a crash course on vacuum

7/30/2019 A crash course on vacuum

1/38

Vacuum

HowItRelatestoRefrigeration

AndA

irCondition

ingService


2/38

Moisture

InARefrig

erationSy

stem

VisibleMo

isture

WaterDroplets

Uncommon,butitcanoccur

InvisibleM

oisture

WaterVa

por

Foundin

allgasses

Foundin

allsolids


3/38

VisibleMoistureProble

ms

FreezeUp

s

Icecrysta

lformationatthepointof

expansion

CapTube

blocked

TXV

FlowRator

Theproblemswillbeintermittent

Whenthe

systemwarm

suptheproblem

stops


4/38

In

visibleM

oisture

Airinthepiping

WetRefrigerant

LeaksUnderaVacuumCondition

Copperan

dBrassComponents

SystemComponentsexposedto

atmosphereduringas

sembly


5/38

In

visibleM

oisture

CausesCorrosion

Moisture

ReactsWithT

heMetals

Metal

H2O

co

rrosion


6/38

Moisture&R

efrigerant

Moisture

Refriger

ant

ACID


7/38

Moisture&R

efrigerant

CFC&HC

FC&HFC

HydrolyzetoformHydrochloricAcid

Hydrofluo

ricAcid

AcidForm

ationIsAcc

eleratedBy

Heat

Copperan

dBrassWillBeAttacke

d

PlatesHo

tSurfaces

Bearings

Seize


8/38

CopperP

lating


9/38

Moisture&Refrigerant&

Oil

Metal

R

efrigerant

Acid

O

il

Sludge


10/38

HowDoYouGetT

heWaterOut?

WeBoilIt

WeCantRaiseTheS

ystem

TemperatureTo212

WeLower

theSystem

PressureT

oA

PointThatWaterBoilsAtAmbient

Temperatures


11/38

PressureVS.B

oilingPoint

Physics101

AsPressureDecreased-TheBoilingPoint

Decrease

s

ToDecrea

seThePressureWeCan

RaiseThe

SystemTo

AHigherAltitude

ThereIsLessAtmosph

ereAboveUsOn

Mt.Evans

LessWeightOfAir=LowerAirPres

sure


12/38

PressureVS.B

oilingPoint

SeaLevel

Pressure

=14.7PSI.

BoilingPoint=212F.

PikesPea

k(14000+

Elevation)

Pressure

=8.32PSI.

BoilingPoint=184F.

StillNotLowEnough


13/38

PressureVS.B

oilingPoint

ToBoilWater@

80F.

ThePressureHasTobeLoweredTo

28.92Inc

hesOfMercu

ry

ToBoilWater@

45F

ThePressureHasToBeLoweredT

o

29.62Inc

hesOfMercu

ryVacuum

or7620M

icrons


14/38

WhatT

heHeck

IsAMic

ron?

1Inch=25400Micron

s

.039Inch=1000Microns=1Millimeter

1Micron=

1/1,000,00

0meter

ToSmallToMeasure

WithAGau

ge.


15/38

HowIs

Vacuum

Measured?

25400m

icronsbetweeneach

mark


16/38

HowIs

Vacuum

Measured?

CompoundGauge

Impossible

VacuumG

auge

Resolutio

nIsNotSuita

ble

ReadingChangeswith

Altitude(pressure)

UTubeManometer

Resolutio

nTo1MMofMercury(100

0

Microns)


17/38

HowIs

Vacuum

Measured?

ThermistorMicronGa

uge

MeasuresTheLastInc

hOfVacuum

RegardlessofAtmosphericPressure

HighRes

olution

Readings

To1Micron


18/38

HowIs

Vacuum

Measured?


