Online Anomaly Detection System

Clogged pipe to flowmeter for gas compressor discharge causes low flow indication, activating process interlock

The operator thought that small changes in the flow reading were within the range of normal disturbances, and decided to wait and see. This resulted in a sudden flow decrease.
When this case was inspected by BiG EYES, it noted high expected values right after the flow reading started to change due to nozzle clogging. The system detected this anomaly at 3:30—five hours before the operator determined the situation to be abnormal at approximately 8:30.

Case studies1

Failure of inner valve of a control valve for reboiler steam supply disrupts process, causing loss of control

The loop in question had a cascade control structure, with a pressure control loop for steam supply pressure as the primary, and the flow control loop as the secondary. The defective control valve had been used for a few decades, and mechanical damage caused the plug to fall inside along with the stem. The operator responded to changes in pressure at approximately 8:00, but the control valve became inoperable immediately afterward.

According to the BiG EYES evaluation, the control output had been rising from approximately 5:30. BiG EYES detected a warning sign at approximately 6:00, when actual control output values exceeded 50, which was significantly above the estimated limit. Additionally, the system detected sporadic occurrences of high expected values from the previous week and produced a visualization showing that this breakdown had been progressing for a few weeks. BiG EYES successfully detected warning signs that were almost unnoticeable to human senses and to the control system alarm functions.

Case studies2


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