Analysis of the emergency shutdown incident of Furnace No. 1 in the midnight shift on December 14
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Analysis of the Emergency Shutdown Incident of Furnace No. 1 #Ende on the Midnight Shift on December 14th1. Incident Overview: At 3:40 am on December 14, 2010, during the midnight shift, the assistant operator noticed a gradual drop in the pressure of the instrument air and promptly informed the shift supervisor. The supervisor assumed it was a fault in the instrument system and instructed the assistant operator to alert the fan operator while he rushed to the air compressor room to activate the backup air supply system. However, due to the rapid decline in instrument air pressure, and with no proper air supply from the backup unit, the pneumatic shut-off valve of Furnace No. 1 automatically closed, resulting in an emergency shutdown of this furnace. In Furnace No. 2, since the pneumatic valve had just started to operate and the instrument air pressure began to rise, there was no emergency shutdown.
2. Cause Analysis: A fault in the instrument air system was the main cause of this shutdown incident. Furnace No. 1 had a lower air flow rate compared to Furnace No. 2; hence, it was forced to shut down. Furnace No. 2 had a slightly higher air flow rate, so even after some of the valves closed, there wasn’t enough backflow to cause a shutdown. Upon inspection of the instrument air system, it was found that the diaphragm seals of the pneumatic valves in the instrument air drying tower had aged and lost their sealing ability, which prevented the valves from functioning properly and led to a disruption in the supply of instrument air.
3. Lessons Learned: Instrument air serves as the power source for pneumatic valves. When there is a fault in the instrument air system, the valves usually stop functioning within 1 minute. This highlights the need to strengthen backup systems and maintenance efforts in future operations, to reduce downtime, and to have a better understanding of the performance of equipment and its vulnerable components, so as to ensure that the equipment remains operational and reliable at all times.
If unfortunately both furnaces stop and the instrument air still does not reach the required pressure, how should one proceed with the subsequent tasks? Public utility systems such as instrument air have a significant impact on production that cannot be ignored.
Instrumentation personnel inspect the compressed air pipelines and related pneumatic valves, while maintenance personnel check equipment such as air compressors. The converter operator conducts a pre-startup inspection of the stopped furnace to ensure it is ready for operation at any time. Once the air to be compressed is normal, start the furnace immediately.