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EASY Why is internal treatment of water essential in boilers?

  • to prevent boiler failure due to remaining impurities (correct)
  • to remove most impurities from boiler feedwater
  • because external treatment is not effective
  • to generate steam for plant or building heating

    • What is the main purpose of internal water treatment in low-pressure steam heating boilers?

  • to prevent sludge formation
  • to generate steam for plant or building heating
  • to control corrosion
  • to prevent scale formation (correct)

    • What is the result of not treating internal water in boilers?

  • corrosion prevention
  • boiler failure (correct)
  • scale formation
  • pH control

    • What is the primary function of internal water treatment in high-pressure boilers?

    <p>to monitor chemical and impurity levels</p> Signup and view all the answers

    What is the purpose of precipitating feedwater hardness in internal water treatment?

    <p>to limit scale formation</p> Signup and view all the answers

    What is the range of the pH value?

    <p>0 to 14</p> Signup and view all the answers

    What is the purpose of internal water treatment in low-pressure hot water boilers?

    <p>to focus on pH control and corrosion prevention</p> Signup and view all the answers

    Why is internal water treatment more extensive in high-pressure boilers?

    <p>due to high make-up water requirements</p> Signup and view all the answers

    What causes pitting in the boiler and condensate lines?

    <p>Dissolved oxygen</p> Signup and view all the answers

    What is the purpose of a deaerator?

    <p>To remove dissolved oxygen from the boiler feedwater</p> Signup and view all the answers

    What is the byproduct of the reaction between oxygen and sodium sulfite?

    <p>Sodium sulfate</p> Signup and view all the answers

    Why is hydrazine no longer commonly used as an oxygen scavenger?

    <p>It is highly toxic</p> Signup and view all the answers

    What is the advantage of using DEHA as an oxygen scavenger?

    <p>It has very low toxicity</p> Signup and view all the answers

    What type of amine is fed directly to the boiler?

    <p>Neutralizing amine</p> Signup and view all the answers

    What is the purpose of filming amines?

    <p>To create a thin coat on piping surfaces</p> Signup and view all the answers

    What is the function of molybdate?

    <p>To inhibit corrosion</p> Signup and view all the answers

    What happens to dissolved oxygen as water temperature increases?

    <p>It decreases</p> Signup and view all the answers

    What is a problem associated with using sodium sulfite as an oxygen scavenger?

    <p>It increases the concentration of dissolved solids</p> Signup and view all the answers

    What does the pH of water indicate?

    <p>The degree of acidity or alkalinity of water</p> Signup and view all the answers

    What is the pH level of neutral water?

    <p>7</p> Signup and view all the answers

    What is the result of water being acidic or excessively basic?

    <p>More boiler corrosion occurs</p> Signup and view all the answers

    What is the typical pH range for boilers to limit corrosion?

    <p>8.5 to 10.5</p> Signup and view all the answers

    What is caustic embrittlement also known as?

    <p>Caustic cracking</p> Signup and view all the answers

    What is the result of caustic embrittlement?

    <p>Both a and b</p> Signup and view all the answers

    What is caustic gouging?

    <p>A type of corrosion caused by sodium hydroxide</p> Signup and view all the answers

    What is the result of caustic gouging?

    <p>The affected metal becomes progressively thinner</p> Signup and view all the answers

    What is the main cause of foaming in boiler water?

    <p>Organic material</p> Signup and view all the answers

    What is the purpose of continuous surface blowdown?

    <p>To remove impurities from the boiler water</p> Signup and view all the answers

    What is the purpose of molybdate in boilers and closed loop cooling systems?

    <p>To precipitate an inert passivating barrier layer on the metal surface</p> Signup and view all the answers

    What is the recommended concentration range of molybdate in boiler water?

    <p>75-125 ppm</p> Signup and view all the answers

    What is the effect of scale formation on heat transfer in a boiler?

    <p>It reduces heat transfer</p> Signup and view all the answers

    What is the estimated increase in fuel costs for a 0.1 cm scale thickness?

    <p>9%</p> Signup and view all the answers

    What is the purpose of adding sodium phosphate to boiler water?

