Introduction of rotary joint mechanical seal-

Introduction of rotary joint mechanical seal

　2017-08-25　　

Introduction of mechanical seal of rotary joint:

The rotary joint is a special mechanical seal that connects the static pipe to the rotating element, which can transfer liquid from the static pipe to the rotating equipment for cooling, heating or pressurizing. At the same time, a large number of types of single-channel and multi-channel unbalanced and balanced devices can be provided to process water-containing coolant, hydraulic oil, heat transfer oil, air, gas or steam.

The following introduces several types of rotary joint structures. Figure 2-7 shows the structure of a single fluid rotary joint. The pipe joint 1 is the rotating part connected with the rotating cavity, and the joint body 6 is the stationary part connected with the static cavity. The sealing part is composed of 7, 8, 9, 10, and 11. There is only one fluid channel. Figure 2-8 shows a dual-fluid rotary joint structure. The pipe joint 1 is the rotating part connected with the dynamic cavity, and the joint body 11 and the pipe joint 9 are static parts, which can be connected to the two fluid static chambers respectively. There is fluid inside and outside the inner tube. , Nos. 6, 10, 12, 13, 14 are sealed parts to prevent fluid leakage; 8 and 16 are sealed to prevent fluids from mixing. This structure is expanded on the basis of Figure 2-7.

Figure 2-7 Single fluid rotary joint

Figure 2-8 Dual fluid rotary joint

From the above two types of rotary joint structures, it can be seen that rotary joints have different structures in different applications, but no matter how the structure changes, they all include three major parts, namely the rotating part, the sealing part and the stationary part. The rotating part is connected with the rotating cavity, and the static part is connected with the static cavity. There is a complete fluid channel between the two parts. The sealing part seals the fluid to prevent fluid leakage and fluid mixing.

When designing a rotary joint, the design form is classified according to pressure, temperature, speed and fluid type. For details, please refer to the corresponding standard JB/T8725-1998. Two typical designs are shown in Figure 2-9 and Figure 2-10.

Figure 2-9 shows a small rotating head with a net inner diameter of 5mm, which is used to inject cooling liquid into a machine tool shaft under a pressure of less than 10.1MPa. An axially movable stainless steel compensation ring is paired with a carbon ring welded to the rotating diaphragm inside the ball bearing. In other words, for abrasive liquids, it can be provided in combination with end faces. In order to minimize friction, the seal diameter should be as small as possible for a given flow area. The device is designed to reach a speed of 1500r/min.

Figure 2-9 High-speed rotating head

Figure 2-10 High temperature rotating head

Figure 2-10 shows a high temperature rotary joint for steam or heat transfer oil up to 2.0MPa. A floating carbon seal ring has a radial end surface on one side and a convex end surface on the other side. A sliding bearing, also made of carbon graphite, transmits the spring force to the sealing interface. When carbon is impregnated with resin, the working temperature is allowed to reach 250°C, and when metal is impregnated, it is allowed to reach 350°C. The temperature-resistant gasket is used for static sealing.

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