REG NASA-LLIS-0211-1993 Lessons Learned - Fluidized Bed Furnace.pdf

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1、Lessons Learned Entry: 0211Lesson Info:a71 Lesson Number: 0211a71 Lesson Date: 1993-06-14a71 Submitting Organization: LERCa71 Submitted by: S. PapellSubject: Fluidized Bed Furnace Description of Driving Event: The furnace involved was a procedyne high temperature fluidbed furnace with an 1850 degree

2、s F maximum operating temperature. The furnace medium consisted of 1000 lbs of an alumina sand and was set to idle at 1200 F overnight. During the run fluidized media was found to be spewing out of the furnace and running down a wall in the furnace room. During the following investigation the alumin

3、a sand showed signs of sintering that suggests overheating conditions in the range of 2000 to 2200 F.Cause of the overheating was found to be the main electrical contactor that had welded shut on 2 of the 3 legs allowing an uninterrupted supply of power to the furnace heater. Further investigation d

4、etermined that a contributing factor to the mishap was the condition of the retort wall that contained a brittle fracture appearance and evidence of a stress failure rather than a thermal failure at meltdown.The retort failed as a result of the increased thermal stress, due to the continued power su

5、pply from the stuck electrical contact, and the inherent mechanical defects in the retort wall that was not able to withstand the 2200 F temperature.Lesson(s) Learned: Electrical contactors on heater circuits can fuse shut unless a proper back-up design is incorporated.Recommendation(s): Install an

6、independent over-temperature control system using solid state electrical switch gear instead of a mechanical contact system.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson:

7、N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Industrial OperationsAdditional Info: Approval Info: a71 Approval Date: 1994-04-19a71 Approval Name: Maria Havenhilla71 Approval Organization: LERC/EBASa71 Approval Phone Number: 216-977-1483Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-