what is swivel unions

A rotary joint is a sealing device that connects stationary pipelines and rotating equipment, achieving leak free fluid transmission under 360 ° rotation. It allows fluid media to flow smoothly between fixed pipelines and rotating machines, and is a key component in industrial equipment.

To choose the correct type of the rotary joint, first to understand the function and classification of the rotary joint. A rotary joint is a transition connection seal that inputs a fluid medium from a static system to a dynamic rotating system. The correct selection of rotary joint, can give full play to its use performance, prolong the service life, improve the working efficiency of the equipment. There are many classification criteria for rotary joints, which can be classified according to the circulation medium, channel number, sealing form, temperature, pressure, speed, etc.

Classification of rotary joints  :

2.According to the number of channels, it can be divided into single-pass rotary joint, double-pass rotary joint and multi-pass rotary joint.

3, according to the different sealing forms, it can be divided into mechanical seal rotary joint and hydraulic seal rotary joint.

4, according to the different pressure, can be divided into low pressure rotary joint, medium pressure rotary joint and high pressure rotary joint.

5, according to the different temperature, can be divided into normal temperature rotary joint and high temperature rotary joint.

6, according to the different speed, can be divided into low-speed rotary joint and high-speed rotary joint.

When selecting the rotary joint, first determine whether the rotary joint is single-pass, double-pass or multi-pass according to the structure and working principle of the equipment: if the input medium and the output medium are the equipment, select the single-channel rotary joint; if the input medium and the output medium are on the same side of the equipment, select the dual-channel rotary joint; if the equipment requires the delivery of multiple media or the medium to multiple locations, select the multi-channel rotary joint. Secondly, select the diameter of the rotating joint according to the flow rate of the input and output medium. Again, according to the pressure, temperature and speed of the medium and the speed of the roller. Finally, according to the roller and rotation connection The connection form of the head rotation shaft determines the flange connection or threaded connection and the connection form of the inner pipe.

1. The connection form of the rotating shaft and the roller of the rotary joint

The connection form of rotary joint rotating shaft and roller mainly includes thread connection and flange connection, thread connection mainly includes English thread, American NPT thread, metric thread, etc., flange connection has quick change flange connection and fixed flange connection.

2. There are two main forms of inner pipe rotation and fixed type (as shown below).

(1) The inner tube rotation type

The inner pipe is installed at the end of the rotary joint and rotates synchronously with the roller and the rotary joint, and the inlet and outlet media are separated by the O-ring or the grinding sleeve seal. Pay attention to the proper coordination tolerance with the installation hole. Too tight fitting will affect the service life of the rotating joint, and too loose fitting will affect the heating or cooling effect of the roller.

inside tube     The grinding sleeve   revolving joint

inside tube   O molding ring   revolving joint

Inner inner tube the O-ring seal

inside tube     Connect thread     revolving joint

Internal pipe fixed type

(2) Internal pipe fixed type

The inner pipe is installed at the end of the rotating joint and is connected with the rotating joint by thread. The inner pipe is static and not rotating between the roller and the rotating shaft of the rotating joint. It should be particularly noted that for the roller connected with the thread, the spiral direction of the inner pipe thread should be consistent with that of the roller thread.

Two questions about customer inquiries.

1. Selection of spiral direction of rotary joint thread (as shown below).

Roller rotation direction

Rotary joint thread rotation

The termination of the rotation direction of the roller

• If the equipment is only rotated in one direction, the rotary joint and the equipment can be threaded or flange connection; if the equipment rotates in two directions, only flange connection can be used.
• For the threaded connected rotary joint, remember that the rotation direction of the thread of the rotating joint is opposite to the rotation direction of the roller, that is, standing at the end of the installed rotary joint to see the roller. If the roller rotates clockwise, select the rotary joint of the left-handed thread, and if the roller rotates counterclockwise, select the rotary joint of the right-handed thread.

2. termination of internal tube length

For the rotating joint of the inner pipe, when the inner pipe is too long, it will cause the rotating joint to beat and grind, which will affect the sealing effect and shorten the service life of the rotating joint. In this case, the inner pipe of the rotating joint can be made into two sections, and the support is added on each section, which can not only minimize the beating of the inner pipe, but also limit the axial movement of the inner pipe, to ensure the smooth operation of the rotating joint after installation. For example, Bruckner production line with meet rotating joint DXSR280K this situation is more common, the following figure is because the inner tube is too long, resulting in the inner tube beating is large, axial movement is severe, so that the case is serious, thread wear.