Short-term Overheating—Stress Rupture (Including Steam Blanketing).pptx

Short-term Overheating—Stress Rupture (Including Steam Blanketing).pptx

1. Short-term Overheating Stress Rupture (Including Steam Blanketing)

2. Description Localized overheating (very high T)  permanent deformation is occurred ( jadi dia low level stress)  bulging and then rupture. Even in less severe temp it will fail.

3. Affected Material All fired heater tube and boiler tube materials and common materials of construction

4. Critical Factor Primary Factor: Temperature Time Stress Local heating (above the design temperature)  Flame impingement, Steam blanketing (DNB) If, T is constant, higher the stress/ pressure, failure will occur If, T is high, lower stress, failure will occur Loss in thickness, can create this failure.

5. Affected Unit or Equipment All fired heater tubes are susceptible. Heaters with coking tendencies (crude, vacuum, heavy oi, hydroprocessing , and coker units)  will low the outlet temp Steam-generating units (fired boilers, waste heat exchangers, steam generators)  sulfur plants, catalytic reformers, hydrogen reformers, and FCC units. In superheaters and reheaters during start-up when condensate blocks steam flow. Hydroprocessing reactors due to inadequate hydrogen quench or flow maldistribution. Catalytic reforming reactors due to coking of the catalyst Refractory lined equipment (FCC unit, sulfur plant, H2 manufacturing plant, and other units) due to refractory damage and/or excessive firing Heater fireboxes due to loss of protective refractory or insulation.

6. Damage Morphology Localized deformation/ bulging (3 % to 10 % diameter) Tube ruptures  “ fishmouth ” failure + “thin, knife edged Microstructure will show severe elongation of the grains at the fracture surface due to the plastic deformation that occurs.

7. Mitigation Minimizing temperature excursions ( meminimalisir perubahan suhu ) Proper burner maintenance and its management Fouling/deposit control to minimize hot spots + localized overheating (localized overheating) in fired heaters and boilers. Produce a more diffuse flame pattern (burner in heater). Proper BFW treatment (conditions that can lead to restricted flow in boilers). Bed thermocouples in reactors will help minimize the likelihood of hot spots. Maintain the refractory

8. Inspection and Monitoring Monitor short-term overheating VT (bulging, sagging, and other types of deformation)  limited to that which is within line-of-sight, and not all damage is visually apparent Infrared thermography monitoring (limited to line-of-sight locations) Thermocouples  can not find hot spot VT for refractory Metallography (FMR)  creep void formation VT using a boroscope to inspect tube internals