Evaporative Condenser PassivationCameron Klein

Strand Associates, Inc.

Evaporative Condenser Wetted Surface Materials of Construction

▪ Galvanized Steel• Protective zinc coating fused to a steel substrate• Zinc layer offers sacrificial protection of steel substrate• Standard construction material• Requires passivation

▪ Stainless Steel• Upgraded construction material• Added equipment cost (varies based on size)• Passivation is not required

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What is White Rust?

▪ White rust is a rapid, localized corrosion attack on zinc (galvanized) surfaces

▪ Corrosion removes protective zinc layer (pitting)▪ Waxy feel when wet▪ Usually occurs on new galvanized surfaces during startup▪ Can occur on existing galvanized surfaces if exposed to

high pH, high conductivity, or if the surface has been scraped or aggressively cleaned

▪ Does not occur on stainless steel surfaces

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What is White Rust?

Picture courtesy of Evapco literature

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What is Galvanized Steel Passivation?

▪ Passivation is the process of the zinc layer oxidizing under controlled conditions

▪ A thin film of zinc oxide is formed on the galvanized surface▪ Protects the zinc layer which protects the steel substrate▪ Water chemistry is key

• If the water starts off in the acceptable range for water chemistry,with evaporation it will not remain in that range without treatmentand blowdown

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Water Chemistry Requirements for Passivation

▪ Varies by manufacturer but generally:▪ pH: 7.0 – 8.0▪ Alkalinity: < 300 ppm▪ Hardness: > 50 ppm▪ Conductivity: < 2,400 μS▪ Chlorides: < 250 ppm▪ Sulfates: < 250 ppm▪ All are important, but pH is very important▪ Ultimately, working with your water treatment supplier is a

critical step in the passivation process

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Passivation Duration

▪ Varies by manufacturer• BAC: 4-8 weeks• Evapco: 4-12 weeks• Marley: minimum of 8 weeks

▪ Varies by climate and water chemistry▪ No load on system during passivation

• Elevated temperature and changing water chemistry make passivation very difficult

• Evaporation can concentrate corrosive ions and increase pH

▪ Coordinate with water treatment supplier to create a plan and to monitor the surfaces to determine when complete

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Visual Difference of Galvanized Surface

▪ Pre-Passivation (new equipment)• Bright and shiny color

▪ Post-Passivation (ready for loading)• Dull gray color

Pictures courtesy of Evapco literature

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Evaporative Condenser Expected Useful Life

▪ ASHRAE Service Life Estimate: 20 Years• Assumed to be fully passivated and water chemistry controlled

during operation

▪ Without passivation and water chemistry controlled, equipment life estimate drops to 5-15 years

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Considerations

▪ Galvanized steel vs. stainless steel▪ Project construction schedule▪ If a passivated surface is damaged, re-passivation of that

surface is critical▪ Consult the manufacturer literature for requirements▪ Water treatment vendor involvement

• Passivation involvement• Ongoing chemical treatment involvement

▪ Not a “set it and forget it” piece of equipment

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Passivation Water Treatment Log

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Questions

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Cooling Tower / Boiler Treatment& Control

Cooling Tower / Boiler Treatment& Control

Joe WennJoe Wenn

IMPURITIES COMMONLY FOUND IN WATER

HARDNESS• Calcium and Magnesium salts expressed as CaC03 either Ca+Mg+• Chief source of scale in heat exchange equipment, boilers, pipelines,

etc. Forms curds with soap, interferes with dyeing.• Softening, Demineralization, Internal boiler water treatment, Surface-

active agents.

HARDNESS• Calcium and Magnesium salts expressed as CaC03 either Ca+Mg+• Chief source of scale in heat exchange equipment, boilers, pipelines,

etc. Forms curds with soap, interferes with dyeing.• Softening, Demineralization, Internal boiler water treatment, Surface-

active agents.

1. Chemical Formula or Name2. Difficulties Caused3. Means of Treatment

1. Chemical Formula or Name2. Difficulties Caused3. Means of Treatment

ALKALINITY• Bicarbonate (HC03), Carbonate (C03), and Hydrate (OH), expressed <1:5

CaC03 • Foaming and carryover of solids with steam, Embrittlement of boiler steel.

Bicarbonate and carbonate produce CO2 in steam• Lime and lime-soda softening, Acid treatment, Hydrogen zeolite softening,

Demineralization, Dealkalization by anion exchange.

ALKALINITY• Bicarbonate (HC03), Carbonate (C03), and Hydrate (OH), expressed <1:5

CaC03 • Foaming and carryover of solids with steam, Embrittlement of boiler steel.

Bicarbonate and carbonate produce CO2 in steam• Lime and lime-soda softening, Acid treatment, Hydrogen zeolite softening,

Demineralization, Dealkalization by anion exchange.

