【Mechanical Equipment Technology Edition】Daily Question 201808023: Refrigeration Systems—Case Analysis (2.4)
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This year, the 【One Question per Day】 series 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 those who comment on this post will receive 1-3 wealth points; those who give a complete answer will get 10-15 points, with the validity period being two days. This device is a Wu Leng type unit, and its lubrication mode is pre-lubrication upon startup. Later, the oil pump stopped working. Could you explain what pre-lubrication means? Under what conditions can pre-lubrication be used? (Image 1) https://attach01.hcbbs.com/forum/201808/22/134523gv33gogp77xlrakh.jpg.thumb.jpg (Image 2) https://attach01.hcbbs.com/forum/201808/22/134552dg4rybkggo1rr8o2.png.thumb.jpg (Image 3) ============================== High-quality promotions: Mechanical equipment——Videos on the repair and adjustment of York compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Process for maintaining 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 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=
At the beginning of compressor startup, the oil pressure required at each oil supply point and slide valve is provided by the pre-lubrication pump. Once the compressor is operating properly and the pressure difference between exhaust and intake reaches the desired value, the pre-lubrication pump is stopped, and lubrication is provided by the pressure difference.
Before starting the propane engine, the pre-lubrication pump is turned on; the engine can only start once the oil pressure reaches the predetermined value. Once the oil pressure reaches the set value, the lubrication pump stops
Pre-lubrication: At the beginning of compressor startup, the pressure oil required for lubricating various points within the compressor, as well as for adjusting the volume ratio via the control valves and for load reduction through the energy control valve, is supplied by a pre-lubrication oil pump. Once the compressor is operating normally, whether the pre-lubrication oil pump continues to run depends on the pressure difference between the exhaust pressure and the suction pressure; the oil pump stops operating when this pressure difference reaches 0.45 Mpa, and it starts operating again when the pressure difference is below 0.35 Mpa.
1. Under what circumstances is a pre-lubrication pump installed? An oil pump system is a common oil circulation system used in screw chillers. In particular, when the compressor employs sliding bearings (main bearings), when the screw speed is high, or when there are speed-increasing gears, a pre-lubrication oil pump must be installed in the chiller. Before each startup, the pre-lubrication pump is started first to establish a certain oil pressure, after which the compressor can start properly. Once the unit is operating stably, the system oil pressure can be supplied either by the oil pump or by the condensing pressure; at this point, the pre-lubrication pump can be turned off. 2. Pre-lubrication: Firstly, this unit operates with oil or in a mixed mode. Before it is started up, the system has only the oil pump to supply oil. To address the lubrication issues before and during startup, the oil pump must keep running until the unit is operating steadily. Once that is achieved, the unit can be supplied with oil by the system’s pressure difference, and the oil pump can then be stopped. In the case of mixed operation, the oil pump needs to continue running in order to address the fuel supply issue together with the system’s fuel supply. Therefore, the lubrication provided by the oil pump before and during driving is called “pre-lubrication”.
1. Pre-lubrication: In units that operate with oil, it is not possible to supply lubricating oil before starting up, as the system lacks the power to deliver oil; as a result, the unit cannot be started. Without resolving this issue, a pre-lubrication pump can be installed to operate before the machine starts, supplying lubricant to the unit. Once the machine is running stably, the system will supply lubricant based on pressure differences, at which point the pre-lubrication pump can be turned off. 2. Under what circumstances is pre-lubrication used? Pre-lubrication is generally employed when the unit uses sliding bearings, operates at high speeds, or is equipped with speed-increasing gears.
This post was last edited by yehuaqi007 on 2018-8-27 at 13:56. Grease pressure settings: 1. Pressure setting for starting the main engine; 2. Pressure setting for shutting down the auxiliary oil pump.
Pre-lubrication involves starting the lubricating oil pump in advance of compressor startup to ensure forced lubrication; once the pressure difference between the inlet and outlet of the compressor reaches a certain value (in our case, it stops at 0.45 MPa and starts automatically at 0.43 MPa), this pressure difference is used to achieve lubrication.