This article contains everything you need to know about vacuum chambers.
You will learn:
- What is a vacuum chamber?
- Types of vacuum chambers
- Industries that use vacuum chambers
- Tests and operations performed in vacuum chambers
- And much more…
Vacuum Chamber from Tenney
Chapter One – What is a Vacuum Chamber?
A vacuum chamber removes air and pressure from a confined enclosure to test the effects of a vacuum on parts, materials, components, and assemblies. It can also be used to test the performance of applications for manufacturing operations. They are designed to withstand the type of pressure that is created by a vacuum and are capable of simulating environmental conditions where a vacuum may exist.
In the space and aerospace industries, vacuum testing is essential to determine a component’s ability to withstand the pressure and vacuum of space. Other industries use vacuum testing to determine the stability of packaging that may be required to travel by air to different locations in the world.
In industrial applications, there is a need for high altitude testing, drying, and offgassing in controlled and replicable vacuum conditions and environments. These types of tests assist in establishing the quality and durability of a product.
Chapter Two – Types of Vacuum Chambers
Vacuum chambers are designed to fit the needs of the industries they serve. This type of chamber can be benchtop for the testing of small parts or for use by small manufacturers. Other varieties can be the size of a room to test large aircraft parts and instruments for use in outer space.
As an offshoot of environmental chambers, vacuum chamber testing can be part of the processes available on a chamber designed to perform a wide range of tests from climatic conditions to the effects of high altitude. Though there are standard vacuum chambers, they can also be specially designed to fit a predetermined set of criteria.
Types of Vacuum Chambers
Vacuum chambers are built in different shapes and sizes with their only limitations being engineering know how. The standard types of vacuum chambers are classified as box, sphere, cylinder, D-shaped, and bell jar.
Box Vacuum Chambers –
There are two forms of box shaped vacuum chambers, which are rectangular and cubic or box chambers. The rectangular version of a vacuum chamber is designed for ultra-high vacuum (UHV), which can reach pressures as low as 100 nanopascals. Box shaped vacuum chambers are capable of performing a full spectrum of vacuum testing tribology, degassing, atmospheric tests, film deposition, and the simulation of outer space.
Each type of box shaped vacuum chamber is required to have thick walls with bracing in order to withstand the extreme pressure conditions.
Spherical Vacuum Chambers –
Spherical chambers are used for surface testing, laser deposition, and UHV testing. The spherical shape allows for the adjustment of concentration from one point on the sample to multiple points. Spherical chambers are equipped with multiple ports to allow for several access entry points.
Cylindrical Vacuum Chambers –
Cylindrical vacuum chambers can be either vertical or horizontal. The shape of the chamber is the determining factor in the method of accessing the chamber, where horizontal chambers can be accessed by openings at either end, while vertical chambers can be accessed in a variety of ways including lifting the chamber off its base.
Cylinder chambers are used for degassing or helium leak testing with an inner diameter ranging from 100 to 2000 mm.
Bell Jar Vacuum Chambers –
Bell jar vacuum chambers are similar to cylindrical vacuum chambers with a welded domed top. They can be made from metal or Pyrex depending on the type of test and product criteria. They come in a variety of sizes in combination with baseplates and feedthrough collars. Bell jar vacuum chambers are used for high temperature applications.
Pyrex bell jar vacuum chambers are a transparent vacuum chamber that is set on a metal base plate.
55 Gallon Drum Vacuum Chambers –
There are a variety of uses for 55 gallon drum vacuum chambers, which include degassing, mixing, and processing. This size vacuum chamber is less expensive and more convenient than other sizes of vacuum chambers. They can be used for mixing materials in a vacuum and are made of heavy duty welded steel. The vacuum capacity allows for degassing and mixing to occur at the same time.
Chapter Three – Industries that Use Vacuum Chambers
A vacuum is a space with low pressure where all matter has been removed that could possibly affect the testing or manufacturing process. Using a vacuum pump, industries produce a vacuum to test their products for leaks, endurance, and stability. Much like environmental chambers, vacuum chambers provide valuable data and insight into a product’s capability such that adjustments can be made to improve the quality of the product.
Testing chambers have been a major step forward for industry. They let a company know the parameters and limits of their products, information that is passed on to users and customers.
