Basicprinciplesofvacuumtechnology,briefoverview …

1 Subjecttochange1 Internet: principles of vacuum technology, brief overviewIntroductionBasic principles of vacuum technologyWhat is a vacuum?Vacuum rangesUnits of measurementA vacuum is a space entirely devoid ofmatter ( absolute vacuum ).In practice we talk about a vacuumwhen the air pressure in a space liesbelow atmospheric [pa]P[mbar]There are a large number of nationaland international units ofmeasurement. The most commonlyused units are Pascal (Pa) and bar100Pa =1hPa1hPa =1mbar1 mbar = barThe vacuum level is often expressedas a % value. However, these arealways relative = Rough vacuumFV = Medium vacuumHV = High vacuumUHV = Ultra-high vacuumWhat is a vacuum used for?Measuring the pressure or vacuumAtmospheric pressureThe vacuum plays a vital role inresearch in the fields of chemistry,biology and is also indispensable in manyindustrial the rough vacuum range, thepressure gauges used are mainlymechanical, but some digital pressuregauges are also the high and ultra-high vacuumrange, highly sensitive pressuregauges are [km]p[hPa]1 Mount Everest2 Festo3 Sea levelUnderstanding vacuumVacuum specification optionsEffects of changes on per m3of air at one barair exert pressure or force on thewalls of a defined space.

2 The fewerparticles there are in the space, thelower the force exerted on the vacuum can be specified as anabsolute value, with a positivesignfrom1to0bar,with0asabsolute zero. Or it can be specifiedas a relative value with a negativesignfrom0to 1bar,with0asareference point, or as a %.As altitude increases, the air pressurein the atmosphere falls. This sameeffect reduces the attainable vacuumlevel of an ejector. Nevertheless, theperformance level of 80% remainsunchanged in this vacuum would mean that thereare no particles present. Pressure = Internet: principles of vacuum technology, brief overviewIntroductionComponents for vacuum generationVacuum ejectorsDisplacement vacuum pumpsKinetic vacuum pumpsThese function according to theventuri principle, they are drivenpurely pneumatically and have amuch simpler design compared withother vacuum flowing into a space ismechanically shut off, compressedand ejected. This allows a very highvacuum to be achieved at a very lowflow is forced to flow in the deliverydirection through the application ofadditional mechanical force.

3 Thismethod achieves only a relatively lowvacuum level despite a high The most important componentsare the jet nozzle (venturi nozzle)and at least one receiver nozzle. Acceleratedcompressedairgenerates a suction effect betweenboth nozzles (vacuum). There are different designprinciples: single-stage and multi-stage ejectors. Depending on the principle, air iseither carried away in a flow by arotating impeller on the suctionside or compressed using vanedchambers. The pump types availableinclude vacuum blowers andvacuum compressors, for side2 Suction side3 Inlet valve4 Exhaust valve5 PistonFeatures High vacuum level with relativelysmall flow rate Maintenance-free and wear-free Low-cost Low-weight, compact design Any mounting position High vacuum level up to baroperating pressure Minimal maintenance expenses Generally large dimensions andhigh weight Restricted mounting position Large flow rates, low vacuum level High maintenance costsApplication Wide range of applications, handling technology andprocess engineering.

