portable air after sales market department basic compressor knowledge

Portable Air After Sales Market Department

Basic compressor knowledge


Effective Absolute pressure

atmosphericpressure

absolutepressure

effectivepressure

total pressure

pressure = 0


Absolute pressure8 bar (118 psi)

Atmospheric pressure 1 bar (15 psi)

Effective pressure7 bar (103 psi)

Effective pressure

• The effective pressure is the difference between absolute pressure and atmospheric pressure

• It is the pressure available to deliver work


Effective pressure

• XRVS 455 Md : receiver pressure during unload is 27 bar (397 psi)

• Forces on the air receiver cover (0.08 m²) is more then 22,000 kgf (about 48k pounds)


Free Air Delivery

• Free Air Delivery :is the measured “real” delivered volume of air (in l/s or m³/min or cfm) at the same conditions of pressure and temperature at the air inlet


Free Air Delivery

• FAD is not equal to the displacement volume of the compressor element, because internal losses in the element (leaks to air inlet)

• FAD is independent from the ambient conditions (temperature & pressure)


Screw Compressor

• Introduced in 1958 by Atlas Copco

• Male and female rotors move towards each other, while the volume between them and the housing decreases.


Screw Compressor

• Screw profile improved in 1966

• Symmetrical screw was changed to an asymmetrical helical profile

• 10% more efficiency


Compression principle

Com

pres

sion

sta

rt

Com

pres

sion

Suc

tion

Del

iver

y


Pressure Ratio

• Each screw element has a fixed, integrated pressure ratio

• This depends on :– length of the rotors– Pitch of the screw– form of the discharge port

• Best efficiency is reached when the pressure ratio is adapted to the required working pressure


Screw Compressor Design Advantages

• High shaft speeds and large flow rate :– gives small exterior dimensions

• Simple and strong design :– no valves and seals reliable and maintenance

friendly– small dirt particles improve the sealing and the

efficiency– almost pulsation free air


Screw Compressor Design Advantages

• Low wear :– guaranteed long life time and constant capacity– life time is determined by the bearing wear

• Absolute oil free design possible

• No inertia forces– vibration free operation– high speeds possible– big power possible


Screw Compressor Design Disadvantages

• Lower efficiency because of internal leaks• High quality bearings on the rotors required

– rotor clearances are small – axial bearings needed

• Noise level (high frequency)• High quality finishing of the rotors required

– expansion of rotors through heat results in blocked elements


Oil injected screw compressors



• Oil is used for :– Cooling : compression heat is absorbed by the oil– Lubrication of rotors, bearings, gears– Sealing between rotors and rotor and housing– Corrosion protection of the internal metal parts



Oil is injected in the bottom of the rotor housing, onto thebearings and gears, and discharged with the compressed air



• Only one rotor is driven, this rotor then drives the other one :– old XAS 90 : female driven rotor– all other compressors : male driven rotor

• When required a gear box or drive belt brings the compressor element to the correct speed


Compressor running condition

• Four major running conditions :– NO-LOAD

Machine started, minimal pressure build-up– LOAD

Receiver tank pressurized and air consumption– UNLOAD

Receiver tank pressurized, no air consumption– BLOW-DOWN

Machine stopped, blow-off of air pressure


• Air filter Compressor Element (AFCE) (with

vacuator valve VV, Safety Cartridge SC and vacuum indicator VI)

• Unloading Valve (UV)

• Compressor Element (CE)

• Temperature Switch (TS)

• Check Valve (CV)

• Air Receiver (AR)

• Non Return Valve• Minimum Pressure Valve (MPV)

• Air Outlet Valve (AOV)

Air system


Air filter

• Filtration of the inlet air in 3 stages :– centrifugal dust separation– paper filter element– safety cartridge (optional)

• Vacuum indicator gives an indication when the pressure drop over the filter element is too high filter element needs to be replaced


Air filter

Air inlet Centrifugal separation

Dust

Filter element

to compressor element

Vacuum indicator


Unloading valve

• Opens and closes the air inlet to the compressor element.– Open position at load condition

=> Air consumption– Closed position at no load condition

=> No air consumption.

• Control of the valve by regulating pressure.


Unloading valve

Valve

Spring loaded

Regulating pressure Air inlet

Integrated blow-down valve

Vent Hole


Unloading valveLOAD UNLOAD

Reg

ulat

ing

pres

sure

Air inlet


Check valve

• Check valve is integrated in the unloader for Series 6 compressors (XAS 185, 375, 400)

• Closes when the compressor is stopped.

• The air receiver is pressurized, which would result in a reverse air flow. the check valve prevents this.


Check valveLOAD BLOW-DOWN

Receiver pressure return after shut-down

Check valve


Air receiver / Separator

Air/Oil

Centrifugal separation

Separator element

Air outlet


Minimum pressure valve / nozzle

• Guarantees a minimum pressure in the oil separator (approx. 45-60 psi)

• Minimum pressure is required to guarantee an continuous oil supply to the element.


