jj618 notes compressed air plant

7/23/2019 JJ618 Notes Compressed Air Plant

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JJ618 PLANT ENGINEERING TECHNOLOGY

COMPRESSED AIR PLANT


1.0 COMPRESSED AIR PLANT SYSTEM

1.1 The function of compresse !ir p"!nt

Compressed air plant used widely in many industries. It is can be assume as a heart of industry.Some of the usage of compressed air plate is:

1. Handling reciprocating tools such as rivet gun, hammer and others2. Handling rotating tools such as air motor, grinder, drill, reamer, air pump and others. !se as spraying mechanism" paint, oil, pesticide, and others#. Handling air piston to energi$e tools such as pressing, lifting and clamping.%. &ir spray for cleaning purpose.'. (neumatic system

1.# T$pic!" compresse !ir p"!nt "!$out.

)irst of all, air will suc* to the system by an air compressor. +ut, before it, a filter is attach incompressor inlet to avoid dust and bad particle from enter the system. !sually, compressed airplant have two compressor. +etween both compressor, an intercooler was installed to increasesystem efficiency. &fter second compressor, an aftercooler was attach to clarify between true airand vapor. he fluid then enter water separator. &s it-s name, water separator remove water fromthe system. he dryer then use to purify the air. & clean air then store on receiver tan*. )romreceiver tan*, a clean air will supply to end user. +ut, once again the air must through the dryer.

&fter that, it must through pass an oil separator oil removal/. his is important to to removelubricant that use to lubricate compressor. 0astly, the clean air supply to local end user throughpressure regulator and gauge.

%i&ure' T$pic!" !ir compressor p"!nt

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN, DUNGUN

PERKASA DENGAN TEKNOLOGI DAN IMAN


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1.( Compresse Air P"!nt E)uipment !n Component

1.3.1 Air Filter

& particulate air filter is a device composed of fibrous materials which removes solid particulatessuch as dust,pollen,mold,moisture, andbacteriafrom the air.

1.3.2 Driver

!sually, the compressor in compressed air plant drives by either electric motor or internalcombustion engine.

Picture: Typical motor electric driver

1.3.3 Compressor

Compresses air to a small volume, increasing the air pressure.

1.3.4 Air Inter Coolers

In a multistage unit compressor, the air is compressed in succeeding cylinders, getting hotter andhotter along the way. &n intercooler will be installed between the cylinders to help cool the airbefore it is ingested into the net cylinder for further compression. his aids in the compressor-sefficiency. Intercoolers in multistage units may function through air cooling or water cooling.

In air cooling the compressed air will pass through a chamber, on the outside of which, issubstantially increased surface area sometimes called fins eposed to the ambientenvironment. he increased surface area will allow the heat inside the compressed air line tomove more readily to the surface and to escape into an area of lower temperature.


http://en.wikipedia.org/wiki/Particulatehttp://en.wikipedia.org/wiki/Particulatehttp://en.wikipedia.org/wiki/Dusthttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Bacteriumhttp://en.wikipedia.org/wiki/Bacteriumhttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Dusthttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Moldhttp://en.wikipedia.org/wiki/Bacteriumhttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Particulate


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Figure: To stage compressor it! intercooler

1.3." A#tercoolers

Compressed air discharged from an air compressor is hot refer figure below/. Compressed air atthese temperatures contains large 3uantities of water in vapor form. &s the compressed air coolsthis water vapor condenses into a li3uid form. &s an eample if an aftercooler is not used, a 244scfm compressor operating at 144 psig introduces #% gallons of water into the compressed airsystem each day.

Figure: A#tercooler system

1.3.$ %ater &eparator

5uring the process of compressing air, atmospheric air along with water vapor and atmosphericcontaminants hydrocarbon or chemical vapors/, are drawn into the compressor inta*e.

&dditionally, the compression chambers of most compressors re3uire oil for lubrication, sealingand cooling. 6nce compressed, the air flows into an aftercooler to remove the heat ofcompression. &s the air cools in the aftercooler, water and hydrocarbon vapors will condense.

&dditional condensation ta*es place as the air is further cooled in the piping and air dryers. hiscondensed moisture must be removed from the compressed air system to prevent damage to




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downstream components and processes. 5rain valves are installed on moisture separators,coalescing filters, air receivers, air dryers and drip legs to remove this condensate from thecompressed air system. he condensate should be piped from automatic drain valves to oil7waterseparators to remove the oil from the condensate prior to discharge to a drain.

