Lubrication and maintenance mechanisms of common machine pumps

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I. Lubrication Mechanism Lubrication involves adding a lubricant between two friction surfaces that are in relative motion, thereby creating a lubricating film between them. This film separates the surfaces that were in direct contact, turning dry friction into friction between the molecules of the lubricant. As a result, friction is reduced, wear is diminished, and the service life of mechanical equipment is extended. 1. Lubrication function ⑴. Controlling friction: After lubrication is applied between the friction surfaces, the lubricant acts as a barrier between them, separating the two surfaces and turning dry friction into friction between the lubricant molecules. As a result, the coefficient of friction and the frictional resistance between the surfaces vary depending on the degree of lubrication present there. ⑵Reduce wear: Lubrication reduces wear because it lowers friction to its minimum, thereby preventing welding and tearing of the metal surfaces. Furthermore, the cleaning effect of liquid lubricants is also very effective in removing impurities such as dust and metal particles from the friction surfaces of mechanical parts, thereby preventing wear. ⑶Cooling down: During the operation of mechanical equipment, it is necessary to overcome the friction at various friction surfaces in order to perform work, and the energy spent overcoming this friction is entirely converted into heat. As a result, the temperature of the friction surface rises, causing thermal deformation of the metal until its melting point is reached, which leads to adhesion between the friction surfaces. (Welcome to follow WeChat: Pump Butler) Lubricants are excellent heat dissippers, as they can carry heat away to the cooling surfaces in a timely manner. ⑷To prevent rusting of the friction surfaces: The friction surfaces of various machines inevitably come into contact with surrounding substances such as air, water droplets, water vapor, corrosive gases and liquids, dust, oxides, etc., which causes the metal surfaces to rust and become corroded and damaged. When the friction surface is covered with a lubricant, rust caused by this can be prevented. ⑸Sealing effect: As lipids have a self-sealing property, they not only prevent the loss of lubricants but also stop the intrusion of moisture and impurities. In a compressor, there is a high degree of sealing between the cylinders and pistons; oil also plays a role in this regard. The hydraulic oil used for hydraulic transmission possesses sealing properties as well. ⑹, transmitting power such as in hydraulic transmission. ⑺, vibration damping – The shock absorbers in cars (and motorcycles) use fluid to reduce vibrations; the piston moves up and down within a sealed cylinder, and the fluid inside the cylinder flows from one end to the other in the opposite direction to the piston’s movement, thereby dissipating the vibrations of the vehicle through friction with the fluid. 2. The importance of equipment lubrication Equipment is one of the elements of enterprise production. To keep the equipment in good technical condition, it is necessary to pay attention to its maintenance during use and to carry out lubrication in a proper and thorough manner. Only in this way can friction be controlled, wear reduced, the energy consumed in the transmission mechanism decreased, the lifespan of the equipment extended, equipment damage and failures minimized, and maintenance costs lowered. Therefore, equipment lubrication is directly related to saving energy, materials, and labor, improving the quality, reliability, lifespan, and safety of mechanical products, and generating more material wealth. According to a statistic, over one-third of the world’s energy is ultimately lost as frictional losses in various forms during the transfer of energy by mechanical devices. 3. Reasons for equipment cleaning and oil change: Lubricating oil (grease) generates heat due to mechanical friction during use, as well as from agitation and mechanical shear. Additionally, factors in the surrounding environment such as air, water vapor, dust, and metal particles can cause it to oxidize and deteriorate over time, resulting in the formation of gums, asphalts, and acidic substances, which reduces its performance until it can no longer be used. If continued use occurs, it will corrode the components, block the oil circuit system, and a large amount of abrasive particles will be reintroduced into the friction surfaces, causing grooving and wear. Therefore, it is very necessary to establish an oil change schedule. II. Common lubrication methods 1. Manual oil (grease) lubrication: The operator regularly fills the oil holes and oil cups with oil using an oil can or oil gun. 2. Drop lubrication: Oil is allowed to flow, under the effect of gravity, through a controllable small hole in a drip device, thereby supplying lubrication to the relevant areas at regular intervals. 3. Lubrication using oil wicks and oil pads: One end of the oil wick and oil pad is immersed in the oil reservoir, while the other end comes into direct contact with the moving surfaces of the friction pair; capillary action is utilized to allow oil to flow into the friction pair for lubrication. 4. Oil ring or oil chain lubrication: In this type of lubrication, an oil ring or oil chain is fitted over the shaft journal, with its lower part submerged in an oil reservoir. As the shaft rotates, friction drives the oil ring to spin, thereby carrying oil into the bearings for lubrication. 5. Oil bath or splash lubrication: The lubrication method in which the friction surfaces are immersed in a pool of lubricating oil is called oil bath lubrication. The lubrication method in which moving parts that rotate by being immersed in an oil pool, or oil-scattering discs and plates attached to the shaft, spread the lubricating oil from the oil pool onto the friction surfaces is known as splash lubrication. The most typical equipment that uses oil bath and splash lubrication is a sealed gearbox. 6. Forced lubrication: An oil wedge or oil film is forced to be formed on the friction surfaces by externally supplied pressurized oil, using devices such as lubrication oil pumps. For example: 1. Rolling bearings use oil bath or splash lubrication in combination with oil ring lubrication, as in ordinary horizontal centrifugal pumps. 2. Sliding bearings are lubricated by forced lubrication, such as through an oil pump. 3. The crankcase is lubricated by oil bath. III. Mechanism of pump maintenance 1. Oil level gauge: Based on the simple principle of a communicating vessel, it maintains a certain liquid level for easy observation; typically, the normal liquid level is set at half to two-thirds of the total height. Structural features: glass tube, with openings on it and a discharge plug on the side, etc. 2. Oil cup: also known as a constant-level oil filler. Features: negative pressure liquid column balance principle, inclined surface design of the outlet, and control of the lowest liquid level. 3. Oil seal: It is usually of the labyrinth type or centrifugal type. But it is only a dynamic seal, not a static seal; therefore, it does not provide absolute sealing, and excess fuel will overflow. 4. The vent plug is usually located next to the fuel filling plug; it helps to balance the pressure inside and outside the tank by releasing excess gas, and it also prevents dust and other particles from entering. 5. The shell walls are often designed as fin-type to facilitate efficient heat dissipation. 6. The water cooling jacket is usually of the finned tube type. 7. Fan blades: commonly used on motors; pumps can be used as an optional component. 8. Common problems: (1) Low oil level – Insufficient oil bath; the oil cannot reach all the friction surfaces, resulting in dry friction that damages the bearings. Generally, the normal oil level should be set at 1/3 to 2/3 of the tank. ⑵Excessive oil filling leads to a smaller cooling space, causing the oil to overheat easily; this first affects the properties of the oil and reduces its lubricating effect. At the same time, under intense stirring, it is easier for excessive gas to dissolve in, resulting in oil foaming (that is, bubbles in the oil). It disrupts the balance of the oil cup; continuous injection leads to an increasing amount of oil, and the more oil there is, the more this phenomenon occurs, creating a vicious cycle. ⑶The deterioration of oil quality is usually caused by expiration, water intrusion or other impurities that lead to emulsification, as well as the mixing of different types of oil.