19/38

Therm

istorMicronGau

ge

Measures

TheThermalConductiv

ityOf

TheGasR

emainingin

theRefrige

ration

System

HasASourceOfHeat

HasAHeatReceptor

TheThermistor


20/38

Therm

istorMicronGau

ge

HeatSource

Thermistor

HosetoSystem

Themoregasleft----ThehighertheTemperatureonThermist

or


21/38

ThermistorMicronGauge

ThermistorMicronGauge

HeatSource

Thermisto

r

HosetoSystem

LessGas

..LessHeatReceived

.LowerReading


22/38

V

acuumPumps

AirCompr

essorType

MovesLa

rgeVolumeO

fAir

AtLowPressures(Can

tAchieveDe

ep

Vacuum)

AtBest28ofMercury

Nowate

rBoiled


23/38

V

acuumPumps

PistonCompressorTy

pe

AtBest29(atSeaLevel)

ThatWon

tBoilWaterUnder80F

RotaryCo

mpressorType

29.63(atSeaLevel)

WaterBo

ils@

45F

UnsuitableForSystem

sLargerThan

HouseholdRefrigerators


24/38

HighVacuumR

otaryVane

Pumps

SingleSta

ge

Smaller

LightWeight

1000Microns

Robinairdownto200M

icrons


25/38

SingleS

tage


26/38

HighVacuumR

otaryVane

Pumps

TwoStageVacuumP

umps

MostCom

monForService

LargerCFMCapacity

SlightlyH

eavierThanSingleStageOf

SameCa

pacity

CanAchieveDeeperV

acuumThan

Single

StageBe

causeSecondStageTakesOver

AtTheLe

vel1stStage

Stops


27/38

HighVacuumR

otaryVane

Pumps

TwoStage(cont..)

CanPullToOneMicro

n

RobinairGuaranty20Microns


28/38

TwoStageVac

uumPumps


29/38

TwoStageVac

uumPumps

1ststage

2ndS

tage

ISOValve


30/38

Rotor&Vanes

OffSetConstruction

VanesCome

OutAt

LowRPMTo

wipe

TheInteriorO

f

Pump

1stStageAre

CeramicVanes

2ndStageAre

Aluminum


31/38

G

asBallastValve

MixesDryAir

With

HighHumidityAir

ReducesMoisture

ThatIsCondensed

IntoTheOil

MakesOilLast

Longer


32/38

G

asBallastValve

OpenValveA

t

Beginning

Evacuation

WhenAlevel

Of

1000Microns

Is

Achieved,Clo

se

Valve


33/38

Spe

edOfEvacuation

SizeOfSystem

Complexity

Of

Piping

System

Components

OilSeparators

Accumulato

rs

Valves

Ambient

Temperature

SizeOfPump

HowYouare

HookedUpTothe

System

High&LowS

ide

SizeOfHoses

AccessFitting

?


34/38

Spe

edOfEvacuation

UseLarge

stHosesYouCan

AddHeatToAreasOfRestriction

GettheAccessFitting

sOutOfWay

MeasureV

acuumAtT

heSystem

IsolateTheSystemAndEqualize

To

GetATrueReading


35/38

AccessCoreR

emovalTool


36/38

HowMuch

Pump?

VacuumP

umpsAreR

atedInCub

ic

FeetPerM

inuteOfFr

eeAirThrou

gh

thePump

AsARule

Ofthumb

1CFMPer7TonsOfS

ystem

I.E.A6CFMRatedPumpWillBe

Good

For42TonsOfSystemCapacity

MultiplePumpsOK


37/38

Make

YourPu

mpLast

25

Years

KeepYourPumpWar

m

ColdStar

tsAreHardO

nThePump

DontStartOrStopPu

mpInAVa

cuum

VanePocket

Fill

WithOilIfThe

PumpIsSh

utDown

InAVacuum


38/38

MakeY

ourPump

Last25Years

MakeY

ourPump

Last25Ye

ars

AlwaysExposePumpTo

AtmosphereOnShutDown

AlwaysExposePumpTo

AtmosphereOn

ShutDown

Chan

geTheO

ilEvery

Time

Chan

geTheO

ilEveryTime

a crash course on vacuum

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