+y referring figure below/ Compressed air enters at point 8&9 air in/ and first is made to rotatewithin an outer chamber at high speed removing moisture, small particulate and oil. he removedmaterial is drained into the bottom bowl via holes 8+9 at the bottom of the outer chamber to collectand be removed from the system utili$ing the automatic drain 8C9. he compressed air in theouter chamber is then directed into an inner chamber 859 for a second rotation and a lower speedpreventing any bac* suction of particulate, oil or moisture. he .; dry, clean compressed airis then directed out and bac* into the system at point 8


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his raises the dew point of the compressed air relative to free atmospheric air and leads tocondensation within pipes as the compressed air cools downstream of the compressor.


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Picture: Air receiver tan*

1.3.+ Pressure regulator

(ressure regulator use to controls air pressure and flow at individual points of use. )urthermore,the regulator will attempt to maintain and control the outlet pressure within limits as otherconditions vary but the regulator will not control f low, only the delivery pressure. & regulator is alsonot to be used as a shutoff device as there is always a small amount of lea*age across the seat.

& shutoff valve must be used downstream of the regulator if isolation is re3uired

1.3.1, Pressure gauge!sually the pressure gauge was attached to pressure regulator.he pressure gauge help the

user to *now the pressure that through out the pressure regulator.

Figure: Pressure regulator and pressure gauge unit




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1.3.11 Distri-ution Piping

0in*s the components. It distributes the air from a main header to branch lines and sub headersto drop points connected to individual tools.

1.3.12 u-ricant

>ost factories and manufacturing facilities use compressed air systems for a variety ofapplications, and *eeping these air compressors running is critical to *eeping the entire operationrunning. ?early all air compressors re3uire a form of lubricant to cool, seal or lubricate internalcomponents. (roper lubrication will ensure that your e3uipment will continue operating, and theplant will avoid costly downtime and repairs.

(roper lubrication also will help air compressors run cooler and consume less electrical energy. Itis simple: reduced friction @ reduced heat @ reduced energy consumption. Compressed airsystems in most manufacturing plants consume a maAority of the daily power re3uirements, so ifyou are loo*ing for a continuous improvement proAect, reducing energy costs through betterlubricant practices is a sure winner.

1., A+!nt!&es of compresse !ir p"!nt !s -orin& !&ent

1. &ir can-t eplode. herefore, an epensive eplosive prevention e3uipment is not re3uire2. &ir system can be control at high velocity, up to 14m7s. 5elivery system of air is simple and can be deliver at long distance#. &ir is clean%. =ecycle system is not re3uired'. he system is fleibleB. &ir pressure and velocity can be adAust easily without considering the system capacity. &ir compressed system relatively cheap.

#.0 COMPRESSOR TYPE

Compressors are broadly classified as: (ositive displacement compressor and 5ynamicCompressor.

(ositive displacement compressors increase the pressure of the gas by reducing the volume.(ositive displacement compressors are further classified as reciprocating and rotaryCompressors.

5ynamic compressors increase the air velocity, which is then converted to increased pressureat the outlet. 5ynamic compressors are basically centrifugal compressors and are furtherclassified as radial and aial flow types.

he flow and pressure re3uirements of a given application determine the suitability of aparticularstype of compressor.




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Figure: Compressor #amily

#.1 Positi+e Disp"!cement Compressors

2.1.1 /eciprocating Compressors

=eciprocating compressors are the most widely used type for air compression. hey arecharacteri$ed by a flow output that remains nearly constant over a range of discharge pressures.

&lso, the compressor capacity is directly proportional to the speed. he output, however, is apulsating one.

=eciprocating compressors are available in many configurations, the four most widely used ofwhich are hori$ontal, vertical, hori$ontal balanceopposed and tandem.

Dertical type reciprocating compressors are used in the capacity range of %4 E 1%4 cfm.Hori$ontal balance opposed compressors are used in the capacity range of 244 E %444 cfm in

multistage design and upto 14,444 cfm in single stage designs.

=eciprocating compressors are also available in variety of types:F 0ubricated and nonlubricatedF Single or multiple cylinderF Gater or aircooled.F Single or multi stage

In the case of lubricated machines, oil has to be separated from the discharge air. ?onlubricatedcompressors are especially useful for providing air for instrumentation and for processeswhich re3uire oil free discharge. However nonlubricated machines have higher specific powerconsumption *G7cfm/ as compared to lubricated types.