Industries that Use Vacuum Chambers
Vacuum chambers are an essential tool for manufacturing. They supply data to ensure the safety of products and highlight any flaws a product may have. The types of tests include a determination of leaks or their resistance to environmental conditions that may contain a vacuum.
One of the most damaging substances during manufacturing is moisture. By subjecting a product in production to a vacuum, moisture is removed as well as any micro sized gas bubbles. A further use of vacuum chambers is to apply protective films, coatings, and finishes.
The aerospace industry makes the greatest use of vacuum chambers due to the nature of the environments their products have to endure. Every aspect and part of a product for aerospace has to be tested and retested to ensure safety and performance. This includes bolts, panels, switches, electrical components, fibrous materials, seat cushions, and latches and door handles.
The agencies that oversee the manufacturing of materials for use in spacecraft and airplanes have strict and stringent requirements regarding the quality of materials to be used. Vacuum chambers allow researchers to simulate adverse conditions and environments to determine the quality and limits of components.
The image below is of a large vacuum chamber for testing of parts and products for aerospace. It is 7 meters tall and 12 meters long with a temperature range of -180° C up to 100° C.
Food and Beverage –
One of the main concerns of the food industry is waste from spoilage or poor environmental control. Food products that have to be maintained at a particular temperature have to be tested to determine their limits to ensure quality. Aside from helping set the boundaries for food products, vacuum chambers are able to remove excess moisture and damaging gases from products that may contain contaminants.
Cold storage is a critical part of food transport. Vacuum chambers assist in speeding up the cooling, freezing, and drying processes to protect a product's cellular integrity, taste, color, and appearance.
The food and beverage industry is closely regulated by a variety of agencies and organizations to ensure the safety of the public, which makes vacuum processing a critical aspect of food production.
The biopharmaceutical industry is one of the most closely watched industries due the nature of its products. During production and development, accurate determinations have to be made regarding the many facets of a product, which include its shelf life, point of deterioration, and susceptibility to environmental factors.
Vacuum chambers are used in the biopharmaceutical industry for drying, degassing, sterilizing, cooling, distilling, and crystallizing medications. They are also used to preserve specimens for study in an uncontaminated environment as well as assist in the creation of new drugs.
Solar Energy –
A key challenge for the production of photovoltaic (PV) is designing and operating linear transport systems through the substrates of multiple fabrication steps. The PV production process uses vacuum deposition chambers, a method for placing a layer of a substance, in the fabrication of solar absorber layers. In most cases, the process employs multiple chambers to move the substrates from point to point.
The movement of substrates from chamber to chamber uses a specialized transport system for high volume product production. The vacuum in each chamber has to be at 10 to 9 mbar, which is required to be maintained for long periods of time.
The process of producing PV panels makes use of larger and more powerful vacuum chambers.
The technology of vacuum chambers is a necessary part of chemical production for processes such as distillation, polycondensation, degassing, and the production of polyurethane. The vacuum process for chemicals has to maintain a constant pressure to avoid damage to the final product, which would make it useless.
The vacuum range for these chambers is between 1 to 10 mbar. A vacuum chamber reduces the thermal load of the materials, which is especially necessary for temperature sensitive materials. The use of a vacuum chamber in the production of chemicals is a method of guaranteeing high quality and performance.
Chapter Four – Tests and Operations Performed in a Vacuum Chamber
Test chambers, in general, have become an essential part of determining the quality and lifespan of products. Their use has enhanced the manufacture and production of many of the products that are used by industry and in the home. Vacuum chambers add another element to product testing by providing the ability to create a particle and atmosphere free environment.
Vacuum chambers are an important part of the testing of parts and components for outer space, which is necessary for ensuring the safety of astronauts. Though this is a critical function for vacuum chambers, they also are used in providing data regarding everyday products such as food, drugs, and chemicals.
The benefit of vacuum chambers is their ability to create environmental conditions with varying pressure, humidity, temperature, and radiation to assist industry in developing and perfecting their products.
Tests and Operations Performed in a Vacuum Chamber
The number two factor that causes damage to products is moisture, which can cause rapid and irreversible deterioration. To combat this problem, producers place products in a vacuum chamber that immediately removes moisture and is more effective than dehydration.
