Analysis of Main Faults of Disc Separator

1. Introduction

Disc separator is a multifunctional and efficient separation machine, which is widely used in chemical, pharmaceutical, food and other industries. Compared with other separation machines, disc separator has its unique structure, which is mainly manifested in:

(1) The drum is composed of more than one hundred parts, and each part has a precise relative position.

(2) The vertical shaft is supported by two rolling bearings, the upper bearing is placed on an elastic support composed of 6 radial springs.

(3) The vertical shaft system is driven by a pair of screw gears, which are used for speed increase transmission.

Therefore, disc separator has a different failure mode from other machines. The usual methods can’t effectively monitor and diagnose the faults. It is necessary to conduct a detailed analysis of the disc separator.

2. Spring Failure

The elastic support of vertical shaft consists of axial springs and radial springs. Axial springs are mainly used to buffer the impact caused by the installation of the drum. The radial springs directly affect the dynamic characteristics of the vertical shaft system. One of its main functions is to reduce the critical speed of vertical shaft system, so that the working speed of disc separator is between the first and second critical speeds of vertical shaft system. The second function is to buffer and reduce vibration, and reduce the vibration transmitted from the vertical shaft system to the machine base.

Radial springs are under the action of large alternating stress. If the stress exceeds the fatigue limit of the spring material, fatigue cracks will appear, the stiffness of the spring will decrease, and then the springs will break. Under normal conditions, the stiffness of the 6 radial springs is basically equal, and the equivalent stiffness of the elastic support in all directions is also basically equal. If the stiffness of a spring decreases or even breaks, it will cause inconsistency in the equivalent stiffness in all directions. This will not only reduce the buffering and vibration reduction effect, but also increase the load of the remaining springs, aggravate the vibration.

Different supporting stiffness in various directions will lead to different vibration amplitudes. In the direction where the equivalent stiffness decreases, the vibration amplitude of the drum will increase, while the vibration amplitude in this direction on the base will decrease. This characteristic can be used to effectively diagnose spring failure.

3. Drum Imbalance

The speed of the disc separator is very high, generally around 7000r/min. The drum is large in size and heavy in weight, a small imbalance will cause a large vibration. Excessive vibration may cause the following adverse consequences:

(1) It increases the dynamic load of the bearing.

(2) It affects the meshing of the screw gears, increases the unevenness of the load between the teeth, and also increases the dynamic load on the gears, shortening the service life of the gears.

(3) The drum will hit the casing or the inlet and outlet pipes.

Therefore, drum imbalance is the most common and serious fault of the disc separator. The drum imbalance faults can be divided into the following two categories:

(1) Permanent deformation of the drum during use.

(2) Loosen of the discs.

4. Bearing Failure

Most disc separators use rolling bearings to support the horizontal and vertical shaft systems. Under normal operating conditions, rolling bearings mainly have the following failure forms:

(1) Pitting.

(2) Permanent deformation.

Improper use and maintenance, poor sealing and lubrication can also lead to abnormal failure forms of rolling bearings, such as wear, bonding, cracking of inner and outer rings and retainers.

5. Screw Gear Failure

Gear failure is also one of the main faults of disc separator. Compared with other machines, the gear transmission of disc separator is unique.

Firstly, its horizontal shaft and vertical shaft are perpendicular to each other, and a pair of screw gears are used for transmission.

Secondly, the working speed of most machines is lower than that of the motor, so the gears are mainly used to reduce speed. However, the disc separator is just the opposite. Its working speed is very high. Therefore, this pair of screw gears is used for speed-increasing transmission, which determines that its failure forms are mainly the following:

(1) Glue bonding.

(2) Wear and tear.

(3) Plastic deformation.

(4) Pitting.

6. Conclusion

This article systematically explains the main faults of disc separator, laying a good foundation for future status monitoring and diagnosis work.