    <p>To precipitate calcium and magnesium compounds in a different form</p> Signup and view all the answers

    What is the recommended phosphate residual in boiler water?

    <p>20-40 ppm</p> Signup and view all the answers

    What is the purpose of chelants in boiler water treatment programs?

    <p>To trap and hold metallic ions</p> Signup and view all the answers

    What is the purpose of organic compounds like starch in boiler water treatment?

    <p>To condition and disperse soft scale</p> Signup and view all the answers

    What can happen to boiler tubes if scale deposition results in local overheating?

    <p>They will overheat, bulge, and eventually rupture</p> Signup and view all the answers

    What is the purpose of intermittent bottom blowdown in boiler water treatment?

    <p>To remove soft scale and sludge from the boiler</p> Signup and view all the answers

    MEDIUM What is the result of high water temperatures on the solubility of oxygen?

    <p>Oxygen becomes less soluble</p> Signup and view all the answers

    What is the purpose of scavenger chemicals in boiler feedwater?

    <p>To react with oxygen and prevent corrosion</p> Signup and view all the answers

    What is a disadvantage of using sodium sulfite as an oxygen scavenger?

    <p>It increases the dissolved solids concentration in the boiler</p> Signup and view all the answers

    What is a characteristic of filming amines?

    <p>They create a thin coat on piping surfaces</p> Signup and view all the answers

    What is the purpose of neutralizing amines in boiler water treatment?

    <p>To neutralize acids formed in the condensate</p> Signup and view all the answers

    What is the function of molybdate in boilers?

    <p>To protect the boiler against general corrosion and oxygen pitting</p> Signup and view all the answers

    Why is hydrazine no longer commonly used as an oxygen scavenger?

    <p>It is toxic and requires special handling</p> Signup and view all the answers

    What is the advantage of using DEHA as an oxygen scavenger?

    <p>It has very low toxicity and high volatility</p> Signup and view all the answers

    What is the result of oxygen pitting in the boiler and condensate lines?

    <p>It causes highly localized corrosion</p> Signup and view all the answers

    What is the purpose of a deaerator in boiler water treatment?

    <p>To remove dissolved oxygen from the water</p> Signup and view all the answers

    What is the primary reason for internal treatment of boiler feedwater?

    <p>Because external treatment cannot remove all impurities</p> Signup and view all the answers

    What happens to the steel in a boiler when a caustic buildup forms under a deposit?

    <p>The magnetite layer is stripped off the wall</p> Signup and view all the answers

    What is the main consequence of not treating internal water in boilers?

    <p>Scale formation and corrosion</p> Signup and view all the answers

    What is the effect of a high concentration of dissolved and suspended solids in boiler water?

    <p>It causes foaming within the boiler</p> Signup and view all the answers

    What is the purpose of controlling the concentration of dissolved and suspended solids in the boiler water?

    <p>To prevent foaming</p> Signup and view all the answers

    What is the primary method of preventing caustic embrittlement?

    <p>Limiting the boiler water NaOH concentration to the minimum required</p> Signup and view all the answers

    What is the typical pH range for boilers to prevent corrosion?

    <p>9-11</p> Signup and view all the answers

    What is the typical pH range for boilers to limit corrosion?

    <p>8.5 to 10.5</p> Signup and view all the answers

    What is the purpose of providing the right level of alkalinity in boiler water treatment?

    <p>To prevent corrosion</p> Signup and view all the answers

    What is the result of caustic gouging?

    <p>The affected metal becomes progressively thinner</p> Signup and view all the answers

    What is the primary reason for internal water treatment being more extensive in high-pressure boilers?

    <p>Greater risk of corrosion</p> Signup and view all the answers

    What is the purpose of precipitating feedwater hardness in internal water treatment?

    <p>To keep hardness in suspension for blowoff</p> Signup and view all the answers

    What is the purpose of continuous surface blowdown?

    <p>To prevent foaming and carryover</p> Signup and view all the answers

    What is the result of a high pH level in boiler water?

    <p>Foaming and carryover</p> Signup and view all the answers

    What is the main consideration for internal water treatment in low-pressure hot water boilers?

