VACUUM BOOSTERS - Everest Blowers

TECHNICAL BULLETIN 6 - REV 1

VACUUM BOOSTERSEVEREST ENHANCING PROCESS EFFICIENCY

ECONOMIC

ISO-9001 REGISTERED

RELIABLE

by IMPROVING VACUUM DURABLEDNV Certification B.V., The Netherlands

with theNEWLY DEVELOPEDEVEREST PROFILE

SALIENT FEATURES 2COARSE VACUUM APPLICATION 4

HIGH VACUUM APPLICATION 15

GLOSSARY 24

APPENDIX 26

WE JUST DON'T PRODUCT RANGE EVEREST TransmissionWE OFFER

OFFER BOOSTERS,SOLUTIONS! Air Blowers~Water Cooled Blowers~ Gas Blowers~ Vacuum Booster Pumps ~ Acoustic Hoods & Enclosures~Dry Vane Pumps

VACUUM BOOSTERSEVEREST

SALIENT FEATURES ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

Mechanical VacuumBooster- Model EVB15

with MechanicalBypass Arrangement

Notes

M e c h a n i c a l Va c u u m B o o s t e r s ,

manufactured by EVEREST, are beingextensively used in chemical processindustry to boost the performance of thevacuum pumps, in low-pressure range,where conventional vacuum pumps havepoor volumetric efficiency.

Everest Vacuum Boosters are capable ofmoving large quantity of gas at low

p r e s s u r e s , w i t h f a r s m a l l e r p o we r consumption than for any otherequipment now available. The internals of aBooster are totally free of any sealant fluid,and therefore the pumping is dry. Alsobecause of the vapor compression action bythe booster, the pressure at the inlet of theBacking pump is relatively high, resulting inhigher volumetric pumping efficiency & lowback streaming of sealing fluid. They act asdynamic one way valve. Everest Twin LobeMechanical Vacuum Boosters are used inseries with a variety of backing pumps toachieve higher speeds and lower ultimatepressures. Since the rotors in a Boosterrotate within the casing with finiteclearances, no lubrication of the internals isrequired and the pumping is totally oil free.

Everest Mechanical Vacuum booster pumpsoffer very desirable characteristics, whichmake them the most cost effective and powerefficient option.

THE MAJOR ADVANTAGES

Can be integrated with any installedvacuum system such as Steam Ejectors,Water Ring Pumps, Oil Sealed Pumps,Water Ejectors, etc.

The vacuum booster is a Dry Pump, asit does not use any pumping fluid. It pumpsvapor or gases with equal ease. Smallamounts of condensed fluid can also bepumped.

Vacuum boosters are power efficient.Very often a combination of VacuumBooster and suitable backup pump resultsin reduced power consumption per unit ofpumping speed.

They provide high pumping speeds evenat low pressures.

Boosters increase the working vacuum ofthe process, in most cases very essential forprocess performance and efficiency. VacuumBooster can be used over a wide workingpressure range, from 100 Torr down to 0.001Torr (mm of mercury), with suitablearrangement of backup pumps.

It has very low pump friction losses,hence requires relatively low power forhigh volumetric speeds. Typically, theirspeeds, at low vacuums are 20-30 timeshigher than corresponding vane pumps /ring pumps of equivalent power.

Use of electronic control devices suchas Variable Frequency Control Driveallows modifying vacuum boostersoperating characteristics to conform to theoperational requirements of the primevacuum pumps. Hence they can be easilyintegrated into all existing pumping setupto boost their performance.

Vacuum boosters don't have any valves,rings, stuffing box etc., therefore, do notdemand regular maintenance.

Due to vapor compression action by thebooster, the pressure at the discharge of

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SALIENT FEATURES ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

EVEREST Transmission

booster is maintained high, resulting inadvantages such as low back streaming ofprime pump fluid, effective condensationeven at higher condenser temperatures andimprovement of the backup pump efficiency.

The Table below gives a rough estimate ofhow the boosters enhance the workingvacuums of the processes when installed incombination with various types of vacuumpumps.

VACUUM PUMP PRESSURE RANGE

Single Stage Ejector 150 Torr

Water Ejector 100 TorrWater Ring Pump 40-60 Torr

Liquid Ring Pump 20-30 TorrPiston Pumps 20-30 Torr

Rotary Piston Pumps 0.1 TorrRotary Vane Pump 0.01-0.001 Torr

They effectively replace multistage steam jetejectors, r esulting in considerable steamsavings and reduced loads on coolingtowers. Mechanical Vacuum Boosters areversatile machines and their characteristicsdepend largely on backing pump. Varioustypes of backing pump can be used,depending upon the system requirement andultimate vacuum needs. However, the finalvacuum is governed by the suitable selectionof the backing pump and boostercombination. The table below gives a broadrange of vacuum achieved w i t h v a r i o u sb a c k i n g p u m p s combinations.

Integrated pumping systems that stage twoor more pumps in series have becomeincreasingly popular in recent years.Integrated Mechanical Systems are builtaround the Rotary-Booster. The Boosterdischarges to a Backing pump whichdischarges to atmosphere. Using Boosters inthis manner extends the range of applicationof liquid ring pump, water ejectors, rotarypiston and rotary vane pumps.

Multi-staging of boosters is also widelyused to achieve high pumping speeds atpressures as low as 0.001 Torr.

Everest Twin Lobe Boosters are usedmainly in two modes: -

1. Compression Mode2. Transport Mode

Compression Mode In compressionpumping, the general application, a boosteris placed in series with a backing vacuumpump whose rated capacity is much lower

than the booster capacity.The ratio of

Booster capacity to BackingPump capacity is termed asSTAGING RATIO and theratio of Booster outletpressure to inlet pressure isCOMPRESSION RATIO. Incompression mode the s t ag i n g r a t i o r a n g e s

between 2-10 while thec o m p r e s s i o nr a t i o s Notes

achieved range between 6-40, depending uponcombination selection and process. Initially,pumping is initiated at atmospheric pressuresby Backing and after achieving therecommended cut in pressure the booster isswitched on. A bypass line around the boostermay be provided for the initial pump downperiod. Boosters with hydrokinematicdrive/Variable Frequency control are alsoavailable which allow simultaneous start-up ofthe Booster & the backing pump. The initialpumping by Backing pump is necessary sincepumping gas at high pressures with thebooster generates considerable heat and thepower input is also considerably high. For thisreason the booster is generally switched on atcut-in pressures between 20 -100 Torr. EverestBoosters combine high pumping c a p a c i t yw i t h r e l a t i v e l y l o w p o w e rconsumption. In chemical process, working inthe coarse Vacuum range (10 -100Torr)Staging Ratio of 3-5 are generally selected andcompression ratio of the order 5-10 can beexpected. For medium vacuum range (<10Torr)higher Staging ratio and compression ratiomay be selected.

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PRESSURE RANGE WITHBOOSTER COMBINATION

15-30 Torr

10-20 Torr

5-10 Torr

2-5 Torr

2-5 Torr

0.01 Torr

0.001-0.0001 Torr

VACUUM BOOSTERSEVEREST ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

COARSE VACUUM APPLICATIONS

Typically in range 1- 100 Torr

Vacuum Drying Application

Tray Dryer

Rotary Vacuum Dryers

Flash Drying

Vacuum Distillation Processes

Solvent Recovery

Vacuum Filtration

Vanaspathi Oil De-odourisation.

Replacement of Steam Ejectors

Enhancing the performance ofWater Ring Pumps /Water ejectors

Vacuum Flash Cooling / Evaporative Cooling

Vacuum Crystallization

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COARSE VACUUM APPLICATIONS ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM


VACUUM PUMP SELECTION

It is important to understand the terms capacityand throughput and Ultimate / Blank-offvacuum of a vacuum pump as they are themajor guiding parameters in selection of thevacuum pumping system. Too small a pumpingsystem would result in inefficient or no processwhereas too large a pumping system wouldresult in high capital and operating cost.

For most of the chemical processes vacuum-pumping system is designed to take care ofprocess load and maintain the process to thedesired levels of pressures. Process Loadsconsist of:

Plant air leakage load

Process non-condensable such as dissolvedgases.Process condensable load - vapors which escape the condenser

The sum of the individual loads must beeffectively pumped out to maintain the processvacuum. All the above loads are Mass Flow rates(Kg/hr) and the pumping system must be able topump them out. Most of the vacuum pumps arerated for Volumetric Displacement FAD (m 3 /hr)and therefore their displacements must match theload at the desired pressure regime.

For example a load of 10Kg of Air at 100 Torr(660mmHg) vacuum, 20ºC needs a pump ofpumping capacity 63 m3/hr and for the sameload at 10 Torr the Pumping speed requiredwould be 630 m3/hr and at 1 Torr would need apumping speed of 6300 m 3/hr.

It is, therefore, important to establish the total loadon basis of which the pumping system should beselected. Pumps generally have their optimumpressure range where their capacities are maximumand must be operated in that range.

The Blank Off Vacuum is generally a measure ofit's ultimate, where the Capacity is ZERO. It is forthis reason series of pumps are used to achieveeffective pumping at the designed pressures.

For example a water ring pump with blank-off50Torr (710mmHg) should be used forprocesses requiring vacuum in the rangearound 70-100Torr (690-660mmHg), and forpressures below it, combination of pumpsshould be used for energy efficiency.

The most important parameter effecting the vacuumpump selection is the suction pressure that must bereached or maintained and throughput the pumpmust handle. Pumping characteristics for the pumpselected are of prime importance as most of thepumps have a working pressure range where theyare most efficient and b e l o w w h i c h t h e i r p e rf o r m a n c e d r o p s considerably. The processworking pressure and load are the major factorsgoverning the pump selection. Generally there isconfusion between the working pressures anddisplacement.

