View source for Engineering:Vacuum chamber

{{Short description|Rigid enclosure from which all internal gases are pumped out}}
{{Citations missing|date=August 2018}}[[Image:Vacuum chamber-being opened by engineer.jpeg|thumb|right|A large vacuum chamber.]]
[[Image:studio vacuum chamber.jpg|thumb|right|A small vacuum chamber for studio or lab use in de-airing materials such as mold rubbers and resins.]]
[[File:Vacuum Chamber Package testing.jpg|thumb|right|Vacuum chamber for testing leaks in [[Social:Packaging|packaging]]]]

A '''vacuum chamber''' is a rigid enclosure from which air and other [[Physics:Gas|gas]]es are removed by a [[Physics:Vacuum pump|vacuum pump]]. This results in a low-[[Physics:Pressure|pressure]] environment within the chamber, commonly referred to as a [[Physics:Vacuum|vacuum]]. A vacuum environment allows researchers to conduct physical experiments or to test mechanical devices which must operate in [[Astronomy:Outer space|outer space]] (for example) or for processes such as vacuum drying or vacuum coating. Chambers are typically made of metals which may or may not [[Physics:Electromagnetic shielding|shield]] applied external [[Physics:Magnetic field|magnetic field]]s depending on wall thickness, [[Physics:Frequency|frequency]], resistivity, and [[Physics:Permeation|permeability]] of the material used. Only [[Chemistry:Materials for use in vacuum|some materials]] are suitable for vacuum use.

Chambers often have multiple ports, covered with [[Engineering:Vacuum flange|vacuum flange]]s, to allow instruments or windows to be installed in the walls of the chamber. In low to medium-vacuum applications, these are sealed with [[Physics:Elastomer|elastomer]] [[O-ring|o-ring]]s. In higher vacuum applications, the flanges have knife edges machined onto them, which cut into a copper [[Engineering:Gasket|gasket]] when the flange is bolted on.

A type of vacuum chamber frequently used in the field of [[Engineering:Spacecraft|spacecraft]] engineering is a [[Engineering:Thermal vacuum chamber|thermal vacuum chamber]], which provides a thermal environment representing what a spacecraft would experience in space.

==Vacuum chamber materials==
Vacuum chambers can be constructed of many materials. "Metals are arguably the most prevalent vacuum chamber materials."<ref>{{cite web|last=Danielson|first=PHil|title=Choosing the Right Vacuum Materials|url=http://www.vacuumlab.com/Articles/VacLab36.pdf|publisher=The Vacuum Lab|access-date=February 10, 2012|archive-url=https://web.archive.org/web/20120724150040/http://www.vacuumlab.com/Articles/VacLab36.pdf|archive-date=July 24, 2012|url-status=dead|df=mdy-all}}</ref>  The strength, pressure, and permeability are considerations for selecting chamber material.
Common materials are:
* Stainless Steel
* Aluminum
* Mild Steel
* Brass
* High density ceramic
* Glass
* Acrylic
* Hardened steel

==Vacuum degassing==
"Vacuum is the process of using vacuum to remove gases from compounds which become entrapped in the
mixture when mixing the components."<ref>{{cite web|title=Vacuum Degassing Epoxy & Silicone|url=http://www.lacotech.com/ProductFiles/SMT-04-1013%20revA1%20(App%2006-14%20Vacuum%20Degassing%20Epoxy%20and%20Silicone).pdf|publisher=LACO Technologies, Inc.|access-date=February 10, 2012}}</ref> To assure a bubble-free mold when mixing resin and silicone rubbers and slower-setting harder resins, a vacuum chamber is required. A small vacuum chamber is needed for de-airing (eliminating air bubbles) for materials prior to their setting. The process is fairly straightforward. The casting or molding material is mixed according to the manufacturers directions.

