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ServiceService

DRY ICE BLASTINGGeneralities, methods,

instrumentsand on site experiences

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Keeping the Electrical Motors cleaned during the whole life cycle is a key priority because itpermits to:

reduce risk of failure

maintain performances

increase reliability

Mechanicaldiagnostics(detecting vibrationsand temperatures)

Electrical & mechanicaldiagnostics (detectingalso electricalparameters: partialdischarges, insulationres., P.I….)

Electrical &mechanicaldiagnostics + partialdisassembling toinspect maincomponents

Electrical &mechanicaldiagnostics +GeneralOverhauling

4.000 hrs 8.000 hrs 20.000 hrs 40.000 hrs

Periodic Maintenance Program

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Risk for motors in critical environments

dust & dirt

sand

grease & oil

efficiency

temperature

Ris

ko

ffa

ilu

res

Risk factor Ambient conditions

Each ambient condition is related to a risk factor

Co

nta

min

an

ts

aging rate

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Dry Ice Blasting PrinciplesDry Ice Blasting Principles

Impact

Upon impact – generated by the speed and massof the CryoPellets – kinetic energy is transformedinto an abrasive cleaning force.

Explosive sublimation

The dry ice pellets temperature is around -79º C;Fast transfer of heat from the pellets to the warmsurface to be cleaned causes instant sublimationto gas phase; Volume increase (500 times) ⇒contaminants blasting.

Thermoshock

Sudden local cooling + differences in shrinkagerate ⇒ tension between contamination & substrate⇒ contamination breaks free from surface.

Glass transition point

Once the temperature drops below the glasstransition point, the material becomes brittle.

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Dry Ice Blasting ProcessDry Ice Blasting Process

Dry Ice Pellets are made by taking liquid carbon dioxide(CO2) from a pressurized storage tank and expanding itat ambient pressure to produce snow. The snow is thencompressed through a die to make hard pellets.

Impact + Explosive sublimation + Thermoshock + Glass transition point

= CLEAN SURFACE

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Dry Ice Blasting Tools and InstrumentsDry Ice Blasting Tools and Instruments

Pellet Storage

Ready to use

Pellets Storage Container

Outer dimensions (lxwxh): 996 x 926 x 810 mm

Capacity: 262 litres (approx. 206 kg pellets)

Dry Ice Blaster

Blasting Hose

Guns & Noozles

Compressed air

OEM’s

indications

Mobile Air Compressor

7380 lt / min

10 bar

Air Preparation Machine

Includes: water separator, pre-filter, freeze

drieer, oilfilter and a thermostatic controlled

aftercooler

AIR

ICE

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Cleaning Electric MotorsCleaning Electric Motors

Cleaning Method Comparison

Dry Ice Blasting Issue Traditional

very low Equipment Downtime high

low Hazardous Waste medium

low Labour Hours medium / high

high Quality of Cleaning medium / low

very lowPotential Equipment

Damagemedium

high Safety medium

low Cost medium / high

Dry Ice Blasting effectively removes the contaminants from all partsof the motor – stator (windings), rotor (internal fans, cage), air ducts(heat exchanger, external fans) and other components (bearings,shields, inner cups, terminal boxes)..

Benefits of Ice Blasting

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On site experienceOn site experience

Contaminants

oil, dust

Timing

2 days for complete stator, rotor and components dry icecleaning vs 4 days as per standard procedure (solventscleaning + oven heating);

Consumables

400kg dry ice used;

Improvements

better insulation measured after stator (from 100MΏ to 4.7 GΏ )& rotor coils cleaning

Tan – delta: close to new manufactured stators

eliminating dangerous contaminants (oil film) results into:

- extended operating life of insulation (=generator)

- improved measurements detected of tan-delta /partial discharges

On site General Overhauling of 11kV – 13.569 kVA – 30 tons generator

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Stator coils before dry ice cleaning

after dry ice cleaning

The coils were completely coveredby a oil film going to affect theinsulating properties of the stator.

Insulating resistance: from 100MΏ to 4.7 GΏ

Tan – delta: close to new manufactured stators

The main electrical parametersmeasured after the Ice BlastingCleaning improved significantly

On site experienceOn site experience

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ShieldsStator

On site experienceIce Blasting Cleaning of single generator components

On site experienceIce Blasting Cleaning of single generator components

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before

after

Rotor

On site experienceIce Blasting Cleaning of single generator components

On site experienceIce Blasting Cleaning of single generator components

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Dry Ice Blasting is a powerful and reliable cleaningtechnique

Main benefits:

– Very low Equipment Downtime

– Reduced labour hours

– High quality of cleaning with no damages onequipment

– Low cost

– Safe to apply and pollution free

ConclusionsConclusions

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