2 Compressed Air Systems

8/7/2019 2 Compressed Air Systems

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A Compressed Air System


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A Compressed Air System


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T ypical Goals For An Air System

A reliable source of compressed air. In many situations, no air means no production

An economical cost to produce and distributecompressed air to the point of use. Money is always limited.The ability to monitor and distribute the cost of compressed air to the users. There is no such thing as free air .


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Compressed Air System Operating Costs

Cost of energy to operate the driverDepreciation (cost to purchase)Cost of moneySpace cost Installation cost Routine maintenance cost

Repair cost Overhaul cost Supervisory cost


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Real World SystemReal World System - - Ideal System LayoutIdeal System LayoutReal World SystemReal World System - - Ideal System LayoutIdeal System Layout

PrePre--filter filter

1000 CFM1000 CFMCompressor Compressor

Air Cooled Air Cooled

1000 to 40001000 to 4000gallongallon

receiver receiver

Refrigerated air Refrigerated air dryer with a 40dryer with a 40 00F dew pointF dew point

oil coalescingoil coalescingfilter filter

W etW etReceiver Receiver

Compressor Compressor

After After--Cooler Cooler Dryer Dryer


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Layout of ComponentsLayout of Components



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Air Compressor Air Compressor

PurposeProvide power for pneumatic equipment

Benefit SafeClean

Lighter weight equipment


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T ypes Of Air Compressor

Divided by energy source Electric motor

Engine Turbine


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Divided Compression Technology Reciprocating Piston

Rotary Screw Centrifugal Other

sliding vanehook and clawaxial flow


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Divided by Air Quality Lubricated

Oil-Free/Oil-less/Non-Lubricated

Downstream clean-up equipment can be used toimprove Air Quality


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Aftercooler Aftercooler


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PurposeReduce discharge air temperature

Typical reduction: ambient plus 15-25 0 FBenefit

Typically removes 60% of moisture content of airInsures air piping temperature is not a safetyhazard

Aftercooler ( Recommended) Aftercooler ( Recommended)


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W etReceiver Receiver




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Wet Receiver (Optional)Wet Receiver (Optional)

PurposeInsure reservoir of air is available to system

Prevent compressor from cycling too frequently

Benefit Acts as heat sink to reduce air temperatureImproves compressor life


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Receivers And Capacity Control

Rarely does a compressed air system require100% of the output of the compressor, thus

the capacity control system.Capacity control matches the output of thecompressor to the demand on the system


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Receivers And Capacity Control

Types of capacity control or unloading Auto start/stop

Constant speed control On-line/off-line control Modulation control

Throttling control Bypass control Variable Speed


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Pre-Filter ( Required)Pre-Filter ( Required)

PurposeRemove dirt rust scaleRemove liquid water

Benefit Keep air passages in dryer clean


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Dryer Dryer


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Dryers ( Recommended)Dryers ( Recommended)

PurposeReduce compressed air moisture content

Benefit Including aftercooler, airline moisturecontent is reduced by over 90%Reduced maintenance for pneumaticequipment Improved product quality


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Dryers ( Recommended)

Different types or technologies of dryers Refrigerated - lowers the temperature of

compressed air to cause moisture to condense,and then be removed Desiccant - adsorb the moisture in the air Desiccant dryers produce dryer air, but cost

more to buy and operate.


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Dryer IssuesDryer Issues

0

20

40

60

80

100

120

140

160

180

M oisture Content of Compressed Air M oisture Content of Compressed Air Gal. W ater/24 Hr./1000 SCF MGal. W ater/24 Hr./1000 SCF M

w /o aftercooler w ith

aftercooler undersizedrefrigerated

dryer

correctly sizedrefrigerated

dryer


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Dryers - Moisture ContentDryers - Moisture Content

6 0F6 0F

100% RH100% RH 100% RH100% RH 100% RH100% RH

80F80F100F100FAftercooler

Air Air Compressor Compressor

Effect of Compressed Air Temperature on sizing of dryingequipment.

A 20 F reduction in temperaturecondenses one half the w ater vapor in saturated air.