Invariably the process demands higher workingvacuums and the process engineer's end upselecting higher capacity pumps adding toconsiderable capital & working costs with littleor no gain in vacuum. For example if a processdemands system pressures to be maintainedat 50 Torr (710mmHg) with non condensableload of 10 Kg/hr at 30ºC , ideal pump shouldhave a capacity of 130m 3/hr at 50 Torr. Use ofwater ring pump which has it's ultimate at710mmHg would be a wrong choice. A Boosterand Water ring combination would be the mostenergy efficient choice.

In case the process loads are known, pumpselection can be easily made by expression,

Savg = 62.511x T {Q1 + Q2 + …Qn }

M1 M2 Mn

PUMPING SPEED vrs PRESSURE WATER

RING PUMPSINGLE

% CAPACITY STAGE JET

OF FULLCAPACITY

2 STAGE

CONDENSINGJET

ABSOLUTE PRESSURE IN Torr

WhereSavg Pump speed m3/hrT Gas/Vapor abs. Temp, in KP Process absolute Pressure in Torr

Notes

Q1, Q2, Qn Gas / Vapor flow rate, inKg/hr.

M1, M2, Mn Molar mass, in Kg/mol.of

gas /vapor.

For example, a pump is to beselected to handle 10Kg/hr of airload and 5 kg/hr of water vaporload at 50 OC and the processvacuum is to be maintained at 20Torr. The pump capacity comes to

5

P



628 m3/hr i.e. pump selected must have pumping Find the Leak rate & the capacity of pump

capacity of 628 m3/hr at inlet pressure of 20 Torr. required to pump it out maintaining systempressure to 50 Torr.

For an installed system air leakage load can beestimated by "Drop Test" method or the Pressure QL = (100-60) x (10 x 1000)

rise test. Air leaks into the system at a constant (10 x 60)rate as long as the pressures in the system arebelow 400 Torr because of critical flow conditions. = 666.6 Torr lt/sec ……leak rateThe system is evacuated to pressures between S

avg

= 3.6 x 666.6

10-100 Torr and isolated. The pressure is allowed 50to rise up to about 250-300 Torr and the timelapsed is noted. = 48 m3/hr.…Pump capacity at 50 Torr.

The Leak Rate "QL" is calculated as,

Pipe SizingQL = P x Vs The piping that connects the vacuum vessel to the

t vacuum pumping system plays a vital role in theWhere overall performance of the system. Sizing of theQL leak tare in Torr Ltrs/sec pipe requires relatively complex calculationsP pressure rise in Torr

based on various factors like Flow conditionsVS

system volume in LitresTurbulent, Steady state, Molecular, friction co-t is elapsed time in secondsefficient, Reynolds's No etc. Too small a pipewould have low conductance (High Resistance)

PUMP-DOWN AND RATE OF RISE CURVErestricting the flow rates due to higher pressurePUMPdrops across it and too large a piping wouldDOWN

CURVE increase the capital cost.PRESSURE

As a thumb rule for pressures in the range of 10-

LEAK 100 Torr pipeline "D" may be selected asp

D = 2.4 (Q)^0.5t

Where

Ddiameter of pipe in mmISOLATION QPumping speed in M3/hrVALVECLOSED For a flow rate of 900 m3/hr the suitable pipe

calculated is 72 mm, as per above and 80 NBTIMEline, the nearest standard size should beselected.

For Air, 20 OC, Molecular Wt. 28.9,

VACUUM PUMP CHOICES

avg

= 3.6 x Q In order to ensure satisfactory operation of anyL Vacuum process it is essential that suitable

P vacuum pump be used. There is generally noWhere

single pump that meets all the requirements of theS Average pump speed in m3/hrNotes

QL Leak rate Torr lt/sec process. Combination of pumps are increasinglybeing used to optimize the process performance.P System Pressure in TorrProcess condensable & non-condensable loads,air leakage loads, out-gassing loads and the

For example, for a system of volume 10m 3 Drop working process pressures are the importantparameters that influence the pump selection.

test is done. The system is evacuated to 60 Torr Various empirical load estimation charts, HEI(700 mmHg) and isolated. After 10 minutes the (Heat exchange Institute) tables and leak testspressure rises to 100 Torr (660mmHg). must be referred for the proper selection of the

Vacuum system. Some of the widely used pumps

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for vacuum process are described below alongwith their limitations.

Ring Type Pumps(e.g. Water Ring Pump, Liquid Ring Pump)These pumps use water or low vapor pressure fluidas the pumping medium. For this reason water ringtype pumps, the ultimate vacuum achieved getslimited to the vapor pressure of the pump fluid at theworking temperature. Owing to the above, WaterRing Pump would stall at around 60 Torr abs. (700mm Hg) and their working range should be between60 150 Torr (700-610 mmHg). They have furtherdisadvantage of being highly energy inefficient,because most of the power is lost in friction lossesof moving the pump fluid inside the pump. Thisrestricts the water ring pump to relatively modestvolumetric pumping capacities. Anotherdisadvantage of ring pumps is that the working fluidoften has to be treated before it can be dischargedor reused as it contains the carry over of condensedproduct.

Steam EjectorsSingle & MultistageSteam ejectors have relatively high volumetricspeeds. However, they require the maintenanceof a complete high pressure steam generationfacility confirming to IBAR regulations andinspection. They are generally not available asstand alone installations but are found wherehigh pressure process steam is readily available.

Multistage steam ejectors demand inter stagecondensing putting considerable load on the coolingtowers. Apart from the direct steam generation cost,large energy and maintenance cost of secondaryequipment such as circulation pumps, cooling tower,softening plant, DM plant and boiler maintenanceadd to recurring expense.

Rotary Vane and Piston PumpsThese type of pumps havehigh power to capacity ratiosa n d a r e t h e r e f o r e , n ot available in large volumetriccapacities. They are effectivef o r p u m p i n g n o n -condensable loads but havelimitations of not being able top u m p l a r g e & r e g u l a rquantities of water vapor(condensable loads) releasedin low-pressure vacuump r o c e s s e s . V a r i o u s

precautions have to be taken

if they are used for food grade applications toavoid contamination of process material by thepump oil or back streaming of oil vapors.

Everest Mechanical Vacuum Booster

Everest Vacuum Booster is a Dry pump that meetsmost of the ideal pump requirements. They work onpositive displacement principle. As its namesuggests, they are used to boost the performance ofwater ring / water ejectors/ oil ring/ rotating vane/piston and in some cases steam ejector pumps. It isused in combination with any one of theconventional pumps, to overcome their limitations.Vacuum Booster pump offer very desirablecharacteristics, making them the most cost effective& power efficient alternative.

S = 2.163 x T X ML

PWhere

S Pumping speed m3/hrT temperature in KM

Lair load in kg/hr Notes

P system pressure in Torr

As evident from above, at low pressures, higherpumping speeds are required to maintain thethrough-put (mass flow rate), since the specificvolume increases with the increase in vacuum.Vacuum boosters enhance the pumping speedsby about 3-10 times by virtue of which one canexpect higher process vacuum and throughputs.

BOOSTER - WATER RING PUMPCOMBINATION

Water Ring Pumps are used throughout theprocess industry. These pumps

providelegitimate alternative to steam jet ejectors in

a p p l i c a t i o n srequiring ruggedp u m p t h a t c a n

tolerate entrainedliquids, vapors and

fine solids. ThesePumps operate in aliquid environment,

generally water anda r e c a p a b l e o f

handling vaporsalong with non-c o n d e n s a b l eloads.

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Notes


They are extensively used in industrial processes WRP loosing on one time pump cost andsuch as filtration, drying, solvent recovery, r e c u r r i n g e n e r g y c h a r g e s . T h e p o w e rdistillation etc. Unfortunately they suffer from two consumption, however, is constant throughoutmajor limitations that restrict the process the range that makes LRP relatively less energyperformance. They being: - efficient in comparison combination.

The final vacuum achievable, as it is largely Curve2 gives a typical combination speed curve.

dependent on the vapor pressure of the pump As the WRP vacuum drops to the range of 60-100fluid corresponding to the working temperatures. Torr (660-700mm Hg), the Mechanical BoosterFor example, for water sealed pump, the lowest boosts the effective speed manifold. As can bepractical operating pressure for two-stage design seen from the curve the booster exhibits relativelywould be in the range of 40 60 Torr (720-700mm flat pumping speed curve in the region 10-1 TorrHg) for exit water temperature at 30-32 ºC. (750-760mm Hg), high pumping speeds and

Their energy consumption per unit of gas better process vacuum is achieved, overcomingpumped is higher since most of it is lost in the limitations of water ring pump, in this range.handling pump fluid. Vacuum boosters overcome The power consumption of the Mechanicalthese limitations of liquid ring pump. A properly Vacuum Booster is relatively low in this range asmatched combination can result in: compared to any other conventional vacuum

Higher working vacuums any where the range pump. Therefore, with little extra energy, theof 50 Torr 1 Torr (710-760mmHg). overall pumping speed and ultimate vacuums

Very high pumping speeds generally to the can be greatly enhanced. Installation of MVBorder of 4-8 times higher than the backing pump. undoubtly results in high pumping speeds and

Vapor/gas compression at the inlet of the water better vacuums. However, to get the best resultsring pump allowing use of higher water in process, its location is important. It can betemperature in the pump. effectively located between the condenser (Post-

Relatively very low energy consumption per unit condenser installation) and the WRP orof pumping speed. between the evaporator and the condenser

followed by WRP (Pre-condenser installation).To enable to determine most effective location

TYPICAL SPEED - PRESSURE CURVE process parameters play an important role.Post Condenser Installations

Processes such as distillation of high boilers

(kettle temp. are generally above 1250C) orprocesses using chilled water condenser orprocesses having direct discharge of vapors toWRP are some cases where post-condenserinstallations can give boost to the process,resulting in higher yields, lower process time andbetter product quality.

