Analysis of the damage of sliding bearings
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Analysis of the damage of sliding bearings
Source: China Bearing Network Time: 2014-08-04
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According to the long-term experience of diesel engine repair, the common methods of early damage of sliding bearings are mechanical damage, bearing cavitation, fatigue pitting, corrosion and so on.
(1) Mechanical damage The mechanical damage of the sliding bearing means that the alloy surface of the bearing bush exhibits a different degree of groove marks; in severe cases, the metal peeling occurs on the touch surface and a large area of ​​messy scratches are present, usually; the touch surface damage and ablation The appearance of the image together. The primary cause of the mechanical damage of the bearing is that the bearing surface is difficult to form an oil film or the oil film is severely damaged.
(2) Under the repeated effect of bearing cavitation sliding bearing in cylinder pressure impact load; plastic deformation and cold work hardening on the outer surface; some loss deformation and sufficiency; gradually forming lines and expanding; then following the falling of wear debris; The surface layer of the loaded outer layer is formed. Usually, when the bearing is cavitation, the pit is firstly formed; then the pit is gradually enlarged and the interface of the alloy layer is cracked; the crack expands along the parallel direction of the interface; until the drop stops. The primary cause of bearing cavitation is; because the cross-section of the oil-slot and oil hole and other layout elements are suddenly changed, causing a fierce imbalance of oil flow; the bubble is formed in the vacuum zone where the oil is lost; then the pressure rises; the bubble collapses and the cavitation 3. Cavitation often occurs in the high load zone of the bearing; such as the lower bearing of the main bearing of the crankshaft.
(3) fatigue pitting corrosion fatigue pitting refers to; because the engine is overloaded; the bearing operation is overheated and the bearing clearance is too large; the formation of the middle of the bearing fatigue damage, fatigue pitting may be tired and fall. This damage is mostly due to overload The bearing gap is too large; perhaps the lubricating oil is unsanitary and the inside is mixed with foreign matter. Therefore, the application should focus on avoiding overloading of the bearing. Do not operate at too low or too high speed. When idling, adjust the engine to stability. To ensure normal bearing clearance; to avoid excessive or too low engine speed, to view and adjust the operation of the cooling system; to ensure that the operating temperature of the engine is suitable.
(4) Bearing alloy corrosion bearing alloy corrosion is usually the area is not pure oil; chemical impurities (acid oxides, etc.) in the lubricating oil cause the bearing alloy to oxidize to form acidic substances; the bearing alloy is somewhat dropped; Regular fine holes or small pits. The primary cause of corrosion of bearing alloys is improper selection of lubricating oil and poor corrosion resistance of bearing data; perhaps engine operation is rough and temperature is too high.
(5) There is a small convex metal surface between the bearing burning fuse journal and the bearing conflicting pair; it has some high temperature; in the case of lack of lubrication and poor cooling; the bearing alloy is black or some is melted. The problem is often caused by the cooperation between the journal and the bearing. The lack of lubricating oil pressure also makes the bearing burned.
(6) bearing the outer circle bearing outer circle is the bearing has a relative transformation in the seat hole. After the bearing goes outside the circle; not only affects the heat dissipation of the bearing; simply makes the alloy inside and outside the bearing ablate; and also causes the bearing back surface damage; When the bearing is burned, its primary cause is; the bearing is too short, the crown is damaged, the processing may not meet the standard.
2. Avoiding the early damage of sliding bearings is much more common than bearing incineration; therefore, it is important to avoid early damage of sliding bearings. The correct protection of sliding bearings is an effective way to reduce the early damage of bearings; it is also a reliable guarantee for the life of extended bearings. Thus; In the normal protection and repair; it is necessary to pay attention to the appearance of the bearing's alloy appearance, reverse surface, end and marginal edge; if there is an abnormal display of half-wearing signs; it is necessary to carefully identify the reasons; and adopt the corresponding method; improve Bearing operating conditions; focus on the early damage to the sliding bearings.
