Reliability Centered Maintenance 101

Bob Appleton

References

• DoDI 4151.22, December 2, 2007 • NAVAIR 00-25-403, 1 March 2003• SAE JA-1011, August 1999• SAE JA-1012, January 2002• Boeing (2010) Statistical Summary of

Commercial Jet Airplane Accidents, Worldwide Operations 1959-2009, Seattle

• Moubray, J. (1997) Reliability-centered Maintenance. New York: Industrial Press

• .

Overview

• Background– Condition Based Maintenance– Changing views of Maintenance

• History and background of RCM• The RCM Process• The RCM team• The Seven Questions• Results of the Analysis

What is RCM?• Definition

– A process used to determine what must be done to ensure that any physical asset continues to do what its users want it to do in its present operating context

– Mitigate the consequences of failure• Yeah, but what is it?

– Highly structured analysis process to: • Devise maintenance policy• Design for ease of maintenance & effective operation

– Consensus from all stakeholders– Identification of critical maintenance practices– Reduction of counterproductive maintenance practice

Key Enabler of Condition Based Maintenance

CBM+ is the application and integration of appropriate processes, technologies, and knowledge based capabilities to improve the reliability and maintenance effectiveness of DoD systems and components. At its core, CBM+ is maintenance performed on evidence of need provided by reliability centered maintenance (RCM) analysis and other enabling processes…

DoDI 4151.22, December 2, 2007

Condition Based Maintenance

Condition based maintenance plus (CBM+) is the primary reliability driver in the total life-cycle systems management (TLCSM) supportability strategy of the Department of Defense. In concert with the other TLCSM enablers, such as continuous process improvement (CPI), cause and effect predictive modeling, and desired outcomes achieved through performance based logistics (PBL), CBM+ strives to optimize key performance measures of materiel readiness - materiel availability, materiel reliability, mean downtime, and ownership costs. Under the authority in DoD Directive 5134.01 (Reference (a)), this Instruction establishes policy and guidance for the Military Departments and Defense Agencies for implementation of CBM+

pursuant to DoD Directive 4151.18 and DoD Instruction 5000.2 (References (b) and (c)).

DoDI 4151.22, December 2, 2007

Condition Based Maintenance

What Does THAT Mean?• Do maintenance based upon the condition of the

asset; not on rigid time based schedules– Reservists change clean oil on schedule even though

the vehicle may have less than 100 miles since the last oil change

• More maintenance is not better maintenance• Excessive preventive maintenance creates failures

– Infant mortality• Asset Health Monitoring is key to successful CBM

– Sensor selection must be examined carefully• CBM is third generation maintenance and is an

important step toward prognostic maintenance

Changing Views of Maintenance

BUILD HEAVY

PREVENTIVE MAINTENANCE

Time Based

CBM/RCM

Reliability, Availability,Maintainability, TOC

Views of Wear Out Patterns

Failure Patterns

Condition Based Maintenance

Origin of RCM• Boeing 747 and United Airlines

– MSG-1 (Maintenance Steering Group)(1968)– DC-8 required 4 million man hours per 20,000 flight

hours• (200 man hours per flight hour)

– Using RCM techniques 747 required 66,000 while improving reliability

• (3.3 man hours per flight hour)• MSG-2 & MSG-3 followed for many military and civilian aircraft• Nowlan & Heap, RCM, 1978• SAE standardized RCM requirements for industrial equipment

with:– JA-1011– JA-1012

• NAVAIR standard – 00-25-403

Record of Improved Safety

The RCM Analysis Team

Officer or Chief

Maintenance Officer or Chief

Maintainer

The RCM Process

• Disciplined and highly structured• Synergy created by the multifunctional team• Collective wisdom of team members from all areas

– Operations– Maintenance– Engineer– Logisticians– Specialists

• Decisions based upon consensus • Cross functional information sharing leading to

deeper understanding of the asset by all

The Seven Questions1. What are the functions and associated performance

standards of the asset in its present operating context?

2. In what ways does it fail to fulfill its functions?

3. What causes each functional failure?

4. What happens when each failure occurs?

5. In what way does each failure matter?

6. What can be done to predict or prevent each failure?

7. What should be done if a suitable proactive task cannot be found?

Break

1. Functions• What are the functions and associated performance

standards of the asset in its present operating context?– What do its users want the asset to do?