Above is a typical water ring pumpspeed curve. The pumping speed is TYPICAL POST CONDENSER INSTALLATION

e q u a l t o t h e r a t e d s p e e d(displacement) during initial pumpingand thereafter drops rapidly reachingto zero at its ultimate (690 720 mmHg). In most of the chemicalprocesses the process vacuum is inthe range of 680-700mmHg wherethe pumping speed of WRP is merely15-20% of its full rated capacity. Thisdemands installation of much larger

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In drying applications where water vapor is performance is not effected by vapors as it canexhausted from the dryer and cooling water of pump both condensable & non-condensable with10°-15°C is available in the condenser, post equal ease.condenser installation would be a good choice.Since the vapor pressure of condensate (Water) Pre Condenser Installationsis low, low process pressures are possible.

For applications where condensate is a low boiler,Double stage WRP having fluid temperature in the low temperature drying or process where

condenser temperature cannot be maintainedrange of 30-35°C would not be able to deliver low, pre-condenser booster installation wouldworking vacuum below 50-60 Torr (710-700 mm give very encouraging results. In Pre CondenserHg). However on installation of Mechanical installation the Booster is installed between theBooster between the condenser and the WRP evaporator and the condenser and handles thewould very conveniently pull down vacuum to the entire process vapors.range of 15-20 Torr (745-740 mm Hg). Still bettervacuums can be possible if the condenser & Principally condensation is just reverse ofcondensate temperatures are lowered further. evaporation and therefore process parameters

favorable for evaporation areVAPOUR PRESSURE vs TEMPERATURE FOR WATER generally not favorable for

condensation and accordinglyprocess parameters favorable

f o r e v a p o r a t i o n a r e n o tfavorable for condensation. In Notes

most of the processes vacuumsystem is installed in the fagend resulting in the entire

process being under similarlevels of vacuum. Thus ac o m p r o m i s e i s m a d eregarding the system vacuumto get optimum results thatgenerally are not the best,leading to high process timeand compromise on product

purity. Installation of BoosterIn some applications of drying/solvent recovery, it between the evaporator and

condenser overcomes the above limitations byis more important to exhaust solvent to very low creating high vacuum conditions at thelevels, typically less than 1%. At those levels evaporator and relatively high-pressurerecovery and collection of solvent may not be very conditions at the condenser, both of which tend tocritical but product purity is of vital importance. In create ideal conditions in the evaporator andsuch applications post condenser booster condenser for maximum efficiency. This wouldinstallations prove very effective. Initially when the accelerate evaporation and at the same timesolvent percentages are high Booster can be by- allow full condensation in the condenser.passed and most of the solvent recovered in thecondenser.

TYPICAL PRE CONDENSER INSTALLATION

As the concentration of the mixtureimproves, leaving low percentage ofsolvent, need for finer vacuums andhigher temperatures are felt. At thisstage the condensate can be drainedout from the condenser and Boosterstarted, give high pumping speedsand finer vacuum. This would greatlyenhance evaporation of solvent,giving high product purity. Booster

9


Notes


Due to lower vacuums in the evaporator, lower drawbacks associated with steam ejectors. Theevaporator temperature and better product purity major advantages of Mechanical Booster being:can easily be achieved in a much shorter time.Similarly due to higher pressure at the condenser, Mechanical Vacuum Boosters are more energyhigher rate of condensation can be expected. efficient.Booster can create favorable conditions both forevaporator and condenser, which over wise may Minimum of auxiliary equipment is needed;not be possible, resulting in better yield, better unlike for steam ejectors, which need largeproduct quality and better recovery of condensers, cooling towers, re-circulation pumpscondensate. etc.Boosters are, therefore, an ideal choice for all Mechanical Vacuum Boosters are dry pumping

major vacuum processes and their installation system and don't give rise to water andwould definitely result in shorter process times atmospheric pollution.and better product quality. Since various factorsinfluences a process, proper selection and Startup time for mechanical booster is very lowinstallation of Booster can yield good results in making them ideal for Batch process operationmost of the cases. where immediate startup and shut down is

essential for energy conservation.Steam Ejectors

Steam ejectors comprise of converging

diverging nozzle through which high-pressuresteam (motive fluid) is forced. The ejector nozzleconverts the high-pressure head of the motivefluid into high velocity stream as it emerges fromthe nozzle into the suction chamber. Due toincrease in velocity head, there is a drop inpressure head causing partial vacuum in thesuction chamber. Pumping action occurs as thefluid / vapors present in suction chamber areentrained by the motive fluid and are carried intothe diffuser, by viscous drag process.In the diffuser section of the nozzle, the velocity

DRY MECHANICAL BOOSTERS of the mixture is recovered to pressure headREPLACE STEAM EJECTOR greater than suction pressure but much lower

than the motive pressure. This pressureSteam ejectors find wide use in vacuum pumping (diffuser pressure) must be equal or higher thanapplications so called dirty application such as in the backing pressure for stable operation.Vapor extraction, Chemical processing,Evaporative Cooling, Vacuum distillation, In order to get low vacuum, multiple stages areVeg e t a b l e o i l d e - o d o u r i z a t i o n , Va c u u m used which are broadly classified in the, tableRefrigeration, Drying etc. In spite of the fact that below:steam ejectors have poor overall efficiency andrelatively high-energy consumption, they NUMBER OPERATING APPROXIMATE STEAMare popular in vacuum applications

OF SUCTION CONSUMPTION PER KGbecause of their simplicity and ease of STAGES PRESSURE OF SUCTION LOADoperation. It's high time now when theindustry should realize the disadvantages 1 200 - 100 Torr 4 - 8 Kg

associated with it and switch over to 2 60 - 40 Torr 15 - 20 Kg

efficient alternatives Dry Mechanical 3 20 - 5 Torr 18 - 25 Kg4 3 - 0.5 Torr 20 - 100 Kg

Vacuum Booster being one of them.Mechanical Vacuum Booster offers an The capacity of steam ejector is directlyefficient replacement to steam ejector, for most of proportional to the weight of the motive fluid.the applications, as they overcome major Generally, the ratio of motive fluid to the gas

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pumped is high, especially under low pressuresand results in excessive demand of steam inmulti-stage systems. The overall performance ofsteam ejector is sensitive to changes in operativeparameters such as motive steam pressure anddischarge pressure. A slight variation in operatingparameters weighs heavily on the systemcapacity.

Multi stage steam ejectors require inter-stagecondensing as each stage adds to the pumpingload for the succeeding stage and for reason ofeconomy, condensation becomes important. Theheat gained during condensation i.e. latent heatof vaporization, adds to the need for additionalequipment such as re-circulation pumps, coolingtowers etc. so that the same can be dissipated. Ina steam ejector, steam comes in direct contactwith gas/vapor pumped and many a times, thismixture of pumped vapor and water needselaborate treatment before it can be discharged /re-used.

Steam ejectors, especially multistage not onlyrequire steam generation facilities but also raisedemand for auxiliary equipment such as D.M.plant for boiler feed water, condensing units, re-circulation pumps, cooling towers, effluenttreatment plant etc. thereby increasing totalenergy consumption and maintenance costs.Steam ejectors are therefore, no longer popularas they were once, because of dramatic increasein cost of steam generation, auxiliary power andeffluent treatment problems.

It is for this reason many steam ejectorinstallations have been replaced by mechanicalVacuum Pumps which use far little energy for thesame service and require no additional auxiliarypower, cooling tower nor give rise to effluent.

VACUUM BOOSTERS FORDRYING/SOLVENT RECOVERY

APPLICATIONS

Drying is a process of removal of a liquid froma solid mixture by thermal means. Variousdrying process & techniques are extensivelyused in the various Process industries,Pharmaceutical industry, Food processingindustry, Dye & Chemical industry, Perfumes &Permitted Food additive industry etc primarilyto achieve one or more of the following:

Product concentration at low temperatures.

Purification by removal of unwantedvolatile elements.

Solvent recovery.

To increase shelf life and to facilitatefurther processing and permit properutilization of the final product.

To reduce shipping costs by reducingweight of the product.

To reduce the rate of biological decay.

To enhance the value of by products of aprocess.

Notes

The diagram below shows typical lowtemperature drying installation. Conventionally,Water Ring Vacuum pump/ WaterEjector/Steam ejector or Piston Pumps areused to create vacuum. They have limitationsto the Ultimate Vacuums achieved, pumpingspeeds, pump fluid contamination andconsume relatively high energy.

TYPICAL LOW TEMPERATURE VACUUM DRYER

A vacuum Booster, when used in conjunction withany of the above, over comes all the associatedlimitations and increases the overall processefficiency by increasing the vacuum and pumpingspeeds with relatively very little extra energy.

11



Notes

In most chemical processes solute is to beconcentrated to high degrees of purity and therelatively volatile solvent is to be recovered forreuse. Initially in the solution, when the soluteconcentrations are low, evaporation of solvent isrelatively fast but as the solute concentrationincreases, the process becomes slow and demandshigher temperatures or lower pressures tocontinue. In most of the processes the increase intemperature is restricted and therefore thepressures must be reduced to continue theprocess.

Let us consider a mixture of two completelymiscible volatile liquids A & B having molefraction xA & xB respectively. Let their partialVapor pressures at any certain temperature T, bePA & PB, and pºA & pºB be their vapor pressures inpure state, corresponding to temperature T.

According to Raoults law: "In a solution, vaporpressure of a component (at given temp.) isequal to the whole fraction of that component inthe solution multiplied by the vapor pressure ofthat component in the pure state". Therefore,

PA = xA pºA & PB = xB pºB

VapourPressure

X A = 1 XA = 0X B = 0 XB = 1

So Ps, Total pressure of solution (according toDalton's law of partial pressure) is equal to thesum of partial pressures.