4 Broad application spectrum inindustry and research. Used mainly for precision processesin Internet: principles of vacuum technology, brief overviewIntroductionVacuum in handling technologyPractical use of vacuumImportant selection factorsBenefits of a vacuumTheextensiverangeofvacuumcomponent variants makes them idealfor use in many Weight, temperature, shape androughness of the workpiece surface Speed per unit of time Stroke travel and conveyingdistances Gentle handling Compact, low-weight, space-savingdesign Fast cycle times possible Low maintenance costs Low-costComparison of ejectorsVariables/criteriaSingle-stageMu lti-stageSuction flow rateAverageHighAt low vacuum level up to approx. 50%Evacuation timeVery shortIn higher vacuum range from 30 .. 50%Very shortIn lower vacuum range up to 30 .. 50%Initial costsLowRelatively highNoise generationRelatively highLowBoth principles have their advantagesand disadvantages which are difficultto compare. With optimally adaptedcomponents, both principles cancoveralargenumberofdifferentareasof comparison variablesEvacuation timeAir consumptionEfficiencySuction flow rateEvacuation time = Time (s) required togenerate a specific consumption = Air consumption(l/min) of the ejector required togenerate a specific efficiency formula makes it easierto compare the different principles:Efficiency = Evacuation time, airconsumption and volume dependenton efficiency of an ejector is often and incorrectly measured using thesuction flow rate at 0 flow rate = Suction air volume(l/min) that an ejector can draw Internet: principles of vacuum technology, brief overviewIntroductionVacuum in handling technologyEnergy cost comparisonTo generate compressed air fromatmospheric air, you need to reckonon approx.

5 Per m3volume at7 bar pressure when calculating thecosts involved ( investment,material, labour, etc.).Vacuum ejectors: High air consumption, butcompensated by its energy-savingfunction Maintenance-free, no moving parts Low weight and componentdimensions and can be installed inany mounting position No electrical connections required Relatively high vacuum level (up to85% vacuum) attainable Low initial costsElectric vacuum pumps: Very high vacuum (up to )attainable High suction rates (vacuum blower)of up to 1,200 m3/hr. possible High current consumption becauseof continuously operated pumps High initial costs and ongoingmaintenance costs Largeweightandunitvolumeaswell as fixed mounting positionFor a comparison of features, acalculation example and an energycost comparison in vacuum systemsWhen a vacuum suction grippercannot fully seal the system againstatmospheric air, we talk about might be caused, for example, byrough and uneven workpiece surfacesor air-permeable workpiece actions to achieve therequired vacuum: Useofhigh-performanceejectors Reduction of the suction cupdiameterSelection aid for vacuum generatorsIn all cases, it is recommended thatyou perform a test setup to determinethe leak rate, thereby enabling you toascertain which vacuum ejector.

6 Determining the leak rate Perform the test setup Read the vacuum value achieved Comparetheresultwiththecourse of the curve in the Suction capacity as a function ofvacuum chart ( 28) Difference with respect to suctioncapacity = leak rate Determining the correct ejector size Intersection of the leak rate (nowknown) with the curves of otherejectors Determine the attainable vacuumby means of projectingdownwards from theintersections with the leak rate Select the ejector that reaches therequired vacuum Internet: principles of vacuum technology, brief overviewIntroductionTypical applicationsSubjecttochange6 Internet: principles of vacuum technologyIntroductionWhat is a vacuum?In physics, a vacuum is defined as a state of emptiness that can beachieved by experiment in otherwords, definition refers to the state of aspace entirely devoid of matter(sometimes also referred to as an absolute vacuum ).In practice, however, this state cannotbe achieved. We therefore talk insteadabout a vacuum when the air pressurein a space is lower than theatmospheric pressure or when thedensity of air molecules is , every space containsparticles of matter such as protonsandelectrons,aswellaszero-masspar ticles photons which transportenergy at the speed of is a vacuum used for?

7 Since the 17th century ( Magdeburghemispheres ) mankind has beenstudying vacuum. Today, we cannotimagine modern research without chemistry, reactions in substancesare investigated in a vacuum, biologyis interested in the effects of avacuum on organisms, while someareas of physics (quantum physics,field theory, etc.) are concerned withparticles that can be examined moreaccurately in a , the vacuum plays a vital role inimportant industrial processes, manyof which would not be possiblewithout it. Noteworthy examplesinclude semiconductor manufactureor mass technology has also played apart in the development andimplementation of new ideas inhandling technology, lifting,holding, rotating and transporting allkinds of vacuumAirisagasmixturecontainingapprox. 1025particles per m3atone bar air the atmosphere, this gas mixture ismade up of the following gases andproportions:78% Nitrogen21% Oxygen1% Other gases( carbon dioxide andargon)NitrogenOxygenOther gasesTo attain a state of vacuum, a spacemust be empty, devoid of allgaseous consequence of this is that thepressure in this space is very low, as itcontains no or only a small number ofparticles, which exert a force on anarea as a result of their impactagainst the is therefore defined asfollows:In theory, in an absolute vacuum, matter in the space, pressure = gaugeSmall number of particlesat constant temperature low pressurePressure gaugeLarge number of particlesat constant temperature high pressureIn reality, however, this is rarelyachievable.