• Primary function – the main purpose the asset was acquired.• Secondary functions

– Safety - Comfort– Environmental - Appearance– Control - Protection– Containment - Economy/efficiency

– What is the Operating Context?• Where, when, under what conditions

– What are the required performance standards?• How much; how fast

Sample Function Statement• PRIMARY FUNCTION - To pump water from tank X to tank

Y at not less than 800 gallons per hour at temperatures ranging from 40 degrees F to 120 degrees F.

• SECONDARY FUNCTION - To contain water within the pump, not permitting leaks exceeding 1 ounce per 8 hour work shift

• SECONDARY FUNCTION – To prevent any contamination at all of the water from lubricating oil.

• SECONDARY FUNCTION – To shut off automatically if the water in tank Y rises above 90% capacity to prevent overflow

Initial Capability

Pump1000 GPH

Output 800 GPH

X Y

Deterioration (Not failed)

Pump800 GPH

Output 800 GPH

2. Functional Failures• In what ways does it fail to fulfill its functions?• “Failure” – The inability of any asset to do what its users

want it to do• “Functional Failure” – The inability of an asset to fulfill a

function to a standard of performance which is acceptable to the user.– Performance standard must be agreed to by all stakeholders

• Total failure – fails to pump any water at all• Partial failure – pumps water at less than 800 GPM

– Partial failure will likely be caused by different failure modes than total failure

– Partial failure is not the same as deterioration– Asset may fail by breaching either upper or lower limits

Failure

PumpNo water at

all

Output 800 GPH

Functional Failure (Partial)

Pump799 GPH

Output 800 GPH

3. Failure Modes (FMEA)• What causes each functional failure?• Failure mode statements should contain a noun and

a verb– “Bearing seized” or “impeller worn”– Not “broken,” fails,” or “malfunctions”

• Ineffective Failure Mode statements lead to unproductive failure management techniques– P: Number 3 engine missing.

S: Engine found on right wing after brief search. – P: Aircraft handles funny.

S: Aircraft warned to straighten up, fly right, and be serious.

– P: Something loose in cockpit.S: Something tightened in cockpit.

3. Failure Modes (FMEA)

• All maintenance is managed at the Failure Mode level– Reactive maintenance identifies failure modes after

the fact– CBM requires that all potential failure modes be

identified beforehand in order to monitor, measure and manage them

• Categories of failure modes– Decreasing capability– Increase in desired performance– Initial incapability

Different Failures; Different Failure Modes

PumpNo

water at all

Output 800 GPH

Pump799 GPH

Output 800 GPH

4. Failure Effects (FMEA)

• What happens when each failure mode occurs?– Evidence of failure– What threat to safety or environment– How does it affect operations– What damage is done by the failure– What must be done to repair the failure

• Consider “down time” vs repair time when measuring effects

• Best sources of FMEA data are the users who work with the asset daily

5. Failure Consequences

• In what way does each failure matter?– How and how much does each failure matter

• Major consequences require great effort to avoid, eliminate or minimize consequences

• Minor consequences may be run to failure• Hidden failure requires special treatment

– Consequence could be a multiple failure• Protected function fails while the protective device

is in a failed state

Different Failure Modes;Different Failure Consequences

PumpNo

water at all

Output 800 GPH

Pump799 GPH

Output 800 GPH

Different Operating Context;Different Failure Consequences

Output 800 GPH

StandbyPump

Primary Pump

Hidden Function; Hidden Failure

Output 800 GPH

StandbyPump

Primary Pump

6. Failure Management Techniques

• What can be done to predict or prevent each failure?– All tasks must be technically feasible and worth

doing. Proactive tasks (preventive)(age related failures)• Scheduled restoration• Scheduled discard• Scheduled on-condition

– Proactive Tasks (predictive)• On-condition maintenance

– Condition Monitoring– Product quality variation– Primary effects monitoring– Human senses

Task Selection

7. Failure Management Techniques

• What if a suitable predictive or preventive task cannot be found?– Default actions

• Failure finding– For hidden failures of protective devices

• Run to failure• Redesign

Outcomes of RCM Analysis• Revised maintenance schedules and practices

• Revised Operating procedures

• Recommended Engineering Changes

• Database of maintenance requirements– Useful to provide documentation for decisions

• Analysis team members gain a deeper understanding of the asset

Questions?