API 574 Study Questions For Damage mechanisms

Dead-legs in hot piping systems may have corrosion rates that are significantly higher due to:

• Caustic vaporizing

• Convection currents

• Crevice corrosion

• Sulfication

Corrosion can occur in dead-legs of tower overhead systems as a result of:

• Dew-point corrosion

• HTHA

• Naphthenic acid

• Temper-embrittlement

Corrosion can occur in some dead-legs at hydrotreating units. This is caused by:

• Ammonium salts

• Oxygen pitting

• SCC

• Sulfidation

CUI can be a major issue on insulated carbon steel piping system operating between:

• 25 – 250 °F

• 10 – 350 °F

• 40 – 125 °F

• 120 – 400 °F

CUI can be a major issue on insulated stainless steel piping system operating between:

• 25 – 250 °F

• 10 – 350 °F

• 40 – 125 °F

• 120 – 400 °F

CUI is an inspection concern for insulated piping operating at 500 °F and:

• Is in intermittent service

• Is made of stainless steel

• Is made of low chromes

• Have poorly maintained insulation

CUI of austenitic stainless steel piping.

• Occurs at temperature between -10 to 125 °F

• Normally appears as stress corrosion cracking

• Is the result of using insulation that contains a sulfur compound

• Normally causes deep isolated pitting

CUI particularly aggressive:

• In dry climates

• When operating temperatures cause frequent condensation and re-evaporation of

  atmospheric moisture

• When operating temperature are above 325 °F

• If the insulation is made of fiberglass

[Open Book] The inspector checks the concrete-to-air interface of buried piping that does not have cathode protection. Deterioration is noted. It may be necessary to remove the concrete and inspect beneath the pipe surface if this piping system is over:

• 5 years old

• 10 years old

• 15 years old

• 25 years old

Sulfidation of carbon steels begins to occur when the sulfur content is greater than 0.5% and the temperature exceeds:

• 250 °F

• 450 °F

• 800 °F

• 900 °F