Labor Hours
How is Maintenance Ratio (MR) calculated using labor hours?
MR = (Cumulative Direct Maintenance Labor Hours Expended) / (Cumulative Life Units Operating) during the same period.
What is the formula for Backlog in 'crew-weeks'?
Backlog (crew-weeks) = (Total Labor Hours on Backlog) / (Average Weekly Labor Hours Available per Work Crew).
How do labor hours feed into MTTR (Mean Time To Repair)?
MTTR = (Total Downtime Time) / (Number of Failures); while MTTR is time, Labor Hours provide the resource cost component to calculate the financial impact of that downtime.
What distinguishes Mean Preventive Maintenance Time from Mean Active Maintenance Time?
Both are expressed in labor hours per action; the former applies to scheduled tasks, while the latter applies to corrective (unplanned) repairs.
In CMMS and reliability engineering, Labor Hours represent the total time (estimated or actual) required by specific crafts to complete maintenance work orders, serving as the primary unit for quantifying workload, backlog, and resource capacity.
On the shop floor, labor hours are entered into work orders to track Actual Labor Hours versus Estimated Labor Hours, enabling the calculation of the Estimating Index (accuracy of planning) and determining if the maintenance department is keeping up with work generation rates. This data helps manage resource allocation, schedule tasks, and assess maintenance efficiency.
Underestimating Work Scope: Planners frequently assign insufficient estimated labor hours to tasks, leading to schedule slippage, rushed repairs, and increased safety risks due to technicians working against unrealistic deadlines.
Ignoring Contractor Hours: Failing to distinguish between internal and contractor labor hours in total maintenance burden metrics masks the true cost of asset reliability and can lead to over-reliance on external vendors instead of building internal capability.
Reactive Labor Dominance: A high percentage of labor hours spent on unplanned reactive maintenance versus planned preventive/predictive tasks indicates a failure in reliability strategy, leading to higher total cost of ownership and reduced asset availability.