Nozzle / Minimum pressure valveMINIMUM PRESSURE VALVE

NOZZLE


Oil system

• Air receiver

• Oil cooler

• Oil filter

• Oil stop valve (where used)

• Compressor element

• Oil separator

• Scavenge line


Oil system (without TBV)


Oil System (with TBV)


Air receiver

Oil flow

Pressure


Oil coolerCool Oil

Warm Oil

Cooling air


Oil filter

Dirty Oil Filtered Oil

By-pass valve


Compressor element

Oil

Oil

Air/Oil

Greasing to the bearings

Air inlet


Oil separator

Air/Oil

Centrifugal separation

Separator element

Oil

Scavenge line


Regulating system

• Regulating valve

• Unloading valve

• Speed regulator

• Blow-down valve

• Safety valve


Regulating system (XAS 185)Regulating Valve

Unloading Valve

Speed Regulator

Safety Valve


Regulating valve

• Regulates the effective pressure in the air receiver

• Provides regulating pressure to :– unloading valve

=> regulates the air inlet according the air requirements

– speed regulator=> regulates the engine speed to reduce fuel consumption


Regulating valve

Spring loaded

Adjusting receiver pressureby changing spring tension

Pressure gauge

to speed regulatorto unloading valve

Regulating pressure

Receiver pressure

to blow-down valve


Regulating valveLOAD UNLOAD


Speed regulator

• Regulates the engine speed in relation to the required air flow

• Load condition : maximum engine speed

• Unload condition : minimum engine speed


Speed regulator

Spring loaded

Regulating pressure Vent Hole

Engine speed

- Min

- Max


Speed regulatorLOAD UNLOAD


Blow-down valve

• Blows off the air receiver pressure once the compressor has shut-down=> this to depressurize the receiver tank

• Integrated in the unloading valve


Blow-down valve

blow

-dow

n va

lve

Receiver pressure

blow-off hole

Air inlet


Blow-down valveLOAD / UNLOAD BLOW-DOWN

Receiver pressure

Receiver pressure return after shut-down

Blow-off receiver pressure


Safety valve

• Blows off the air receiver pressure once this pressure raises above the design pressure.


Electrical system

• Battery voltage : 12 or 24 V

• Starting system– cuts-out starter motor when engine is running– avoids cranking when receiver tank is pressurized

• Safety shut-downs

• Instrument indications


Safety shut-downs

• Compressor :– Compressor element outlet temperature

• Engine :– Coolant temperature– Coolant level– Oil pressure– Fuel level

• Emergency stop


Air treatment options

• Aftercooler

• Water separator

• Fine filters PD / QD

• Re-heater


Air treatment options


Aftercooler - Water separator

• The aftercooler is a heat exchanger, which cools the hot compressed air to precipitate the water that otherwise would condensate in the air hose.

• The outlet temperature is ambient + 7°C.• It is followed by a water separator that separate

the condensate and drains it• Used for : sandblasting, fibre optic cable steering,

pipe cleaning


Aftercooler - Water separator

Water separator

Aftercooler


Fine filters PD / QD

• PD filter will separate oil and solid particles.

• QD filter or carbon filter will separate oil and water vapour.

• Discharge air is instrument quality--nearly “oil free”.

• Only 0.003 ppm oil present in the air outlet


Fine filters PD / QD

PD filter

QD filter


Re-heater

• The re-heater is a heat exchanger, which warms up the compressor outlet air to ambient + 60°C.

• The water and oil will be vaporized resulting in hot and dry air, this avoids condensate problems.

• XAS 46-96 : engine oil warms up the compressed air.

• XAS 146-186 : compressor oil warms up the compressed air


Product nominationoil injected compressors

X A M S 750 C d

Product rangeX : Oil injected portable compressor

Working principleA : Single stage compressorR : Two stage compressor

Working pressure Single stage Two stage

: standard pressure 7 bar/100psi 17 bar/250psiM : medium pressure 8.6 bar/125psi -T : “ten” pressure 10.3 bar/150psi -H : high pressure 12 bar/175psi 20 bar/295psiV : very high pressure 14 bar/200psi 25 bar/365psi

Silencing : Un-silencedS : Silenced

Capacity (FAD)Liter/secCFM (US-version)

Engine supplierC : CaterpillarD : DeutzG : Detroit DieselJ : John DeereK : KubotaY : Yanmar

Prime moverd : diesel engineE : electric motor


60

Contact Numbers•Main Number Atlas Copco Technical Support 800-732-6762 Option 3

•Ed Kukfisz – Compressors – Supervisor 281-542-2562 direct & 832-385-4697 mobile

•Andrew Stevenson – Compressors: Low Pressure720-479-2486 direct & 404-751-6717 mobile

•Andrew Calendar – Compressors: High Pressure720-479-2487 direct & 404-242-6203 mobile

•Scott Ellinger – Compressors720-479-2476 direct & 720-375-1795 mobile

•Robert Walsh – Generators – Supervisor 803-487-0256 direct (mobile)

•Will Hudson – Generators/Compressors 800-732-6762 Ext. 12920 & 832-454-8123 mobile

•Brandon Hobbs – Hydraulic Attachments /Handheld Construction Tools – Supervisor 303-287-8822 direct & 913-424-4039 mobile

•Al Eckenfels – Hydraulic Attachments/Handheld Construction Tools800-760-4049


Committed tosustainable productivity.

portable air after sales market department basic compressor knowledge

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