The performance of vacuum pump is measured through the parameter of its pumping speed. The pump speed is determined by the rate of the volume flow of a pump form its inlet. This is measured in volume per unit of time. The pumping rate depends on the type of vacuum pump being used and the gases being worked with. Thus, it means that the chemical composition of the gases will have a say in the average volume flow rate of the pump.
Another factor which influences the performance level of a vacuum pump is the throughput which means pumping speed multiplied by the gas pressure in the inlet. Therefore, a number of molecules pumped out of per unit time at a constant temperature is known as throughput.
Vacuum Pump operates by removing the air from the enclosed system by suction. This is done to decrease the air density of the enclosed space so as to create a vacuum. When the vacuum pump draws out all the air from the confined system, the mechanical input energy of a rotating shaft is converted into pneumatic energy.
As a result, the internal pressure level in a sealed volume becomes lower than that of the outside atmosphere. This pressure difference between internal and external atmosphere determines the amount of energy produced. The energy produced also depends on the volume of gas or air removed.
Types of Vacuum Pumps
There are different types of vacuum pumps which run on a common function based on the scientific principle to remove air, gases, and vapor from a confined space to create a vacuum in that space.
But basically, there are three different types of vacuum pumps:
1. Positive Displacement Vacuum Pumps
Positive displacements vacuum pumps find application where there is a need to create low vacuums. The primary use of such pumps is to enlarge a cavity so that gases can eject out of a sealed atmosphere.
The examples of such pumps are liquid ring vacuum pumps and roots blower which find extensive application in the industries where it is imperative to create a vacuum in a constricted space.
After this, the cavity is again sealed and exhausts the chamber. The rudiments of the principle on which positive displacement vacuum tubes work entail creating a vacuum by expanding the volume of the container.
For instance, in manual water pumps, a small sealed cavity or chamber is expanded and a deep vacuum is created. This leads to a pressure difference and some fluid from the chamber is drawn by the pump’s small cavity.
Once the fluid is pushed into the cavity it is sealed from the chamber and opened to the atmosphere and again shrunk to its smaller size.
Another case in point regarding the positive displacement vacuum pump is found inside our very body- diaphragm muscle. This muscle expands the chest cavity and increases the volume of the lungs.
These expanded lungs cause a partial vacuum and reduce the pressure. filled by air pushed in by atmospheric pressure.
2. Momentum Transfer Vacuum Pumps
As conjectured by the name, in momentum transfer vacuum pumps, the gas molecules accelerate from the vacuum side to rush towards the exhaust side. The pump’s function is based on the scientific principles of fluid dynamics which explain that matter flows differently at different pressures.
To understand momentum transfer vacuum pumps, one must know about viscous flow. The gas molecules under atmospheric pressure and mild volumes are in constant interaction and push each other. This is called viscous flow.
These molecules also strike against the walls of the chamber or container. Therefore, when the distance between molecules increases, the interaction between the molecules and walls also increases. This stage of high vacuum is said to be more effective than positive displacement pumps.
The momentum transfer vacuum pumps are further categorized into two types of vacuum pumps – diffusion pump and a turbomolecular pump. Both these pumps shove gas molecules to get diffused into the pump.
The major difference between these two pumps is that turbomolecular pumps use high-speed fans to blow out the gas molecules and diffusion pumps make of jets of oil to effectuate the purpose.
3. Entrapment Pumps
Entrapment pumps exploit chemical and therefore are more than efficient on performing the work as they are placed inside the chamber. The molecules in the air create a thin film.
This film is removed by the chemical reaction with the internal surface of the pump which is triggered by the entrapment pumps. Such vacuum pumps use cold temperatures to condense gases to a solid state.
To create ultra-high vacuum chambers, the entrapment pumps are used along with positive displacement vacuum pumps and momentum transfer vacuum pumps.
The aforementioned pumps are further classified into chemical process pumps, liquid ring vacuum, single cone vacuum pumps, close couple vacuum pumps, two stage vacuum pumps, and twin lobe roots blower.
What are the main components of Vacuum Pumps
There are many people who intend to use vacuum pumps for unconventional purposes and might not have an understanding of the parts of the vacuum system. Before you take to using this system, you must have basic knowledge about the functions of the major components of the vacuum pump.
Below are the prominent parts of the vacuum system and with their functions:
- Vacuum suction cups or Special grippers: These provide the interface between the vacuum system and the work piece.
- Mounting elements: They ensure quick and flexible connection of the vacuum components with the tooling system.
- Vacuum generators: They create a centralized or decentralized vacuum generation by using ejectors, pumps or blowers.
- Switches and system monitoring: They belong to the measuring and control components which ensure the safety of the users.
- Filters and connectors: The main function of filters is to protect the vacuum generator; hoses and connectors connect the components.
- Valves: Valves are used to control the vacuum as well as the compressed air.
What are the applications of Vacuum Pump
Vacuum Pumps have great utility in numerous industrial and scientific applications. They are used extensively in many industries like chemicals, cement, pulp & paper, sugar mills, treatment plants, process industries & power plants, pharmaceuticals, etc.
Below mentioned are some of the industrial uses:
Advantages and Disadvantages of Vacuum Pumps
- Composite molding
- Automobile industry
- Medical applications which require suction like radiotherapy, radiosurgery and radiopharmacy
- Flight instruments,
- Production of vacuum tubes and electric lamps
- Semiconductor processing such as ion implantation, dry etching, and in the deposition of PVD, ALD, CVD, and PECVD
- Analytical instrumentation which analyzes solid, gas, surface, liquid and biomaterials
- Electron microscopy
- Uranium enrichment
- Print presses
- Trash compacting
- Glass and stone cutting factories
- Cabinetry fabrication
- Ophthalmic coating
- Sewage systems
- Vacuum coating and engineering are required for decoration, durability etc.
- Glass coating
- Dairy equipment such as milking machines
- Air conditioning service
- Vacuum Pumps are easy-to-use options as compared to other kinds of pumps
- They make less noise and vibrations
- These pumps are more efficient in handling condensable loads
- They work on very slow rotational speed and augment the durability of the condition of the pumps
- They come very handily in fabricating using any castable metal
- They require less maintenance and re-building them is very easy
- It dispenses with the need of doing internal lubrication as metal-to-metal contact is not there in the compression chamber.
- These pumps may lead to cavitations
- Their motors are in large in size
- Efficiency and vacuum degree is a bit low