Modular Procedural Automation Improves Operations

Using a Standard Automation Methodology Also Prevents Incidents by Allowing Operators to Share Best Practices

By A.N. Vennavelli, A.Y. Ogundeji

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The newly arrived operator needed to continue to start the isomerization unit and control two other units, all with virtually no input and assistance. Due to a malfunctioning liquid-level alarm, he had no idea whether he was starting with six feet or 175 feet of liquid in the bottom of the raffinate splitter tower. The truth proved to be closer to the latter, and the tower overflowed into the blow-down drum, and the hot gasoline then overflowed and ignited.

If the BP control room had used MPA, the following would have been possible:

  1. The newly arrived operator would have had on-screen information regarding all of the steps that the previous shifts had taken, including the exact times of those steps;
  2. A safety warning could have been provided on-screen regarding the overflowing of the raffinate splitter tower, which had already happened a few times in the past;
  3. Out-of-date procedures would have been updated for the sake of the programming of the new software; and
  4. The MPA software could have shut the unit down in time to avoid the explosion.

If MPA had been correctly implemented, the lone operator of the three units would not have been alone.

Sterigenics Oxidizer Accident

This accident was described in a CSB video (Reference 5) and in the associated report (Reference 6). This accident did not occur because an operator was alone, but because a standardized procedure was not obeyed, and the operators did not understand the ramifications of diverting from that procedure.

The Sterigenics plant was located in Ontario, Calif. This facility sterilized medical equipment in large chambers using ethylene oxide gas. Subsequent to sterilization, according to procedure, the ethylene oxide gas was purged from the chambers using a three-step process. On the day of the accident, one of those steps was purposely skipped. As a result, a concentrated ethylene oxide gas stream was sent to the oxidizer, and the chamber exploded.

If the Sterigenics control room had used MPA, the software could have provided a message to the operators along these lines: "If Step 2 is skipped, a concentrated ethylene oxide gas stream will flow to the oxidizer, and an explosion might result." Upon seeing this message, the operators may very well have taken corrective action.

With MPA, Operators Are Never Alone

Regardless of the reasons, the control rooms of the western world do not seem to be as well-manned as those of 20 or 40 years ago. To address this situation, MPA can be used to transfer the knowledge and experience of the best remaining operators, engineers and technicians to new operators. This makes new operators more effective and efficient. When MPA is correctly implemented, no operator needs to start, run or stop an operating unit alone.

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