Corrosion on HVAC equipment
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Corrosion on HVAC equipment Causes & Remedies. Effects of corrosion in HVAC system. Decreasing the capacity of HVAC system Increasing the power consumption of HVAC system Shortening the life expectancy of HVAC system Increasing the emission of CO 2. Decreasing Capacity.

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Corrosion on HVAC equipment Causes & Remedies

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November 2008

Corrosion on HVAC equipment

Causes & Remedies

corrosion on HVAC


November 2008

Effects of corrosion in HVAC system

  • Decreasing the capacity of HVAC system

  • Increasing the power consumption of HVAC system

  • Shortening the life expectancy of HVAC system

  • Increasing the emission of CO2

corrosion on HVAC


November 2008

Decreasing Capacity

  • By loss of bondage between copper tube and aluminum fin.

  • By corrosion of the fins (reduced heat transfer area).

  • By pollution on the fins (reduced air flow).

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Q-AIRCondenser Capacity(m3/h)(kW)

84.400258

75.960241

-50%

-36%

67.250222

59.080202

50.640183

42.200162

25.320111

Decreasing Capacity

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November 2008

Increasing power consumption

Case Study

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Shortening Life Expectancy

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Fuel + Oxygen  CO2 + Water

An increase of power consumption leads to more fuel combustion.

More fuel combustion leads to more CO2 emission.

Increasing CO2 emission

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November 2008

What is corrosion?

  • Chemical reaction of a metal and a non-metal, which produces a chemical compound.

  • Corrosion affects all types of metals, even corrosive resistant metals, over time and under certain conditions

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Types of Corrosion

  • Galvanic Corrosion

    • Cause

    • Effect

    • Visual Appearance

  • Environmental Corrosion

    • Cause

    • Effect

    • Visual Appearance

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November 2008

Cause of Galvanic Corrosion

  • Two dissimilar metals (CU + Al)

  • Electrolyte (f.e. humidity)

    If any of these factors is not present, galvanic corrosion will not occur

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November 2008

Effects of Galvanic Corrosion

  • Galvanic Corrosion of the unprotected coil begins at the bi-metallic coupling between the copper tube (more noble material) and the aluminum fins (less noble material)

  • The result leads to dissolving of the less noble material (fin)

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November 2008

Visual Appearance of Galvanic Corrosion

corrosion on HVAC


November 2008

Cause of Environmental Corrosion

  • Environmental Corrosion is the degradation of the metal, caused by a reaction with the environment, such as oxidation and chemical attack of the metal surface

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Cause of Environmental Corrosion

  • Environmental Corrosion can be caused by different types of environment:

    • MarineNaCl

    • IndustrialSOx NOx

    • Marine/IndustrialNaCl SOx NOx

    • UrbanSOx NOx

    • RuralH2S NHx NOx

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November 2008

Effect of Environmental Corrosion

  • The effect of the formation of a non-protective layer on the material surface. Unprotected metal will continue to react with the contaminant and corrode.

  • The fins will often become very brittle.

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Visual Appearance of Environmental Corrosion

On Aluminum

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Visual Appearance of Environmental Corrosion

On Copper

Different colors shows different corrosion process

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November 2008

Visual Appearance of Environmental Corrosion

On Copper

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Types of Corrosion Protection

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Quality standards

  • Neutral Salt Spray Test

  • Marine by ASTM B-117 / ISO 9227 / SS DIN 50021This salt spray test shows no defects after 10.000 hours.Reflecting ten years extension of life time in real life atthe sea side.

  • Acid Salt Spray Test

  • Urban by ASTM G-85 / ISO 9227 / ESS DIN 50021City life causes acid rain, Thermoguard shows no defectsafter 3.000 hours.Reflecting nine years of exposure to an urban climate.

  • Kesternich Test

  • DIN 50018 / SFW 2,0SHundred and twenty cycles or ten years of heavy pollutedsulfuric air have been a proven success for Thermoguard.

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November 2008

Quality standards

  • Abrasion Resistance Test

  • ASTM D 4060Desert Area. The Taber Abraser test concludes about exposure to erosive conditions like sandstorms. Thermoguard passed this test as extremely resistant to mechanical impacts.