Ps = PA + PB

xA pºA + xB pºB

(1- xB) pºA + xB pºB (since xA = 1- xB) (pºB - pºA) xB + pºA

When xA= 1 i.e liquid is pure A, then the total pressure, Ps = pºA

When xB = 1 i.e liquid is pure B, then the total pressure, Ps = pºB

In case of solvent recovery / productconcentration, product A can be taken as non-volatile solute in volatile solvent B. That is, thevapor pressure pºA, at any given temperature isrelatively very low in comparison to pºB or inother words the Boiling point of A is relativelyhigher than product B.

The equation (I) can be re written as,

Ps = pºB . xB

Ignoring pº A , being relatively small

Initially the vapor pressure, Ps of the solution,when molar concentration of B is relativelyhigh, is close to pB (vapor pressure of pure B atthe specific temperature T) As the solventevaporates, molar concentration of B dropsresulting in drop of the vapor pressure of themixture.

This indicates that as the process ofconcentration proceeds, the amount of solventpresent in the solution reduces and formaintaining the same evaporation rates eitherthe pressure must be reduced or temperatureincreased. In case any of the above is notdone, the rate of evaporation / solvent recoverywould fall drastically.

If a solution contains, WA kg of solute of MolWt. MA dissolved in WB kg of solvent of Mol.Wt. MB, we have,

WA

MA

PºB - P S = ........................W

A

MA +

W B

MB

Where

PºB Vap. Pressure of Pure Solvent

PS Vap. Pressure of Solution

WA Mass of solute

MA Molecular Wt. Of Solute

WB Mass of solvent

MB Molecular Wt. of Solvent

Since ( PºB - PS) = lowering of vapor pressure ofsolution, expression 1 can be expressed as "Therelative lowering of vapor pressure of a solution,containing non volatile solute, is equal to themole fraction of the solute in the solution".

12



ExampleLet us take solution of Solute 'A' (Mol. Wt 45)in solvent Acetone (Mol. Wt. 58) in which theconcentration of solute A is 1%. The vaporpressure of Pure Acetone at 25ºC is, say,195mm Hg (abs).

Now Vapor Pressure of Solution PS at temp 25ºwould be less than PS by amount,

1/45 x 195 = 2.5 mm Hg(1/45 + 99/58)

Ps = 195 - 2.5 = 192.5 mm HgNow when the solvent evaporates, say 90gm isevaporated the concentrations then are now 1gmand 9 gm for solute and solvent respectively.

The vapor pressure drop would be

1/45 x 195 = 24.4 mm Hg(1/45 + 9/58)

The pressures must be dropped by at least 25mmHg or temperatures raised to new boilingpoint levels, to enable evaporation to continue.

Further, when say 98gm of solvent hasevaporated and the concentration is 1gm of

Booster Operation

Power Constraint and temperature riserestricts the total differential pressures acrossthe booster. This demands to ensure the totaldifferential pressure across the Booster mustnot exceed the rated limits. This can beensured by any of the following means:

Manual methods Initially the backing pump isswitched on until the required cut in pressure isachieved and thereafter the booster isswitched on.

solute and 1gm of solvent, the drop in vaporpressure would be

1/45 x 195 = 109.8 mm Hg(1/45 + 1/58)

Ps = 195 - 190.8 = 85.2 mm HgThis explains why lower and lower vacuums arerequired in a process where solvent evaporation isdone to achieve fine concentrations and puritylevels. High bottom product purity and maximumsolvent recovery both can be effectively achieved.In cases where the evaporator temperatures areclose to the boiling point of solvent, the boostercan be initially bypassed, as the condenser wouldmaintain the required differential pressures forvapor flow. However, as the concentrationincreases BP of the solution increases and theneed for reduced pressures become essential forprocess to continue. At this stage the booster canbe operated to create lower pressure in the

Notes

evaporator and relatively higher pressure in thecondenser creating higher differential pressures,which would speed up the entire process.Considerable reduction in process time, higherproduct purity and better solvent recovery caneasily be achieved.

Auto method Installation of mechanical By-pass arrangement across the booster or hydrokinematic drive or Variable Frequency Drive(VFD). In this arrangement, the booster andbacking pump can be started simultaneouslyfrom atmosphere.

ELECTRONIC VARIABLE SPEEDCONTROL DRIVE (VFD) FOR EVEREST

BOOSTERS

For process industry, VFD is stronglyrecommended for Mechanical Boosters as theyprovide total operational safety anduninterrupted operations. It makes the processso flexible that various operating conditions, asrequired by the process can easily be achievedby just press of button or can be easilyprogrammed for total automation. These drivesenhance the overall performance of theBoosters and offer various advantages for thetrouble free operation of Boosters.

13



Notes

MAJOR ADVANTAGES

Booster can be started directly fromatmosphere

No need for separate pressure switch, bypass line or offloading valves.

Considerable saving in power.

Prevent over-heating of Boosters.

Protect the Booster against overload andexcessive pressure.

Offers complete protection to electric motoragainst over voltage, under voltage, overcurrent, over-heating, ground fault.

Eliminates the needs of separate starter andoverload relays for the Motor.

A u t o m a t i c a l l y a d j u s t s t h e s p e e d of Booster/Motor to meet the current set parameter.

The Electronic Variable FrequencyDrive is a microprocessor basedelectronic drive which is speciallyprogrammed to meet the demands ofthe Booster allowing it to operatedirectly from atmosphere along withsuitable fore pump. Principally a v a cu u m b o o s t e r s h o u l d o n l ydischarge into a fore pump as itcannot discharge into atmospheredirectly due to power constraints.Boosters are primarily meant toenhance the pumping speeds andultimate vacuums of the fore pump,which may be Rotary Oil sealed type,Water ring type, Steam ejector, Watere j e c t o r, P i s t o n P u m p e t c .Conventionally the fore pumps areinitially started and after achievingcut-off vacuum boosters are started.Use of Pressure Switch, Hydrokinematic drive and mechanical by-pass valves are necessary to preventthe overloading of the Booster.However, with the installation ofElectronic Variable Frequency Driveall the conventional methods can beb y p a s s e d s i n c e t h e d r i v e is p r o g r a m m e d t o r e g u l a t eautomatically the Booster speed,keeping the load on Motor withinpermissible limits.

The drive limits the Booster speed to safe speedand as the vacuum is created the Booster speedpicks up to the final preset speed, giving mostoptimum performance over the entire range. Thisdrive can be set to achieve higher motor speedsthan the motor rated speeds since increase infrequency beyond 50 Hz., results in higher speedof the Motor without causing any harm to it.

S i n c e a l l t h e p a r a m e t e r s a r e e a s il y programmable, one can adjust the boosterpumping speeds to match the systemrequirements easily and quickly. The drivelimits the current to the Motor and safeguardsthe motor against over voltage, under voltage,electronic thermal, overheat ground fault…. i.e.protects the Motor against all possible faults.

External computer control over all aspects ofbooster performance is possible via RS485serial interface built into the drive electronics.This enables the Booster to be integrated intoany computer-controlled operating system.

14

ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM


HIGH VACUUM APPLICATIONS

Typically in range 0.001- 1 Torr

Efficient backup for Diffusion Pump Systems

Thin Film Deposition /Coating Short path/

Molecular Distillation Solvent Recovery

CFL, Tube Light & General Lighting industryNotes

Object & Roll Metallisers

Vacuum Heat Treatment andDegassing / Vacuum Furnaces

Semi Conductor Processing

Transformer oil De-humidification

Chemical Laser Applications

Freeze Drying

Vacuum Impregnation

De-humidification

De-gassing

15


HIGH VACUUM APPLICATIONS ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

HIGH VACUUM APPLICATIONS

In compression pumping, the generalapplication, a booster is placed in series with arotary pump whose rated speed is much lowerthan the booster speed. The ratio of Boosterspeed to Pump speed is termed as STAGINGRATIO and the ratio of Booster outlet pressureto inlet pressure is COMPRESSION RATIO.

In compression mode the staging ratio rangesbetween 2 - 15 while the compression ratiosachieved range between 10-40, depending upon

combination selection. Initially, pumping is i n i t i a t e d a t

A Typical performance curve is drawn for aBooster combination indicating the individualand combination performance with single stage& double stage rotary pump.

In transport mode pumping, the Booster is usedin series with the rotary pump with staging ratio 1.Both the pumps are started simultaneously atatmospheric pressures since the critical pressuredrop can never exceed. This combination effectshigher ultimate pressure without much increase inpumping speed. However, throughput at lowerpressures increases resulting in higher ultimatepressure.

Notes

a t m o s p h e r i cpressures by Rotary TYPICAL PERFORMANCE CURVE FOR EVEREST EVB30 BOOSTER

pump/Fore pumpand after achievingthe recommended BOOSTER COMBINATION 1

cut in pressure the IDEAL CURVE

booster is switched PUMPING CUT-INPRESSURE

on. A bypass line SPEED COMBINATION 2around the booster Lt/m*1000

may be provided for HP

the initial pumpCURVE

d o w n p e r i o d . DOUBLE SINGLE

B o o s t e r s w i t h STAGE STAGE

h y d r o k i n e m a t i c RP RP

d r i v e / V a r i a b l eFrequency control PRESSURE IN Torr

are also availablew h i c h a l l o w Combination 1 Everest Booster EVB30 backed by 3000 LPM rotary pump single stage

Combination 2 Everest Booster EVB30 backed by 3000 LPM rotary pump double stagesimultaneous start-up of the booster &the fore pump. This initial pumping by fore pumpis necessary since considerable heat isgenerated by pumping gas at high pressures withthe booster and the power input is alsoconsiderably higher. For this reason the booster isgenerally switched on at cut-in pressures of 20-60Torr. A suitable vacuum switch can be installed The use and application of Everest Boostersbetween the booster & the fore pump, set for cut-

in Industryin pressure, so that the booster is switched ononly on achieving the designed cut-in pressures. Vacuum Roots Blowers are widely used in theHowever, for short duration the booster can with-

industry. Until recently their use in India wasstand excessive differential pressure across it.restricted because the item was imported andThe Booster-Rotary Pump combination are

generally recommended when speed of 3000 therefore very expensive. However, for the pastLPM or higher are required since the combination few years Everest Blowers have been making theis most economical and power saving than any item and its usage has increased by leaps androtary pump of similar capacity. bounds. Today there are hundreds of

installations using this product.As evident from the Typical Performance Curve,booster is most effective in the pressure range of So this is a good time to look at various1 -0.001 Torr having high pumping speeds and applications and see how Everest Boosters canrelatively low power consumption for this range. improve performance and reduce energy costs.