The method of drying varies depending on the product. More resilient products can be very aggressively dried with a rapid creation of a vacuum, while more sensitive products may require a gentler approach.
Vacuum coating or thin film deposition uses a vacuum chamber to apply a thin and steady layer of coating on the surface of the substrate to protect it from wear down and reduction of its efficiency. The thickness of vacuum coatings varies between 0.25 to 10 microns, which is between 0.01 to 0.4 thousandths of an inch.
There are several types of coatings applied using a vacuum coating, which include PVD, sputtering, cathodic arc, and atomic layer deposition. Vacuum coating is used by injection molding companies, semiconductor producers, medical tools manufacturers, aerospace, and automotive manufacturers.
Vacuum degassing is a method for removing dissolved gases from a liquid by lowering the pressure inside a container that has the liquid in it. During the production of metals, the materials can become infused with excess gases, which can lead to imperfections and impact the performance of the metal.
In the production of molten steel, vacuum degassing is used to remove hydrogen and oxygen from the heated material. By lowering the pressure in a vacuum chamber, the gas becomes less soluble and separates from the melted metal. Once the gas is removed, it is forced out of the chamber, and the chamber returns to normal pressure.
Product Testing –
Vacuum chambers are capable of duplicating various environmental and atmospheric conditions. When a product is to be used at high attitudes, deep in the ocean, or in outer space, its performance must be tested to ensure its ability to work when being stressed. Vacuum chambers can be set and adjusted for any depth or height to test the limits of a part.
One of the benefits of using a vacuum chamber, over other traditional testing methods, is the amount of time required to complete the test since a variety of conditions and atmospheres can easily be programmed into the chamber. This is especially true for products that will face extreme conditions. It is imperative that they be tested and certified for the safety of those who will rely on them.
The crystallization process is an example of how vacuum chambers can save time and money. The formation of crystals happens when a liquid solution leaves behind solid deposits. Under natural and normal conditions, this process takes several hours or centuries.
Modern production does not have the time to wait for the natural process of crystallization. Vacuum chambers speed up the process by removing liquids from saturated solutions to leave behind crystal deposits.
Vacuum drying is one of the simplest ways to reduce the size of crystals and improve their uniformity by reducing the separation effect.
Vacuum distillation (VDU) is performed at pressure that is below atmospheric pressure, which is unlike atmospheric distillation. The concept is that compounds boil at a lower temperature when pressure is lowered. The process of vacuum distillation is able to separate compounds at a lower temperature due to the lower pressure. The central function of the process is to have liquids boil to produce a vapor such that the materials in the vapor can be separated. Once the separation process is completed, the separated materials are condensed and reliquefied.
Vacuum chambers are designed to remove all materials, particles, contaminants, and other matter in an environment under low pressure. The process produces a condition where there is no living matter. When moisture and air pockets are removed, it also removes any microbial contamination.
In the manufacture of medical instruments, before being packaged, they are placed in a vacuum chamber under low pressure to remove any bacteria, fungi, viruses, or other contaminants. This ensures that the equipment is parasite and bacterial free before being shipped for use.
The use of vacuum chambers for cooling is a rapid removal of moisture from products with a high water content. As the pressure lowers, moisture is released, which also causes heat to be lost. The lowered pressure, aside from removing moisture, also takes away any energy in the product in the form of heat that creates rapid cooling.
The process of vacuum cooling takes approximately 15 to 30 minutes. The method cools products uniformly and evenly, which adds to their shelf life. An added benefit of vacuum cooling is its cost effectiveness since it requires far less energy than traditional cooling methods.
Chapter Five – Vacuum Chamber Design
There are several considerations that have to be explored when choosing or designing a vacuum chamber. The first concern is materials that are capable of withstanding the amount of pressure created. Design flaws can debilitate the ability of the chamber to perform properly and complete its desired function.
A well designed and constructed vacuum chamber is capable of providing accurate and repeatable functions. When examining the available chambers, the things that need to be examined are the shape of the chamber, types of materials, the various structural components, surface finish, and the control mechanism.
Vacuum Chamber Design
Most test chambers use the same metals and materials for their construction, which are a steel alloy and stainless steel. Vacuum chambers can be built from a variety of materials due to the nature of how a vacuum is formed. The one guiding rule is that the material has to be able to withstand drastic changes in pressure.
