Tame Your Transient Operations

Use a special method to identify and address potential hazards.

By Scott W. Ostrowski and Kelly K. Keim, ExxonMobil Chemical Company

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Unit startup, shutdown, emergency operator intervention and other transient activities often involve flaring, thermal oxidizers, scrubbing systems, generation of more or different waste streams, etc. As a result, part-time support from an environmental engineer will provide value and typically is justified.

Pre-selection of unit activities and related procedures. The leader, operations representative(s), and process design/technology representative should conduct a first-pass screening of all required unit activities and related procedures to identify those that meet the criterion of a "higher risk" transient operation. This will streamline subsequent review and ensure consistent application of the HAZOP technique.

Assembly of reference documentation. The team must have access to the same information that's required for a traditional HAZOP study, including: material safety data sheets (MSDSs), simplified flow diagrams, detailed MFDs or P&IDs, electrical area classification drawings, pipe specifications, facilities siting studies, unit operations, maintenance, and emergency procedures, reports of incidents that occurred on the unit, and a list of employee concerns.

Solicit comments and concerns from employees and affected contractors — involve the first line supervisor and other line management in the communication process. Focus on potential loss of containment and human factors issues. Place special emphasis on the experience of operators during abnormal and non-routine operation but consider all concerns during the HAZOP process.

Final selection of unit activities and related procedures for review. This is the full team's responsibility. During its initial meeting provide a "HAZOP Kick-off Summary" to introduce the team to the TOH's purpose, scope and methodology. After the kick-off, the entire team should look over all incident report summaries assembled for the unit under review. Focus on process safety and environmental incidents and near misses. Review in detail reports on incidents that involve transient operations with an actual or potential release of hazardous materials to identify operations to include in the scope of the review. Next, the team should assess all identified employee concerns, to determine operations and related procedures with which employees may have issues. Carefully consider this information when selecting the operations and tasks to include in the scope of the review. Finally, the team leader and process design/technology representative should inquire about higher-risk unit activities and practices that may not be documented. Capture findings where procedures or adequate procedural controls aren't in place on the HAZOP worksheet as follow-up items and risk-assess them, with potential improvements documented for consideration.

The entire team should review the first-pass screening of all documented unit activities and related procedures to be included in the study. Team discussions then can lead to adding or removing items from the list.

Conducting procedural review. The leader should orient team members lacking training in the TOH approach. Often this means explaining the guide word sheets and discussing examples (see Table 1). Review each guide word and corresponding explanations. Typically this activity requires about 30 minutes. The 20 guide words serve as memory joggers to bring out the knowledge and experience of the team. The TOH methodology uses this knowledge and experience as well as documented procedures to guide the team through the unit and facilitate identification of hazards.

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