A 20 F. rise in temperature doublesthe moisture holding capacity of theair.

Rule of Thumb


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Dryers - Moisture ContentDryers - Moisture Content

6 0F6 0F

100% RH100% RH 100% RH100% RH 100% RH100% RH

80F80F100F100FAftercooler

Air Air Compressor Compressor

Rule of Thumb

Example: Refrigerated Dryer

Compressor Discharge Dryer Size

1,000 SCFM @ 100 F 1,000 SCFM

1,000 SCFM @ 120 F 2,000 SCFM


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Dryer Dryer

After After--filter filter


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After Filter (Recommended) After Filter (Recommended)

PurposeReduce oil carryover

Benefit Improved air qualityImproved product quality Instrument air applications Painting


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After After--Cooler Cooler

Dryer Dryer

After After--filter filter

DryReceiver Receiver


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Dry Receiver ( Recommended)Dry Receiver ( Recommended)

PurposeProvide a reservoir of clean dry airto meet fluctuating system demands

Benefit When sized and installed correctlycan minimize airline pressurefluctuationsPrevents short term capacityrequirements from overloadingcleanup equipment


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B asicSelection CriteriaB asicSelection Criteria

Real World SystemsReal World Systems


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Design Criteria Air Quality

Moisture Oil Contaminant

Pressure DropDemand Characteristics


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Moisture Content Pressure Dewpoint - Temperature at which water vapor condenses intoliquid in a compressed airline

Select a dewpoint 10-20 0 F below thelowest temperature the compressedairlines will see


Rule of thumb: Rule of thumb:


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This appl i es only to generalindustrial application . S p ecific applications hav e sp ecific

d ew point r eq uir eme nts (i .e.,paint booths, instrum ents, e tc .)

WARNINGWARNING: :

Contact equipment OEMsContact equipment OEMs


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Oil Content TerminologyOil carryover - the amount of

compressor lubricant or coolant passed down stream of thecompressor

PPM - parts per million (by weight).Industry standard for determiningoil carryover


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Typical Compressor Carryover Values:Typical Compressor Carryover Values:

Reciprocating CompressorsReciprocating CompressorsLubricatedLubricated 50-100 PPM50-100 PPM

Non - Lubricated Non - Lubricated 0 PPM0 PPM

Rotary CompressorsRotary Compressors

Oil Flooded 3-10 PPM3-10 PPMOil FreeOil Free 0 PPM0 PPM

Centrifugal CompressorsCentrifugal Compressors 0 PPM0 PPM


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Oil Content RequirementsWhether the oil is removed at the compressor or at the point of use, should be determined byoverall plant requirements


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WARNINGWARNING: :


A lthough som e eq uipm ent may be n efit from (or ev en r eq uir e)lu bricant in compr ess ed air, many oth er applications (paint

booths, instrum entation) cannot tol erat e it Aga in over all system requirementsAga in over all system requirementsshou ld d ict a te system des i g n s hou ld d ict a t e sys t em des i g n


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Contaminant Content Dependent on ambient conditions, acompressor can ingest substantialamounts of dirt, dust, etc...

A centralized filter will remove thesecontaminants


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Pressure DropPressure Drop is the cost of air quality

Every air clean up device will utilize 2-10 PSI toperform its function Air dryers typically 3-5 PSI Air filters typically 2-10 PSI (dependent on how long

the element has been in place)

Remember @ 1/2% energy for each PSI, additionalfilters may become needlessly expensive


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Demand CharacteristicsReceiver size and placement varies

depending on plant demand cycle andreceiver sizePossible to supply a new intermittent large air user with a properly sizedand installed receiver tank


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Demand CharacteristicsThe same air user without a tank might require an additional air compressorOld Rule Of Thumb, one gallon of systemcapacity for each CFM of compressorcapacity provides minimum reserve volume

New Rule Of Thumb, size receiver to handlethe largest event the system willencounter.


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How Are We Doing?

Questions?Comments?

Understanding of Air and the CompressionProcess?Compressed Air System Understanding?

What is in a system, and why?Ready to move on?

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2 Compressed Air Systems