Selection and assembly of main bearings for paper machinery
Imported bearings are indispensable general parts in rotating machinery. Wrong selection, poor installation, improper use, and untimely maintenance will affect the life of the bearing, cause equipment failure, and cause major economic losses. Therefore, the correct selection and use of bearings has always been one of the most important issues for paper companies. Zhongshan United Hongxing Paper Co., Ltd., after continuous exploration and improvement on the use of the company's% u0026 paper width paper machine bearings, summarized some experience in the use of bearings, changed many bad habits in the use and assembly of bearings, and received certain results. The selection principle of the bearing The normal service life of the bearing is called the narrow life. When the bearing is running, the rolling surfaces of the inner and outer rings of the bearing and the rolling surfaces of the rollers, due to repeated loading, the material produces fatigue pitting. The occurrence of the raceway surface and the rolling surface is usually called spalling ('()*+,- ) The scale-like damage of the fish. The principle of selecting rolling bearings is generally based on load, speed and working environment (mainly temperature) as reference values. The rated life of rolling bearings is calculated by the following formula: !'. $' //' #($%)! Where: #——— Rotation Speed%——— Equivalent Dynamic Load!—— Life Index (Ball bearing is #, rolling The sub-bearing is $'#)$——Rated dynamic load ($. u0026 '·u0026'u0026#·u0026()) where: u0026 '——— Life Coefficient u0026#——— Speed u200bu200bCoefficient u0026(——— Temperature Coefficient u0026'——— Load factor. Correct the rated dynamic load according to the actual use temperature and speed and other parameters, and then select the basic model of the bearing according to the direction and size of the rated dynamic load. Of course, the actual service life of the bearing is also related to other factors Such as material, size, cage structure, type of lubricating grease, etc. are related, so I won’t repeat them here. The most worn-out bearings in the paper machine are: dryer bearings, transmission gear bearings, press rolls, net-driving rolls and other large roller bearings The most commonly used bearing is a double-row cylindrical roller bearing with tapered bore. The working load is relatively large, the static load is mostly $' 0 !12, the rotation speed is 1'' 0/'' 3 4u0026+, and the ambient temperature is relatively high. !'! The selection and use of the bearings in the dryer section and the use of the company’s cutting width% u0026 the paper machine is the first domestically largest paper machine ($55! put into production every year). The total weight of a single dryer (including media) is about $' 2. Design When considering that the load on the transmission side is larger than the operation side, the operation side bearing adopts #$$#6%The mating design adopts transitional mating 86 4 */ (base hole system, it should be the base shaft system), the inner ring is fixed with push-off sleeve. But refer to Sweden 9:; the diameter of the tapered hole double row cylindrical roller bearing provided by the bearing manufacturer According to the standard for adjusting the clearance, the bearings of the ordinary clearance group cannot meet the minimum allowable clearance and the minimum clearance reduction at the same time! The conditions. After that, the clearance is adjusted to the minimum clearance of the operating side according to a certain tightening force $!' 'u0026, the minimum clearance on the transmission side $1' 'u0026. In actual use, the temperature rise of most bearings is higher, and some of them reach more than $''<, and even burn out, and they are forced to shut down for maintenance.!'# The selection and use of the press section and wire section bearings. Positive pressure rolls, composite: large rolls such as pressure rolls, vacuum rolls, and screen drive rolls are the most commonly used tapered hole double row cylindrical roller bearings. $$#/%%. The design of the dryer section has similar bearing fits, and bearing sintering often occurs. Several situations often encountered during bearing use ($) The inner ring and the shaft head rotate relative to each other due to the fact that the bearing does not meet the requirements of the pre-tightening force when the bearing is installed The journal is severely worn; sometimes the installation tightness is too large, and the bearing is in operation, due to insufficient thermal expansion space, which causes the inner ring to burst, the rollers fall off, and even other equipment. (!) Improper fit between the bearing housing and the outer ring of the bearing When the tightness is too high, the two materials have different expansion coefficients. The bearing seats are mostly gray cast iron or cast steel. The inner and outer rings of the bearing are made of high-carbon chromium steel. Under a certain temperature, the transition fit becomes Interference fit, when the amount of interference exceeds a certain range, it will cause the outer ring to burst. When the gap is too large, the outer ring of the bearing Rotate relative to the bearing seat, wear the bearing seat, cause the roller to vibrate violently, and cause paper breakage and difficulty in guiding the paper. The above accidents are caused by incorrect use of bearings.