1.Roller labyrinth seal form
At present, Chinese belt conveyor idler sealing structure is labyrinth seal form, it mainly adopt annular seal teeth, via the neat arrangement of a number of annular seal teeth form a cavity and throttle gap between the two teeth, a number of sealing teeth can form a plurality of mazes, which is known as the labyrinth seal structure.The neat arrangement of the sealing teeth is to convert potential energy into kinetic energy, and the role of the cavity is to convert kinetic energy back into pressure energy, so as to provide power energy for the idler.Maze effect mainly refers to some chain reactions. When the fluid flows through the maze, it will be hindered and the flow rate will be weakened, which will lead to the creation of ventilation effect, thermodynamic effect and velocity contraction effect. The working principle adopted in the labyrinth seal form of conveyor idler is to use the sealing medium as a turning point, through the gap in the maze to create a throttling effect to complete the sealing leakage resistance work, it can provide power for the idler.But there are many defects for labyrinth seal, which is closely related to the working environment of belt conveyor.The working environment of belt conveyor is relatively poor, especially it is wet under the mine, therefore,we must strengthen the waterproof processing of the supporting roller structure. In essence, Labyrinth seal belongs to non-contact seal which lead to the labyrinth seal waterproof performance is poorer, at the same time seal has direct correlation with the belt conveyor speed, the faster the speed, the higher the roller work efficiency. It is necessary to combine the labyrinth seal with other seal forms so as to effectively improve the working efficiency of the roller In the design of the sealing structure.
2.Other sealing form for conveyor idler structure
The biggest technical difficulty of belt conveyor is the sealing of idler structure. In order to maximize the idler performance, it is necessary to strengthen the innovation of sealing form.Multiple sealing forms can be combined to ensure to improve the idler performance.
(1)Material upgrade produce a new structure of idler
The common material of conveyor idler is steel which is easy to be corroded and leads to the decrease of service life.In order to improve the corrosion resistance of idlers, nonmetallic idlers have been studied.Currently, nylon idler, resin idler and ceramic idler are widely used.Their service life is extended although the production cost is increased.Rollers made of these new materials are lighter in weight, resistant to corrosion and abrasion.
(2)Lip seal form
In order to replace the labyrinth seal, human began to study the contact seal, the most successful is the lip seal form,it will not affected by the roller running state and strengthen the treatment of the idler waterproof performance.The principle of lip type sealing form is relatively simple, mainly is to carry on special treatment to seal strip, adopted polyurethane cool material, this material stability is strong, not easy to be corroded and will not produce static electricity.In the installation of the idler, attention should be paid to the matching of the lip structure and the idler, so that the sealing effect is good when the idler works. No matter the idler works or stops, the sealing effect will not change.
(3)Other forms of sealing structure
Beside above mentioned two types idler seal structure, there are some special seal structure which are basically used in a specific environment, such as special seal structure.The parts of this structure need to be specially treated, using the principle of centrifugal force to throw the impurities out of the oil cup bearing when it pass through the idler.Because of the high cost, it is not widely used in industrial production now.