    <p>pH control and corrosion prevention</p> Signup and view all the answers

    What is the effect of steam blanketing on the boiler metal?

    <p>It allows salts to concentrate on the boiler metal surface</p> Signup and view all the answers

    What is the purpose of adding anti-foaming agents to the boiler water?

    <p>To control foaming and carryover</p> Signup and view all the answers

    What is the typical location of caustic embrittlement on boiler tubes?

    <p>At the points where the tubes are rolled into sheets, drums, or headers</p> Signup and view all the answers

    What is the primary reactant that forms a passivating barrier layer on the metal surface in boilers and closed loop cooling systems?

    <p>Molybdate</p> Signup and view all the answers

    What is the main consequence of scaling in boilers?

    <p>Increased fuel costs and risk of tube rupture</p> Signup and view all the answers

    What is the purpose of adding sodium phosphate to boiler water?

    <p>To prevent scale formation</p> Signup and view all the answers

    What is the effect of local overheating on boiler tubes?

    <p>Tube bulging and eventual rupture</p> Signup and view all the answers

    What is the purpose of chelants in boiler water treatment programs?

    <p>To trap and hold metallic ions</p> Signup and view all the answers

    What is the recommended concentration range of molybdate in boiler water?

    <p>75 to 125 ppm</p> Signup and view all the answers

    What is the purpose of organic compounds like starch in boiler water treatment?

    <p>To condition sludge and prevent deposition</p> Signup and view all the answers

    What is the estimated increase in fuel costs for a 1 cm scale thickness?

    <p>70%</p> Signup and view all the answers

    What is the result of not maintaining a sufficient phosphate residual in boiler water?

    <p>Increased risk of scale formation</p> Signup and view all the answers

    What is the purpose of intermittent bottom blowdown in boiler water treatment?

    <p>To remove sludge and precipitated solids</p> Signup and view all the answers

    What is the primary mechanism of caustic embrittlement?

    <p>Concentration of caustic under deposits</p> Signup and view all the answers

    What is the purpose of adding sodium nitrate, lignins, and tannins to boiler water?

    <p>To prevent caustic embrittlement</p> Signup and view all the answers

    What is the result of caustic gouging?

    <p>Progressive thinning of tube metal</p> Signup and view all the answers

    What is the purpose of continuous surface blowdown?

    <p>To prevent foaming</p> Signup and view all the answers

    What is the effect of high pH levels in boiler water?

    <p>Increased corrosion rates</p> Signup and view all the answers

    What is the result of carrying over liquid water into the steam line?

    <p>Priming</p> Signup and view all the answers

    What is the purpose of adding anti-foaming agents to boiler water?

    <p>To reduce foaming</p> Signup and view all the answers

    HARD What is the effect of acidic or excessively basic boiler water?

    <p>Increased corrosion rates</p> Signup and view all the answers

    What is the purpose of limiting NaOH concentration in boiler water?

    <p>To prevent caustic embrittlement</p> Signup and view all the answers

    What is the result of concentrated caustic buildup under deposits in boiler tubes?

    <p>Caustic gouging</p> Signup and view all the answers

    What is the primary reason for internal treatment of boiler feedwater in high-pressure boilers?

    <p>To remove impurities that were not removed by external treatment</p> Signup and view all the answers

    What is the main purpose of precipitating feedwater hardness in internal water treatment?

    <p>To limit scale formation by keeping it in suspension</p> Signup and view all the answers

    What is the primary function of internal water treatment programs in low-pressure steam heating boilers?

    <p>To focus on pH control and corrosion prevention</p> Signup and view all the answers

    What is the main consequence of not treating internal water in boilers?

    <p>Boiler failure</p> Signup and view all the answers

    What is the primary purpose of internal water treatment in low-pressure hot water boilers?

    <p>To focus on pH control and corrosion prevention</p> Signup and view all the answers

    What is the main reason for stricter internal water treatment requirements in high-pressure boilers?

    <p>Higher risk of impurities causing damage</p> Signup and view all the answers

    What is the primary function of internal water treatment programs in low-pressure steam heating boilers with respect to make-up water?