IMPURITIES COMMONLY FOUND IN WATER

FREE MINERAL ACID• Hi-SO, HCl, etc., expressed as CaC03 • Corrosion.• Neutralization with alkalies.

FREE MINERAL ACID• Hi-SO, HCl, etc., expressed as CaC03 • Corrosion.• Neutralization with alkalies.

1. Chemical Formula or Name2. Difficulties Caused3. Means of Treatment

1. Chemical Formula or Name2. Difficulties Caused3. Means of Treatment

CARBON DIOXIDE • CO2 • Corrosion in water lines and particularly steam �d condensate lines.• Aeration, Deaeration, Neutralization with alkalies.

CARBON DIOXIDE • CO2 • Corrosion in water lines and particularly steam �d condensate lines.• Aeration, Deaeration, Neutralization with alkalies.

pH• Hydrogen ion concentration defined as pH + log 1L(H)• pH varies according to acidic or alkaline solids in water. Most natural

waters have a pH of 6.0- 8.0.• pH can be increased by alkalies and decreased by acids.

pH• Hydrogen ion concentration defined as pH + log 1L(H)• pH varies according to acidic or alkaline solids in water. Most natural

waters have a pH of 6.0- 8.0.• pH can be increased by alkalies and decreased by acids.

EXTERNAL TREATMENT

Sodium Zeolite-Most common• Polystyrene Resins - 32,000 grains/cubic foot • NaCl - Regenerate . • Complete Hardness Removal • Turbidity, Iron, and Oil Detrimental to Resin. • No Reduction in Alkalinity or Solids • Increased CO2 • Increase in Corrosion Tendencies due to ·Dissolved Gases 02 and

CO– Four cycles

• - Backwash• - Brine Draw• - Fast Rinse• - Service

– - 2.6 Lbs. Salt/Gallon Water - Saturation– - Resin can be cleaned to Remove Iron with

• 1). Hydrochloric Acid 2). Citric Acid 3) Sodium Hydrosulfite and Bisulfite

Sodium Zeolite-Most common• Polystyrene Resins - 32,000 grains/cubic foot • NaCl - Regenerate . • Complete Hardness Removal • Turbidity, Iron, and Oil Detrimental to Resin. • No Reduction in Alkalinity or Solids • Increased CO2 • Increase in Corrosion Tendencies due to ·Dissolved Gases 02 and

CO– Four cycles

• - Backwash• - Brine Draw• - Fast Rinse• - Service

– - 2.6 Lbs. Salt/Gallon Water - Saturation– - Resin can be cleaned to Remove Iron with

• 1). Hydrochloric Acid 2). Citric Acid 3) Sodium Hydrosulfite and Bisulfite

Softening -Removal of Calcium and MagnesiumSoftening -Removal of Calcium and Magnesium

EXTERNAL TREATMENT

Lime Soda Softening • Lime and Soda Ash (Sodium Carbonate) or Caustic Soda -

needed Regenerants 1 - 1 1/2 hours retention time • Hardness reduced to 10 - 25 ppm Hot Process used for Boiler

Make-up • Ca+ precipitates CaCO3 • Mg+ precipitates MgOH• Bicarbonate Alkalinity Converted to Carbonate then CaCO3 • Silica is Precipitated .• Turbidity is removed (Calcium Hydroxide)

Lime Soda Softening • Lime and Soda Ash (Sodium Carbonate) or Caustic Soda -

needed Regenerants 1 - 1 1/2 hours retention time • Hardness reduced to 10 - 25 ppm Hot Process used for Boiler

Make-up • Ca+ precipitates CaCO3 • Mg+ precipitates MgOH• Bicarbonate Alkalinity Converted to Carbonate then CaCO3 • Silica is Precipitated .• Turbidity is removed (Calcium Hydroxide)

Softening -Removal of Calcium and MagnesiumSoftening -Removal of Calcium and Magnesium

EXTERNAL TREATMENT

Split Stream Dealkalizer• Polystyrene Resins Used • 2 Tanks-Each Regenera!e Separately

– One withNaCI– The other Sulfuric Acid (2--6% Solution)

• Zero Hardness Low Alkalinity • Blended Byproduct is Carbonic Acid • Degasifier used to remove excess Carbonic Acid

Split Stream Dealkalizer• Polystyrene Resins Used • 2 Tanks-Each Regenera!e Separately

– One withNaCI– The other Sulfuric Acid (2--6% Solution)

• Zero Hardness Low Alkalinity • Blended Byproduct is Carbonic Acid • Degasifier used to remove excess Carbonic Acid

Softening -Removal of Calcium and MagnesiumSoftening -Removal of Calcium and Magnesium

