TM 5-698-2, Reliability-Centered Maintenance (RCM) for Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities (6 October 2006)

Overview

TM 5-698-2 gives a method for applying reliability-centered maintenance (RCM) to the mechanical, electrical and control systems of C4ISR facilities. RCM starts from this observation: it was once widely believed that every item had a right time for preventive maintenance (PM), that replacement or overhaul would reduce failure frequency, yet results often told a different story and PM sometimes made things worse by creating more chances for maintenance-induced failures. US airlines formed a task force with the FAA, which found that PM is effective only for items with a certain failure pattern and that, apart from safety, the PM decision should rest on economics.

The RCM precepts are six: the objective of maintenance is to preserve function, the focus is the end system, reliability is the basis for decisions (conditional probability of failure at specific ages), safety comes first and then economics, maintenance cannot raise inherent reliability and can only sustain it, and the process is continuing. The four Ws (what can fail, why, when, and what are the consequences) are the core of the logic. Chapter 5 extends from FMEA data to a decision logic tree (adapted from MSG-3) with separate branches for evident and hidden failures by hazardous, operational and economic effect.

The manual also describes how RCM applies to facility types: mechanical systems (chillers, cooling towers, valves, piping, boilers, HVAC distribution, generators, fuel systems), electrical systems (transformers, switchgear, circuit breakers, motor control centres, UPS and batteries) and SCADA control systems. In an existing facility whose PM programme is not RCM-based, supporting analyses such as FMEA must be done first; data is often missing and engineering judgment is used. It lists implementation pitfalls: run-to-failure shock, not accepting the preserve-function principle, resistance to challenging the past, organisational structure and fear of staff reduction.

Chapter 6 treats outsourced maintenance and derives performance measures from availability: maximum downtime, maximum time to restore for a single failure and turn-around time. An incentive example rewards a contractor whose downtime stays below 140 hours against a 150-hour annual maximum. The manual is dated 2006 and conceptual; it gives a method, not equipment-specific maintenance intervals. Appendix B covers the exponential, Weibull, normal and lognormal distributions, and Appendix E gives an example of a flexible RCM methodology.

Key points

1. Operational availability Ao = MTBM / (MTBM + mean downtime), counting all maintenance including preventive and support delays.
2. Inherent availability Ai = MTBF / (MTBF + MTTR), counting only corrective maintenance for design failures and ignoring support-system effects.
3. Airline experience: moving turbine engine overhaul from scheduled to on-condition cut engine shop maintenance costs by 50 percent versus the DC-8; structural inspections required 4,000,000 hours with the traditional approach for the DC-8 against 66,000 hours with RCM for the B747.
4. Of six age-reliability failure patterns, infant mortality accounts for 68 percent and constant failure rate 14 percent; 89 percent of items cannot benefit from an operating-age limit (only wearout 2 percent, bathtub 4 percent and gradual rise 5 percent can).
5. For an exponential failure distribution with constant failure rate, an item with a 1000-hour MTBF has only a 37 percent probability of surviving 1000 hours of continuous operation.
6. RCM is driven first by safety and then by economics; when safety is not an issue PM must be justified economically, and run-to-failure is sometimes cheaper.
7. Criteria for applying RCM: many PM tasks, very high maintenance cost, frequent corrective maintenance, or hazardous conditions possible on failure.
8. In an existing facility supporting analyses such as FMEA must be done before RCM starts if absent; where data rights were not procured, engineering judgment and more time are needed.
9. An outsourced maintenance contract uses three availability measures: maximum downtime (for example 150 hours per year), maximum time to restore for any single failure and turn-around time; incentives may be positive or negative.
10. The three main RCM candidate systems are mechanical, electrical and control; generators and fuel systems are noted as mission critical yet frequently neglected.

Using it in design

• At design stage carry out an FMEA for each critical system and record failure modes, effects and detection methods as input to the RCM decision logic; the text stresses that RCM starts in design and continues for the life of the facility.
• Separate PM tasks by age-failure pattern: an age limit for mechanical parts that show wearout, condition monitoring or run-to-failure for randomly failing electronics.
• Build maintainability into the design: access, diagnostics and repair time set MTTR and thus availability; adding redundancy is comparatively easy in a facility in terms of space and weight.
• When drafting a maintenance contract write the annual maximum downtime, maximum time to restore per failure and spare turn-around time, and divide supply and authority between contractor and customer in detail.
• Explicitly add flooded and gel lead-acid UPS batteries, chillers, generators and fuel systems to the RCM candidate list; they are critical yet often neglected.
• When reducing a PM programme plan for staff resistance, run-to-failure shock and training needs, and explain the preserve-function principle to the team.

Who should read it

Operations and design engineers working on data centre maintenance strategy, maintenance contracts and design for maintainability.

Document contents

1. Chapter 1 Introduction to Reliability-Centered Maintenance: availability, the RCM concept, benefits, origins
2. Chapter 2 Essential Elements of a Successful RCM Program
3. 2-1 RCM implementation plan
4. 2-2 Data collection requirements
5. 2-5 RCM as a part of design
6. 2-6 Focus on the four Ws
7. Chapter 3 Maintenance of Systems: categories of maintenance, maintenance concepts, packaging a maintenance program
8. Chapter 4 Fundamental Concepts of a Reliability-Centered Maintenance Program: objectives, applicability of PM, failure, modeling
9. Chapter 5 The Reliability-Centered Maintenance Process
10. 5-2 C4ISR candidates for RCM analysis
11. 5-5 The RCM process (decision logic)
12. 5-6 Specific considerations for implementing RCM for C4ISR facilities
13. 5-7 Evaluation of alternatives
14. Chapter 6 Contracting for Maintenance: measures of performance, scope, monitoring, incentives
15. Appendix B Statistical Distribution Used in Reliability and Maintainability
16. Appendix C Availability and Operational Readiness
17. Appendix E Flexible RCM Methodology Example

Read the document

Publication details

Authors

Headquarters, Department of the Army

Publisher

U.S. Army Corps of Engineers

Year

2006

Document language

English

Source type

Government / public

Access

Open licence — downloadable

Licence

U.S. public domain — U.S. Government work; free to reuse

Licence evidence

www.copyright.gov

Citation