API 571 pt 3 Questions With Complete Solutions
Galvanic Corrosion - Critical Factors Correct Answers Two
different materials with different potentials
Electrically coupled together
Immersed or in contact with the same electrolyte
Galvanic Corrosion - Inspection Correct Answers VT and UT
Permanent thicknesses sensors
Angled beam for under bolts and washers
Gaseous Oxygen-enhanced Ignition and Combustion - Affected
Eq Correct Answers Any systems that use O2 or enriched air
for combustion or other process reactions
SRUs, FCCs, gasification units, partial oxidation units (POX)
Gaseous Oxygen-enhanced Ignition and Combustion -
Appearance Correct Answers Fires
External heat damage
Burning valve seat without kindling other parts
Gaseous Oxygen-enhanced Ignition and Combustion - Critical
Factors Correct Answers <500 psi moderate or mild effect on
metal burning reactions
High velocity O2, high friction, high ignition potential
Metals in high purity O2 auto ignite <1650F
Non metallics in high purity O2 auto ignite <300F
Metallic fines, oils, greases ignite easily
Elbows, tees, valves are high-risk ignition zones.
Flowing O₂ particles strike surfaces
Valve opening/closing leads to turbulence and ignition
,Use oxygen-service-cleaned items for high-purity O₂.
Thin geometries ignite easily
Gaseous Oxygen-enhanced Ignition and Combustion -
Description Correct Answers Many metals are flammable in
O2>25% air even in low pressures.
They are non flammable in air
Gaseous Oxygen-enhanced Ignition and Combustion -
Inspection Correct Answers Fire damage or malfunctioning
valves
Blacklights for H2 contamination
Cant be inspected for in advance
Gaseous Oxygen-enhanced Ignition and Combustion - Materials
Correct Answers CS in O2>15 psig partial pressure
300 in O2>200 psig partial pressure
Cu (>55% Cu) and Ni (>50%) are resistant
Al is avoided
Non metallics easiest to ignite
Titanium very weak and avoided
Gaseous Oxygen-enhanced Ignition and Combustion -
Prevention Correct Answers Cleanliness
Keep velocity < 100 fps
Ensure all replacement parts are oxygen-compatible.
Minimize lubricants
Avoid unnecessary opening
Avoid plastic piping in oxygen systems
,Graphitic Corrosion of Cast Irons - Affected Eq Correct
Answers Soft water, saltwater, mine waters, dilute acids, and in
underground piping as well as in BFW equipment.
Graphitic Corrosion of Cast Irons - Appearance Correct
Answers Charcoal Grey
Widespread or localized
Damaged areas soft and easily gouged with knife or tool
Graphitic Corrosion of Cast Irons - Critical Factors Correct
Answers Occurs with moisture or aqueous phase below <200F
Can take months or years to progress.
Lower pH, faster progression.
Iron matrix corrodes preferentially
Graphite becomes cathodic to surroundings
Graphitic Corrosion of Cast Irons - Description Correct
Answers Form of dealloying in low pH and stagnant conditions
Graphitic Corrosion of Cast Irons - Inspection Correct Answers
VT misleading since surface can appear fine
Soft surface test not definitive, only flags suspect zones.
UT not reliable alone but can locate corrosion
Acoustic methods
Hardness test
Core sampling
Hammer test
Metallography
Graphitic Corrosion of Cast Irons - Materials Correct Answers
Grey Cast and nodular iron
, Graphitic Corrosion of Cast Irons - Prevention Correct Answers
Coatings, cement linings, CP
Use different material
Graphitization - Affected Eq Correct Answers FCC, catalytic
reforming, and coker units.
Bainitic more resistant than coarse pearlite
Eyebrow lowers creep rupture strength
Graphitization - Appearance Correct Answers Hard to see, use
metallography
Advanced stage will have microvoids, microfissuring,
subsurface cracking, or surface-connected cracking
Graphitization - Critical Factors Correct Answers Exact cause
unknown
Adding 0.7Cr eliminates risk
Risk is low below 800F
Random graphitization
Eyebrow graphitization with chains/planes of graphite nodules.
HAZ graphitization occurs at low-temperature edge of HAZ.
Multi-pass welds can have overlapping weak graphite bands
extending through the whole cross section.
Non-weld; along ferrite/pearlite boundaries, or planes of
localized yielding (cold work, bending).
