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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A Different Focus
The Transient Operation Procedural Focused HAZOP (or Transient Operation HAZOP for short) differs from a conventional HAZOP. It focuses on operational tasks and procedural controls, which are believed to yield greater returns, specifically in the third or later cycle of a more traditionally focused HAZOP.

The Transient Operation HAZOP (TOH) process centers on identification of required unit-specific activities (tasks) with a potential for an acute loss of containment and an in-depth review of the procedural controls necessary for safe and successful completion of those tasks. Timely identification of hazards, adequacy of procedural and design controls to ensure correct sequencing, early feedback of potential errors, clarity and completeness of transient operations all are carefully assessed. The technique uses a combination of knowledge and experience of a cross-functional team, guide words and reference lists to drive a disciplined approach to identify and suggest enhancements for procedural and design-related issues.

The TOH process offers manufacturing sites a number of potential benefits:
• an in-depth fresh look at "higher risk" transient operations requiring human intervention where procedural controls are used to manage residual risk;
• more-complete and easier-to-follow procedures where procedural controls are key to safe operations during the transient condition/phase or state of the process;
• increased operator awareness of hazards, design controls and potential consequences of not understanding the operation and procedural controls of a transient condition;
• greater consistency in procedural controls as well as potential identification of needed additional design controls for transient process conditions; and
• experience in applying procedural controls that can be applied beyond transient operations.
The TOH approach can provide stand-alone analysis prior to a planned transient operation. It also can be used in conjunction with a traditional HAZOP based on mechanical flow diagrams (MFDs) or piping and instrumentation diagrams (P&IDs). Finally, it can support revalidation of an MFD- or P&ID-based HAZOP/PHA for units needing revalidation.

The Approach
The TOH method involves several distinct steps.

Team formation. The team's composition and experience requirements are the same as for an MFD- or P&ID-based HAZOP with the following exceptions:

The leader should be trained in the TOH process and should have participated in a TOH run by a qualified leader. This person is responsible for facilitating the work process and producing the final report.

The operations (process) representative(s) should be qualified in both field and control console operations, and be intimately familiar with the tasks being reviewed — particularly how they actually are completed in the field. While one person with adequate experience in both areas would suffice, having a second operations representative (preferably from a different shift) likely will add substantial depth and breadth. We recommend having two operations representatives. The operations representative(s) walks the team through the details of transient operations under review and may be assigned to capture "redlined" changes to procedures.

The process design/technology representative must know the type of process and equipment being studied as well as the company's design standards and practices. This helps in communicating design intent of the equipment. The process design/technology representative is responsible for following the operation under review on the MFDs or P&IDs.

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