In this article, you will learn what vacuum is, existing vacuum levels, what characteristics to choose a vacuum pump, what is the classification of vacuum pumps, the principle of operation of a vacuum pump on the example of screw, diaphragm and rotary vane models.
The content of the article
- Vacuum, its levels. Purpose of the vacuum pump
- Characteristics of the vacuum pump
- Types of vacuum pumps
- How Rotary Vane Vacuum Pumps Work
- How Diaphragm Vacuum Pumps Work
- How Screw Vacuum Pumps Work
Vacuum, its levels. Purpose of the vacuum pump
Vacuum is the complete absence of matter in a region of space. It is also called a vacuum when the pressure of a gas in space is less than atmospheric pressure. There are 4 vacuum levels:
- Small (one hundred pascals or more)
- Medium (one hundred to one tenth pascals)
- Large (from one tenth to one ten-thousandth of a pascal)
- High (less than one ten-thousandth of a pascal)
A vacuum pump is used to create a vacuum of different levels. All of them work on the principle of suction from the gas tank, while the pressure decreases. Many factors can affect the operation of a vacuum pump: the tightness of the connection and container, the exhausted gas, and the power of the equipment.
Characteristics of the vacuum pump
There are five main characteristics of a vacuum pump that you need to pay attention to when choosing:
- Initial pressure
- final pressure
- Maximum pump vacuum level
- Power
- Vacuum time
Types of vacuum pumps
Vacuum pumps are divided into two large groups - gas-transfer and sorption. The same are divided into other types, types. For example, according to the type of construction, they distinguish:
- Mechanical
- Magnetic discharge
- Inkjet
- Sorption
- cryogenic
Below we will analyze the three most popular types of vacuum pumps - rotary vane, diaphragm and screw mechanical vacuum pumps.
How Rotary Vane Vacuum Pumps Work
The principle of operation of rotary vane vacuum pumps is similar to the classic ones - they both "suck" the gas / liquid from the tank:
The motor rotates the axle with the disk. A lot of blades / plates are installed on the disk, which are tightly pressed against the walls of the housing inside which they are installed. The vanes form sealed cells inside the pump. Such a cell is filled with gas from a container. The motor turns the wheel and another cell blocks the inlet tube. The blades push a portion of the gas in the cell to the exit tube. Gas occupies the entire volume from the vane to the tube valve. The blades continue to spin - the volume decreases, the pressure increases. Gas presses on the valve, opens it and gets out. Condensation occurs due to the pressure difference.
How Diaphragm Vacuum Pumps Work
The principle of operation of diaphragm pumps is based on a change in the volume of space. For this, flexible membranes are used.
The pump housing has one or two working chambers. They are installed on a flexible membrane and two rods - upper and lower. When the membrane is “sucked” inward, the pressure in the sealed space decreases. Because of this, the lower rod rises - a ball or damper that shuts off the gas supply. The gas from the evacuated tank fills the open space. After that, the membrane expands and begins to put pressure on the gas. The lower stem hermetically shuts off the gas supply, and the upper stem opens under high pressure. From the top stem, the gas goes to the outlet tube. After that, the membrane is again blown away, the container is filled with air, and it expands, pushing it through the upper rod into the tube. The cycle is repeated.
How Screw Vacuum Pumps Work
Screw vacuum pumps are a pair of "threaded" screws in a sealed housing. Screw vacuum pumps have two gas inlet and outlet tubes. Gas enters through them and enters a sealed housing with two screws tightly pressed against the walls and each other. Between them there is a space, which is occupied by gas. This space is limited by the "thread" of one of the screws. After the motor starts to rotate the screws, their “threads” create a common chamber / cell. This space is filled with gas, after which the "thread" blocks the entrance to the chamber. So the gas moves along the entire screw to the exit tubes. Of these, it is also pushed out by the "carving". That is, the gas moves through the sealed cells between the “threads” of the screws, and it is also pushed out of the pump by them.