Graphitization - Description Correct Answers 800 °F to 1100
°F microstructure change in CS and 0.5Mo
Galvanic Corrosion - Critical Factors Correct Answers Two
different materials with different potentials
Electrically coupled together
Immersed or in contact with the same electrolyte
Galvanic Corrosion - Inspection Correct Answers VT and UT
Permanent thicknesses sensors
Angled beam for under bolts and washers
Gaseous Oxygen-enhanced Ignition and Combustion - Affected
Eq Correct Answers Any systems that use O2 or enriched air
for combustion or other process reactions
SRUs, FCCs, gasification units, partial oxidation units (POX)
Gaseous Oxygen-enhanced Ignition and Combustion -
Appearance Correct Answers Fires
External heat damage
Burning valve seat without kindling other parts
Gaseous Oxygen-enhanced Ignition and Combustion - Critical
Factors Correct Answers <500 psi moderate or mild effect on
metal burning reactions
High velocity O2, high friction, high ignition potential
Metals in high purity O2 auto ignite <1650F
Non metallics in high purity O2 auto ignite <300F
Metallic fines, oils, greases ignite easily
Elbows, tees, valves are high-risk ignition zones.
Flowing O₂ particles strike surfaces
Valve opening/closing leads to turbulence and ignition
,Use oxygen-service-cleaned items for high-purity O₂.
Thin geometries ignite easily
Gaseous Oxygen-enhanced Ignition and Combustion -
Description Correct Answers Many metals are flammable in
O2>25% air even in low pressures.
They are non flammable in air
Gaseous Oxygen-enhanced Ignition and Combustion -
Inspection Correct Answers Fire damage or malfunctioning
valves
Blacklights for H2 contamination
Cant be inspected for in advance
Gaseous Oxygen-enhanced Ignition and Combustion - Materials
Correct Answers CS in O2>15 psig partial pressure
300 in O2>200 psig partial pressure
Cu (>55% Cu) and Ni (>50%) are resistant
Al is avoided
Non metallics easiest to ignite
Titanium very weak and avoided
Gaseous Oxygen-enhanced Ignition and Combustion -
Prevention Correct Answers Cleanliness
Keep velocity < 100 fps
Ensure all replacement parts are oxygen-compatible.
Minimize lubricants
Avoid unnecessary opening
Avoid plastic piping in oxygen systems
,Graphitic Corrosion of Cast Irons - Affected Eq Correct
Answers Soft water, saltwater, mine waters, dilute acids, and in
underground piping as well as in BFW equipment.
Graphitic Corrosion of Cast Irons - Appearance Correct
Answers Charcoal Grey
Widespread or localized
Damaged areas soft and easily gouged with knife or tool
Graphitic Corrosion of Cast Irons - Critical Factors Correct
Answers Occurs with moisture or aqueous phase below <200F
Can take months or years to progress.
Lower pH, faster progression.
Iron matrix corrodes preferentially
Graphite becomes cathodic to surroundings
Graphitic Corrosion of Cast Irons - Description Correct
Answers Form of dealloying in low pH and stagnant conditions
Graphitic Corrosion of Cast Irons - Inspection Correct Answers
VT misleading since surface can appear fine
Soft surface test not definitive, only flags suspect zones.
UT not reliable alone but can locate corrosion
Acoustic methods
Hardness test
Core sampling
Hammer test
Metallography
Graphitic Corrosion of Cast Irons - Materials Correct Answers
Grey Cast and nodular iron
, Graphitic Corrosion of Cast Irons - Prevention Correct Answers
Coatings, cement linings, CP
Use different material
Graphitization - Affected Eq Correct Answers FCC, catalytic
reforming, and coker units.
Bainitic more resistant than coarse pearlite
Eyebrow lowers creep rupture strength
Graphitization - Appearance Correct Answers Hard to see, use
metallography
Advanced stage will have microvoids, microfissuring,
subsurface cracking, or surface-connected cracking
Graphitization - Critical Factors Correct Answers Exact cause
unknown
Adding 0.7Cr eliminates risk
Risk is low below 800F
Random graphitization
Eyebrow graphitization with chains/planes of graphite nodules.
HAZ graphitization occurs at low-temperature edge of HAZ.
Multi-pass welds can have overlapping weak graphite bands
extending through the whole cross section.
Non-weld; along ferrite/pearlite boundaries, or planes of
localized yielding (cold work, bending).
Graphitization - Description Correct Answers 800 °F to 1100
°F microstructure change in CS and 0.5Mo
