With frequent linestops, however, a pre-tested spare pump is substituted each time for the pump that will be overhauled. In turn, the actual reconditioning is completed external of shutdown time. Therefore, only the removing and replacing time is required for the twelve pumps annually, reducing the overall shutdown time for these pumps from 16 hours to 6 hours. Moving work items from internal to external is a quick changeover methodology for maintenance. See section 8.3. 

A review of the shutdown tasks revealed that a good portion of the work was periodic maintenance jobs of 6 hours or less, and numerous jobs were similar to the pump example above. This work was well defined and had a high probability of starting back up without problems.

A linestop strategy not only exploits the key mechanics work time, it also reduces the total annual internal shutdown work hours. In this case it was estimated about 15 percent of the internal work was reduced. This means about 15 percent of 16,000 work hours or 2,400 shutdown work hours was moved to external (non-shutdown time) work to be accomplished by key mechanics between linestops.

If nearly all PM type work was accomplished on maintenance linestops, then the shutdown work plan could focus all resources on the project and major overhaul maintenance items, increasing overall effectiveness.