The lubrication system is a system for delivering lubricants to the friction points of machines or units, including a complete set of devices for conveying, distributing, regulating, cooling and purifying lubricants as well as the reference, alarm and monitoring of parameters such as pressure, flow and temperature and failure. In the lubrication work, according to the actual conditions of various equipment, reasonable selection and design of the lubrication method, lubrication system and device, to ensure that the equipment has a good lubrication condition and working performance and maintain a long service life, has very important significance.
Generally speaking, the lubrication system of mechanical equipment should meet the following requirements:
1) Ensure that a certain pressure of lubricant is supplied uniformly and continuously to each lubrication point, and the oil is sufficient, and can be adjusted according to needs.
2) High working reliability. Use effective sealing and filtration devices to keep the lubricant clean, prevent dust and moisture from the outside environment into the system, and prevent pollution of the environment due to leakage.
3) Simple structure, as far as possible standardized, easy maintenance and high-speed adjustment, easy to check and replace lubricant, low initial investment and maintenance costs.
4) With the indicator of working parameters, alarm protection and condition monitoring device, can detect the lubrication fault in time.
5) When the lubrication system needs to ensure appropriate lubricant working temperature, it can be equipped with cooling and preheating devices and heat exchangers
Three lubrication elements must be considered in the design of the lubrication system, namely: (1) the type of friction pair (such as bearings, gears, rail and other supporting components) and its operating conditions (such as speed, load, temperature and oil film formation mechanism); (2) Types of lubricants (such as lubricating oil, fat or solid, gas lubricants) and their properties; (3) Types of lubrication methods and oil supply conditions.
1. Classification of lubrication systems and methods
1) Classification of lubrication systems and methods
At present, there are many types of lubrication systems and methods used in mechanical equipment. Usually, according to the use of lubricants and the situation, it is divided into two categories: decentralized lubrication system and centralized lubrication system; At the same time, these two types of lubrication systems can be divided into total loss and cyclic lubrication.
In addition to the above classification, according to the type of lubricant provided, the lubrication method can be divided into lubricating oil lubrication (or thin oil lubrication), lubricating grease lubrication (or dry oil lubrication), solid lubrication, gas lubrication, etc.
(1) Dispersion lubrication is often used to lubricate the lubrication points of dispersion or individual components. In its lubrication can also be divided into total loss (or "a junction lubrication") type and circulation type two basic types, such as the use of portable refueling tools (oil pot, oil gun, hand brush, chlorosol spray gun, etc.) on the oil, oil nozzle, oil cup, rail surface lubrication point manual refueling, and oil rope or oil pad lubrication, splash lubrication, oil ring or oil chain lubrication.
(2) centralized lubrication uses complete oil supply devices to supply oil to many lubrication points at the same time, which is often used for the lubrication of transmission, feed box, the whole or complete set of mechanical equipment and automatic production line. The centralized lubrication system can be divided into manual control, semi-automatic control and automatic control according to the way of oil supply. It can also be divided into total loss system, circulation system refers to the lubricant sent to the lubrication point, no longer recycling recycling, often used for lubricant recovery is difficult or no recovery, the amount of oil is small, difficult to place oil or oil pool occasions. The lubricant of the circulating lubrication system is sent to the lubrication point for lubrication and then flows back to the tank for recycling. The hydrostatic lubrication system is a system that uses the external oil supply device to transport the lubricant with a certain pressure to the hydrostatic support for lubrication.
2) Type of centralized lubrication system
Centralized lubrication system is the most widely used system in mechanical equipment. There are many types, which can be roughly divided into the following 7 types:
(1) Throttle type uses fluid resistance distribution lubricant, the distributed lubrication dose is proportional to the pressure and flow hole size, the oil supply pressure range is 0.2 ~ 1.5MPa, the lubrication point can be more than 300.
(2) The single-line lubricant is fed to the nozzle through the single-line main path at intermittent pressure (direct or delayed) and then to the lubrication points. The oil supply pressure range is 0.3 ~ 21MPa, and the lubrication point can be more than 200.
(3) Under the action of pressure, the dual-line lubricant is sent to the quantitative distributor through two main channels which alternately change the flow direction of a direction control valve. Depending on the alternating rise and fall of the lubricant pressure in the main channel, the quantitative distributor is ahead of the alternating rise and fall of the lubricant pressure in the main channel to control the quantitative distributor, so that the quantitative lubricant is sent to the lubrication point. Oil supply pressure range 0.3 ~ 40MPa lubrication points up to 2000.
(4) The multiple outlets of the multi-line multi-head oil pump have a pipeline that directly sends the quantitative lubricant to the corresponding lubrication point. Piping can be arranged in parallel or in series. Oil supply pressure range 0.3 ~ 40MPa, lubrication points can be up to 2000.
(5) Progressive by the pressure lifting control of the quantitative distributor according to the predetermined progressive procedure to send the lubricant to the lubrication points. Oil pressure range 0.3 ~ 40MPa, lubricating points in more than 800.
(6) Oil mist/oil-gas mist/oil-gas lubrication is a lubrication method in which compressed air and lubricating oil are mixed and sent to the lubrication point by the condensing nozzle or nozzle with oil mist or fine oil droplets. The oil supply can be adjusted, the lubricating oil can be suspended with the compressed air containing oil mist, pollution to the environment, when necessary, the ventilation device can be used to eliminate waste gas.
When this lubrication method is used, compressed air must be used after moisture removal and purification. At the same time, the lubricating oil is best with antioxidant additives.
The difference between oil mist and oil and gas lubrication is that the former has oil particle size of 1 ~ 3m, while the latter has oil particle size of 50 ~ 100m, usually in the form of tiny oil droplets, which can be transported over a much shorter distance than the former.
(7) Hybrid lubrication system composed of the above lubrication system.
2. Selection principle of lubrication system
In the design of the lubrication system, the lubrication requirements of each part of the mechanical equipment should be comprehensively analyzed to determine the types of lubricants used and minimize the types of lubricants and lubricating devices. In order to ensure the good lubrication of the main parts, the lubrication of other lubrication points should be considered comprehensively to ensure the lubrication quality. The lubrication system should not only meet the needs of lubrication in the operation of the equipment, but also adapt to the working conditions and operating environment of the equipment, so as to avoid inappropriate friction, temperature, noise and premature failure. The oil supplied by the lubrication system should be kept clean to prevent the intrusion of external dust and other causes pollution and damage to the friction surface, so as to improve the reliability in use. The main components of complex lubrication system such as pump, distribution valve, filter, etc. should be properly combined and standardized as far as possible, easy access to maintenance, cleaning, reduce equipment operation and repair, maintenance costs, to prevent the occurrence of personal and equipment safety accidents.
In the selection of lubrication system, attention should be paid to the degree of automation and reliability of the system, pay attention to the installation of indication, alarm and condition monitoring devices, predict and prevent early lubrication failure, in order to improve the operation rate and service life of the equipment.
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