Source Of Contamination

Three Type Of Contamination on Fluid

Type Of Contamination

Solid Contamination

 

• •Wear is primarily caused by abrasion, adhesion and surface fatigue. •Damage increases with particle hardness and the number of particles.

•Major wear is caused by particles about the same size as the critical dynamic clearances.

•There is a significant increase in the number of particles as the particle size decreases.

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Liquid Contamination

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•Water contamination in fluid systems causes:

–Fluid breakdown, such as additive precipitation, oil oxidation, acid formation, thickening, varnish & sludge.

–Cavitation, foaming & air entrainment problems.

–Reduced lubricating film thickness leading to accelerated metal surface fatigue.

–Corrosion.

–Bacterial & fungal growth.

–Poor filterability & valve stiction.

–Reduced dielectric properties.

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Water can be present in two forms:

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Disolve WaterFree (emulsified or droplets).

Dissolved (below saturation).

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Typical sources of water ingress

•Through system vents / breathers.

•From leaking coolers and heat exchangers.

•Through leaking seals & reservoir covers.

•Condensation.

•Precipitation of dissolved water due to a fall in temperature.

•Introduction of contaminated top-up fluid.

Rain leaking into incorrectly stowed barrels & external reservoirs.

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Gaseous Contamination

•Air contamination in fluid can be in the following forms:

-Dissolved air causes oxidation & accelerates additive depletion.

-Entrained (10-3 to 1 mm bubbles); cause oil compressibility, poor heat transfer, film strength failure, oxidation, cavitation & varnishing.

-Free (trapped air pockets); cause hydraulic compressibility, corrosion, vapor lock & loss of system controls.

Foam (> 1 mm bubbles); has a similar effect to Free air.

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Gaseous Contamination

•The level of contamination is also measured as a % by volume.

•In the case of air contamination, the various categories are usually defined as:

-Dissolved - Up to 10% air (typical for mineral oils).

-Entrained - 10 to 30% air.

-Foam - Over 30% air.

Foaming is considered to be a problem requiring action if:

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The equipment is lubricated with foam instead of oil

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The foam inhibits heat transfer and encourages oxidation and thermal failure of the oil. The foam leads to air locks and inability to effectively supply oil to lubricated components.

The oil spills onto the floor creating a safety hazard. The oil level in the sump or reservoir becomes impossible to control.