16



SOME OF THE APPLICATION AREAS FOR EV E R E S T M E C H A N I CA L VAC U U MBOOSTER

BOOSTING THE PERFORMANCE OFDIFFUSION PUMP SYSTEMS

Vacuum metallizing plants are widely used to p r o du c e a v a s t r a n g e o f m e t a l l i z e dplastic/glass/metallic objects, such as reflectors,mirrors, clock and radio cabinets. A typical plant isshown in Figure before. For fast production, atypical cycle time is 6 to 10 minutes, though times inexcess of 30 minutes are not unknown. A seriescombination of a rotary oil-=sealed mechanicalpump and a Diffusion pump are generally used. Theproblem is that in the pressure range 10 3 Torr to 1Torr, the speed of both the pumps is very low, hencepump-down times are generally slow. A look at thespeed characteristics of typical Oil-Sealed RotaryPump will show that the pump speed rapidly startsfalling at pressures below one Torr. The speed of thediffusion pump starts to fall rapidly at pressuresabove 0.001 Torr. Hence, in the transition pressurerange of 0.0001 to 1 Torr both rotary and diffusionpumps perform w e l l b e l o w t h e i r o p t i m u m le v e l s . T h e consequence of this is that theoverall process cycle is lengthened. This results inhigh energy and overhead costs. Everest Boosterhas its peak pumping speeds in the pressure rangeof 0.001 Torr and 1 Torr. Further because there islittle friction in the rotating parts, high pumpingspeeds are possible at low power consumption. Inthe transition pressure range Everest Booster canprovide five to ten times more pumping speed thanthe Rotary Pump of the same HP. Thus, to boost theperformance of a Diffusion Pumped system, themodern trend is to use a Mechanical Boosterbetween the rotary pump and diffusion pump.Everest Vacuum Booster inserted between theDiffusion and Rotary pump provides a high orboosted pumping speed and thereby enables a fastpump-down process cycle. The productivityimprovement can be as high as 100% to 200%.

Advantages of using Everest Booster

Higher pumping speed by a factor of 5 to 10times that of the rotary pump.

Power Saving: The Everest Booster, byvirtue of speed enhancement and shorterprocess cycles, saves power.

Long service life and very low maintenancebecause there are no rubbing/mechanicalfriction between internals.

Less frequent oil changing.

IMPROVING THE QUALITY OF LAMPS

For quality Bulb, Tube Light or CFL good vacuumi s a n e s s e n t i a l p r o c e s s r e q u i r e m en t . Conventional vacuum pumps are unable tooffer high pumping speeds in the vacuum rangeof 10 -2-10 -3 torr as they approach there ultimate,where pumping speeds drop to almost zero.Mechanical Vacuum Boosters are ideal pumps forsuch applications as they not only enhance theultimate vacuum levels but also increases thepumping speeds many fold. These VacuumBoosters are compact and low energy consumingmachines and can easily be integrated into theexisting setup. In most of the cases they can bedirectly mounted on top of the rotary pumps,requiring no additional space, foundations, pipingetc. Mechanical Boosters offer high pumpingwhich ensures total evacuation of the bulb prior toits sealing. The requirement of high-speedmachine operation where frequent leakagesoccur due to breakage and wear and tear places

heavy demands on pumping systems. The consequence of this is that rotary pumps are Notes

frequently replaced due to deterioration inperformance.

Everest Booster improves matters by

Increasing the speed of the Rotary pumpsby a factor of 3-5 times.

Enables less frequent maintenance of therotary pump, since it can deliver less than peakperformance and still provideadequate/superior vacuum to the machine.

In the production of vacuum lamps usingEverest Booster substantially improves theproduct quality and life.

USE IN VACUUM HEAT TREATMENT ANDDEGASSING

Vacuum annealing is necessary for those specialsteels, which would get embrittled due toincorporation of oxygen if heated in air. Heatingunder vacuum and subsequent quenching in inertgas is sometimes the only method that is possiblefor treatment of such steels. Since heatingimposes considerable gas loads on the rotarypump, Everest Booster provides the benefit ofbeing able to handle these heavy gas loads atlow pressures in an economical way.

A major advantage with Everest Booster is easy andinstantaneous startup, unlike diffusion pump or oilbooster, which requires substantial heat up time(and consequent waste of energy) to come up toa state of operational readiness.

17



Notes

USE IN DRYING APPLICATIONS

Everest's Mechanical Vacuum Booster find greatuse in low temperature drying applications suchas pharmaceuticals, food grade products andother thermally sensitive products. Since thespecific volume increases many fold with thedecrease in pressure the need for a goodpumping system is felt which can maintain largepumping speeds at low pressures. VacuumBoosters offer a ideal solution to meet the aboveneed as they have high pumping speed forrelatively low energy consumption. The pumpingis totally dry as there is no sealing/motive fluidinvolved. These boosters can pump bothcondensable and non condensable loads withequal ease. As the pumping is dry they can beused conveniently for food grade andpharmaceutical applications where dry pumpingis an essential requirement. Various industriessuch as milk drying, mechanized brick drying,katha drying, and thermally sensitive chemicalsdrying units are already using Vacuum Boosters.

They also acts as barriers / one way valvesdue to their high pumping action, minimizingback streaming of Backup pump fluid. Due toeffective vapor compression at their dischargethey increase the efficiency of traps andsecondary condensers, thereby increasing thebackup pump life and minimizing backup pumpfluid contamination. In certain typical distillationprocesses the process time can be reduced byalmost 50%. Boosters can be easily integratedinto any vacuum setup as they do not requireany major installation modifications nor requireany process utilities. In many cases theyeffectively replace cumbersome steamejectors. Mechanical Vacuum Boosters are lowmaintenance machines and do not have anyvalve, stuffing boxes, pistons etc. a constantsource of nuisance for maintenance engineers.

USE IN SHORT PATH / MOLECULARDISTILLATION

Everest's Mechanical Vacuum Boosters offermost energy efficient alternative to industriesperforming short path and high VacuumMolecular Distillation. Mechanical Boosters aredry vacuum pumps requiring no sealing /motivefluid and for this reason energy consumption isvery low in comparison to any other vacuumpump. They can be easily integrated with most ofthe vacuum systems, to enhance the ultimatevacuum and pumping speeds. Boosters are veryversatile and can be used with any backing pump

such as water ejectors, water ring pumps,steam ejectors, oil sealed rotary pumps etc. Inmany installations they have effectivelyreplaced cumbersome Steam ejectors.

Vacuum Boosters can easily achieve vacuumlevels of the order of below 1Torr required edfor such applications. This not only enhancesthe product quality and purity but also lowersthe kettle temperatures yet maintaining highthroughputs. Vacuum Boosters have beensuccessfully installed in Menthol distillationindustry, Vegetable oil deodorization and othersimilar processes. In fact for any applicationwhere large pumping speeds in the vacuumrange below 1 Torr are required, there boostersoffer most cost effective and energy efficientalternative

The outstanding advantages of using EverestVacuum Booster

Negligible environmental pollution comparedto steam ejectors.

Dry operation. This means that no workingfluids are used in the operation of the pump and th e r e f o r e t h e r e a r e n o p r o b l e m s o fcontaminations of or by the condensate.

Instantaneous startup and shut down.

High energy efficiency per unit of pumpingcapacity.

USE IN GAS-RECIRCULATION AND GASPRESSURE BOOSTING

In systems that re-circulate gases, such aslasers, heat exchangers and chemical processplants, the use of Everest Booster is essentialto overcome the pressure losses of pipelineand sealed chambers. Everest Boosters havethe outstanding advantage that they offer dry

18



operation, which can be totally sealed off from the USE IN FREEZE DRYINGsurrounding atmosphere.

