Phases of a Shutdown, Turnaround, or Outage (STOs)


STOs have six main phases spanning scope selection through evaluation

Last week, we covered the basics around Shutdowns, Turnarounds, and Outages.

Beyond their financial implications, STOs with proper management and execution create safer operations, reduce environmental risk, and improve relationships with upstream & downstream partners.


So, what happens in an STO?


STOs generally break down into six phases: Scoping, Preparation, Shutdown, Execution, Startup & Commissioning, Post-Evaluation.


While each company may have its own terminology for describing the phases of an STO, they are similar at a fundamental level.


These phases are described in detail below.


Scoping: A dedicated STO team, led by a facilitator, will begin meeting with key stakeholders to identify potential STO scope. The STO team will evaluate the proposed scope against the scope qualification criteria for its given justification category. This vetting process minimizes costly discretionary work and achieves run lengths without unplanned shutdowns. For example, an STO team may immediately allow proposed scope that is considered mandatory for environmental compliance; while scrutinizing financially-driven proposed scope for not achieving a target return on investment. At the end of this phase (usually 8-18 months before STO execution), the scope is “frozen” and requires higher authorization levels for scope changes.

Turnaround engineering & operations activities
TAR Activity List | TenSix Consulting Demo of Primavera

Preparation: The preparation phase transforms each piece of defined scope into a detailed, meticulous work list plan, totaling thousands or hundreds of thousands of steps involving multiple crafts and contractors. Preparation is often the lengthiest part of the process and includes an integral set of activities spanning engineering, material ordering, material

staging, work package preparation (ex: walking down a job, gathering electronic and paper documentation together for each task), work and manpower schedules, hiring and onboarding contractors, cost estimations, and performing any STO pre-work.



Shutdown: The goal of the shutdown phase is to safely isolate and clean any equipment involved in the upcoming STO execution. Shutdowns represent one of the largest shifts in process pressure, temperature, and flow. These circumstances create higher chances of personnel and process safety risks. Among other process safety precautions, shutdown procedures manage the heightened risk present during the shutdown’s abnormal operation. The shutdown procedure guides operations and their supporting crafts during this phase.


Shutdown support engineers
Shutdown support as workers enter a tower | North Gas Company

Execution: This is where the fun begins! During this period, the process has been shutdown and with every passing second, the plant is losing more money. Maintenance and supporting personnel are working 24/7. The relatively small STO area is frenetic with loads of people, large equipment, and activity. Equipment is opened, inspected, repaired, and closed up,

hopefully aligning closely with the plan.

While inspection occurs, unexpected issues

inevitably arise. This discovery work is then evaluated for its inclusion in the work plan. The STO plan is constantly updated with job progress and justified discovery work every 12 hours at minimum. STO teams are monitoring performance metrics such as costs, manhours, productivity.


Startup & Commissioning: The goal of the startup phase is to bring the equipment online and back to normal operation with the help of startup procedures. Similar to shutdowns, this is a high-risk set of activities. After equipment maintenance is complete, the equipment is bottled up and, where required, inert gas displaces oxygen to prevent the ignition of combustible material. Crews will test equipment and instrumentation for readiness. Finally, process feed is allowed into the equipment and the pressure, temperature, and flow is worked back to normal operation.


Post-Evaluation: To create the STO plan, the team utilizes certain factors based on industry benchmarking and previous STO performance. After each STO, these factors are reviewed again. These factors and any lessons learned are used to adjust future STO assumptions and actions.


STOs are a critical part of an asset’s life cycle. Proper management of STOs can lead to safer operations, reduced environmental risk, significant cost savings, and better relationships with upstream and downstream partners.

Stay tuned for more next week as we dive into methods for managing scope in these critical events!