Switching off a process plant and equipment to inspect and service it in accordance with safety requirements, then starting everything back up again is no simple matter. The good news is that with running times in today’s process plants having been considerably extended, shutdowns and turnarounds (TARs) are being performed less often than in the past. The bad news is that when a scheduled shutdown/turnaround does take place, more tasks must be carried out during the event than might have been required previously. Effective planning, clearly, is crucial.
Management usually is preoccupied with planning and preparing the downtime long before it is scheduled to occur. In fact, this stage of the undertaking, required by law, takes up considerably more time than the actual event. There is so much to consider, however—which poses so many opportunities for things to be underestimated or missed.
On top of the standard inspection, maintenance and repairs that are to be conducted during the shutdown and TAR, other value-enhancing projects may have to be carried out, including, for example, capacity expansion or the replacement of complete machine components. The scope and complexity have increased, too, because a TAR project usually combines multiple asset groups. The number of employees involved rises with the size of the plant and the number of separate projects that have to be completed in the shortest timeframe possible. Whereas a maximum of 600 might have been normal just a few years ago, nowadays, up to 1000 personnel may work on a TAR, including plant staff, contract firms and subcontractors.
With this comes a process that must incorporate a careful gate-keeping element. The rigor around gate-keeping is driven by a predetermined business process map that meets the requirements to deliver a world-class shutdown at the most optimal cost. The business map and timeline, along with gate-keeping of all the elements that need to be managed throughout the course of the TAR is critical to success.
High costs, but great savings potential
The costs incurred by a shutdown and turnaround are substantial. First of all, the plant owner or operator loses sizable sums through the plant downtime. The large number of personnel needed also swallows up significant sums. Each unscheduled hour of the shutdown increases the costs exponentially.
The challenge for management is to plan between 10 and 150,000 individual tasks with the optimum usage of all necessary resources such as personnel and equipment in a way that the duration of the shutdown can be kept to a minimum and resources can be used effectively to meet the requirements of the whole project. In individual cases, this can mean that particular resources are only used to 50% capacity. In the attempt to find a balance between resource costs and the entire task duration, planners frequently make the serious mistake of roughly basing the shutdown duration or costs on values from past shutdowns. In the case of smaller, easily manageable downtimes, this approach poses few problems. However, with more complex TAR projects, it usually results in targets not being reached. About half of all shutdown projects are delayed by more than 20%, about 80% of such endeavors go over budget by more than 10%. In some cases, the work scope increases unexpectedly by up to 50%.
Professional risk management vs. positive thinking
That the goals set by project management are frequently not fulfilled is not only the fault of the complexity of the project. It is due also to the fact that turnaround projects are characteristically subject to constantly changing conditions. The success of a TAR project is often dependent on unpredictable factors. Either employees find the equipment to be in a state that deviates from the original assumptions, or it becomes evident that the time and resource requirements for individual work processes were estimated inaccurately at the planning stage. These are just a few of the many risk factors which can cause well-intentioned plans to fail.
In order to overcome this particular challenge, planning and risk management must be as realistic as possible. Risk management can be understood as a formalized process to deal with risks that serve to identify and evaluate critical areas. Contrary to the attitude often popular to management following the motto “we’ll manage it somehow,” this new planning approach takes into account that the length of time needed to complete particular jobs cannot be precisely predicted in advance. That means expected risks are built in to the project plan with flexible dimensions (minimum and maximum resource usage/ requirements) and are calculated in terms of their impact.
The human factor
A further approach to an innovative planning management of TAR projects is the so-called critical chain. Expanding on well-known critical path methods for computing schedules, the concept of the critical chain focuses more closely on the human factor. In other words, this approach is based on the assumption that estimates and plans and their execution are carried out by people and not computers. Therefore, it is to be expected that when staff, for example, estimate the duration of jobs, they will always include a time buffer as a precaution. Generally, this type of buffer is used to the limit during implementation—even when no actual problems occur (Parkinson’s Law). Consequently, the possibility of ending a task earlier than scheduled is excluded from the outset in many projects. The common aim is to finish projects punctually and on time—not to finish them as early as possible or before the scheduled time.
Another pattern that is revealed in conventional planning is that of multi-tasking. For example, according to a plan, one work crew will be allocated to three different pieces of equipment over three consecutive days. Yet, because all three equipment groups already are experiencing difficulties in meeting the schedule, each of the three coordinators urgently demands their crews to do more than originally planned. The result is inefficient multi-tasking, with time being wasted as the teams readjust to each new activity. Furthermore, the possibility that at least one of the jobs could be finished earlier is also ruled out.
Many planners fail to adequately consider these demands because they operate merely in a static rather than a dynamic time and resource optimization mode. This is not only true for the advance planning of a TAR; in the execution phase, project leaders frequently neglect to dynamically recalculate the schedules that were created—with a lot of effort—through use of a project planning tool. Instead, rescheduling often takes place by hand on a drawing board.
The time-cost-tradeoff approach
A project plan with optimum costs and evenly allocated resources can be realized in two steps.
- First, the relation between time and costs must be optimized. In this initial step, the respective durations are set for each of the jobs and tasks and for the whole shutdown with the goal of keeping costs as low as possible.
- Second, a time-cost curve is applied to calculate and illustrate the combinations that, on the one hand, could lead to a reduction in the overall project duration, while on the other hand keep additional costs to a minimum. Building on this, the second step deals with resource allocation: the main aim is to link all required jobs in such a way that all resources involved are optimally utilized throughout the shutdown. This can be achieved by moving non-critical jobs to the end, i.e. jobs that do not have a designated start time and do not influence the completion of other tasks and thus the overall completion date.
The result is a critical path focusing on resources that takes the philosophy of the critical chain into account.
To ensure the project is completed on time and to reduce the risk of delays in specific processes, the precautionary time buffers normally built into each scheduled task duration are removed and bundled at the end of the chain. What does that actually mean time-wise? How long are the buffers that have been incorporated into each step of the project—and can they be removed?
The comparison of project plans and current data on completed turnarounds and shutdowns shows that a large part of the estimated duration can be seen as safety buffers. Such a buffer now serves the whole project and creates the needed flexibility, so jobs that are finished early or those that are delayed end up balancing each other out. In addition, this method ensures that built-in reserves are not wasted but rather are of benefit to the whole project cycle. An example of the TAR optimization process is shown in the accompanying sidebar. MT
Larry Olson is operations director for T.A. Cook Consultants Inc., headquartered in Raleigh, NC. Telephone: (919) 510-8142; e-mail: email@example.com
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