===Process===
Since the material may expand 4–5 times under a vacuum, the mixing container must be large enough to hold a volume of four to five times the amount of the original material that is being vacuumed to allow for the expansion; if not, it will spill over the top of the container requiring clean-up that can be avoided. The material container is then placed into the vacuum chamber; a vacuum pump is connected and turned on. Once the vacuum reaches {{nowrap|29 inches}} (at sea level) of mercury, the material will begin to rise (resembling [[Chemistry:Foam|foam]]). When the material falls, it will plateau and stop rising. The vacuuming is continued for another 2 to 3 minutes to make certain all of the air has been removed from the material. Once this interval is reached, the vacuum pump is shut off and the vacuum chamber release valve is opened to equalize air pressure. The vacuum chamber is opened, the material is removed and is ready to pour into the mold.

Though a maximum vacuum one can theoretically achieve at sea level is 29.921 inches of mercury (Hg,) this will vary significantly as altitude increases. For example, in Denver, Colorado, at one mile (1.6&nbsp;km) above sea level, it is only possible to achieve a vacuum on the mercury scale of 24.896 Hg. 

To keep the material air-free, it must be slowly poured in a high and narrow stream starting from the corner of the mold box, or mold, letting the material flow freely into the box or mold cavity. Usually, this method will not introduce any new bubbles into the vacuumed material. To ensure that the material is totally devoid of air bubbles, the entire mold/mold box may be placed in the chamber for an additional few minutes; this will assist the material in flowing into difficult areas of the mold/mold box.

==Vacuum drying==
Water and other liquids may accumulate on a product during the production process. "Vacuum is often employed as a process for removing bulk and absorbed water (or other solvents) from a product. Combined
with heat, vacuum can be an effective method for drying."<ref>{{cite web|title=Vacuum Drying|url=http://www.lacotech.com/ProductFiles/SMT-04-1011%20revA1%20(App%2005-07%20Vacuum%20Drying).pdf|publisher=LACO Technologies, Inc.|access-date=February 10, 2012}}</ref>
<ref>{{cite web|last=Danielson|first=Phil|title=Desorbing Water in Vacuum Systems: Bakeout or UV?|url=http://www.vacuumlab.com/Articles/VacLab22%20.pdf|publisher=The Vacuum Lab|access-date=February 10, 2012|archive-url=https://web.archive.org/web/20110516110517/http://www.vacuumlab.com/Articles/VacLab22%20.pdf|archive-date=May 16, 2011|url-status=dead|df=mdy-all}}</ref>

==World's largest vacuum chamber==

[[Organization:NASA|NASA]]'s [[Organization:Space Power Facility#Thermal-Vacuum Test Chamber|Space Power Facility]] houses the world's largest vacuum chamber. It was built in 1969 and stands {{convert|122|ft|m}} high and {{convert|100|ft|m}} in diameter, enclosing a [[Engineering:Bullet|bullet]]-shaped space. It was originally commissioned for nuclear-electric power studies under vacuum conditions, but was later decommissioned. Recently, it was recommissioned for use in testing [[Astronomy:Spacecraft propulsion|spacecraft propulsion]] systems. Recent uses include testing the airbag landing systems for the [[Astronomy:Mars Pathfinder|Mars Pathfinder]] and the [[Astronomy:Mars Exploration Rover|Mars Exploration Rover]]s, Spirit and Opportunity, under simulated Mars atmospheric conditions.
<ref>{{cite news |last1=Peter |first1=Alex |title=Thermal coating for windows |url=http://sketchnano.com/ |access-date=12 November 2021}}</ref>
Each arm{{what?|date=July 2023}} of the [[Astronomy:LIGO|LIGO]] detectors in Livingston, Louisiana, and Hanford, {{wipe|Washington (state)}}, is a vacuum chamber {{convert|4|km|mi}} long, making them the longest vacuum chambers in the world.

==See also==
*[[Organization:Bell jar|Bell jar]]
*[[Astronomy:Optical window|Optical window]]
*[[Engineering:Thermal vacuum chamber|Thermal vacuum chamber]]
*[[Engineering:Vacuum engineering|Vacuum engineering]]
*[[Organization:Space Power Facility#Thermal-Vacuum Test Chamber|NASA Space Power Facility]]

==References==
{{Reflist}}

{{DEFAULTSORT:Vacuum Chamber}}
[[Category:Vacuum systems|Chamber]]
[[Category:Laboratory equipment]]

{{Sourceattribution|Vacuum chamber}}