Modern food processing industries are rapidlyIn long pipelines, Everest Boosters can be used to switching over to Freeze Drying as it offers longerboost the gas pressure. This reduces the shelf life and maintains the basic nutrients andrequirement of high driving pressures to pump aroma. In freeze drying water is frozen and thengases through pipes and because Everest sublimed. For this process large pumpingBooster is totally sealed and oil free, even speeds at low pressure is an essentialinflammable gases such as biogas, L.P.G, C.N.G, requirement for the pumping system. Mechanicaletc., can be easily pumped. Vacuum Boosters are found to be the most

suitable pumps as they have high pumping speedUSE IN SEMI-CONDUCTOR PROCESSING in the vacuum range of 10-1-10 -4 torr and are

capable of handling large volumes of vapor. TheEverest Mechanical Vacuum Boosters are used internals are dry and therefore the machines arein Semi-conductor processing industry as a part safe for food grade applications. They also act asof dry pumping / oil-free pumping systems. Such a one way valve due to high pumping speedssystems are necessary to handle the high preventing back streaming of pumping fluid of thecorrosive and often poisonous gases used in backing pump. Since the internals run dry andsemi-conductor production. The main there is no internal friction, the poweradvantage of the Everest Booster is its sealed off consumption for these boosters per unit ofoperation and long life between maintenance pumping speed is very low in comparison to anyprocedures. other available pump. They are capable of

operating at high speedswhich makes them very NotesTYPICAL INSTALLATION IN VACUUM METALISING PLANT

c o m p a c t a n d h i g h l y

effic ient. They can work

under large range oftemperatures and their

volumetric efficiency isindependent of the vapor

l o a d s i n c e n ocondensation takes place

inside the pump. Boostersare so versatile that they

can work with variousTypical arrangement of Booster installations are types of backing pumps to

meet the individual process requirements.shown. The booster can be directly mounted on They have a wide vacuum operating rangethe suction of the fore pump or mounted on a typically 10 -4 Torr to a few mm of Hg. The powerbase frame with connection to fore pump. For consumption is directly proportional to thea p p l i c a t i o n s i n v o l v i n g p u m p i n g o f differential pressure across the inlet and theCONDENSABLE VAPOR like in distillation, a discharge and therefore when working in thesuitable condenser can be installed in between vacuum range of less than 1 mm Hg the powerthe Booster & Fore pump. In such cases the Fore requirement is very low.pump size can be reduced drastically, to matchthe NON -CONDENSABLE load. USE IN TRANSFORMER OIL

Initially the fore pump is switched on until the DEHUMIDIFICATION

required cut in pressure is achieved and there- Everest's Mechanical Vacuum Boosters areafter the booster is switched on. In case extensively used in Transformer Oil Purificationmechanical By-pass arrangement across the systems to meet the need of high pumpingbooster or hydrokinematic drive or Variable

speeds at low pressures of the order of 10 -1 -3

Frequency drive is used , the booster and fore -10torr. Generally, most of the rotary oil sealed pumps

pump can be started simultaneously from are unable to maintain pumping speeds at suchatmosphere. vacuum levels and demand frequent oil change.

Vacuum Boosters when used in such a systemovercomes the above limitations making the

19

VACUUM BOOSTERSEVEREST HIGH VACUUM APPLICATIONS ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

entire process more effective, efficient and faster. above they are highly energy efficient machinesVacuum Boosters offer dry pumping as the as most of the power spent is on gas / vaporinternals do not need any lubricant. By virtue of compression with very little frictional loss, unlike

other pumps where considerable amount ofTYPICAL INSTALLATION IN OIL FILTERATION PLANT power is wasted in friction.

With the use of auxiliary equipment such as

mechanical bypass valve, hydro kinetic drive orvariable frequency control drive they can bestarted directly from atmosphere. However, theyare most effective and efficient in the vacuumrange below 1 torr. Their pumping speed peaks atabout 10-1 torr. With proper selection one canexpect increase in pumping speeds up to 10times the backup pump speed.

1.) The Rotary Vacuum Pumps RP I ,single stage & RP II, Double stage data indicated above is from RotaryPump manufacturer's catalague and is only for reference purpose. Actual data may vary from manufacturerto manufacturer. Please confirm with manufacturers catalogue.

2.) Everest Booster is to be switched on only after roughing is done and Cut-in pressures are obtained. Startingprior to the cut-in limits would result in excessive power consumption and booster heating resulting in seriousdamage. Use of pressure switch is recommended. In case it is desired that the Booster & Rotary pump shouldstart simultaneously use of hydrokinematik drive/Variable Frequency Control drive is recommended.

3.) The Boosters can be used with any other Backing pump like Rotary Piston pumps, Liquid Ringpumps,Water or Steam Ejectors - to increase the overall pumping speed and ultimate vacuums.

20



EVEREST BOOSTER COMBINATION DETAIL

BACKUP PUMP DETAIL COMBINATION DETAILCAPACITY ULTIMATE CUT-IN PR. STAGING

Lt/min mBar H.P. Lt/min mBar mbar Ratio

EVEREST R.P I 500 0.020 1.0 4400 0.0008 25 13.4

R.P II 0.002 1.0 0.0002

EVB05 R.P I 750 0.020 3.0 4900 0.0008 25 8.9R.P II 0.002 3.0 0.0002

400 m3 /hr R.P I 1000 0.020 3.0 5300 0.0008 40 6.7(6700 lpm R.P II 0.002 5.0 0.0002

R.P I 2000 0.020 5.0 5900 0.0008 60 3.4R. II 0.002 7.5 0.0002

R.P I 750 0.020 3.0 7800 0.0008 20 17.7

EVEREST R.P II 0.002 3.0 0.0002R.P I 1000 0.020 3.0 8700 0.002 20 13.3

EVB15 R.P II 0.002 5.0 0.0002R.P I 1500 0.020 3.0 9800 0.0008 40 8.9

800 m3 /hr R.P II 0.002 5.0 0.0002Notes

(13300 lpm) R.P I 2000 0.020 5.0 10500 0.0008 40 6.7R.P II 0.002 7.5 0.0002R.P I 5000 0.020 7.5 12000 0.0008 60 2.7R.P II 0.002 10 0.0002

EVEREST R.P I 1500 0.020 3.0 16000 0.0008 20 18.5

R.P II 0.002 5.0 0.0002

EVB30 R.P I 2000 0.020 5.0 17900 0.0008 30 13.9R.P II 0.002 7.5 0.0002

1670 m3 /hr R.P I 5000 0.020 7.5 22700 0.0008 40 5.6(27800 lpm) R.P II 0.002 10 0.0002

R.P I 7500 0.020 10 24200 0.0008 60 3.7R.P II 0.002 15 0.0002

EVEREST R.P I 2000 0.020 5.0 24700 0.0008 10 24.4

R.P I 0.002 7.5 0.0002

EVB50 R.P I 5000 0.020 7.5 35100 0.0008 20 9.8R.P II 0.002 10.0 0.0002

2940 m3 /hr R.P I 7500 0.020 10.0 38700 0.0008 30 6.5(48800 lpm) R.PII 0.002 15.0 0.0002

R.P I 10000 0.020 15.0 40800 0.0008 40 4.9R. II 0.002 20.0 0.0002

EVEREST R.P I 5000 0.020 7.5 42800 0.0008 20 13.3

R.P II 0.002 10.0 0.0002

EVB60 R.P I 7500 0.020 10.0 48300 0.0008 20 8.7R.P II 0.002 15.0 0.00023910 m3 /hr 10000 51600 30 6.5

(65000 lpm) R.P I 0.020 15.0 0.0008R.P II 0.002 20.0 0.0002R.P I 15000 0.020 10X2 55400 0.0008 40 4.3R.P II 7500X2 0.020 15X2 0.0002

NOTES( CONVERSIONS - lts/min * 0.06 = m3/hr : lts/min * 0.0353 = cfm : 1mBar *0.76 = 1 Torr )

21



Notes

ADVANTAGE OF USING ELECTRONICVARIABLE SPEED CONTROL DRIVE

WITH EVEREST BOOSTERS

At Everest we have developed specialElectronic Variable Speed A.C., Motor drive foruse with Everest Mechanical Booster RootsBooster Dry Vacuum Pump. These drivesenhance the overall performance of theBoosters and offer various advantages for thetrouble free operation of Boosters.

The major advantages are

Booster can be started directly fromatmosphere

No need for separate pressure switch, bypass line or offloading valves

Considerable saving in power

Prevent over-heating of Boosters.

Protect the Booster against overload andexcessive pressure

Offers complete protection to Motor againstover voltage, under voltage, over current, over-heating, ground fault.

Eliminates the needs of separate starter andoverload relays for the Motor.

Automatically adjust the speed of Boosterbetween 100rpm to 3000rpm giving Highpumping speeds with relatively low inputpower. A standard 1500rpm motor can be usedfor this purpose.

The Electronic Variable Frequency Drive is amicroprocessor based electronic drive which isspecially programmed to meet the demands ofthe Booster allowing it to operate directly fromatmosphere along with suitable fore pump.Conventionally, the Boosters can be started onlyafter achieving fore vacuum to the range of 30 50Torr, as they are not recommended for directdischarge into the atmosphere. Use of PressureSwitch, Hydro kynamatic drive and by passvalves are necessary to prevent the overloadingof the Booster. However with the installation ofElectronic Drive all the conventional methods canbe bypassed since the drive is programmed toregulate automatically the Booster speed,keeping the load on Motor within permissible

limits. This allows the Booster to startsimultaneously with fore-pump.

Initially when the fore-pump and Booster are startedthe drive reduces the Booster speed to thepredetermined levels and as the vacuum is createdthe Booster speed picks up to the final p r e s e n t sp e e d , g i v i n g m o s t o p t i m u m performanceover the entire range. This drive can be set toachieve higher motor speeds than the Motor ratedspeeds since increase in frequency beyond 50 Hz.,results in higher speed of the Motor without causingany harm to it. This function enables the Boostercapacity to be enhanced by 50% to 90% of capacityat 1440rpm.

S i n c e a l l t h e p a r a m e t e r s a r e e a s il y programmable, one can adjust the boosterpumping speeds to match the systemrequirements easily and quickly. The drivelimits the current to the Motor and safeguardsthe motor against over voltage, under voltage,electronic thermal, overheat ground fault…. I.e.protects the Motor against all possible faults.

When the systems achieves a vacuum to theorder of 1 Torr or better, the load on theBooster is reduced drastically and under suchconditions the Booster speed can be easilyincreased without overloading Motor, resultingin higher pumping speeds.

External computer control over all aspects ofbooster performance is possible via RS485serial interface built into the drive electronics.This enables the Booster to be integrated intoany computer-controlled operating system.

22



TYPICAL EVEREST BOOSTER ROTARY PUMP COMBINATION

SPEED

Curve 4

Curve 3

Curve 2

Curve 1

PRESSURE mbar

The above curves are a typical Everest Booster and Rotary Pump combination curves

Curve (1) indicates the speeds corresponding tovarious pressures for a double stage rotary pump.

