FTCFCCU 火炬分液罐出口管控制阀实际关闭而控制系统指示开→20 吨烃溢流释放并爆炸（另有多起次生火）
控制阀实际关闭而控制系统的指示为开；仪表/设备维护不足；改造未做后果评估；控制室人机界面缺陷
The mechanism code FTC shown on this card is the KB's internal damage-mechanism abbreviation (not an ISO 14224 code); it describes how the equipment failed. The 'ISO 14224 Mapping' block above maps it to the correct ISO functional failure code (which describes what the equipment failed to do) — these are two distinct dimensions in ISO 14224. The mechanism follows the narrative in the card body.
fmValve-seat Surface Damage -> Internal Leak fm_2Valve-plug Erosion fm_3Valve Stem Sticking / Bending fm_4Packing Wear -> External Leak fm_5Diaphragm Rupture fm_6Spring Fatigue / Fracture fm_7I/P Converter Failure i_pFeedback Link Loosening fm_8Coil Burnout fm_9Valve Plug Sticking -> Failure to Actuate fm_10Contact Corrosion / Poor Contact fm_11Filter-element Blockage -> Insufficient Supply fm_12Pressure-Relief Valve Set-point Drift fm_13