New Zealand Engineering 1999 March

Energy

Plant maintenance is becoming increasingly sophisticated as techniques for optimising when and precisely what maintenance work is done in a plant are being adopted. Achieving improved levels of equipment reliability or availability while reducing costs is a key objective for a maintenance group.

Achieving cost effective plant shutdown is an integral part of the focus on reducing routine maintenance costs. This article discusses how dedicated shutdown planning can be used to provide worthwhile savings in overall maintenance costs.

For a continuous process plant, maintenance shutdown costs can represent up to 40 percent of the annual maintenance budget. This should imply that preparing for a shutdown warrants comprehensive planning, preparatory work and briefing of personnel to ensure the shutdown is well organised. However, this preparation is often the responsibility of the plant maintenance group whose first priority is to maintain the plant on a day to day basis rather than perform longer term planning work for shutdowns.

This article discusses the approach taken by companies Beca has worked with to prepare their shutdowns - to an accepted schedule and budget. The company is currently providing scheduling advice for a major shutdown at a NZ refining company and a large equipment replacement project for Methanex NZ Ltd.

What is shutdown planning

I have heard many times that: "Developing the plan is a cost to the shutdown; management say we have to do it but after the first day of the shutdown the plan goes out the window because of the changes and problems that arise. Besides, the planner develops his own schedule and then tries to tell us how he thinks we should do our work!"

The shutdown plan must be used as a tool to aid the preparation and execution of the work. From our experience we have concluded that the key shutdown planning activities should be:

• Early identification, review and approval of the worklist. (A cut off date for jobs to be added to the worklist is recommended.)

• Eliminating non-shutdown work from the worklist. (It is usually less costly to do outside the shutdown).

• Ensuring the supervisor decides how he will do the work. The planner then reflects the supervisor’s requirements in the plan, creating commitment.

• Breaking the plan down into packages of work to be handled by each supervisor and then having the supervisor check that each crew can progress logically and efficiently through their work.

• Identifying the interfaces with other groups and ensuring there are no loose ends where an important service isn’t planned, causing delay. We do not advocate that routine functions such as transport or cleaning be scheduled. It is important to keep the schedule simple by excluding such detail.

• Developing an overall programme for the shutdown. It is vital that clear targets for the completion of various stages be set and a "picture" or schedule for the overall shutdown be created.

• Recording and tracking the work that must be done prior to the shutdown.

• Levelling of Important Resources: this is a key to optimising the number of people and types of equipment required. This has the added advantage that the quantity and duration of these resources is specified and avoids any expectation that they will be required on site for the total duration of the shutdown, eg. large cranes.

• Creating an historical record of the shutdown that can be used as the basis for the planning of subsequent shutdowns. An important step after the shutdown is to hold a constructive debrief so that the lessons learned can be recorded and incorporated in the plans for the next shutdown.

The PC based scheduling software commonly used today offers features which simplify the processing of information related to the shutdown. Through a task coding structure it is possible to use the software to track the shutdown expenditure on labour and hired equipment against the budget and provide a variety of reports. The cost of materials allocated to jobs can also be included to enable specific costs on a job by job basis to be reported.

There are secondary benefits to preparing a shutdown plan such as:

- Discussion between supervisor(s) and planner results in more thorough understanding and preparation of the work

- Greater awareness to provide float or slack time on jobs and build in an overall contingency.

Features of the planning system

The figure (click here to see figure) outlines the main elements of a planning system which BCHF has found to be appropriate for shutdown projects in the course of our work for petrochemical/heavy industry clients in New Zealand and Indonesia.

The Main Schedule is the "picture" of all the work scheduled which we recommend is plotted on A1 size sheets and prominently displayed.

During the shutdown the supervisor is required to "colour in" (using a different pen for each day) the schedule showing his progress so that the shutdown manager can see at a glance any variances to the plan. Another positive effect of the schedule being displayed is competition between the workgroups.

The schedule will be revised each day with the daily updates of progress so that the shutdown manager can assess the effect on completion date and resources due to changes in the scope and/or time available to do the work. Unless something unforeseen causes a major change in the workscope, we do not advocate repeated changes to the printed schedule to be issued during the shutdown. This will alter each work group’s completion targets and could lead to confusion.

The nature of maintenance shutdown work is that many of the tasks can be done in parallel and, while a critical path will exist, there is often little benefit to focus on this. If necessary, labour can usually be reallocated to work on a particular job requiring attention for a short period without compromising the overall schedule.

The Summary Level Schedule is prepared when there is a requirement to report to senior management who may not be directly involved with the shutdown. The planned v actual progress and forecast completion date must be presented in this report.

The Resource Histogram and S Curve provides another means of presenting the resources used on the shutdown. A second S Curve can be used if it is required to present work achieved (earned work) against manhours expended as a measure of effectiveness of the work being done. The S curve is the best indicator of overall variances to the schedule and resource budget.

The Look Ahead Chart will be issued to each supervisor so that it is clear what jobs he must prepare for in detail to achieve good utilisation of his work group. We advocate that this preparation during the shutdown is performed at least a shift in advance.

Work Lists are used when the jobs for certain tasks are sequential and can be performed within the team. The use of work lists has two main advantages:

- The list is specific to a job and may contain other information (spare parts, special tools, previous problems etc)

- The list reduces the level of detail carried in the main schedule.

Time Sheets/Progress Assessment

Time sheets can be used, but we have found, particularly on large jobs, that the information obtained becomes unnecessarily detailed and cumbersome to manage. Automated transfer of timesheet data and material costs into the scheduling system is possible although not necessary to create an overview of what is happening in the shutdown.

It is, however, essential that the planner receives daily updates of progress from the supervisors and then updates the schedule.

This information gathering should be structured so that the process is simple and efficient.

The realistic assessment of progress is vital. According to Beca senior planner, Ray Flint, people usually overestimate how far through the job they actually are. It is recommended to forecast time to complete than assess the percentage complete for each task.

The available budget for the shutdown work should force a critical analysis of the worklist once it is frozen. Jobs will have differing priorities, therefore it should be possible to either defer or assign lowest priority jobs to a contingency worklist, to be done if the shutdown schedule and budget permits.

With thorough preparation plant shutdowns needn’t be times when uncertainty prevails and there is difficulty in predicting a total cost and completion date for the work. A shutdown planner, working closely with those in charge of the work can develop a schedule which becomes an effective tool for the control of expensive resources.

Shutdown planning is another technique not to be overlooked in the drive to further reduce plant maintenance costs.

Roger Foy is industrial group principal, Beca Carter Hollings & Ferner Ltd