by John Swaren
| September 25, 2014
A current consulting client has expressed interest in modeling scheduled overhauls, above and beyond scheduled maintenance. The latter is well-addressed by TruePlanning. Our challenge is to utilize the model and its calculated lifecycle metrics to estimate the former as well. We have recently developed an approach to address this specific need that I’d like to share with you here.
Terminology is important to level-set. Notwithstanding replacement procurement, restoring equipment readiness via operations & maintenance activities usually falls into one of three funded categories:
Scheduled Overhauls are typically characterized by the second category above, with no development or production procurements (as is the case for the first category as well). The modeling approach that we developed internally is basically a five step process, whether for overhaul at Depot or at Contractor, (given definition #2 above). I’ve written a detailed step-by-step article for our next newsletter, with screenshots and instructions on use of lifecycle inputs, for modeling both overhaul cases. For now, this blog will give you a simple overview of utility.
In the case of Overhaul at the Depot level, we utilize Maintenance Concept (9):Replace part at Depot.Essentially, unit-level lifecycle inputs are applied in an overhaul model to represent an LRU equipment with five equivalent repairs. The approach is to scale both unit mean time to repair and part production cost to capture labor/material costs of these equivalent repairs at the Depot level. Typically, overhauls are based on peace-time inspections after a prescribed mileage or “programmed” hour interval, notwithstanding those overhaul candidates nominated say after war-time operations.
In the case of Overhaul at the Contractor, we utilize “Maintenance Concept” at (19):Repair/ Replace part at Contractor.In this scenario, we again scale part costs by equivalent repairs to estimate LRU-equipment material, as above. However for labor, since there is no equivalent input for time to repair at contractor, a scaled cost is applied. Specifically, (and unlike in the above depot overhaul), the contractor unit repair cost is scaled to account for the portion of effort specific to LRU replacement.
Overall, we apply this five-step technique to each overhauled LRU-level equipment. For example, for a vehicle’s drivetrain, the motor and transmission would be modeled separately. If their subsystems are estimated at a lower module level (say piston, versus block, versus crankshaft), then in step two above, add their individual part production and unit mean times from step one. In other words, do overhaul modeling at the equipment level only, as that is how the LRU system will be initially broken down once at the depot level. For best results (as always) consult with your SME on the level commensurate with their operations and funding categories.
We are continuing to investigate this approach for overhaul estimation, using customer data to validate and refine. If anyone would like to utilize their data and needs further mentoring support here, we’d be happy to support you!
 Government Accounting Office, GAO Report 12-133, Warfighter Support, May 2012, pg.5