    <p>To reduce the need for make-up water</p> Signup and view all the answers

    What is the main purpose of internal water treatment programs in boilers with respect to suspended solids?

    <p>To prevent suspended solids from adhering to the boiler metal</p> Signup and view all the answers

    What is the primary mechanism by which oxygen scavengers like sodium sulfite and hydrazine prevent corrosion in boilers?

    <p>By reacting with oxygen to form a stable compound</p> Signup and view all the answers

    What is the primary advantage of using diethylhydroxylamine (DEHA) as an oxygen scavenger over hydrazine?

    <p>DEHA is less toxic and has a higher volatility than hydrazine</p> Signup and view all the answers

    What is the primary function of filming amines in boiler water treatment?

    <p>To create a thin coat on piping surfaces to protect against corrosion</p> Signup and view all the answers

    What is the result of high water temperatures on the solubility of oxygen in water?

    <p>The solubility of oxygen decreases</p> Signup and view all the answers

    What is the primary disadvantage of using sodium sulfite as an oxygen scavenger in high-pressure boilers?

    <p>It increases the dissolved solids concentration in the boiler</p> Signup and view all the answers

    What is the primary purpose of neutralizing amines in boiler water treatment?

    <p>To neutralize acids formed in the condensate</p> Signup and view all the answers

    What is the primary function of molybdate in boiler water treatment?

    <p>To inhibit general corrosion and oxygen pitting</p> Signup and view all the answers

    What is the result of oxygen pitting in the boiler and condensate lines?

    <p>Localized corrosion of the metal surface, resulting in pitting</p> Signup and view all the answers

    What is the primary purpose of a deaerator in boiler water treatment?

    <p>To remove oxygen from the water</p> Signup and view all the answers

    What is the primary advantage of using scavenger chemicals in boiler feedwater?

    <p>They remove oxygen from the water, preventing corrosion</p> Signup and view all the answers

    What is the chemical formula for the reaction product of molybdate and iron in boiler water treatment?

    <p>Fe2(MoO4)3</p> Signup and view all the answers

    What is the primary reason for using sodium phosphate in boiler water treatment?

    <p>To precipitate calcium and magnesium compounds as soft scale</p> Signup and view all the answers

    What is the estimated increase in fuel costs for a 1 cm scale thickness in a boiler?

    <p>70%</p> Signup and view all the answers

    What is the purpose of using chelants in boiler water treatment programs?

    <p>To trap metallic ions and make scales more soluble</p> Signup and view all the answers

    What is the result of local overheating caused by scale deposition in a boiler tube?

    <p>The tube expands and bulges, potentially leading to rupture</p> Signup and view all the answers

    What is the purpose of adding organic compounds like starch to boiler water treatment?

    <p>To coat scale precipitates and prevent them from adhering to boiler internals</p> Signup and view all the answers

    What is the recommended concentration range of molybdate in boiler water?

    <p>75 to 125 ppm</p> Signup and view all the answers

    What is the primary function of intermittent bottom blowdown in boiler water treatment?

    <p>To remove sludge and scale precipitates from the boiler</p> Signup and view all the answers

    What is the result of not controlling scale formation in a boiler?

    <p>The boiler is at risk of overheating and physical damage</p> Signup and view all the answers

    What is the purpose of using EDTA as a chelant in boiler water treatment?

    <p>To trap metallic ions and make scales more soluble</p> Signup and view all the answers

    Study Notes

    Importance of Internal Water Treatment

    • Internal water treatment is essential to prevent boiler failure caused by impurities in the feedwater.
    • Chemicals are added to the water after it enters the boiler to soften, deaerate, and condition the water.

    Purposes of Internal Water Treatment

    • Limit scale formation by precipitating feedwater hardness and keeping it in suspension.
    • Ensure suspended solids in the boiler do not adhere to the boiler metal.
    • Control the concentration of dissolved and suspended solids in the boiler water without causing foaming.
    • Eliminate oxygen from the boiler water.
    • Provide the right level of alkalinity to prevent boiler corrosion.

    pH Control and Corrosion Prevention

    • The pH value is a number between 0 and 14, indicating the degree of acidity or alkalinity of water.
    • A pH of 7 is neutral, less than 7 is acidic, and higher than 7 is basic (or alkaline).
    • Boilers are typically kept at a pH of about 9.5 to 10.5 to limit corrosion.
    • Sodium hydroxide (NaOH) solution is often used to raise pH to the required level within the boiler.