When manufacturers choose the materials to construct a vacuum chamber, they make their decision based on the materials strength, pressure, and penetrability. Unlike environmental chambers, vacuum chambers can be made of glass and plastic as well as aluminum, brass, high density ceramic, and acrylic.
On many occasions, when people envision a vacuum chamber, they think of the small glass chambers that are found in schoolrooms. In the design phase of a vacuum chamber, after selecting the material, the next choice is the shape of the chamber, which can be a vertical or horizontal cylinder, spherical, and cube or rectangular box shape.
This aspect of the decision is determined by the application for which the chamber will be used from testing products to applying finishes. In the case of vacuum chambers in assembly operations, it has to be able to apply pressure rapidly between product cycles.
Structural Components –
There are an endless number of structural factors to be considered when planning a vacuum chamber since they can be configured in so many different ways. The essential concern in this aspect of the planning is the stability and resilience of the chamber. Making poor choices can be detrimental to the chamber’s performance.
The structural components of a vacuum chamber may not seem to be important in regard to its performance due to the fact that they are minor and secondary. Weak hinges of the wrong material or poor sealants can affect as well as shorten a vacuum chambers lifespan and its performance. Stiffeners, stands, fasteners, hinges, and lifting points have to be carefully examined and considered in vacuum chamber design.
Surface Finish –
Another, what might seem to be a minor concern, is the finish on the inside of a vacuum chamber. In the past, the finish of a vacuum chamber was not considered to be a crucial design concern. Recent research has proven that the surface finish of a vacuum chamber has a varying effect on the pumping speed depending on the pressure range.
The greatest effect of the surface finish has been found to be more prominent in the higher pressure ranges. The data seems to indicate that to achieve the best performance from a vacuum chamber, it is critical that the interior have a smooth finish and be kept clean.
Choosing the correct joining method is important in the prevention of leaks from the chamber. The three most common joining methods are welding, brazing, and gluing.
- Welding: Welding is the best method for sealing a vacuum chamber and preventing leaks. There are a variety of welding techniques that can be used but must be performed by highly trained welders since welding changes the properties of metals. The types of possible methods are butt, lap, corner, tee, and edge welding.
- Brazing: Brazing is a method of joining metals by melting a metal into the joint between metals. The metal being melted has a lower melting point than the metals being joined. For this method to succeed, the metals being joined must be strong and ductile. Also, brazing is an expensive method and has to be carefully chosen.
- Gluing: In the construction of a vacuum chamber, gluing can be a method for joining materials but is only applicable under special conditions. The types of glues would include high performance epoxy for sealing aluminum chambers. The chosen adhesives must be resistant to solvents, lubricants, alcohol, and certain select acids.
Valves and Gauges –
All vacuum chambers are equipped with valves and gauges. Metering valves assist in removing internal particles and moisture as well as providing an inlet for process gases. For safety precautions, vacuum chambers have bleed valves, which protect the chamber and samples. Gauges are necessary for measuring and displaying vacuum chamber pressure.
Much like all testing chambers, there are many choices when it comes to a controller for a vacuum chamber. Some systems are completely manual, which require adjustments and monitoring. Automated controllers allow users to set the parameters of the process. As the procedure unfolds, the system makes adjustments in pressure, temperature, and any other programmed factors.
Automated control systems are configurable with customizable software and a variety of data collection methods. The choice of controller is normally determined by how critical the application is and the size of the vacuum chamber. Smaller chambers may only need a simple gauge for monitoring pumping and pressure, while larger chambers may demand a more aggressive and sophisticated system.
- A vacuum chamber removes air and pressure from a confined enclosure to test the effects of a vacuum on parts, materials, components, and assemblies or perform applications for manufacturing operations.
- In industry, there is a need for high altitude testing, drying, and off gassing in controlled and replicable vacuum conditions and environments. These types of tests assist in establishing the quality and durability of a product.
- Vacuum chambers are designed to fit the needs of the industries they serve.
- A vacuum is a space with low pressure where all matter has been removed that could possibly affect the testing or manufacturing process.
- The benefit of vacuum chambers is their ability to create environmental conditions with varying pressure, humidity, temperature, and radiation to assist industry in developing and perfecting their products.