【Mechanical Equipment Technology Edition】Daily Question 201801027: Common Faults in Refrigeration Systems (8.4)
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This post was last edited by YORK Industrial Refrigeration on 2018-1-29 at 08:39. Starting from now, in order to enhance communication among users, a \"Question of the Day\" activity 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. Are there any requirements regarding oil temperature when the compressor is started? Why? Everyone’s analysis is good – when the machine starts up, the oil temperature should not be too low; if it is, the viscosity of the lubricating oil increases. The oil temperature is too high, resulting in low viscosity of the lubricant. Too high or too low viscosity can affect the lubrication effect! In winter, when the oil temperature is low, do not start loading too quickly; wait until the oil temperature rises before beginning to load, otherwise oil leakage may occur! High oil temperature occurs when the machine is started; if the viscosity of the oil is too low, oil leakage is likely to happen, and the lubrication effect will also be significantly reduced! This situation is usually caused by a lack of refrigerant, or issues with the liquid supply, or problems with heat exchange in the condenser. ============================== High-quality promotions: Mechanical equipment——Maintenance procedures for York screw compressors https://bbs.hcbbs.com/thread-1806833-1-1.html Mechanical equipment——Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment——Major repairs for GEA Grasox screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment——Disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment——Disassembly and maintenance of Japanese Maekawa MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
Are there any requirements regarding oil temperature when the compressor is started? Why? Answer: The oil temperature must not be lower than 15 degrees. Low oil temperature and high viscosity can easily cause compressor vibration and poor oil return.
There must be requirements, as the viscosity of oil is related to temperature
There are requirements. Excessively high oil temperature reduces the effectiveness of cooling the bearings, leading to an increase in their temperature. Furthermore, an increase in oil temperature also reduces the viscosity of the lubricating oil, which can lead to the breakdown of the local oil film, resulting in loss of lubrication. This reduces the bearing’s load-carrying capacity, and in severe cases, it can even cause the lubricating oil to carbonize and lead to bearing damage. If the oil temperature is too low, the viscosity of the oil increases, which in turn raises the frictional force resulting from the oil film lubrication; as a result, the power consumption of the bearings increases. Furthermore, it also thickens the oil film, resulting in machine vibration caused by the vibration of the oil film.
When the compressor starts up, the oil temperature should be 30 degrees. The viscosity of lubricating oil increases at lower ambient temperatures. Stall or overload may be displayed during startup.
The tank temperature is kept at around 60°. This applies to lubricating oils. At 60°, the viscosity of the lubricating oil is the optimal level for lubricating the unit’s bearings!
Answer: Starting conditions are generally specified in the compressor design: the oil temperature must be above 20 degrees; otherwise, it cannot start. Keeping the oil temperature above 20 degrees is intended to prevent the lubricant temperature from dropping too low in winter, which could result in excessive viscosity, difficulty in starting the compressor and the oil pump, as well as inadequate lubrication. The oil temperature is too low, resulting in high viscosity of the oil, which causes instability of the oil film and leads to vibration.
There are requirements regarding oil temperature when starting the compressor; the oil must be heated to a certain temperature in order to be fully degassed and for its viscosity to meet the requirements for operation.
Before starting the turbine, the oil system should be activated first, with the oil temperature maintained between 35–45°C. Keeping an appropriate oil temperature is necessary to enable the lubricating oil to form a proper oil film in the bearing shells. If the oil temperature is too low, the viscosity of the oil increases, resulting in an overly thick oil film. This not only reduces the load-bearing capacity of the oil film but also leads to unstable operation. However, if the oil temperature is too high, the oil viscosity decreases, making it difficult to form an oil film and thus preventing lubrication.