8 In an ultra-high vacuum,the pressure may indeed be low(approx. 10 8to 10 11mbar), but theparticle number density is stillapprox. x 1013particles per following rule therefore applies:The fewer particles there are, thelower the Internet: principles of vacuum technologyIntroductionVacuum rangesIn practice, the large vacuum rangethat can technically be achieved which now consists of more than16 powers of ten is generallysubdivided into smaller vacuum ranges below areclassified according to physicalattributes and [pa]P[mbar]GVHandling range:This vacuum range is used in = Rough vacuumFV = Medium vacuumHV = High vacuumUHV = Ultra-high vacuumVacuum rangePressure range (absolute)ApplicationsRough vacuumAtmospheric pressure .. 1 mbarApplications in industrial handling practice, the vacuum level is often specified as a percentage, the vacuumis defined in proportion to its ambient pressure. The material and the surfacefinish of workpieces play a major role in vacuum vacuum10 degassing, light bulb production, drying of plastics, freeze drying offoodstuffs, vacuum10 8mbarSmelting or annealing of metals, electron tube vacuum10 11mbarSpraying of metals, vacuum metallizing (coating of metals) as well as electronbeam the pressure or vacuumPressure is defined as the force of many particles (atoms andmolecules).

9 These particles are incontinuous motion. Wherever theymeet, they exert a pressure and vacuum aremeasured by taking a specific unitarea and measuring the number andintensity of this impact on this are necessary in orderto be able to check and this reason, all measuringinstruments must be calibrated , individual measuring instrumentswith the same function must beadjusted so that they produce thesame result under the the vacuum medium, thereare a number of items of technicalequipment that are indispensable forapplications in the fields of industryand gauges (vacuum gauges) areused generally as well as in the roughvacuum range. These gauges arescaled according to the level ofaccuracy required. Pressure gaugeswork according to many differentoperating principles and can functionmechanically or most common mechanicalfunction types are: Bourdon tube pressure gauge Aneroid pressure gauge Diaphragm pressure gauge Digital pressure gaugeIn the high and ultra-high vacuumrange, pressure gauges with highlysensitive response mechanisms areused.

10 A great many additional factorsplay a role in determining themeasurement results in this is important to remember that thereare two different options for specifyingor representing the samemeasurement tube2 Spring support3 Spring end piece4 Segment5 Tie rod6 Gearing7 Indicator shaft8 Coil spring9 IndicatoraJDial faceSubjecttochange8 Internet: principles of vacuum technologyIntroductionVacuum designations and specification optionsIt is important to mention at this pointthat there a number of differentdesignations for the term vacuum inboth colloquial and order to avoid any uncertainty ormisunderstanding, these designationsneed to be explained designation specified as %only in the range 0 .. 1 bar pressureVacuum as an absolute valueVacuum as a relative valueCorrect designation, operatingpressure of 0 bar relative pressure isequivalent to 1 bar absolute vacuum is generally specified asrelative operating pressure, with anegative pressure can be specifiedcorrectly in two different ways, options are also appliedto vacuums and are explained in moredetail :In the field of science as well as in themedium-high and high :Vacuum is specified as an absolutevalue in proportion to absolute zero, 0 bar is the lowest value andcorresponds to 100% vacuum.