After creating the schedule, you should plot it out for review. Gantt chart (bar chart) plots of the complete schedule allow you to see the big picture and analyze the schedule for refinements.

Critical Path Refinements

One of the first things you may want to do is to verify that the critical path ends at or near the desired turnaround completion date (expected or dictated by management). Is the overall duration reasonable, defensible? Or is it different from the expected/mandated? If so, why? Review the entire sequence of activities to ensure sound logic. Review the time estimates, in particular the large ones. If you need to trim back time, have every supervisor involved review, revise or agree with every change needed to improve the schedule. Never make any duration changes on your own without the field supervisor's approval, this could cause big problems if the schedule is rejected or ignored and the blame for an extension falls upon you for not getting their input!

Include in your review and analysis all near-critical work as well. Some of it could become critical at any time. Just like the critical path review, request input from the supervisors.

For these initial scheduling reviews, it is advisable to only plot a bar chart limiting the float (slack) to a shift or two (8-24 hours). After the critical path has been reviewed, revised, and agreed upon, then you will be ready to check the rest of the schedule.

Interference Studies

Filter the schedule to display all heavy lifts, so that they stand out. Are all lifts properly sequenced or are many scheduled to take place during the same shift? If too many lifts are scheduled for a shift, you could delay less important work (which has a larger float/slack value), so that the crane may used more efficiently, and the total time span for crane rental can be better managed.

When scheduling several lifts in different locations or at different heights, you need to determine if it is necessary to re-rig the boom, or move the crane, as this requires time and reduces the effective utilization of the crane. If a few heavy lifts are scheduled early and there is a gap or waiting period until more lifts are scheduled, then you might want to delay the initial lifts (float/slack permitting) to eliminate paying for idle crane rental time.

Some considerations to evaluate for specific equipment types include:

• Towers - Tower work should be scheduled to start immediately after the unit/plant is shut down. Check to see how many crews can be working inside, and if the timing looks workable. Segregate the activities at every level where crews are working, to group the work logically. In other words, organize your tower work in sections according to how the work should flow.
• Heat Exchangers - Use a plot plan or unit equipment layout to verify that the bundle pulling sequence is not causing interference with other work in the immediate vicinity, or vice-versa. The schedule should not allow a bottleneck of cherry picker activity to happen.
• Air Coolers - Check that air cooler work is scheduled after all major work underneath is done, to avoid having water washing interrupt more important work. If you have a gap between shifts, you can schedule this work at that time to prevent this problem from happening.
• Pumps - Pump work should ideally be started after heat exchangers have been unheaded and bundles pulled, if they are in their immediate vicinity. Pumps are frequently located in a bay under pipe racks. This work is seldom critical or high priority.
• Control and Safety Valves - Control valves and safety valves should be scheduled for early removal. Reinstallation is usually not critical, but they need to be sent to the shop early in case there are some requiring major repairs.
• Piping - Generally, piping and valve work can be scheduled at any time after all blinding is complete. Piping work involved with tie-ins has priority. There may some piping work that involves equipment; in this case you must coordinate to make sure you have good timing to correspond with the equipment work, testing, inspection, insulation, etc. Tie-ins are usually scheduled during a short time period when all utilities (steam, water, air) are down. Any utility outages should be scheduled after all preparatory work is complete and ready, to avoid delays.
• Electrical - Electrical work can be scheduled at any time except where certain equipment is de-energized for a short time within the turnaround span. This schedule is dictated by the electrical department.
• Instrumentation - Instrument work can likewise be generally scheduled at any time, with the exception of instrument control panel replacement/rework. Be sure to include operator training in you activities if the control panel is changed.

Day/Night Work Activities

Some activities, such as heavy crane lifts, must be scheduled for the day shift only. This is due to safety considerations, as good visibility (illumination) is required. Ask supervisors to identify all day-only work.

The same applies for night-only activities, such as air cooler washing, x-rays, hydroblasting or grit blasting, etc.

Revise / Update the Schedule

Mark any schedule changes on the plotted bar chart schedule, showing all logic modifications, additions or deletions, day/night shift changes, etc. Then make the changes in your project management software and reprint the bar charts. It could take two, three or more reviews and editing sessions to produce the final, workable turnaround schedule.

Preliminary Schedule Studies

Often it becomes necessary to prepare a schedule in order to determine the total duration of the turnaround, even if not all work orders scopes have been defined. The main objective is to determine the critical path, and near-critical activities.

This can be done as long as the most important work orders have been scoped out, which consist of the greatest amount of work for major equipment.

The best way to accomplish this is to first review the work order scopes suspected or expected to be involved in the critical (and near critical) path(s), to ensure their completeness and reasonable time estimates.

After these work order scopes have been reviewed, inactivate (or filter out) all other work orders on file. Keep active only the ones that have a high probability of being the critical path. Then, create a schedule with only these few work orders, and plot the schedule out for review and comments. Incorporate any logic changes as necessary, and re-plot the schedule. You will need it for the final scheduling effort.

You should continue developing the additional work order scopes until the entire turnaround work scope has been defined. After all work order scopes have been reviewed you will be ready to prepare your final schedule by merging the remaining scope with the existing schedule.