Demineralized • Cation - Anion • Regenerants - Sulfuric Acid and Caustic Soda• Strong Basic Resin removes Silica • Aerator needed for CO2 removal• Used for High Pressure Boiler

Demineralized • Cation - Anion • Regenerants - Sulfuric Acid and Caustic Soda• Strong Basic Resin removes Silica • Aerator needed for CO2 removal• Used for High Pressure Boiler

EXTERNAL TREATMENT

Dealkalizers - Chloride Cycle • One Tank • Regenerated with NaCl and NaOH

Dealkalizers - Chloride Cycle • One Tank • Regenerated with NaCl and NaOH

Softening -Removal of Calcium and MagnesiumSoftening -Removal of Calcium and Magnesium

Reverse Osmosis • Membrane Technology_ • Reduces make-up minerals by 90 to 95%. • Pretreatment (water softener and carbon filter) typically required• Substantially reduce boiler blowdown requirements and chemical

usage

Reverse Osmosis • Membrane Technology_ • Reduces make-up minerals by 90 to 95%. • Pretreatment (water softener and carbon filter) typically required• Substantially reduce boiler blowdown requirements and chemical

usage

White Rust

White Rust

Control

Control

STEAM AND RETURN LINE CORROSION

Oxygen• Iron pipe will show pitting • 4 Fe +6(H20) +3(02) = 4 Fe(OH)3 Iron Ferric Hydroxide • 02 can increase carbonic acid corrosion lOx

Oxygen• Iron pipe will show pitting • 4 Fe +6(H20) +3(02) = 4 Fe(OH)3 Iron Ferric Hydroxide • 02 can increase carbonic acid corrosion lOx

TYPES AND CAUSES OF CORROSION TYPES AND CAUSES OF CORROSION

2). Carbon Dioxide • Iron pipe has grooving or etching usually at elbows or

horizontal runs • CO2 +H20 = H2CO3 (Carbonic Acid) 2 (HzCO3) +Fe:= Fe

(HCO3)2 + H2 (Ferrous Bicarbonate) • Boiler Alkalinity converts to CO2

– 1 ppm Bicarbonate Alkalinity evolves to . 79 ppm CO2– 1 ppm Carbonate Alkalinity evolves to .35 ppm CO2– 100% of Bicarbonate Alkalinity completes reaction at Boiler P .S.I. 0 - 50 – 10 - 30% of Carbonate Alkalinity completes reaction at Boiler P.S.I. 50- 150 – 30 - 80% completes reaction at Boiler P.SJ. 150 and over – 80 - 100% completes reaction

2). Carbon Dioxide • Iron pipe has grooving or etching usually at elbows or

horizontal runs • CO2 +H20 = H2CO3 (Carbonic Acid) 2 (HzCO3) +Fe:= Fe

(HCO3)2 + H2 (Ferrous Bicarbonate) • Boiler Alkalinity converts to CO2

– 1 ppm Bicarbonate Alkalinity evolves to . 79 ppm CO2– 1 ppm Carbonate Alkalinity evolves to .35 ppm CO2– 100% of Bicarbonate Alkalinity completes reaction at Boiler P .S.I. 0 - 50 – 10 - 30% of Carbonate Alkalinity completes reaction at Boiler P.S.I. 50- 150 – 30 - 80% completes reaction at Boiler P.SJ. 150 and over – 80 - 100% completes reaction

STEAM AND RETURN LINE CORROSION

Hydrazine Breakdown from Excessive Use - Ammonia is formed and in presence of 02 and pH above 8.3 copper is severely attacked

Hydrazine Breakdown from Excessive Use - Ammonia is formed and in presence of 02 and pH above 8.3 copper is severely attacked

TYPES AND CAUSES OF CORROSION TYPES AND CAUSES OF CORROSION

Sulfite - Will breakdown at high temperature; 1000 degrees F to Hydrogen Sulfide

Chlorine - From faulty heat exchanger on pool

Coil Leakage

Sulfite - Will breakdown at high temperature; 1000 degrees F to Hydrogen Sulfide

Chlorine - From faulty heat exchanger on pool

Coil Leakage

Ammonium Hydroxide or Ammonia - Will stop carbonic acid attack but with 02 and pH above 83 copper and brass are attacked

Ammonium Hydroxide or Ammonia - Will stop carbonic acid attack but with 02 and pH above 83 copper and brass are attacked

Closed Systems- Boilers

Issues• Water Volume relative to system Volume

• Madison Water Quality– High Harness (Scaling)

• Boilers Fail

Solution

• Soft Water

Issues• Water Volume relative to system Volume

• Madison Water Quality– High Harness (Scaling)

• Boilers Fail

Solution

• Soft Water

Real World Examples