API RP-571 - DAMAGE MECHANISMS QUESTIONS
The 19 damage mechanisms are as follows... 1. ... embrittlement 2. ... fracture. 3. ....
fatigue. 4. ..... 5. ... fatigue. 6. ... corrosion. 7. ....insulation. 8. ... water corrosion. 9. ...
water .... corrosion. 10. ....dation. 11. ....cracking. 12. ... fatigue. 13. ....cracking. 14.
....corrosion. 15. ....water corrosion. 16. ....cracking. 17. ....damage. 18. .... Corrosion
19. .... attack. - Answer -Temper. Brittle. Thermal. Erosion. Mechanical. Atmospheric.
Corrosion under. Cooling. Boiler condensate. Sulfur. Chloride stress corrosion.
Corrosion. Caustic stress corrosion. HCL. Sour. Amine stress corrosion. Wet H2S.
Caustic. High temp hydrogen.
What is temper embrittlement? - Answer -Reduction in toughness that occurs in low
alloy steels to to long term exposure to a certain heat range.
Temper embrittlement heat range? - Answer -650-1070F
Temper embrittlement affected materials? - Answer -2.25Cr-1Mo low alloy steel, 3Cr-
1Mo and low alloy Cr-Mo-V rotor steels
Materials resistant to temper embrittlement? - Answer -C-0.5Mo and 1.25Cr-0.5Mo
Monitoring temper embrittlement? - Answer -Temper coupons inside reactor and
impact test. Proper pressurisation sequences.
When does temper embrittlement fracture usually occur? - Answer -Start-up and
shutdown
What is brittle fracture? - Answer -Sudden rapid fracture of a material under stress
including residual where no plastic deformation occurs.
Brittle fracture affected materials? - Answer -Carbon steels and low alloy steels. 400
series are also affected.
Brittle fracture susceptible equipments? - Answer -Those constructed prior to Dec
1987. Thick walled vessels. During start up, shutdown and hydro testing.
Appearance of brittle fracture cracks. - Answer -Straight and non-branching. Cleavage.
Monitoring for brittle fracture? - Answer -Try to find pre-existing flaws
What is thermal fatigue? - Answer -Cracking caused by variations in temperature.
What materials are affected by thermal fatigue? - Answer -All materials
, How do you monitor thermal fatigue? (It's surface cracking) - Answer -VT, MT and PT.
External shear wave UT.
What is erosion? - Answer -Accelerated mechanical removal of surface material due to
the movement or impact between solids, liquids, vapour or a combination.
Erosion affected materials? - Answer -All metals, alloys and refractory.
Monitoring for erosion? - Answer -VT, UT or RT. Infrared scans on refractory.
What is mechanical fatigue? Are they below the YS of the material? - Answer -Cracking
due to cyclic stresses. Yes.
Affected materials by mechanical fatigue? - Answer -All alloys.
Monitoring of mechanical fatigue? - Answer -PT, MT and SWUT. VT can be used to
detect movements that could lead to cracking.
What is Atmospheric corrosion? - Answer -Corrosion from moisture in the air.
Affected materials by atmospheric corrosion? - Answer -Carbon steel, low alloy steels
and copper alloyed aluminium
Is atmospheric corrosion general or localised? - Answer -Both
What sort of rust occurs with atmospheric corrosion? - Answer -Red rust
Monitoring of atmospheric corrosion? - Answer -VT or UT
What is CUI? - Answer -Corrosion due to entrapment of water under insulation or
fireproofing.
Affected materials by CUI? - Answer -Carbon steel, low alloy steels, 300 series, duplex.
CUI temp range for CS? - Answer -10-350F
CUI temp range for Austenitic and duplex SS? - Answer -140-400F
Monitoring for CUI? - Answer -Strategic inspection plan considering operating temp,
type/age of coating, type/age of insulation.
What is cooling water corrosion? - Answer -General corrosion from cooling water due
to metals, salts, organic compounds or bacteria in the water.