(1) Improve the depiction of the bearing and the process of drawing or selecting the bearing; consider the heat balance of the bearing to control the temperature rise. Because the bearing works in conflict situations; because the internal friction (viscosity) of the lubricating oil constitutes power consumption; After the heat is generated, the temperature rise of the bearing is caused; the viscosity of the lubricating oil is lowered, and the gap is changed; the babbitt alloy of the bearing is softened; when the sever is severe, the "burning the shaft and holding the shaft" is caused. Thus; in the layout depiction; the upper bearing of the bearing (from the bearing) The non-loading area) is opened into the oil hole; the lubricating oil is introduced from the non-load bearing area, and the oil groove is opened in the longitudinal direction or the lateral direction with the oil inlet hole in the inner and outer surfaces of the bearing bush; the lubricating oil is evenly distributed on the journal to control the temperature rise. According to the operation of the bearing; the bearing information needs to have the following functions: conflict coefficient. Bad both the blade and the smashing stool. The ridiculous 20. The mellow oyster mushroom Hanxia 芰 浚 浚 浚 愎 愎 慷 慷Benzene is coated. Therefore, the bearing material can be selected from babbitt. Babbitt alloy can work well under stable load; but cavitation is easy to occur under unsteady load; so it is not suitable for high power engine. Lead base And low-tin-lead-based alloys have higher strength and hardness; stronger fatigue resistance and cavitation resistance; better application in high-power engines. In recent years, foreign countries have exhibited sputtering methods using physical vapor deposition. Copper-lead bearing external nickel plated with 20% tin alloy coated with pure tin may be plated with pure tin; the effect is very good. In addition; the full round oil groove bearing bush is changed to semi-circular oil groove or some oil groove bearing bush; this can not only improve the lubrication of the engine sliding bearing Situation; and can also improve its carrying ability.
(2) The repair of the improved bearing and the quality of the equipment improve the quality of the hinge of the bearing; ensure that the reverse lubrication of the bearing is not mottled; the positioning bump is intact, and the amount of spring opening is 0. 5-1. 5mm; this ensures the rear bearing of the equipment With its own elastic force and the bearing housing hole tightly fit, each end of the upper and lower bearing pads installed in the bearing housing should be 30-501μm higher than the bearing seat plane; the high output can ensure the bearing cap bolts are tightened according to the regular torque. The bearing seat is closely cooperated; the self-locking force of the conflict is satisfied; the bearing is not loose; the heat dissipation effect is good; the bearing ablation and wear are avoided; the working surface of the bearing cannot be measured by the scraping method to reach 75%-85% touch impression; When the joint is not scraped, the cooperation gap between the bearing and the journal can reach the demand. In addition, the equipment should pay attention to the processing quality of the crankshaft journal and the bearing; strictly implement the repairing process standard; avoid the equipment failure due to improper loading method and The bearing bolts have uneven torque or do not conform to the rules; then the occurrence of tortuous deformation and stress gathering; inducing early bearing damage.
(3) Reasonable selection and filling of lubricating oil In the process of application, lubricating oil with small oil film surface tension should be selected; the impact of oil flow will be reduced when the bubble formed is reduced.è ¡ ã–鹊 ã–鹊 ã–鹊 ã–鹊 æ«è±¢ åº é»¾ åº é»¾ åº é»¾ åº é»¾ åº é»¾ åº é»¾ ç° ç° ç° ç° . . . . . . . . . . . . . . . . . . . . Huan Le Valley Weisong ç•šé”– 耄 耄 耄 北 北 北 北 北 北 北 北 芊庑Ч 芊庑Ч 芊庑Ч æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡. Different quality, different viscosity grades and different types of lubricants are used to stop mixing; the deposition time before lubricating oil filling is usually not less than 48h.
(4) When properly protecting and protecting the bearing of the engine equipment; the surface of the shaft and the bearing should be coated with the regular brand of sanitary oil. After the engine bearing is installed, the fuel switch should be closed before the initial start; I idling a few times; when the engine oil pressure gauge appears, turn it on again, turn the fuel switch on; turn the throttle to the low speed position; start the engine to investigate the operation. The idle speed can not exceed 5 minutes. Do the new machine and the overhaul engine In the running-in period, the grinding industry cooperates; during the running-in period, the load is suddenly increased and the load is sharply increased and the operation is high. The engine is completed after full-load operation for a long time; it cannot be stopped immediately; it is necessary to let the engine work at no load for medium and low speed for 15 minutes. Stop; otherwise the internal heat will not be able to dissipate. Strengthen the sanitation and protection of the oil filter and crankcase ventilation equipment; replace the filter element in time according to the requirements of the manual to ensure the normal operation of the engine cooling system; control the normal temperature of the engine; avoid heat dissipation "opening the pot"; prohibit driving without cooling water, use fuel properly; precisely adjust the gas phase and burn Burning timing, etc.; avoiding abnormal engine burning, timely reviewing and adjusting crankshaft and bearing skills.
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