Direct impact on STO cost and schedule. With STO preparations often starting 1-2 years prior to the planned execution, the STO parameters used for determining the scope are only estimates, constantly changing and extremely volatile. During STO execution, as equipment is inspected, scope uncertainty becomes known and STO execution inevitably encounters scope growth. Decisions for inclusion or rejection of discovery scope are impacted by STO constraints – such as labor, materials, plant, schedule and budget – and the long-term effect on the facility and future maintenance program. This requires the STO management team to make rapid and informed decisions and understand the holistic impact, in order to maintain STO success and the long-term integrity and performance of their facility.

There is a strong correlation between STO cost and the STO scope, schedule and quality. But since cost estimating requires complete and holistic data, cost estimates are often uncertain and unfortunately only realized too late. Furthermore, the calculation and allocation of cost contingencies is a very important factor to determine accurate total STO cost. Such contingencies should be derived from risk analysis and allocated at the activity or work order level, rather than being a singular value calculated as a factor of the total known expenditure. 

STO schedules are reliant on scope, constrained by resources, and can have a major impact on quality and cost. Since units are down and not producing products/revenue during an STO, quality schedules are essential to ensure minimum downtime. But STO schedules are highly complex and volatile, because of the sheer magnitude of data involved and the constant changes that require continuous reworking of the schedule and execution plan.

Quality has a major impact on STO scope and cost. Poor work quality typically requires rework, which in turn increases the scope of the STO and impacts the total cost. And if poor quality is not identified and corrected, it can have much more significant consequences, causing unpredicted downtime or worse.

EHS can have a major impact on STO cost and schedule. While the protection of personnel, equipment and the environment should always be the primary focus, as extreme VUCA environments STOs pose enormous challenges. At best, an EHS incident will shut down an STO, directly impacting the STO schedule and cost; at worst, it can result in death, damage or irreversible destruction, and involve associated penalties and ongoing reputational damage. Very similar to poor quality, poor EHS is typically the result of a poor schedule and/or inadequate resources, lack of sufficient supervision or adherence to work procedures.