High speed rotating joint
High speed rotating joint
Author Qing Bang; Zhu Xun;
The first problem of high-speed rotating joints is the speed problem. With high speed bearings, this one knows. But when rotating at high speed, the bearings represent only their own rotational speed problems. It is not only the bearings that determine the speed of the high speed rotating joints, but also the accessories that play a decisive role. And to solve the problem of sealing, it is necessary to solve two problems, one point is how to reduce the friction resistance of the sealing surface, how to solve the problem of high-speed rotation without leakage.
Domestic high-speed rotating joints are also manufactured by referring to foreign products. A high hardness mirror ring is used to reduce the friction of the sealing surface. For the time being, silicon carbide and ceramic rings are the most common. A sealing ring made of alloy is also used. The benefits of mirror rings made from alloys are not broken. You can use glue without setting it up. A method of high temperature pressing. But few high-speed couplings are seen in the country. Occasionally, some rotary joints from Japan and Korea will be inside. Silicon carbide or ceramic rings are used more and may be easier to make. But some of the domestic enterprises produced this kind of silicon carbide ring can not be used. Large silicon carbide rings may have some small pores, with little impact and are easy to spot. The difficulty is that the rotary joints are very small in size and require very high silicon carbide. Leaks are caused by a few pores. There is one thing, the most terrible, that is, the silicon carbide ring and the axis of concentricity. If there is a deviation of concentricity, it is easy to leak.
Some rotary joint production enterprises in order to solve the problem of concentricity, another static ring is made into a composite body. Thus, even though the silicon carbide ring is not concentric, it can be adjusted according to the assembly of the static ring. This effect is good. It solves the problem that the silicon carbide insert may not be concentric.
Another point is to solve the problem of high-speed rotating leakage. This is a dilemma. Spring is too tight will cause rotation is not flexible, not too loose spring top sealing ring function. Most of the rotating joints in China prefer to tighten the springs rather than loosen them. Worry about rotating joint, leak it up. In fact, this ignores a point. The centrifugal force at which the rotating joint rotates at high speed. As we see in the eye of the typhoon vortex. It was stormy outside, but inside it was relative. There was no wind or rain. The same is true of high speed rotating joints, because of centrifugal force when rotating at high speed. The medium of circulation is hard to close to the edge of the cover. So we don't need to exaggerate the function of the spring when we consider the speed, pressure and other problems of the high speed rotating joint. Just install the usual swivel joint to fit the spring.
High speed rotary joints also have to pay attention to, that is, bearing grease. Grease used in high speed bearings is different from plain bearings. We usually add grease to the bearings in order to increase the life of the bearings when we assemble the ordinary rotating joint. This can prolong the loss of the bearing grease, and can also play a role in reducing the temperature of the bearing. The high speed rotating joints are different. If the addition of grease will increase the resistance of the bearing rotation, not only can not play the role of cooling, but will affect the normal rotation of bearings. Therefore, the high speed rotary joint bearings can not add grease.
In order to cool the bearings of the high speed rotating joint, some rotating joints separate the two bearings at a distance. In this way, two bearings can be avoided to produce friction synchronously, and the utility model can also play the role of ventilation and cooling for bearings. At present, the distance between the bearings is usually between 5-10mm. It's better to have a few more vents at the separation of the bearings.
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Of course, the speed of the use of high-speed joints, because the speed is different, so the method is not the same. At present, there are eight thousand to ten thousand rotating joints, the sealing surface of the corresponding location of the shell, the opening is equipped with water pipes, so that water just a hole through the cover around, and then from the other side of the outflow. This is mainly aimed at sealing surface cooling. Air-cooled, too. The effect is not as good as water cooling. If the speed is not particularly high, you can consider in the face of the shell should be sealed in a few ventilation holes on it. This is for high speed rotating joints of over five thousand revolutions per minute.