    Caustic Embrittlement and Gouging

    • Caustic embrittlement occurs when metal under stress is attacked by a concentrated caustic solution.
    • Sodium hydroxide (NaOH) can concentrate in areas of high heat transfer, leading to caustic corrosion.
    • Caustic gouging is a form of corrosion that occurs when sodium hydroxide concentrates under deposits on tube surfaces.
    • Preventing caustic embrittlement and gouging requires limiting boiler water NaOH concentration to the minimum required.

    Foaming, Carryover, and Priming

    • Foaming in the boiler is caused by a high concentration of dissolved and suspended solids in the boiler water.
    • Foaming can lead to carryover, which is the entrainment of boiler water in the steam.
    • Priming is a type of carryover that contains large volumes of water.
    • Foaming can be controlled with continuous surface blowdown and the use of anti-foaming agents.

    Oxygen Corrosion

    • Dissolved oxygen causes pitting in the boiler and condensate lines.
    • Oxygen scavengers such as sodium sulfite (Na2SO3) and hydrazine (N2H4) are used to combat oxygen corrosion.
    • Sodium sulfite reacts with oxygen to form sodium sulfate (Na2SO4).
    • Hydrazine is toxic and its use is decreasing.

    Scale Formation

    • Scale formation is caused by the reaction of dissolved solids in the boiler water with other ions.
    • Scale reduces heat transfer, increases fuel costs, and can lead to physical damage.
    • Chemicals such as sodium phosphate (Na3PO4) are added to prevent scale formation by precipitating impurities in a different form.
    • Chelants are used to trap metallic ions and make scales more soluble.

    Sludge Deposits

    • The sludge produced by the precipitation of soft scale in the boiler must be conditioned to stay fluid and well dispersed.
    • Organic compounds such as starch, tannin, lignin, and alginates are used to coat scale precipitates and prevent them from adhering to the boiler internals.

    Importance of Internal Water Treatment

    • Internal water treatment is essential to prevent boiler failure caused by impurities in the feedwater.
    • Chemicals are added to the water after it enters the boiler to soften, deaerate, and condition the water.

    Purposes of Internal Water Treatment

    • Limit scale formation by precipitating feedwater hardness and keeping it in suspension.
    • Ensure suspended solids in the boiler do not adhere to the boiler metal.
    • Control the concentration of dissolved and suspended solids in the boiler water without causing foaming.
    • Eliminate oxygen from the boiler water.
    • Provide the right level of alkalinity to prevent boiler corrosion.

    pH Control and Corrosion Prevention

    • The pH value is a number between 0 and 14, indicating the degree of acidity or alkalinity of water.
    • A pH of 7 is neutral, less than 7 is acidic, and higher than 7 is basic (or alkaline).
    • Boilers are typically kept at a pH of about 9.5 to 10.5 to limit corrosion.
    • Sodium hydroxide (NaOH) solution is often used to raise pH to the required level within the boiler.

    Caustic Embrittlement and Gouging

    • Caustic embrittlement occurs when metal under stress is attacked by a concentrated caustic solution.
    • Sodium hydroxide (NaOH) can concentrate in areas of high heat transfer, leading to caustic corrosion.
    • Caustic gouging is a form of corrosion that occurs when sodium hydroxide concentrates under deposits on tube surfaces.
    • Preventing caustic embrittlement and gouging requires limiting boiler water NaOH concentration to the minimum required.

    Foaming, Carryover, and Priming

    • Foaming in the boiler is caused by a high concentration of dissolved and suspended solids in the boiler water.
    • Foaming can lead to carryover, which is the entrainment of boiler water in the steam.
    • Priming is a type of carryover that contains large volumes of water.
    • Foaming can be controlled with continuous surface blowdown and the use of anti-foaming agents.