Single cylinder machines are generally aircooled, while multicylinder machines are generallywater cooled, although multistage aircooled types are available for machines up to 144*G. Gatercooled systems are more energy efficient than aircooled systems.

wo stage machines are used for high pressures and are characteri$ed by lower dischargetemperature 1#4 to 1'4C/ compared to singlestage machines 24% to 2#4C/. In some cases,multistage machines may have a lower specific power consumption compared to single stagemachines operating over the same total pressure differential. >ultistage machines generallyhave higher investment costs, particularly for applications with high discharge pressure above Bbar/ and low capacities less than 2% cfm/. >ulti staging has other benefits, such as reduced




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pressure differential across cylinders, which reduces the load and stress on compressorcomponents such as valves and piston rings.

he main advantages of the reciprocating compressor are that it can achieve high pressure ratiosbut at comparatively low mass flow rates/ and is relatively cheap.

It is a piston and cylinder device with automatic/ spring controlled inlet and ehaust valves.5elivery is usually to a receiver. he receiver is effectively a store of energy used to drive eg/compressed air tools.

=eciprocating compressors usually compress air but are also used in refrigeration where theycompress a superheated vapour to which the gas laws strictly do not apply/.

In order to be practical there is a clearance between the piston crown and the top of the cylinder.&ir -trapped- in this clearance volume is never delivered, it epands as the piston moves bac* andlimits the volume of fresh air which can be induced to a value less than the swept volume.

Figure: /eciprocating compressor system

2.1.2 /otary Compressors

=otary compressors have rotors in place of pistons and give a continuous, pulsation freedischarge air. hey are directly coupled to the prime mover and re3uire lower starting tor3ue ascompared to reciprocating machine. hey operate at high speed and generally provide higherthroughput than reciprocating compressors.

&lso they re3uire smaller foundations, vibrate less, and have a lower number of parts whichmeans less failure rate. &mong rotary compressor, the =oots blower also called as lobecompressor/ and screw compressors are among the most widely used. he roots blower isessentially a lowpressure blower and is limited to a discharge pressure of 1 bar in singlestagedesign and up to 2.2 bar in two stage design.




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he most common rotary air compressor is the single stage helical or spiral lube oil flooded screwair compressor. hese compressors consist of two rotors, within a casing where the rotorscompress the air internally. here are no valves. hese units are basically oil cooled with aircooled or water cooled oil coolers/ where the oil seals the internal clearances. Since the coolingta*es place right inside the compressor, the wor*ing parts never eperience etreme operatingtemperatures.

he oil has to be separated from discharge air. +ecause of the simple design and few wearingparts, rotary screw air compressors are easy to maintain, to operate and install. he oil free rotaryscrew air compressor uses specially designed air ends to compress air without oil in thecompression chamber producing true oil free air.

hese compressors are available as aircooled or water cooled types and provide the samefleibility as oil flooded rotary compressors. here is a wide range of availability in configurationand in pressure and capacity. 5ry types deliver oilfree air and are available in si$es up to 24,444cfm and pressure upto 1% bar. 0ubricated types are available in si$es ranging from 144 to 1444cfm, with discharge pressure up to 14 bar.

Figure: /oot -loer compressor

Figure: /oot -loer compressor operating system




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#.# D$n!mic Compressors

5ynamic compressors are mainly centrifugal compressors and operate on similar principlesto centrifugal pump. hese compressors have appreciably different characteristics as comparedto reciprocating machines. & small change in compression ratio produces a mar*ed change incompressor output and efficiency.

Centrifugal machines are better suited for applications re3uiring very high capacities, typicallyabove 12,444 cfm. he centrifugal air compressor depends on transfer of energy from a rotatingimpeller to the air. he rotor accomplishes this by changing the momentum and pressure of theair. his momentum is converted to useful pressure by slowing the air down in a stationarydiffuser.

he centrifugal air compressor is an oil free compressor by design. he oillubricated runninggear is separated from the air by shaft seals and atmospheric vents. he centrifugal is acontinuous duty compressor, with few moving parts, and is particularly suited to high volumeapplications, especially where oil free air is re3uired.

& singlestage centrifugal machine can provide the same capacity as a multistage reciprocatingcompressor. >achines with either aial or radial flow impellers are available.

&ial flow compressors are suitable for higher compression ratios and are generally moreefficient than radial compressors. &ial compressors typically are multistage machines, whileradial machines are usually singlestage designs.

Figure: A0ial compressor




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Figure: /adial compressor

Capacity o# a CompressorCapacity of a compressor is the full rated volume of flow of gas compressed and delivered atconditions of total temperature, total pressure, and composition prevailing at the compressorin"et. It sometimes means actual flow rate, rather than rated volume of flow. his also termedas %ree Air De"i+er$ /%AD i.e. air at atmospheric conditions at any specific location. +ecausethe altitude, barometer, and temperature may vary at different localities and at different times,it follows that this term does not mean air under identical or standard conditions.



jj618 notes compressed air plant

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