[Mechanical Equipment Technology Edition] Daily Question 201805005: Common Faults of Screw Refrigeration Compressors (8)
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This post was last edited by YORK Industrial Refrigeration on 2018-5-7 at 11:40. This year’s 【Daily Question】is divided into three categories: screw refrigeration compressors, refrigeration systems, and oil circuits, aiming to provide a comprehensive understanding of refrigeration technology. (If you encounter something you don’t know or can’t answer, please actively look up information; as you do so, your skills will improve!) ) All participants in the comments on this post will receive 1-3 wealth points; those who give complete answers will get 10-15 points, with the validity period being two days. ============================== Common faults of screw refrigeration compressors (8): Continuing from Common faults of screw refrigeration compressors (6), I have a question: what are over-compression and under-compression, and what damage do they cause to the equipment? Under-compression: the external pressure ratio is greater than the internal pressure ratio. Over-compression: the internal pressure ratio is greater than the external pressure ratio. In both cases, power consumption increases and gas flow rate decreases. Furthermore, an increase in the current of the equipment leads to an increased load on the compressor, causing severe vibrations in the equipment and resulting in damage to the compressor. ============================== High-quality promotions: Mechanical equipment——Videos on the repair and calibration of York compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Maintenance procedures for York screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment——Major repairs of GEA Grasso 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=
Over-compression refers to a power-consuming process in which the pressure at the end of compression by the compressor is higher than the condensing pressure under which the system is operating, causing the exhaust valve to open momentarily to release gas from the system. Under-compression, on the other hand, is a power-consuming process in which the pressure at the end of compression is lower than the condensing pressure, resulting in some gas flowing back into the compressor until pressure equilibrium is reached. Both over-compression and under-compression increase the additional power consumption of the compressor, reduce its performance, and also cause the exhaust temperature to be higher.
When the external pressure ratio is greater than the internal pressure ratio, it is called under-compression; when the external pressure ratio is less than the internal pressure ratio, it is called over-compression. Both conditions lead to a decrease in the efficiency of the unit
At the moment when the compressor starts discharging, the gas pressure within the working volume is not equal to the pressure Pdk in the discharge chamber; this results in undercompression during isovolumetric compression and overcompression during isovolumetric expansion. This not only increases the cost of equipment manufacturing, but also, due to the longer process, the resistance in the pipelines increases, which in turn leads to higher power consumption... This results in over-compression or under-compression, thereby reducing economic efficiency.
The main faults of screw compressors – Main unit: Bearing damage; seal leakage; rotor seizure; solenoid valve failures, incorrect operation of the slide valve, friction between the rotor and the walls of the main cylinder, leading to increased vibration and rising temperatures. Auxiliary units: Cooler leakage, oil pump not delivering sufficient flow, evaporator leakage, blockages in the cooling water, etc. Overcompression refers to a power-consuming process in which the pressure at the end of compression by the compressor is higher than the condensing pressure under which the system is operating, causing the exhaust valve to open momentarily to release gas from the system. Undercompression, on the other hand, is a power-consuming process in which the pressure at the end of compression is lower than the condensing pressure, resulting in some gas flowing back into the compressor until pressure equilibrium is reached. Both overcompression and undercompression increase the additional power consumption of the compressor, reduce its performance, and also cause the exhaust temperature to be higher.
At the moment when the compressor starts discharging, the gas pressure within the working volume is not equal to the pressure Pdk in the discharge chamber; this results in undercompression during isovolumetric compression and overcompression during isovolumetric expansion.
Over-compression refers to a power-consuming process in which the pressure at the end of compression by the compressor is higher than the condensing pressure under which the system is operating, causing the exhaust valve to open momentarily to release gas from the system. Under-compression, on the other hand, is a power-consuming process in which the pressure at the end of compression is lower than the condensing pressure, resulting in some gas flowing back into the compressor until pressure equilibrium is reached. Both over-compression and under-compression increase the additional power consumption of the compressor, reduce its performance, and also cause the exhaust temperature to be higher.
When the external pressure ratio is greater than the internal pressure ratio, it is called under-compression; when the external pressure ratio is less than the internal pressure ratio, it is called over-compression. Both conditions lead to a decrease in the efficiency of the unit