Affected materials by cooling water corrosion? - Answer -Carbon steel, all grades of
SS, copper, aluminium, titanium and nickel based alloys
The 19 damage mechanisms are as follows... 1. ... embrittlement 2. ... fracture. 3. ....
fatigue. 4. ..... 5. ... fatigue. 6. ... corrosion. 7. ....insulation. 8. ... water corrosion. 9. ...
water .... corrosion. 10. ....dation. 11. ....cracking. 12. ... fatigue. 13. ....cracking. 14.
....corrosion. 15. ....water corrosion. 16. ....cracking. 17. ....damage. 18. .... Corrosion
19. .... attack. - Answer -Temper. Brittle. Thermal. Erosion. Mechanical. Atmospheric.
Corrosion under. Cooling. Boiler condensate. Sulfur. Chloride stress corrosion.
Corrosion. Caustic stress corrosion. HCL. Sour. Amine stress corrosion. Wet H2S.
Caustic. High temp hydrogen.
What is temper embrittlement? - Answer -Reduction in toughness that occurs in low
alloy steels to to long term exposure to a certain heat range.
Temper embrittlement heat range? - Answer -650-1070F
Temper embrittlement affected materials? - Answer -2.25Cr-1Mo low alloy steel, 3Cr-
1Mo and low alloy Cr-Mo-V rotor steels
Materials resistant to temper embrittlement? - Answer -C-0.5Mo and 1.25Cr-0.5Mo
Monitoring temper embrittlement? - Answer -Temper coupons inside reactor and
impact test. Proper pressurisation sequences.
When does temper embrittlement fracture usually occur? - Answer -Start-up and
shutdown
What is brittle fracture? - Answer -Sudden rapid fracture of a material under stress
including residual where no plastic deformation occurs.
Brittle fracture affected materials? - Answer -Carbon steels and low alloy steels. 400
series are also affected.
Brittle fracture susceptible equipments? - Answer -Those constructed prior to Dec
1987. Thick walled vessels. During start up, shutdown and hydro testing.
Appearance of brittle fracture cracks. - Answer -Straight and non-branching. Cleavage.
Monitoring for brittle fracture? - Answer -Try to find pre-existing flaws
What is thermal fatigue? - Answer -Cracking caused by variations in temperature.
What materials are affected by thermal fatigue? - Answer -All materials
, How do you monitor thermal fatigue? (It's surface cracking) - Answer -VT, MT and PT.
External shear wave UT.
What is erosion? - Answer -Accelerated mechanical removal of surface material due to
the movement or impact between solids, liquids, vapour or a combination.
Erosion affected materials? - Answer -All metals, alloys and refractory.
Monitoring for erosion? - Answer -VT, UT or RT. Infrared scans on refractory.
What is mechanical fatigue? Are they below the YS of the material? - Answer -Cracking
due to cyclic stresses. Yes.
Affected materials by mechanical fatigue? - Answer -All alloys.
Monitoring of mechanical fatigue? - Answer -PT, MT and SWUT. VT can be used to
detect movements that could lead to cracking.
What is Atmospheric corrosion? - Answer -Corrosion from moisture in the air.
Affected materials by atmospheric corrosion? - Answer -Carbon steel, low alloy steels
and copper alloyed aluminium
Is atmospheric corrosion general or localised? - Answer -Both
What sort of rust occurs with atmospheric corrosion? - Answer -Red rust
Monitoring of atmospheric corrosion? - Answer -VT or UT
What is CUI? - Answer -Corrosion due to entrapment of water under insulation or
fireproofing.
Affected materials by CUI? - Answer -Carbon steel, low alloy steels, 300 series, duplex.
CUI temp range for CS? - Answer -10-350F
CUI temp range for Austenitic and duplex SS? - Answer -140-400F
Monitoring for CUI? - Answer -Strategic inspection plan considering operating temp,
type/age of coating, type/age of insulation.
What is cooling water corrosion? - Answer -General corrosion from cooling water due
to metals, salts, organic compounds or bacteria in the water.
Affected materials by cooling water corrosion? - Answer -Carbon steel, all grades of
SS, copper, aluminium, titanium and nickel based alloys