Curve (2) indicates combination speed ofBooster and Rotary Pump with pressure switcharrangement, in which Booster comes intooperation at a set pressure of 30 Torr. Duringthe initial period from atmosphere to 30 torr,the pumping speed is equal to the pumpingspeed of Rotary Pump only and higher speedsare achieved only beyond cut in pressure whenthe booster comes into operation.

Curve (3) indicates the speed of combination inwhich both the Booster and Rotary Pump are

started simultaneously from the atmosphere forthis arrangement Auto speed control (variablefrequency drive) or hydro kynamatic drive isnecessary. The curve shows that the pumpingspeeds are relatively larger in the initial zoneresulting in quick pump down time.

Curve (4) indicates the Booster Rotary Pump combination speed with Auto speed control drive set to 150% of Motor rated speed. The Drive automatically, in the range of pressures < 1 Torr, increases the Motor speed to 150% of its rated speed, boosting the overall pumping speed substantially.

23


GLOSSARY ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

Notes

VACUUM AND TERMS USED IN VACUUMTECHNOLOGY

What is Vacuum?Vacuum is simply a pressure below atmosphere. To createvacuum in a system, a pump is required to remove mass(gas/vapor) from the system. The more mass is removed,lower is the pressure that exists inside the system. Variousvacuum levels are defined depending upon the ultimatevacuum

Range Absolute pressure rangeCoarse Vacuum 10 - 760 TorrMedium Vacuum 0.001 - 10 TorrFine Vacuum 10 ^-3 - 10 ^-7 TorrUltra High Vacuum

< 10^-7

Accommodation Coefficient (for free-molecule heattransfer). The rate of the energy actually transferred betweenimpinging gas molecules and surface and the energy whichwould be theoretically transferred if the impinging moleculesreached complete thermal equilibrium with the surface.

Back Streaming The direct flight of vapour molecules byscattering from the hot vapour jot or evaporation from hotnozzle parts in the direction of the mouth or intake port of avapour pump.Baffle A System of cooled walls, plates, or tubing placednear the inlet of a vapour pump to condense back streamingvapour at a temperature below that of the room and returnthe fluid to the boiler. The baffle plates may be located in the"Head" of the pump or in a separate housing attached to theinlet.Booster Pump A vapour pump or a specially designedmechanical pump used between a vapour pump and aforepump to increase the maximum gas throughput whichcan be handled. The limiting or breaking forepressure of thebooster at this maximum throughput must be appreciablygreater than that of the vapour pump which it backs.

Cold Trap A vessel designed to hold a refrigerant, or cooledby coils in which a refrigerant circulates, inserted into avacuum system so as to condense on its inner surfacevapours present in the system.Collision Rate The average number of collisions per secondsuffered by a molecule or other particle through a gas. Alsocalled the collision frequency per molecule.Compression Chamber The decreasing space within amechanical pump in which the gas is compressed beforedischarging through the outlet.Condensation Coefficient The ration of condensation rate toimpingement rate.Condenser Part of a vacuum system with large coolingsurface (usually water cooled) for the condensation of largequantities of vapour (frequently water vapour)Conductance (measured value) The throughput understeady-state limited conditions divided by the measureddifference in pressure between two specified cross sectionsinside a pumping system.Critical Backing Pressure The value of the backingpressure at any stated throughput which, if exceeded, causesan abrupt increase of pressure on the high vacuum side of thepump. In certain pumps the increase does not occur abruptlyand this pressure is not precisely

determinable.Diffusion Coefficient The absolute value of the ratio of themolecular flux per unit area to the concentration gradient of agas diffusing through a gas or a porous medium where themolecular flux is evaluated across a surface perpendicular tothe direction of the concentration gradient.

Diffusion Pump A vapour pump with a vapour stream oflow density, capable of pumping gas with full efficiency atintake pressures below 10-2 Torr. The pumping action of eachvapour jet occurs by the diffusion of gas molecules throughthe low, density scattered vapour into the denser forwardmoving core of a freely expanding vapour jet.Ejector Pump A vapour pump with a dense vapour stream.The operating range depends on the pump fluid and isbetween 10-4 and 102 Torr. At higher pressures the mixing ofentrained gas and vapour is effected by turbulence, at lowerpressures by diffusion of gas into the vapour at the boundaryof the dense vapour stream.Forepressure The total pressure on the outlet side of a pumpmeasured near the outlet port. Sometimes called the backingpressure.Forepump The pump which produces the necessary fore-vacuum for a pump which is incapable of discharging gasesat atmospheric pressure. Sometimes called the backingpump.Fractionating Pump A multi-stage vapour pump in whichthe vapour supplied to the first stage (jet nearest the highvacuum) has been purged of the more volatile i m p u r i t i es , r e s u l t i n g f r o m d e c o m p o s i t i o n o rcontamination, by the partial condensation and refluxing ofvapour in the condenser and the circulating of the condensedpump fluid through a series of boilers feeding the variousstages so that the unwanted volatile constituents will beejected in the stages closest to the fore-vacuum.

Free Air Displacement (for mechanical pumps) (a)Measured value the volume of air passed per unit timethrough a mechanical pump when the pressure on the intakeand exhaust sides is equal to atmospheric pressure. Alsocalled free air capacity.(b) Calculated value product of the geometric volume of thecompression chamber X atmospheric pressure X revs/min ofthe pump.Gas Ballast The venting of the compression chamber of amechanical pump to the atmosphere to prevent condensationof condensable vapours within the pump. Also called ventedexhaust.Impedance of Flow The reciprocal of the conductance. Alsocalled resistance. W = 1/L.Impingement Rate The number of molecules which strike aplane surface per square centimeter per second in a gas atrest. Also known as rate of incidence.Inlet Pressure The total static pressure measured in astandard testing chamber by a vacuum gauge located near theinlet port of a vacuum pump (or: pressure in the inlet port ofan operative vacuum pump.)Leak In vacuum technology a hole, or porosity, in the wallof an enclosure capable of passing gas from one side of thewall to the other under action of a pressure or concentrationdifferential existing across the wall.Leak Rate In leak detection practice, leak rate is defined asthe rate of flow (in pressure X volume units per unit time)through a leak with gas at a specified high pressure

24

GLOSSARY ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM


(usually atmospheric pressure) on the inlet side and gas at apressure on the exit side, which is low enough to havenegligible effect on the rate of flow.Liquid Ring Pump A pump for liquids or gases whichentrains the fluid between the teeth of a pair of gears and thewall of the pump casing which fits closely around the gearsexcept in the exhaust region where the teeth engage and theintake region where the teeth disengage.Load of a Pump The quantity of gas (not including pumpfluid vapour) in mass units flowing across the inlet port of apump in unit time. Typical units are pounds per hour orgrams per hour.Mean free path (of any particle) The average distance that aparticle travels between successive collisions with the otherparticles of an assembly. In vacuum technology the assemblyof particles of interest comprises only the molecules in thegas phase.Mean Molecular Velocity The average velocity of molecules in a gas at rest under equilibrium conditions. Mechanical Pump A pump which moves the gas by the cyclic motion of a system of mechanical parts such as pistons, eccentric rotors, vanes, valves, etc.Partial Pressure The pressure of a designated component ofa gaseous mixture. The total pressure in a mixture of perfectgases is equal to the sun of the pressures exerted by thecomponent gases were each to occupy the same volume byitself.Pressure after Compression The pressure at the exhaust port of an operating vacuum pump. Reciprocating Pump A pump which moves the gas by means of a system of reciprocating pistons and valves. Residual Gas Pressure The pressure of all non-condensable gases in a container in which ultimate pressure has been obtained.

Residual Vapour Pressure The vapour pressure in a systemwhich has reached the ultimate or limiting value of totalpressure.Reynolds Number As applied to the flow of gas through acircular tube the Reynold's number is a dimensionlessquantity equal to the product of the gas density in grams percubic centimeter times the flow velocity in centimeters persecond times the tube diameter in centimeters times the flowvelocity in centimeters per second times the tube diameter incentimeters divided by the viscosity coefficient in poises, Re

= qvd/n.Roots (blower) Pump A rotary blower pump having a pairof two-lobe inter-engaging impellers of special design.

Rotary Blower Pump A pump without a discharge valvewhich moves the gas by the propelling action of one or morerapidly rotating members provided with lobes, blades, orvanes. Sometimes called a mechanical booster pump whenused in series with a mechanical forepump. Rotary blowersare sometimes classified as either axial flow or cross flowtype depending on the direction of flow of gas.

Sliding Vane Rotary Pump A liquid-sealed mechanicalpump employing a rotor, stator and sliding vanes, dividingthe pump chamber in three compartments.Rotary Piston Pump A liquid-sealed mechanical pumphaving a cylindrical plunger (or piston) which is moved byan eccentric rotor in a sliding rotary motion with a liquid sealagainst the walls of a cylindrical stator and which divides thestator into two compartments by means of an attached vaneor blade which slides through a slot in a

cylindrical bearing in the water wall.Saturation Vapour Pressure The vapour pressure in anisolated system under equilibrium conditions in the presenceof the condensed phase.Separator (trap) Reservoir for separating two intermixedmaterials (e.g water-oil; oil-air) by centrifugal force or bydeposition under the influence of gravity.Sorption Pump A pump with a renewable trapping surfacewhich reduces the partial pressure of gases by absorption,absorption, or chemisorptions.Specific Speed Pumping speed of a diffusion pump per unitarea of nozzle clearance area.Speed of Exhaust The magnitude of the rate of reduction ofpressure in the system multiplied by the volume and dividedby the measured pressure.Speed of a Pump The pumping speed for a given gas is theratio of the throughput of that gas to the partial pressure ofthat gas at a specified point near the mouth (or inlet port) of apump.Sputtering Pump A gettering pump in which the getteringsurface is produced by sputtering the getter material in anelectric gas discharge.Standard Atmosphere a) the standard atmosphere, ornormal atmosphere is defined (independently of barometricheight) as a pressure of 1,013,250 dyn/cm2 .(b) the normal atmosphere has also been defined as the pressure

exerted by a mercury column 760 mm in height Notes at 00C under standard acceleration of gravity of 980-665 cm/sec2. Assuming a density of mercury at 00 of 13-59509 g/cm3, this is equal to 1,013,249 dyn/cm2.Throughput Under conditions of steady-state conservativeflow the throughput across the entrance to a pipe is equal tothe throughput at the exist. In this case the throughput can bedefined as the quantity of gas flowing through a pipe inpressure X volume units per unit time at room temperature.

