Buell and Smedley (1) define Lean Manufacturing as "a systematic approach to identifying and eliminating waste
through continuous improvement”. Waste is further defined as “anything that adds no value to the manufacturing
process. Common sources of waste in manufacturing are identified (2) as:
· Overproduction – Producing product quantity in excess of requirement or demand.
· Inventory – Producing levels of end product or work in progress above the optimum.
· Waiting – Delays in the production process.
· Transportation – Transporting end product or work in progress unnecessarily.
· Motion – Unnecessary motion of workers, assets or materials associated with production.
· Processing – Redundant steps or activities in the production process.
Reducing the Cost of Preventive Maintenance
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· Defects – Producing defective products
The application of the term “Lean” to maintenance similarly aims to target waste. Bever (3) estimates that
between 18% and 30% of every dollar spent on maintenance is wasted. Greg Folts is reported (4) as observing
that maintenance operations may be wasting up to 25 percent of available labour and that up to 60 percent of
this waste results from activities that add no value to the performance of the plant.
Similar categories of waste identified for Lean Manufacturing can be applied to the exploration of Lean
Maintenance. Building on a list developed by O’Hanlon (3), seven categories of waste in maintenance are
summarised as follows:
· Overproduction - Performing preventive and predictive maintenance activities at intervals more often than
optimal
· Inventory – Overstocking maintenance spares with slow moving parts and secret inventories.
· Waiting - Waiting for tools, parts documentation, transportation, etc.
· Transportation – Time spent walking, running, driving, and flying associated with maintenance work
· Motion –PM performed that adds no value to the prevention of downtime.
· Processing– Opportunity to improve the quality of repairs in reactive or breakdown maintenance.
· Defects – Asset failure caused by under-maintaining assets or maintenance rework.
Waste in maintenance can be considered as a problem of strategy, planning and control. This paper is
specifically concerned with waste arising from strategic decision making. This particularly targets maintenance
waste associated with “overproduction”, “inventory” and “motion” from the above list. These three topics are
referred to specifically as over-maintaining.