    Oxygen Corrosion

    • Dissolved oxygen causes pitting in the boiler and condensate lines.
    • Oxygen scavengers such as sodium sulfite (Na2SO3) and hydrazine (N2H4) are used to combat oxygen corrosion.
    • Sodium sulfite reacts with oxygen to form sodium sulfate (Na2SO4).
    • Hydrazine is toxic and its use is decreasing.

    Scale Formation

    • Scale formation is caused by the reaction of dissolved solids in the boiler water with other ions.
    • Scale reduces heat transfer, increases fuel costs, and can lead to physical damage.
    • Chemicals such as sodium phosphate (Na3PO4) are added to prevent scale formation by precipitating impurities in a different form.
    • Chelants are used to trap metallic ions and make scales more soluble.

    Sludge Deposits

    • The sludge produced by the precipitation of soft scale in the boiler must be conditioned to stay fluid and well dispersed.
    • Organic compounds such as starch, tannin, lignin, and alginates are used to coat scale precipitates and prevent them from adhering to the boiler internals.

    Importance of Internal Water Treatment

    • Internal water treatment is essential to prevent boiler failure caused by impurities in the feedwater.
    • Chemicals are added to the water after it enters the boiler to soften, deaerate, and condition the water.

    Purposes of Internal Water Treatment

    • Limit scale formation by precipitating feedwater hardness and keeping it in suspension.
    • Ensure suspended solids in the boiler do not adhere to the boiler metal.
    • Control the concentration of dissolved and suspended solids in the boiler water without causing foaming.
    • Eliminate oxygen from the boiler water.
    • Provide the right level of alkalinity to prevent boiler corrosion.

    pH Control and Corrosion Prevention

    • The pH value is a number between 0 and 14, indicating the degree of acidity or alkalinity of water.
    • A pH of 7 is neutral, less than 7 is acidic, and higher than 7 is basic (or alkaline).
    • Boilers are typically kept at a pH of about 9.5 to 10.5 to limit corrosion.
    • Sodium hydroxide (NaOH) solution is often used to raise pH to the required level within the boiler.

    Caustic Embrittlement and Gouging

    • Caustic embrittlement occurs when metal under stress is attacked by a concentrated caustic solution.
    • Sodium hydroxide (NaOH) can concentrate in areas of high heat transfer, leading to caustic corrosion.
    • Caustic gouging is a form of corrosion that occurs when sodium hydroxide concentrates under deposits on tube surfaces.
    • Preventing caustic embrittlement and gouging requires limiting boiler water NaOH concentration to the minimum required.

    Foaming, Carryover, and Priming

    • Foaming in the boiler is caused by a high concentration of dissolved and suspended solids in the boiler water.
    • Foaming can lead to carryover, which is the entrainment of boiler water in the steam.
    • Priming is a type of carryover that contains large volumes of water.
    • Foaming can be controlled with continuous surface blowdown and the use of anti-foaming agents.

    Oxygen Corrosion

    • Dissolved oxygen causes pitting in the boiler and condensate lines.
    • Oxygen scavengers such as sodium sulfite (Na2SO3) and hydrazine (N2H4) are used to combat oxygen corrosion.
    • Sodium sulfite reacts with oxygen to form sodium sulfate (Na2SO4).
    • Hydrazine is toxic and its use is decreasing.

    Scale Formation

    • Scale formation is caused by the reaction of dissolved solids in the boiler water with other ions.
    • Scale reduces heat transfer, increases fuel costs, and can lead to physical damage.
    • Chemicals such as sodium phosphate (Na3PO4) are added to prevent scale formation by precipitating impurities in a different form.
    • Chelants are used to trap metallic ions and make scales more soluble.

    Sludge Deposits

    • The sludge produced by the precipitation of soft scale in the boiler must be conditioned to stay fluid and well dispersed.
    • Organic compounds such as starch, tannin, lignin, and alginates are used to coat scale precipitates and prevent them from adhering to the boiler internals.

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    Description

    Learn about the importance of internal treatment of boiler feedwater to prevent impurities and boiler failure. Understand the process of adding chemicals to soften, deaerate, and condition the water.

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