seal of roots blower

The seal of Roots blower includes three seals at the shaft extension of the driving shaft, the oil seal at the end of the bearing seat, and the shaft seal at the wall plate. The shaft seal of the wallboard is mainly to prevent gas leakage. In addition to preventing oil leakage, the other two parts sometimes also require gas sealing.

 Hermetic sealing device

Generally, the structure that mainly seals gas is called hermetic sealing device, and the one that plays the role of oil sealing alone is called oil sealing device. Roots blower wallboard shaft sealing devices commonly used include labyrinth seals, packing seals, expanding ring seals and mechanical seals; commonly used sealing devices for driving shaft extensions include skeleton oil seals or mechanical seals. The oil seal at the end of the bearing seat often adopts an oil return groove structure or a skeleton oil seal group to seal.

1. Auxiliary oil tank 2. Shaft extension seal of the driving shaft 3. Oil seal at the end of the bearing seat

4. Shaft seal of wall panel 5. Main fuel tank 6. Wall panel 7. Chassis

1. Labyrinth seal

It is a non-contact dynamic seal that uses fluid to flow through a series of throttling gaps and expansion cavities to make the working medium produce a throttling effect to limit leakage. Labyrinth seals are widely used in the shaft seals of the wallboards of Roots blowers. The sealing mechanism can be simply explained as that the fluid passes through many tortuous passages, and after many times of throttling, a great resistance is generated, making it difficult for the fluid to leak, so as to achieve the purpose of sealing. Its advantages are that it is not restricted by the speed and temperature, the structure is simple, the maintenance is convenient, and the service life is long. Appropriately increasing the number of sealing teeth can be used for high-pressure gas sealing; if the seals are processed and assembled well, they will generally not malfunction during operation and do not need to be replaced frequently. The main disadvantage is that the sealing parts require high machining accuracy.

Due to the small sealing gap, friction and wear will occur when the machine runs poorly, thereby reducing the sealing performance. This kind of seal is generally suitable for the occasion of conveying air, and its use is restricted when conveying toxic, flammable and explosive gases. The standard type Roots blower wallboard seal generally adopts this form of seal.

2. Packing seal

Packing seal is a form of sealing that uses packing to fill the leakage channel to prevent leakage. The packing seal has simple structure, convenient assembly and disassembly, and low cost, so it has been widely used. In the packing and sealing structure of Roots blower, packing packing, molded polytetrafluoroethylene packing and skeleton oil seal group packing are more commonly used. Because this type of seal is a contact type seal, it is easy to cause wear of the shaft (the part in contact with the oil seal lip or PTFE packing).

3. Expanding ring seal

The expansion ring seal is to put several elastic rings with slits in the sealing groove. Due to the elastic force of the expansion ring itself, the outer circle of the expansion ring is tightly attached to the shell, and there is no relative rotation between the outer diameter of the expansion ring and the shell. The gas can only leak downstream through the gap between the expansion ring and the annular groove. When working, the expansion ring is closely attached to the downstream end surface of the annular groove under the action of the gas pressure difference on both sides. The high-pressure gas entering the gap fills the back gap space, which further strengthens the seal between the outer circle of the expansion ring and the inner hole of the sealing seat, and the remaining leakage channel is only the notch of the expansion ring. Since the cut gap is very small, and the slices are installed in a staggered position during installation, after several expansion rings are sealed, only a few go out. If the pressure gas sealing device is installed, the sealing effect will be better. Because this type of seal is a contact type seal, the sealing effect is better, but it needs to be greased and lubricated during use. The newly developed expansion ring made of special material can be used without grease. The shaft seal of the wallboard adopts the above three sealing forms. When the wallboard structure is open, the conveyed gas will not leak into the fuel tank, but may leak to the atmosphere. The lubricating oil will not leak into the casing. When a closed wall panel structure is used, the conveyed gas may leak into the fuel tank. When used as a vacuum pump, lubricating oil may leak into the casing when pumping a vacuum.