Characteristics of LC Roots Pump and Vacuum Sealing Materials

1、 LC Roots Pump Characteristics Roots vacuum is a mechanical booster pump used to obtain medium and low vacuum, and also belongs to dry vacuum pumps. It can generate suction and exhaust effects by synchronously rotating two 8-shaped rotors in the pump chamber. Its principle is similar to that of a Roots blower, but due to its operation in a low pressure range, the molecular free path of the extracted gas is larger, and the resistance to gas leakage through small gaps during backflow is greater, thus achieving a higher compression ratio. The conventional Roots pump can only be used as a booster pump, and it cannot work alone to directly discharge the extracted gas into the atmosphere. It needs to be used in series with the front stage vacuum pump. The gas extracted by the LC Roots pump needs to be discharged through the front stage vacuum pump before it can be discharged into the atmosphere

Classification

The differentiation method is mainly based on the number of rotor blades.

The common name for an LC Roots pump generally refers to a two blade LC Roots pump, with two "8" rotors inside the pump

At present, there are also three blade LC Roots pumps that are widely produced, and the rotor inside the pump body is a three blade type

Note: If you do not understand the two differences mentioned above, please refer to the corresponding rotor

The difference between ZJP and ZJ on the model is only that the air outlet is different, and the internal mechanism is still the same. The ZJP type has both downward and lateral flow and an overvoltage protection valve, while the ZJ type only has downward flow

Features

1: There are gaps between the rotor and the pump body, side cover, and between the rotor and the rotor, which are not in contact with each other. Therefore, A. There is no friction between the moving parts of the pump chamber, resulting in low power consumption and low operating and maintenance costs.

. B. The moving parts inside the pump chamber do not require oil lubrication and sealing, avoiding contamination of the vacuum system caused by oil vapor backflow. C. The LC Roots pump is not sensitive to small amounts of dust contained in the extracted gas

2: The rotor has good geometric symmetry, runs smoothly, has low vibration, low noise, high direct transmission speed, small size, and light weight.

3: The pump chamber of the LC Roots pump does not experience internal compression like other mechanical vacuum pumps, so it does not require an exhaust valve. Therefore, when its front stage pump uses a water ring vacuum pump, it can extract gas containing a large amount of water vapor.

4: Fast start-up, able to reach vacuum in a short period of time, and high pumping efficiency

5: The pump operates over a wide pressure range (1.3X10 ³~ 1.3 Pa), with a high pumping efficiency, can quickly discharge sudden gas emissions, compensating for the diffusion pump and oil sealed mechanical pump at 1.3X10 ³~ The defect of low pumping efficiency at 1.3 Pah

6. Working: Each friction pair in the pump chamber is well lubricated, and the bearings are separated from the pump chamber. The pump shaft is equipped with a shaft sleeve at the shaft seal, so the main shaft will not wear. After the shaft sleeve is worn, it can be turned back and used again. Adopting a vertical structure, the tension of the belt counteracts the gravity of the pump pulley, resulting in lower bearing load and longer lifespan. The main components, large oil tank structure, are conducive to oil and gas separation and cooling, and have a large oil storage capacity, which has a good self separation effect on the impurities contained in the oil. According to the working conditions, it can also be equipped with a filter blocking bypass to automatically connect the filter, and an oil flow display device. Therefore, the pump can work for a long time and have a long service life, and can work in harsh working conditions

7. Small size and light weight: The design speed is moderate, the structure is compact and reasonable, and the utilization rate of the inside and outside of the pump chamber is high. The appearance is simple and the volume is small

2. Vacuum sealing material for Roots pumps

is a vacuum equipment suitable for harsh environments, so the performance advantages of this equipment are relatively high. Among them, in terms of vacuum sealing material in the equipment, the selection and use of sealing material are crucial for its sealing performance.

1. Vacuum wax: It is made from petroleum residue oil with low vapor pressure and high asphalt content, which has been properly treated

Features: In addition to low saturated vapor pressure and good adhesion to glass and metal, there is also a small shrinkage force, which remains brittle and does not crack even in large temperature changes. It is used for sealing the ground joints of metal pipes in vacuum systems, as well as blocking sand holes or loopholes on glass instruments. Its saturated vapor pressure (at 20 ℃) is generally below 10-6 torches and can be used in high vacuum sections

2. Vacuum mud: It is a plastic oil putty made by mechanically mixing high viscosity and low vapor pressure refined petroleum grease with high mountain residual soil

Features: Good plasticity, easy to shape, and small temperature dependent plasticity, with good adhesion to metals and glass. It is not easy to dry when exposed to air. In addition, it is a black mud like homogeneous body with a saturated vapor pressure not exceeding 10-3Mpa. The temperature range for use should not exceed 30 ℃ to avoid softening and deformation

In terms of the selection of sealing materials for Roots pumps, there are mainly two types: vacuum wax and vacuum mud. The performance of these two products is different, and the usage requirements will also change accordingly. Therefore, when making the selection, it is necessary to clarify one's own usage needs in order to choose the sealing material