Abstract: This paper analyzes the failure of bearing bush of feedwater pump and puts forward a solution. The hundred tons of alkaline boiler is the key design of Yue Paper's “alkali recycling workshopâ€, and its high-pressure feed pump is of course the focus of maintenance. However, no matter if How to maintain it, its "small temper" is not changed, and from time to time, it is necessary for you to replace it with its "two-leg" sliding bearing.
This feed pump is a sub-high pressure boiler feed pump, model DG45-80x7, with two pairs of plain bearings, corresponding to the shaft diameter! 55; with its matching motor power is 150kW, speed 2950rpm. Due to production needs, the feed pump long-term in a high-speed, high-load operation, so it is easy to make people think that this failure of the bearing should be within the normal range, but the fact Not so.
The structure of the sliding bearing is shown as follows: The bearing is a split type sliding bearing consisting of two upper and lower watts. The center of the upper bearing is provided with a filler groove, which is specially designed for the lubrication of the oil ring (note that the bearing was originally lubricated with oil, and has now been changed to molybdenum disulfide lithium grease, the oil ring has been canceled); There are no oil guides in the direction.
Of course, the key to the problem is hardly seen here only from the structure of the bearing. We also need to compare the bearings after failure, see.
It can be seen from the figure that some parts of the lower bearing bush are quite worn, and there are regular and near-defective parts near the middle; the upper bearing shell has a little wear on the edge, but the other parts are still better. It can therefore be concluded that the failure of the bearing should be an abnormal failure and it is still far from its life limit. Here we can use the backstepping method. Let's assume that the failure of the bearing is due to the excessive load. We know that the load surface acting on the bearing surface is uniform and the bearing surface should be the entire bearing surface, not the Part of, that is to say, the failure should be the failure of the entire work surface at the same time, should not be part of it; the same reason, can also be denied to the limit of life. Why is it because of what caused it? Let's analyze it slowly.
Let's take a look at the position of the unworn portion, near the middle, and correspond to the tank groove of the upper bearing. The grease is easy to reach and replenish. The oil film is easy to form. This is the advantage of the relative wear part, so it is obvious. Failure is due to lubrication reasons. The first is the structure. The lower bearing shell is not designed with oil guiding grooves. Because the sliding bearing uses the oil film formed between the shaft and the bearing shell to achieve its function, it is conditional on the smooth lubrication of the supply grease to the oil film, and we do not design here. The oil guide groove, together with the relatively small clearance between the upper shaft and the lower bearing shell under the load, makes it difficult for the oil to reach all the sliding surfaces, it is difficult to form a certain oil film, or the oil film is difficult to be supplemented after the oil film is damaged to form a solid one. The oil film causes the bearing to be burned for a long time under the action of dry friction or mixed friction; secondly, the choice of bearing grease is not very good, although the molybdenum disulfide lithium grease in the molybdenum disulfide is attached to the metal surface. The force is very strong, it can generate a strong film, can withstand high contact pressure and high friction speed, but due to the common fault of grease, poor fluidity, poor cooling and cooling, it also makes it difficult to reach the entire sliding surface of oil, even the oil film Difficult to form, simply can not talk about what is used to carry the use of welding shrinkage top pressure welding Li Jia Yue Yang Lin paper set Co., Ltd. (414002) Abstract This paper mainly introduces the practical new technology of how to repair welding under high temperature and high pressure. It has been considered for many years that high pressure vessels and pipelines are not suitable for welding under high temperature and high pressure. On the other hand, high-pressure medium is easy to injure people at the repair welding site. However, in actual production, leakage of high-pressure vessels and pipelines is always inevitable. In order to repair containers and pipelines, it is necessary to reduce the pressure and stop production. The resulting losses and waste are inestimable. With the development of industrial production, the pressure of more and more mediums in the application of high-pressure vessels and pipelines is also increasing. The possibility of cracking and leakage has also increased. In order to ensure the continuous and normal production of the product, I have explored some welding welding work experiences in more than 20 years of welding practice, and found some welding techniques for cracks and cracked welding as top pressure welding.
Under normal circumstances, when the two flat plates are butt-welded in a free state, the gap between the workpieces should be opened to a certain angle before welding. With the progress of welding, the angle of opening is gradually reduced, and the welding burrs can be compared. Standard weldment. If the two plates are placed in parallel with a small gap, the two plates overlap in the welding, so that the welding work cannot be continued. The reason for the overlap is mainly caused by the internal stress generated during welding, which causes the welding seam to contract. Due to the shrinkage of the weld seam, various deformations of the welded structure can result, and therefore, the arrangement of the opening angle of the weld gap is quite important, and it is too small, resulting in too large overlap and slow shrinkage.
In the actual production of high pressure vessels, pipeline crack shape, from any end to the middle of the most competitive part and the welding plate so that the gap opening angle is very similar.
Mastering the law of welding shrinkage, the method of preventing welding deformation is applied to the welding work of high-pressure vessels and pipelines, and the welding speed is reasonably grasped. With the pressure generated by the shrinkage of the weld seam, the cracks are partially tensioned. Before cracking on both sides of the metal, the metal is generally an integral part. During the cracking process, it is generally not “drinking slag and lacking in flesh,†and the deformations on both sides are almost the same. Therefore, under the action of a sufficiently large external force, it can be tight and the weld joint shrinks. Under the effect of stress, the scorpion can achieve strict closure. Only the part that has been welded is strictly sealed during welding, and a section of stenosis is added. The section of welding will be tightened for a period of time. This is repeated until all welding is completed. This is a method of top pressure welding using welding deformation.
For example, the chemical workshop sent chemical caustic soda tube cracking, according to conventional must stop row of alkali, otherwise it can not repair welding, but the use of top pressure welding deformation method, the welding effect is better to save time without stopping row of alkali increase the benefits. Time June 2003 welding target concentrated alkali pipe diameter! 200mm tube pressure 4MPa repair welding time: 3 minutes repair welding effect use 4 months no leakage.
This method is only effective for cracks, but the operation must be proficient to move faster. In addition, pressure welding methods for the perforation of pipes, steam pipes, trachomas, and pores include: hammer welding, pipe welding, and plugging welding. These methods are often used in production. It is also relatively good, and it has played a great role in creating innovation and reducing consumption in the workshop.
Ability.
As for the solution, based on the above analysis, it is nothing more than to start from those two aspects. The first is to add the oil guide trough. Regarding the number and position of the oil guide trough, as long as it can ensure that the grease reaches full sliding, the oil will not drip or stagnate; secondly, the choice of lube oil product, according to the above parameters, we can Calculate the journal speed: Yanni is not suitable for grease.
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