  • Cycle Exchange Test

  • ISO 20340/BBecause of insufficient correlation between the results of salt spray tests and results in the field, exchange tests are more reliable and used.

  • Flexibility Test

  • NEN-ISO 1520 C1 / DIN 53156Metal expand and shrink by fluctuations in temperature. Flexibility is measured by Erichsen tests.

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Mass loss in acetic salt spray test

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Parameters effective coating

  • Optimal layer thickness: thick enough for a good protection and thin enough to avoid pressure drop and bridging

  • Negligible effect on heat conductivity

  • UV resistance

  • Minimal dirt adhesion

  • Superior chemical resistance

  • Flexible to cope with expansion and contraction

  • Easy application (onsite / in workshop)

  • Not sensitive to application conditions

  • Repairable

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Pre-Coating

  • Fins are made out of aluminum sheets.

  • With a pre-coating those sheets are already protected by a coating before cutting

  • After cutting the sheets, new unprotected surfaces are created (a louvered fin has more cutting edges)

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Pre-Coating

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Corrosion begins here!

Pre-Coating

Al

Corrosion begins here!

Unprotected at Cutting edges

Pre-Coating

  • Only protect part of fins: no protection on the cutting edges

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Pre-Coating

  • Pre-coated material: epoxy

  • Epoxy bases pre-coating is not resistant to UV radiation, so not suitable for exposure to the sun.

A condenser with pre-coated fins needs a roof to prevent decaying!

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Pre-Coating

  • With a pre-coated fin the coating forms an insulation between the copper tube and the aluminum fin.

  • This decreases the heat transfer (about 5 to 7%)

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Post-Coating

  • With a post-coating the coating is applied after full production of the coil.

  • No unprotected surfaces are present

  • All metals are protected from the environment by the post-coating

  • The coating forms a barrier between the metals and the electrolytes. No galvanic corrosion can occur

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Protect all the area of Coil!

Also Protect copper tubes of Coil!

Al

Double Protection Layers

No open area of Al Fins and Copper Tubes

Post-Coating

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Post-Coating is a Poly Urethane, which gives a good resistance against UV radiation.

Poly Urethanes are highly flexible to cope with expansion and contraction.

Post-Coating contains aluminum pigments to increase the heat transfer through the coating.

If there is a gap between the fin and the tube, this gap will be filled with the coating, due to the low viscosity. This results in:

A better bonding (heat transfer)

No more galvanic corrosion.

Post-Coating

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Minor effect on the heat transfer and air side pressure drop!

Post-Coating

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Post-Coating

  • The Post-Coating system can be applied:

  • In the factory

  • Before installation

  • (years) after installation

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Post-Coating

  • High chemical resistance

Acids

Alkalines

Salts

Aromatic HydrocarbonsAliphatic Hydrocarbons

Halogenated Hydrocarbons

Ethers and Esters

Alcohols

Fuel and oil

Softeners

Ketones and Aldehydes

Amines

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Comparison Pre-Coating vs. Post-Coating

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The function of an air-conditioning system is to maintain a good thermal climate and acceptable indoor air quality.

Besides the corrosion problems, the units also have to deal with the growth of micro organism.

Anti-Microbial

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Anti-Microbial

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An effective solution is applying a special designed coating that prevents growth of micro organism, such as:

Bacteria

Yeast

Moulds

Algae

Anti-Microbial

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By applying these special coatings, adhesion of dust, dirt and micro organism to the surface is avoided.

Anti-Microbial

  • Anti microbial is available for all types of coatings (heat exchanger, casing, floor)

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Before

Anti-Microbial

After

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CO2 Emission Reduction

  • Power consumption of an unprotected system vs. post-coating

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CO2 Emission Reduction

  • Reduction of power consumption leads to a reduction of CO2 emission.

Calculation Sheet (website)

Calculation Sheet (laptop)

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Organization and Application Facilities

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Conclusion

  • Unprotected coils will have a limited lifetime and decreasing performances.

  • Applying any kind of Corrosion protection gives a lot of advantages.

  • Durability of a Post-Coating is better than a Pre-coating.

corrosion on HVAC


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