What Is a Vacuum Ejector?
A vacuum ejector is a device that generates a vacuum by means of the Venturi effect using compressed air.
Unlike vacuum pumps and other vacuum generating devices with complex mechanical structures, vacuum ejectors are characterized by their simple design, featuring a vacuum generating structure inside the device that uses the Venturi effect. Vacuum ejectors generate the vacuum necessary for tasks like lifting parts using compressed air, which is used in production processes.
Applications of Vacuum Ejectors
Vacuum ejectors are often used in automated production lines. They are also used for dust collection and powder conveying.
1. Workpiece Suction Applications
A suction pad is attached to the vacuum line and pressed against the workpiece to create a suction. The shape and material of the suction pad must be selected according to the weight, size, and material of the workpiece.
Vacuum ejectors and suction pads are used to pick up parts and transfer workpieces. By using multiple vacuum ejectors and suction pads, the system can also be used to pick up and transfer heavy objects such as windshields in automobile production plants.
2. Dust Collection Applications
When a vacuum ejector is used indoors, airflow to the vacuum port of the vacuum ejector is generated to suction dust and dirt from the room. Vacuum ejectors are used to clean rooms in environments where dust and dirt are undesirable, such as semiconductor and electronic component manufacturing lines and food production lines.
3. Powder Conveying Applications
The vacuum conveyor is sealed and the pressure is reduced using a vacuum ejector. When air is injected through the nozzle port, the powder or grain can be conveyed along with the airflow in the piping.
Principle of Vacuum Ejector
The structure of a vacuum ejector consists of a compressed air inlet, nozzle, diffuser, and compressed air outlet in a straight line inside the equipment. A vacuum generating line is installed vertically between the nozzle and diffuser sections, and this structure allows the Venturi effect to be achieved.
The principle of vacuum generation by the Venturi effect is that the nozzle, which has a smaller diameter than the compressed air inlet, squeezes the fluid at high speed, causing the pressure to drop in the space between the nozzle and the diffuser, thereby generating a vacuum. The vacuum generated causes the mixture of suctioned fluid and compressed air to flow at high speed toward the diffuser section and outlet, where it is discharged. This results in a high degree of vacuum.
How to Select a Vacuum Ejector
1. Workpiece Ventilation
Ejector selection is based on the amount of air leakage that occurs when the workpiece surface and pad are adsorbed. A simple type of vacuum ejector is suitable for partial suction or when the pad is attached to a flat surface with low air permeability.
When carrying a workpiece with an uneven surface and good air permeability, select a vacuum ejector with a large suction volume.
2. Average Suction Volume
As stated on the website of each manufacturer, select a vacuum ejector with an average suction volume Q of 2 to 3. Average suction volume Q = V x 60 ÷ T1
If there is an air leakage volume, add it to the calculated one.
*V: Piping capacity l T1: Time to reach 63% of stable pressure after suction.
Other Information on Ejector
1. Difference Between Energy-Saving and Normal Types of Vacuum Ejectors
There are two types of vacuum ejectors: normal and energy-saving. Normal vacuum ejectors create a vacuum while air is flowing through them, but have the disadvantage that air is always needed while a vacuum is being created.
Energy-saving types of vacuum ejectors can automatically turn off the electricity and air supply once a vacuum is created. Since the vacuum is maintained as long as no air leaks out, this can lead to significant energy savings when transporting large workpieces.
However, if the surface of the workpiece is uneven or otherwise leaks a large amount of air, the vacuum pressure fluctuates greatly and requires frequent switching, which tends to shorten the life of the product.
2. Vacuum Ejector vs. Vacuum Pump
Ejectors and vacuum pumps both create a vacuum space. Compared to vacuum pumps, vacuum ejectors have the advantages of simple construction, low initial cost, space saving, and no power supply required.
On the other hand, vacuum ejectors come with disadvantages such as high running cost, low vacuum flow rate, as well as long tact time due to the fact that compressed air is always consumed during vacuum generation.
Therefore, vacuum ejectors are suitable for applications that require a small vacuum flow rate, while vacuum pumps are used when a large flow rate of vacuum air is required. Vacuum pumps are also advantageous in processes where the tact time for workpiece transfer is 1 second or less.