Back-Fit RCM User Guide

1. Introduction

Back-Fit RCM is a methodology to validate existing system maintenance requirements captured over its operational life. It forms part of a continuous improvement process that ensures any changes made to maintenance requirements are effective and fundamentally sound. The Back-Fit RCM analysis validates existing maintenance tasks by using the latest operational and maintenance information and adjusting task intervals and content where appropriate — this increases the effectiveness of the current maintenance program.

The Back-Fit RCM methodology is developed to validate existing maintenance requirements by using defect reporting, operational experience, partitioning, identification, and analysis of the system. The methodology determines if degradation failure modes are prevalent in the system, i.e. if a history of age degradation exists, current tasks are analyzed for applicability and effectiveness. If failure modes do not occur, then the existing preventative maintenance tasks are no longer relevant and can be eliminated.

Back-Fit RCM is a continuous improvement process that forms the final step of Classic RCM, where applicable and effective maintenance tasks are initially developed for new systems and smaller units of equipment during the acquisition stage (see Figure 1: "Classic & Back-Fit RCM Processes in Planned Maintenance Development"). Effective maintenance programs build on operational experience in a dynamic maintenance program to optimize a set of maintenance tasks over the service life of a system.

Back-Fit RCM requires sufficient operating data to confirm assumptions that were made when the original maintenance program was developed, validating existing maintenance requirements or recommending changes as appropriate.

The Back-Fit RCM methodology uses a road map with filters for Age Degradation, Task Applicability, Task Effectiveness, and Recommending Change (see Figure 2: "Back-Fit RCM Roadmap (NAVSEA)" — this is the NAVSEA roadmap referenced throughout the guide).

2. Back-Fit RCM Workflows

(Figure 3: "Classification of Maintenance Action in Back-Fit RCM"; Figure 4: "Assessment of Maintenance Action in Back-Fit RCM" — workflow diagrams/images with captions only, no additional extractable body text. These figures define the decision-tree structure elaborated in section 3.3 "NAVSEA Roadmap" below.)

2.1 Pre-requisites

In MADE, the Back-Fit RCM editor uses 8 pages to represent the steps used to evaluate existing maintenance requirements. Prior to beginning the Back-Fit RCM analysis, the following pre-requisites are required:

• Identified critical model items where maintenance is authorized/performed through FMEA or FMECA Criticality Analysis
• Maintenance History/Records for the maintainable item to determine whether the dominant failure modes are valid
• Step 4 (Failure Effects) in a Classic RCM Analysis, in order for age degradation to be verified
• Mean Time to Failure (MTTF) to establish the effectiveness of maintenance for the time duration of the Back-Fit RCM analysis

If there is evidence of reliability degradation, the analyst will proceed to the third Back-Fit RCM page in MADE; if not, maintenance action will be recommended for deletion.

The Applicability, Failure Consequences, and Effectiveness pages correspond to the Classic RCM Logic tree. For both Applicability and Effectiveness, the analyst assesses the validity of current tasks and recommends them for the appropriate actions. The Back-Fit decision logic assesses tasks that should satisfy the criteria for maintenance task relevance and value. This assessment determines whether or not the current maintenance task serves to prevent the intended failure in a cost-effective manner. If not, the task may be eliminated or revised in scope and/or periodicity.

To summarize, applying the Back-Fit RCM analysis to a system and its model items (subsystems, components, and parts) is to establish:

• Effective maintenance
• Maintenance of the appropriate systems and equipment
• The appropriate maintenance interval

2.2 Project Files

This guide requires the Vehicle System model created from the RAM Module manual. The completed model is also available from the MADE Library.