Time of Evacuation The time required to pump a givensystem from atmospheric pressure to a specified pressure.Also known as pump-down time.Torr The torr is defined as 1/760 of a standard atmosphere or1,013,250 / 760 dyn/cm2 . This is equivalent to defining theTorr as 1333.22 microbars and differs by only one part inseven million from the International Standard millimetre ofmercury. 1 mm Hg = 1.00000014 Torr.

Total Pressure Total pressure usually refers to the pressuredetermined by all of the molecular species crossing theimaginary surface.Ultimate Pressure The limiting pressure approached in thevacuum system after sufficient pumping time to establishthat further reductions in pressure will be negligible.

Vapour A gas whose temperature is below its criticaltemperature, so that it can be condensed to the liquid or solidstate by increase of pressure alone.Vapour Pressure (a) the sum of the partial pressures of allthe vapours in a system.(b) the partial pressure of a specified vapour.Vapour (stream) Pump Any pump employing a vapour jetas the pumping means. Applies to ejector pumps as well as todiffusion pumps.

25


APPENDIX ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM

Notes

APPENDIX IComposition of Atmospheric Air

% of weight %of volume Partial pressure, mbar

N2

75.51 78.1 792

O2 23.01 20.93 212Ar 1.29 0.93 9.47CO2 0.04 0.03 0.31Ne 1.2x10 -2 1.8x10 -3 1.9x10-2

He 7x10-5 7x10-5 5.3x10-3

CH4 2x10-4 2x10-4 2x10-3

Kr 3x10-4 1.1x10 -4 1.1x10-3

N2O 6x10-5 5x10-5 5x10-4

H2 5x10-6 5x10-5 5x10-4

Xe 4x10-5 8.7x10 -6 9x10-5

O3

9x10-6 7x10-6 7x10-5

100 % 100 % 1,013

50% RH at 20oC

1.6 1.15 11.7

Note RH = Relative HumidityTaking into account the relative humidity ,the total pressure as read by the barometer amounts to 1,013 + 11.7 = 1,025mbar

APPENDIX IIVacuum Units and Formulae

Units of Pump Speed (Volume / Time)1 L/s = 2.12 ft3/min = 3.6 m3/h1 ft3/min = 0.47 L/s = 1.69 m3/h1 L/m = 0.035 ft 3/min = 0.06 m3/hr

Units of Gas Quantities PV1 molar volume = 22.41 L (at standard conditions-STP)1 mol = 6.023 x 1023 molecules1 L.atm = 2.69 x 1022 molecules1 std cm3 = 2.69 x 1019 molecules1 torr.L = 3.53 x 1019 molecules1 std cm3 = 0.76 torr.L1 std cm3 = 1 atm . Cm3

1 std ft 3 = 7.6 x 10 23 molecules

Standard conditions are 1 atm at 273o K

(PV = work; work/time = power)1 std cm3/s = 760 µm (Hg) L/s

= 1.6 torr.ft3/min1 torr ft 3/min = 0.62 std cm3/s

472 µm (Hg) L/s

1 um (Hg.) L/s = 1.32 x 10-3 std cm3/s

2.12 x 10-3 torr ft3/min

Ideal Gas Law P = nkT

n : No. of moleculesk : Boltzmann's constantT : Absolute temperature

(P1V1/T1 ) = (P2 V2 /T2 )Molecular VelocityRoot mean square velocity C =(3 kT/m) 1/2

= 1.58 X 104 (T/M)1/2 cm/secm : molecular massM : Molecular weight

Average velocity Ca = ( 8 kT / m) 1/2

= 1.46 X 104 (T. M) 1/2 cm/sec Most Probable velocity Cp = (2 kT/m) 1/2

= 1.29 X 10 4 (T/M) 1/2 cm/secImpingement Rate (v)

V = P( 2 mkT) 1/2

3.5 X 10 22 p (MT)1/2 molecules/sec cm2 p in TorrMean Free Path ( )= 1/2 1/2 n 2 = Molecular diameter

5 X10-3 / P (Torr) cm

Flow RegimesViscous Flow :R < 1200 and Kn <0.01Turbulent Flow :R >2200 R: Reynolds's numberMolecular Flow : Kn >1 K n = /d Knudsen's numberConductanceConductance : C= q/(P2-P1)Conductance's in parallel:CT = C1 + C2 + C3+…..Conductance's in series : 1/ CT = 1/C1 + 1/C2 +1/C3+…Viscous Conductance, long circular tube:Cv = ( d 4 /128 l ) (P1 + P2)/2

= (182 d4 /l) Pav l/s for air at 20o Cd : Tube diameter ,cm l : Tube length ,cm: coefficient of viscosity, poiseMolecular Conductance ,long circular tubeC = ( 2 kT/m) 1/2 (d3/6 l)

= 12.1 d3 /1 for air at 20o CMolecular conductance ,circular tubes of arbitrary length

C = (12.1 d 3 / l) l/s =clausing's factor

= [ 15(1/d) + 12 (1/d)] / [ 20 + 32 (1/d) +12 (1/d) ]Molecular conductance ,small aperature C =3.64 A (T/M) 1/2

11.6 A l/s for air at 20o CA : Area of aperture ,cm2

Molecular conductance ,long rectangular duct

C = [ 30 a2b2 /(a+b) l] K Where K is given byb/a 1.0 0.8 0.6 0.4 0.2 0.1

K 1.1 1.12 1.13 1.17 1.29 1.44 Pumping Speed: S = q/pEffective Pumping Speed 1/Seff = 1/S +1/CSeff = S C/(S+ C)PumpDown Time(viscous Region for Pressure < 10-3 Torr)

t = K .2.3 (V/S) log (p1/ p2) t = Time .minutesV = volume, litersS = Effective Pumping Speed, l/m p 1 = Intial Pressure ,TorrP2 = Final Pressure, Torrk = Factor depending on pressure rangePressureRangeK760-1 Torr 1.11 0.01 Torr 1.50.1- 0.001 Torr 4PumpDown Time (Molecular Region, Theoretical)

t = ( V/Seff) 2.3 log [(pl pu)/((p pu)] V = Volume of Chamber ,litersSeff = Effective pumping speed at the chamber , l/s p l = Intial Pressure ,Torrp = Pressure after t sec, Torrp u = Ultimate pressure in the chamberp

u = Q

g

/ Seff

Gas LoadQg = QL+ QD + QV + QP

QL = Gas load due to real leaksQD = Gas load due to outgassing

QV = Gas load due to vapor pressure

26

APENDIX ENHANCING PROCESS EFFICIENCY by IMPROVING VACUUM


CONVERSION TABLES

PRESSUREP Torr mbar bar Pa atm psi kg/cm2

Torr 1 1.33 1.33 x 10 -3 133.32 1.32x10 -3 1.90x10-2 1.34x10-3

mbar 0.75 1 1x10-3 100 9.87x10 -4 1.40x10-2 9.86x10-4

bar 750.06 1000 1 1x10-5 0.987 14.5 1.022Pascal 7.5x10-3 0.01 1x10-5 1 9.87x10 -6 1.45x10-4 1.02x10-5

atm 760 1013 1.013 101325 1 14.69 1.035psi 51.71 68.95 0.069 6895 0.068 1 0.07kg/cm2 733.95 978.64 0.979 97861 0.965 14.19 1

PUMPING SPEED/CONDUCTANCES/C Lit/Sec. lit/min m3/hr Cu.ft/min

Lit/sec 1 60 3.6 2.119

Lit/min 0.017 1 0.06 0.035m3/hr 0.278 16.67 1 0.59Cu.ft/min 0.47 28.32 1.69 1

THROUGHPUT / LEAK RATEq/qL Torr l/sec mbar l/sec W std.cc/sec std.cc/min

Torr l/sec 1 1.33 0.133 1.32 78.9

mbar l/sec 0.75 1 0.1 0.99 59.2pa m 3/sec (W) 7.5 10 1 9.87 592std.cc/sec 0.76 1.01 0.101 1 60std.cc/min 1.27x10 -2 1.69x10 -2 1.69x10 -2 1.7x10 -2 1

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TECHNICAL SPECIFICATIONS

MODEL SPEED RATED LINE SIZE MAX DIFF. RECOMMENDED

(SWEPT VOLUME @ 1500 RPM) MOTOR HP (MM) PRESSURE BACKING PUMP(PR. RANGE 10-103 TORR) (1500 RPM) (TORR) (LPM)

LPM (m3

/hr)EVB01M 4300(260) 1 / 1.5 65 35 / 70 300- 500EVB05 6700(400) 2 / 3 65 50 / 90 500 - 1000

EVB15 13300 (800) 3 / 5 80 30 / 70 1000- 3000

EVB30 27800(1670) 5 / 7.5 125 30 / 55 3000- 5000

EVB50 48800(2930) 7.5 / 10 125 20 / 40 5000 - 10000

EVB60 65100(3900) 10 / 15 200 30 / 50 Consult Everest

EVB70 87000(5250) 10 / 15 200 20 / 36 Consult Everest

The maximum differential pressures indicated correspond to the motor power and recommended backing pump indicated above is only for reference which may changedue to change in process parameters. For further assistance, please consult Everest.

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