； · The exhaust resistance is high. 9. Fault phenomenon: The main engine gets stuck, causing the unit to shut down. · The unit uses low-quality lubricant, which increases the frictional resistance of the main engine under high temperature and pressure, leading to its sticking ； · The bearings of the host need to be replaced after long-term use ； · The belt or pulleys are not installed correctly.
This post was last edited by “Hasty Passerby” on January 12, 2018, at 10:58. “Stable performance of screw compressors” should at least encompass the following aspects: 1. The unit operates normally; 2. It meets performance indicators such as cooling efficiency; 3. The continuous operating time meets the required standards. Therefore, the necessary conditions (from the perspective of the compressor itself) should be: proper leveling of the housing, proper alignment of the rotor, appropriate clearance, airtight sealing of the housing, and no additional external stresses
The lubrication and cooling systems are very important provided that the installation components are correct.